U.S. patent application number 10/629491 was filed with the patent office on 2004-02-05 for method and system for sensing cardiac contractions during a medical procedure.
Invention is credited to Hill, Michael R.S., Jahns, Scott E., Keogh, James R..
Application Number | 20040024422 10/629491 |
Document ID | / |
Family ID | 28455139 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040024422 |
Kind Code |
A1 |
Hill, Michael R.S. ; et
al. |
February 5, 2004 |
Method and system for sensing cardiac contractions during a medical
procedure
Abstract
A system of performing a medical procedure, such as surgery, is
provided. The system comprises a sensor to sense a state of cardiac
tissue, such as an impending contraction and an indicator to
indicate the state of the cardiac tissue. Methods and devices for
performing the medical procedure are also provided.
Inventors: |
Hill, Michael R.S.;
(Minneapolis, MN) ; Jahns, Scott E.; (Hudson,
WI) ; Keogh, James R.; (Maplewood, MN) |
Correspondence
Address: |
CARDINAL LAW GROUP
Suite 2000
1603 Orrington Avenue
Evanston
IL
60201
US
|
Family ID: |
28455139 |
Appl. No.: |
10/629491 |
Filed: |
July 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10629491 |
Jul 29, 2003 |
|
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09669335 |
Sep 25, 2000 |
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Current U.S.
Class: |
607/9 ;
607/3 |
Current CPC
Class: |
A61N 1/36114 20130101;
A61N 1/385 20130101 |
Class at
Publication: |
607/9 ;
607/3 |
International
Class: |
A61N 001/36 |
Claims
We claim:
1. A system for performing a medical procedure, comprising: a
sensor to sense a state of a cardiac tissue; and an indicator to
indicate the state of the cardiac tissue.
2. The system of claim 1 further comprising: a cardiac stimulator
in communication with the sensor to stimulate beating of a heart
when the state indicated by the indicator is a contracting
state.
3. The system of claim 1 further comprising: a nerve stimulator in
communication with the sensor to inhibit beating of a heart when
the state indicated by the indicator is a non-contracting
state.
4. The system of claim 1 further comprising: drug delivery means
for delivering at least one drug during the medical procedure.
5. The system of claim 4 wherein the drug delivery means is
selected from the group consisting of: a spray, a cream, an
ointment, a medicament, a pill, a patch, a catheter, a cannula, a
needle and syringe, a pump, and an iontophoretic drug delivery
device.
6. The system of claim 4 wherein the drug is selected from the
group consisting of: a beta-blocker, a cholinergic agent, a
cholinesterase inhibitor, a calcium channel blocker, a sodium
channel blocker, a potassium channel agent, adenosine, an adenosine
receptor agonist, an adenosine deaminase inhibitor, dipyridamole, a
monoamine oxidase inhibitor, digoxin, digitalis, lignocaine, a
bradykinin agent, a serotoninergic agonist, an antiarrythmic agent,
a cardiac glycoside, a local anesthetic, atropine, a calcium
solution, an agent that promotes heart rate, an agent that promotes
heart contractions, dopamine, a catecholamine, an inotrope
glucagon, a hormone, forskolin, epinephrine, norepinephrine,
thyroid hormone, a phosphodiesterase inhibitor, prostacyclin,
prostaglandin and a methylxanthine.
7. The system of claim 4 wherein the drug is naturally
occurring.
8. The system of claim 4 wherein the drug is chemically
synthesized.
9. The system of claim 3 wherein the nerve stimulator stimulates a
nerve selected from the group consisting of: a vagal nerve, a
carotid sinus nerve, a fat pad.
10. The system of claim 3 wherein the nerve stimulator stops
stimulation automatically when the state indicated by the indicator
is a contracting state.
11. The system of claim 1 wherein the sensor is selected from the
group consisting of: an electrical sensor, a chemical sensor, an
electromagnetic interference sensor, an electrochemical sensor, a
pressure sensor, a sound wave sensor, a magnetic sensor, an
ultraviolet sensor, a visible light sensor, an infrared sensor, a
radiation sensor, a flow sensor, a temperature sensor, a gas
sensor, an optical sensor, a pH sensor, a potentiometric sensor, a
fluorescence sensor, a depolarization sensor and a biosensor.
12. The system of claim 1 wherein the sensor comprises at least one
electrode.
13. The system of claim 12 wherein the electrode is selected from
the group consisting of: cardiac stimulation electrodes, clip
electrodes, needle electrodes, probe electrodes, pacing electrodes,
epicardial electrodes, patch electrodes, intravascular electrodes,
balloon-type electrodes, basket-type electrodes, tape-type
electrodes, umbrella-type electrodes, suction-type electrodes,
endotracheal electrodes, endoesophageal electrodes, transcutaneous
electrodes, intracutaneous electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes and cuff electrodes.
14. The system of claim 2 wherein the cardiac stimulator comprises
at least one electrode.
15. The system of claim 14 wherein the electrode is selected from
the group consisting of: cardiac stimulation electrodes, clip
electrodes, needle electrodes, probe electrodes, pacing electrodes,
epicardial electrodes, patch electrodes, intravascular electrodes,
balloon-type electrodes, basket-type electrodes, tape-ype
electrodes, umbrella-type electrodes, suction-type electrodes,
endotracheal electrodes, endoesophageal electrodes, transcutaneous
electrodes, intracutaneous electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes and cuff electrodes.
16. The system of claim 2 wherein the sensor and the cardiac
stimulator are the same.
17. The system of claim 3 wherein the nerve stimulator comprises at
least one electrode.
18. The system of claim 17 wherein the electrode is selected from
the group consisting of: nerve stimulation electrodes, endotracheal
electrodes, endoesophageal electrodes, intravascular electrodes,
transcutaneous electrodes, intracutaneous electrodes, balloon-type
electrodes, basket-type electrodes, umbrella-type electrodes,
tape-type electrodes, suction-type electrodes, screw-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire electrodes, patch electrodes,
cuff electrodes, clip electrodes, needle electrodes and probe
electrodes.
19. The system of claim 1 further comprising a breathing
regulator.
20. The system of claim 19 wherein the breathing regulator
stimulates a phrenic nerve.
21. The system of claim 19 wherein the breathing regulator controls
a respirator.
22. The system of claim 19 wherein the breathing regulator
comprises at least one electrode.
23. The system of claim 22 wherein the electrode is selected from
the group consisting of: nerve stimulation electrodes, endotracheal
electrodes, endoesophageal electrodes, intravascular electrodes,
transcutaneous electrodes, intracutaneous electrodes, balloon-type
electrodes, basket-type electrodes, umbrella-type electrodes,
suction-type electrodes, screw-type electrodes, tape-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire electrodes, patch electrodes,
cuff electrodes, clip electrodes, needle electrodes and probe
electrodes.
24. The system of claim 1 wherein the medical procedure is selected
from the group consisting of: a surgical procedure, a non-surgical
procedure, a fluoroscopic procedure, a cardiac procedure, a
vascular procedure, a neurosurgical procedure, an electrophysiology
procedure, a diagnostic procedure, a therapeutic procedure, an
ablation procedure, an endovascular procedure, a liver procedure, a
spleen procedure, a pulmonary procedure, an aneurysm repair, an
imaging procedure, a CAT scan procedure, a MRI procedure, a
pharmacological therapy, a drug delivery procedure, a biological
delivery procedure, a genetic therapy, a cellular therapy, a cancer
therapy, a radiation therapy, a transplantation procedure, a
coronary angioplasty procedure, a stent delivery procedure, an
atherectomy procedure, a procedure that requires precise control of
cardiac motion, a procedure that requires precise control of
bleeding, a non-invasive procedure, a minimally invasive procedure,
an invasive procedure, a port-access procedure, an endoscopic
procedure, a sternotomy procedure, a thoracotomy procedure and a
robotic procedure.
25. A method for performing a medical procedure, comprising:
inhibiting beating of a heart; performing the medical procedure;
and sensing a state of cardiac tissue while beating of the heart is
inhibited.
26. The method of claim 25, further comprising: inhibiting beating
of the heart automatically when the state of cardiac tissue is a
non-contracting state.
27. The method of claim 25 further comprising: stimulating a nerve
to inhibit beating of the heart when the state of cardiac tissue is
a non-contracting state.
28. The method of claim 27 further comprising: stopping stimulation
of the nerve when the state of cardiac contraction is a contracting
state.
29. The method of claim 25, further comprising: allowing beating of
the heart to occur when the state of cardiac tissue is a
contracting state.
30. The method of claim 25, further comprising: stimulating beating
of the heart automatically when the state of cardiac tissue is a
contracting state.
31. The method of claim 25 further comprising: delivering at least
one drug during the medical procedure.
32. The method of claim 25 further comprising: stopping breathing
when the state of cardiac tissue is a non-contracting state.
33. A device for performing a medical procedure, comprising: a
processor; a sensor to sense a state of cardiac tissue, the sensor
operatively connected to the processor; and at least one nerve
stimulation electrode, the nerve stimulation electrode operatively
connected to the processor wherein the processor receives a signal
from the sensor and adjusts output from the nerve stimulation
electrode in response to the signal.
34. The device of claim 33 wherein the sensor is selected from the
group consisting of: an electrical sensor, a chemical sensor, an
electromagnetic interference sensor, an electrochemical sensor, a
pressure sensor, a sound wave sensor, a magnetic sensor, an
ultraviolet sensor, a visible light sensor, an infrared sensor, a
radiation sensor, a flow sensor, a temperature sensor, a gas
sensor, an optical sensor, a pH sensor, a potentiometric sensor, a
fluorescence sensor, a depolarization sensor and a biosensor.
35. The device of claim 33 wherein the nerve stimulation electrode
selected from the group consisting of: endotracheal electrodes,
endoesophageal electrodes, intravascular electrodes, transcutaneous
electrodes, intracutaneous electrodes, balloon-type electrodes,
basket-type electrodes, umbrella-type electrodes, tape-type
electrodes, suction-type electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes, patch electrodes, cuff
electrodes, clip electrodes, needle electrodes and probe
electrodes.
36. The device of claim 33 further comprising: at least one cardiac
stimulation electrode to stimulate beating of the heart, the
cardiac stimulator operatively connected to the processor wherein
the processor receives a signal from the sensor and adjusts output
from the cardiac stimulation electrode in response to the
signal.
37. The device of claim 36 wherein the cardiac stimulation
electrode is selected from the group consisting of: clip
electrodes, needle electrodes, probe electrodes, pacing electrodes,
epicardial electrodes, patch electrodes, intravascular electrodes,
balloon-type electrodes, basket-type electrodes, tape-type
electrodes, umbrella-type electrodes, suction-type electrodes,
endotracheal electrodes, endoesophageal electrodes, transcutaneous
electrodes, intracutaneous electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes and cuff electrodes.
38. The device of claim 36 wherein the cardiac stimulation
electrode and the sensor are the same.
38. The device of claim 33 further comprising: at least one
breathing regulation electrode for controlling breathing, the
breathing regulation electrode operatively connected to the
processor wherein the processor adjusts the output from the
breathing regulation electrode in response to the signal.
39. The device of claim 38 wherein the breathing regulation
electrode is selected from the group consisting of: nerve
stimulation electrodes, endotracheal electrodes, endoesophageal
electrodes, intravascular electrodes, transcutaneous electrodes,
intracutaneous electrodes, balloon-type electrodes, basket-type
electrodes, umbrella-type electrodes, suction-type electrodes,
screw-type electrodes, tape-type electrodes, barb-type electrodes,
bipolar electrodes, monopolar electrodes, metal electrodes, wire
electrodes, patch electrodes, cuff electrodes, clip electrodes,
needle electrodes and probe electrodes.
40. The device of claim 33 further comprising: a drug pump for
delivering at least one drug, the drug pump operatively connected
to the processor wherein the processor adjusts the output of the
drug.
Description
PRIORITY
[0001] This application claims priority as a divisional application
to 09/669,335 filed on Sep. 26, 2000.
FIELD OF THE INVENTION
[0002] This invention relates to methods and systems for performing
a medical procedure, especially procedures during which it is
necessary to adjust the beating of the heart. More particularly,
this invention relates to methods and systems for sensing imminent
cardiac contractions during such a procedure.
BACKGROUND OF THE INVENTION
[0003] The current leading cause of death in the United States is
coronary artery disease in which the coronary arteries are blocked
by atherosclerotic plaques or deposits of fat. The typical
treatment to relieve a partially or fully blocked coronary artery
is coronary artery bypass graph (CABG) surgery.
[0004] CABG surgery, also known as "heart bypass" surgery,
generally entails using a graph to bypass the coronary obstruction.
The procedure is generally lengthy, traumatic and subject to
patient risks. Among the risk factors involved is the use of a
cardiopulmonary bypass (CPB) circuit, also known as a "heart-lung
machine", to pump blood and oxygenate the blood so that the
patient's heart may be stopped during the surgery.
[0005] Conventional CABG procedures are typically conducted on a
stopped heart while the patient is on a CPB circuit. A stopped
heart and a CPB circuit enables a surgeon to work in a bloodless,
still operative field. However, there are a number of problems
associated with CABG procedures performed while on CPB including
the initiation of a systemic inflammatory response due to
interactions of blood elements with the artificial material
surfaces of the CPB circuit and global myocardial ischemia due to
cardioplegic cardiac arrest. For these reasons, avoiding the use of
CPB or cardioplegic cardiac arrest may help minimize post-operative
complications.
[0006] One method, as disclosed in U.S. Pat. No. 5,651,378 to
inventors Matheny and Taylor and in U.S. Pat. No. 5,913,876 to
inventors Taylor et al., for facilitating coronary bypass surgery
on a beating heart and thereby avoid the use of CPB and
cardioplegic cardiac arrest includes stimulating the vagal nerve
electrically in order to temporarily stop or substantially reduce
the beating of the heart. This may be followed by pacing the heart
to start its beating.
[0007] Another method, as disclosed in two published PCT
applications, WO 99/09971 and WO 99/09973, both to inventor Puskas,
involves stopping the beating of the heart during coronary bypass
surgery using electrical stimulation of the vagal nerve in
combination with administration of drugs. Another method, as
disclosed in U.S. Pat. No. 6,060,454 to inventor Duhaylongsod,
involves stopping the beating of the heart during coronary bypass
surgery via the local delivery of drugs to the heart.
[0008] Although it is desirable to stop the heart for a period of
time in order to allow the surgeon to accomplish a required task
without interference from heart movement, i.e. a motionless
operative field, it is undesirable to have the heart stopped for
too long a period of time since the body needs, among other things,
a constant supply of oxygen. In fact, it is particularly important
to maintain sufficient blood flow, and therefore oxygen flow, to
the brain. Stopping the heart for prolonged periods of time may
cause damage to the patient.
[0009] Moreover, once stopped or still, the heart may still
contract occasionally. This is sometimes referred to as an "escape
beat." Such an "escape beat" may occur without any warning to the
surgeon and the movement associated with the escape beat may
interfere with the medical procedure being carried out.
[0010] It would be desirable therefore to provide a method for
temporarily stopping or slowing the heart in order to control blood
flow during a medical procedure.
[0011] It would further be desirable to provide a means for sensing
an imminent cardiac contraction during the procedure.
[0012] It would further be desirable to provide a means for
alerting the surgeon of an imminent contraction during the
procedure.
SUMMARY OF THE INVENTION
[0013] One aspect of the present invention provides a system for
performing a medical procedure. The system includes a sensor to
sense a state of a cardiac tissue and an indicator to indicate the
state of the cardiac tissue.
[0014] The system may also include a nerve stimulator in
communication with the sensor to inhibit beating of a heart when
the state indicated by the indicator is a non-contracting state.
The nerve stimulator may stimulate a nerve such as a vagal nerve, a
carotid sinus nerve, a fat pad. The nerve stimulator may be, for
example, one or more electrodes, such as nerve stimulation
electrodes, endotracheal electrodes, endoesophageal electrodes,
intravascular electrodes, transcutaneous electrodes, intracutaneous
electrodes, balloon-type electrodes, basket-type electrodes,
umbrella-type electrodes, tape-type electrodes, suction-type
electrodes, screw-type electrodes, barb-type electrodes, bipolar
electrodes, monopolar electrodes, metal electrodes, wire
electrodes, patch electrodes, cuff electrodes, clip electrodes,
needle electrodes and probe electrodes.
[0015] The system may also include a cardiac stimulator in
communication with the sensor to stimulate beating of a heart when
the state indicated by the indicator is a contracting state. The
cardiac stimulator may be, for example, one or more electrodes,
such as cardiac stimulation electrodes, clip electrodes, needle
electrodes, probe electrodes, pacing electrodes, epicardial
electrodes, patch electrodes, intravascular electrodes,
balloon-type electrodes, basket-type electrodes, tape-type
electrodes, umbrella-type electrodes, suction-type electrodes,
endotracheal electrodes, endoesophageal electrodes, transcutaneous
electrodes, intracutaneous electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes and cuff electrodes.
[0016] The sensor may be an electrical sensor, a chemical sensor,
an electromagnetic interference sensor, an electrochemical sensor,
a pressure sensor, a sound wave sensor, a magnetic sensor, an
ultraviolet sensor, a visible light sensor, an infrared sensor, a
radiation sensor, a flow sensor, a temperature sensor, a gas
sensor, an optical sensor, a pH sensor, a potentiometric sensor, a
fluorescence sensor, a depolarization sensor and a biosensor. The
sensor may also comprise one or more electrodes, such as cardiac
stimulation electrodes, clip electrodes, needle electrodes, probe
electrodes, pacing electrodes, epicardial electrodes, patch
electrodes, intravascular electrodes, balloon-type electrodes,
basket-type electrodes, tape-type electrodes, umbrella-type
electrodes, suction-type electrodes, endotracheal electrodes,
endoesophageal electrodes, transcutaneous electrodes,
intracutaneous electrodes, screw-type electrodes, barb-type
electrodes, bipolar electrodes, monopolar electrodes, metal
electrodes, wire electrodes and cuff electrodes. The sensor and the
cardiac stimulator may be the same.
[0017] The system may also include drug delivery means such as a
spray, a cream, an ointment, a medicament, a pill, a patch, a
catheter, a cannula, a needle and syringe, a pump, and an
iontophoretic drug delivery device to deliver at least one drug
during the procedure. The drug may be a beta-blocker, a cholinergic
agent, a cholinesterase inhibitor, a calcium channel blocker, a
sodium channel blocker, a potassium channel agent, adenosine, an
adenosine receptor agonist, an adenosine deaminase inhibitor,
dipyridamole, a monoamine oxidase inhibitor, digoxin, digitalis,
lignocaine, a bradykinin agent, a serotoninergic agonist, an
antiarrythmic agent, a cardiac glycoside, a local anesthetic,
atropine, a calcium solution, an agent that promotes heart rate, an
agent that promotes heart contractions, dopamine, a catecholamine,
an inotrope glucagon, a hormone, forskolin, epinephrine,
norepinephrine, thyroid hormone, a phosphodiesterase inhibitor,
prostacyclin, prostaglandin and a methylxanthine. The drug may be
naturally occurring or chemically synthesized.
[0018] The system may also include a breathing regulator, which may
control a respirator. The breathing regulator may stimulate a
phrenic nerve. The breathing regulator may be, for example, one or
more electrodes such as nerve stimulation electrodes, endotracheal
electrodes, endoesophageal electrodes, intravascular electrodes,
transcutaneous electrodes, intracutaneous electrodes, balloon-type
electrodes, basket-type electrodes, umbrella-type electrodes,
suction-type electrodes, screw-type electrodes, tape-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire electrodes, patch electrodes,
cuff electrodes, clip electrodes, needle electrodes and probe
electrodes.
[0019] The medical procedure may be a surgical procedure, a
non-surgical procedure, a fluoroscopic procedure, a cardiac
procedure, a vascular procedure, a neurosurgical procedure, an
electrophysiological procedure, a diagnostic procedure, a
therapeutic procedure, an ablation procedure, an endovascular
procedure, a liver procedure, a spleen procedure, a pulmonary
procedure, an aneurysm repair, an imaging procedure, a CAT scan
procedure, a MRI procedure, a pharmacological therapy, a drug
delivery procedure, a biological delivery procedure, a genetic
therapy, a cellular therapy, a cancer therapy, a radiation therapy,
a transplantation procedure, a coronary angioplasty procedure, a
stent delivery procedure, an atherectomy procedure, a procedure
that requires precise control of cardiac motion, a procedure that
requires precise control of bleeding, a non-invasive procedure, a
minimally invasive procedure, an invasive procedure, a port-access
procedure, an endoscopic procedure, a sternotomy procedure, a
thoracotomy procedure and a robotic procedure.
[0020] Another aspect of the present invention provides a method
for performing a medical procedure. Beating of a heart is
inhibited. The medical procedure is performed and a state of
cardiac tissue is sensed while beating of the heart is inhibited.
The beating of the heart may be inhibited automatically when the
state of cardiac tissue is a non-contracting state. A nerve may
also be stimulated to inhibit beating of the heart when the state
of cardiac tissue is a non-contracting state. Stimulation of the
nerve may be stopped when the state of cardiac contraction is a
contracting state. Beating of the heart may be allowed to occur
when the state of cardiac tissue is a contracting state. Beating of
the heart may also be stimulated automatically when the state of
cardiac tissue is a contracting state. At least one drug may be
delivered during the medical procedure. Breathing may be stopped
when the state of cardiac tissue is a non-contracting state.
[0021] Another aspect of the present invention provides a device
for performing a medical procedure. The device includes a processor
a sensor to sense a state of cardiac tissue at least one nerve
stimulation electrode. The processor receives a signal from the
sensor and adjusts output from the nerve stimulation electrode in
response to the signal. The sensor may be an electrical sensor, a
chemical sensor, an electromagnetic interference sensor, an
electrochemical sensor, a pressure sensor, a sound wave sensor, a
magnetic sensor, an ultraviolet sensor, a visible light sensor, an
infrared sensor, a radiation sensor, a flow sensor, a temperature
sensor, a gas sensor, an optical sensor, a pH sensor, a
potentiometric sensor, a fluorescence sensor, a depolarization
sensor and a biosensor. The nerve stimulation electrode may be, for
example, one or more electrodes such as endotracheal electrodes,
endoesophageal electrodes, intravascular electrodes, transcutaneous
electrodes, intracutaneous electrodes, balloon-type electrodes,
basket-type electrodes, umbrella-type electrodes, tape-type
electrodes, suction-type electrodes, screw-type electrodes,
barb-type electrodes, bipolar electrodes, monopolar electrodes,
metal electrodes, wire electrodes, patch electrodes, cuff
electrodes, clip electrodes, needle electrodes and probe
electrodes.
[0022] The device may also include at least one cardiac stimulation
electrode to stimulate beating of the heart. The processor receives
a signal from the sensor and adjusts output from the cardiac
stimulation electrode in response to the signal. The cardiac
stimulation electrode may be, for example, one or more electrodes
such as clip electrodes, needle electrodes, probe electrodes,
pacing electrodes, epicardial electrodes, patch electrodes,
intravascular electrodes, balloon-type electrodes, basket-type
electrodes, tape-type electrodes, umbrella-type electrodes,
suction-type electrodes, endotracheal electrodes, endoesophageal
electrodes, transcutaneous electrodes, intracutaneous electrodes,
screw-type electrodes, barb-type electrodes, bipolar electrodes,
monopolar electrodes, metal electrodes, wire electrodes and cuff
electrodes. The cardiac stimulation electrode and the sensor may be
the same.
[0023] The device may also include at least one breathing
regulation electrode for controlling breathing. The processor
adjusts the output from the breathing regulation electrode in
response to the signal. The breathing electrode may be, for
example, one or more electrodes, such as nerve stimulation
electrodes, endotracheal electrodes, endoesophageal electrodes,
intravascular electrodes, transcutaneous electrodes, intracutaneous
electrodes, balloon-type electrodes, basket-type electrodes,
umbrella-type electrodes, suction-type electrodes, screw-type
electrodes, tape-type electrodes, barb-type electrodes, bipolar
electrodes, monopolar electrodes, metal electrodes, wire
electrodes, patch electrodes, cuff electrodes, clip electrodes,
needle electrodes and probe electrodes.
[0024] The device may also include a drug pump for delivering at
least one drug. The processor adjusts the output of the drug.
[0025] The foregoing, and other, features and advantages of the
invention will become further apparent from the following detailed
description of the presently preferred embodiments, read in
conjunction with the accompanying drawings. The detailed
description and drawings are merely illustrative of the invention
rather than limiting, the scope of the invention being defined by
the appended claims in equivalence thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic view of one embodiment of a system for
sensing imminent cardiac contractions during a medical procedure in
accordance with the present invention;
[0027] FIG. 2 is a schematic view of one embodiment of a medical
device in accordance with the present invention;
[0028] FIG. 3 is a flow diagram of one embodiment of a method of
performing a medical procedure in accordance with the present
invention; and
[0029] FIG. 4 is a timeline view of one embodiment of a system for
sensing imminent cardiac contractions during a medical procedure in
accordance with the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0030] FIG. 1 shows a schematic view of one embodiment of a system
for performing a medical procedure in accordance with the present
invention at 100. System 100 comprises a cardiac contraction sensor
6, a nerve stimulator 10, and a cardiac stimulator 20. System 100
may also feature a controller 30 and a breathing regulator 40.
[0031] FIG. 2 shows one embodiment of the present invention at 200.
In this embodiment, the elements named above may be combined or
connected to a control unit along with other components. The unit
200 may be used to coordinate the various elements.
[0032] Cardiac contraction sensor 6 may be any suitable sensor,
e.g., an electrical sensor, a chemical sensor or a biosensor, for
detecting one or more signals indicative of a cardiac contraction
or heartbeat. In one embodiment, as seen in FIG. 2, cardiac
contraction sensor 6 may also comprise a sensor 206 incorporated
with a control unit 200.
[0033] In one embodiment, as shown in FIG. 2, sensor 206 may be a
monitor for mounting on or near the heart during surgery. Such a
monitor may monitor the electrical activity of the heart by picking
up and amplifying electrical signals from the heart and displaying
an output. For example, the output may be displayed on display 216.
The surgeon may check this output periodically to see if the output
reaches a level that indicates an escape beat is probable.
Alternatively, the monitor may be programmed to indicate by a
signal, such as an audio or visual signal, that the electrical
activity has reached a predetermined level that is indicative of an
imminent escape beat.
[0034] Cardiac contraction sensor 6 may also be a sensor that
detects cardiac depolarizations. The electrical signal generated by
the sinus node of the heart causes the atria to contract to force
blood into the ventricles. After a brief delay, the ventricles
contract to force blood out through the body. The contraction of
the ventricles is reflected by the passage of a depolarization
wavefront through the heart muscle. If a depolarization is sensed,
an escape beat is likely to occur. One such depolarization sensor
is disclosed in U.S. Pat. No. 5,156,149 entitled "Sensor for
Detecting Cardiac Depolarizations Particularly Adapted for use in a
Cardiac Pacemaker", Oct. 2, 1992, to inventor Hudrlik. This patent
is assigned to Medtronic, Inc. and is incorporated herein by
reference.
[0035] Cardiac contraction sensor 6 may also be coupled to cardiac
stimulator 20. Such a sensor may detect the response of tissue near
the stimulator 20. If the tissue is stimulated during the procedure
by stimulator 20, the cardiac stimulation may cause an escape beat
even after stimulation has been reduced or stopped, particularly if
cardiac stimulation is only reduced during the procedure rather
than fully stopped. One such detector is disclosed in U.S. Pat. No.
5,265,603 entitled "Electronic Capture Detection for a Pacer," Nov.
30, 1993, to inventor Hudrlik. This patent is assigned to
Medtronic, Inc. and is incorporated herein by reference.
[0036] Cardiac contraction sensor 6 may be an apparatus that senses
power levels of depolarizations in heart tissue. Such a sensor may
be used to distinguish between normally conducted and ectopic heart
beats while the heart is beating or may be used to sense an
imminent heart beat while the heart is slowed or substantially
stilled during a medical procedure. One apparatus that may serve as
such a sensor is disclosed in U.S. Pat. No. 5,411,529 entitled
"Waveform Discriminator for Cardiac Stimulation Devices", May 2,
1995, to inventor Hurdlik. This patent is assigned to Medtronic,
Inc. and is incorporated herein by reference.
[0037] Other suitable sensors may also serve as cardiac contraction
sensor 6.
[0038] All or a portion of cardiac contraction sensor 6 may be
placed in any suitable manner for sensing an imminent cardiac
contraction. For example, sensor 206 may incorporate a lead as
shown at 226, which may be used to attach the sensor to the heart.
The lead may also be used to monitor electrical signals of the
heart as described above. Sensor 206 may be placed in any suitable
area of the heart. For example, sensor 206 may be placed near the
location of the cardiac stimulator 220 as described above. Sensor
206 may be placed near the right ventricle, the left ventricle, the
right atrium, or the left atrium. Other suitable placements of the
sensor 206 may be possible. The sensor's optimal location will
depend primarily on the sensor's mode of operation.
[0039] As indicated above, sensor 206 and/or control unit 200 may
be incorporated into system 100. System 100 may also include a
nerve stimulator 10. In one embodiment, the nerve stimulator 10 may
be used to electrically manipulate cardiac rhythm by stimulating
the vagus nerve. This vagal stimulation may produce asystole
(slowing or stopping of the heart's beating.) Once this induced
asystole is stopped, i.e. once the vagal stimulation is stopped,
the heart may be allowed to return to its usual cardiac rhythm.
Alternatively, the heart may be paced with an electrical pacing
system, thereby maintaining a normal cardiac output. Vagal
stimulation, alone or in combination with electrical pacing, may be
used selectively and intermittently to allow a surgeon to perform a
medical procedure during intermittent periods of asystole.
[0040] It is known that stimulation of the vagus nerve can reduce
the sinus rate, as well as prolong AV conduction time or, if
stimulation energies are high enough, induce AV node block. Use of
vagal nerve stimulation to treat supraventricular arrhythmias and
angina pectoris is disclosed in the article "Vagal Tuning" by
Bilgutay et al., Journal of Thoracic and Cardiovascular Surgery,
Vol. 56, No. 1, July, 1968, pp. 71-82. It is also known that
stimulation of the carotid sinus nerve produces a similar result,
as disclosed in the article "Carotid Sinus Nerve Stimulation in the
Treatment of Angina Pectoris and Supraventricular Tachycardia" by
Braunwald et al., published in California Medicine, Vol. 112, pp.
41-50, March, 1970.
[0041] As set forth in "Functional Anatomy of the Cardiac Efferent
Innervation" by Randall et al., in Neurocardiology, edited by
Kulbertus et al, Futura Publishing Co., 1988, direct surgical
excision of the fat pad associated with the SA node affects the
functioning of the SA node without significantly affecting the AV
node. Similarly, excision of the fat pad associated with the AV
node affects functioning of the AV node without significantly
affecting the SA node.
[0042] As set forth in the article "Parasympathetic Postganglionic
Pathways to the Sinoatrial Node," Bluemel et al., Am. J. Physiol.
259, (Heart Circ. Physiol. 28) H1504-H1510, 1990, stimulation of
the fat pad associated with the SA node results in slowing of the
sinus rate without the accompanying prolongation of AV conduction
time which normally results from vagal nerve stimulation. The
article also indicates that stimulation of the fat pad associated
with the AV node is believed to produce corresponding effects
limited to the AV node, i.e., extension of the AV conduction time
without concurrent slowing of the sinus rate.
[0043] As set forth in the article "Neural Effects on Sinus Rate
and Atrial Ventricular Conduction Produced by Electrical
Stimulation From a Transvenous Electrode Catheter in the Canine
Right Pulmonary Artery" by Cooper et al., published in Circulation
Research, Vol. 46, No. 1, January, 1980, pp. 48-57, the fat pads
associated with both the AV node and the SA node may be stimulated
by means of electrodes located in the right pulmonary artery. The
results obtained include both a depression of the sinus rate and a
prolongation of the AV conduction time in response to continuous
stimulation at 2-80 Hz at up to 50 ma.
[0044] Generally in healthy individuals, the SA node functions as
the pacemaker. Normal heart rhythm associated with the SA node is
typically referred to as sinus rhythm. When the SA node fails, the
AV node generally takes over creating a heart rate of approximately
35 to 60 beats per minute. Heart rhythm associated with the AV node
is typically referred to as nodal rhythm. When the AV node itself
is blocked or injured, a new even slower pacemaker site may form at
the junction of the AV node and the His bundle. Heart rhythm
associated with this junction is typically referred to as
junctional escape rhythm. When this junction site is inhibited, the
Purkinje fibers in the His bundle or below may act as a pacemaker
creating a heart rate of approximately 30 beats per minute. Heart
rhythm associated with the Purkinje fibers is typically referred to
as idioventricular rhythm.
[0045] In one embodiment of the present invention, nerve stimulator
10 may be used to electrically manipulate cardiac rhythm by
stimulating the carotid sinus nerve, the fat pad associated with
the SA node, the fat pad associated with the AV node, the junction
of the AV node and the His bundle and/or the Purkinje fibers.
[0046] In one embodiment of the present invention, nerve stimulator
10 is used alone or in combination with other heart rate inhibiting
agents to temporarily stop or slow the beating heart, thereby
eliminating or reducing heart motion and/or blood flow during a
medical procedure. For example, the present invention may be used
to eliminate or reduce motion in the anastomosis field during CABG
procedures such that a facilitated anastomosis procedure may be
performed safely and effectively. The number of occasions that the
vagal nerve may be stimulated depends on the type of medical
procedure to be performed. Likewise, the type of medical procedure
to be performed will dictate the duration of the individual
electrical stimulations.
[0047] Nerve stimulator 10 may be powered by AC current, DC current
or it may be battery powered by a disposable or re-chargeable
battery. Nerve stimulator 10 may be configured to synchronize
activation and deactivation of breathing regulator 40 with vagal
stimulation, thereby minimizing or eliminating unwanted heart and
chest motion associated with the patient's breathing. Nerve
stimulator 10 may comprise a surgeon controlled switch box. A
switch may be incorporated in or on one of the surgeon's
instruments, such as surgical site retractor, or any other location
easily and quickly accessed by the surgeon for regulation of the
nerve stimulator 10 by the surgeon. The switch may be, for example,
a hand switch, a foot switch, or a voice-activated switch
comprising voice-recognition technologies.
[0048] A visual and/or audible signal used to alert a surgeon to
the completion or resumption of vagal nerve stimulation may be
incorporated into nerve stimulator 10. For example, a beeping tone
or flashing light that increases in frequency as the nerve
stimulation period should end or begin may be used.
[0049] Nerve stimulator 10 may be slaved to cardiac stimulator 20
or cardiac stimulator 20 may be slaved to nerve stimulator 10. For
example, the output of cardiac stimulator 20 may be off whenever
the output of nerve stimulator 10 is on. Software controlling
cardiac stimulator 20 may be designed to automatically commence
cardiac pacing if the heart does not resume beating within a
pre-determined interval after cessation of vagal nerve stimulation.
In addition, the software controlling nerve stimulator 10 may be
designed to automatically stop vagal nerve stimulation if the heart
has been stopped for too long.
[0050] System 100 may also include cardiac stimulator 20 which may
be used to stimulate the heart as desired. As with nerve stimulator
10, cardiac stimulator 20 may be intermittently stopped and started
to allow the surgeon to perform individual steps of a medical
procedure.
[0051] Cardiac stimulator 20 may be a conventional ventricular
demand pacer or dual chamber (atrial-ventricular) pacer. Cardiac
stimulator 20 may be powered by AC current, DC current or it may be
battery powered by a disposable or re-chargeable battery. Cardiac
stimulator 20 may be configured to synchronize activation and
deactivation of breathing regulator 40 with pacing, thereby
minimizing or eliminating unwanted heart and chest motion
associated with the patient's breathing. Cardiac stimulator 20 may
be any conventional pacing device suitable for ventricular demand
pacing and having leads electrically coupled to a switch box.
Cardiac stimulator 20 may be combined in a single unit with a
switch box. Cardiac stimulator 20 may comprise a surgeon controlled
switch box. A switch may be incorporated in or on one of the
surgeon's instruments, such as surgical site retractor, or any
other location easily and quickly accessed by the surgeon for
regulation of the cardiac stimulator by the surgeon. The switch may
be, for example, a hand switch, a foot switch, or a voice-activated
switch comprising voice-recognition technologies. A single switch
may be used to regulate both cardiac stimulator 20 and nerve
stimulator 10.
[0052] A visual and/or audible signal used to prepare a surgeon for
the resumption of pacing may be incorporated into cardiac
stimulator 20. For example, a beeping tone or flashing light that
increases in frequency as the pacing period ends may be used. A
single signaling method or device may be used for both cardiac
stimulator 20 and nerve stimulator 10.
[0053] Sensor 6, nerve stimulator 10 and/or cardiac stimulator 20
may be slaved to a robotic system or a robotic system may be slaved
to sensor 6, nerve stimulator 10 and/or cardiac stimulator 20.
Breathing regulator 40 and other components may also be slaved to
such a system. Computer and voice-controlled robotic systems that
position and maneuver endoscopes and/or other surgical instruments
for performing microsurgical procedures such as anastomoses through
small incisions may be used by a surgeon to perform precise and
delicate maneuvers. These robotic systems may allow a surgeon to
perform a variety of microsurgical procedures including endoscopic
CABG. Endoscopic CABG may allow multiple occluded coronary arteries
to be bypassed without a thoracotomy or mini-thoracotomy. Heart
valve repair and replacement may also be other surgical
applications for these robotic systems. In general, robotic systems
may include head-mounted displays that integrate 3-D visualization
of surgical anatomy and related diagnostic and monitoring data,
miniature high-resolution 2-D and 3-D digital cameras, a computer,
a high power light source and a standard video monitor.
[0054] System 100 may also include a breathing regulator 40. In one
embodiment, the breathing regulator 40 may be used to stimulate the
phrenic nerve in order to provide a diaphragmatic pacemaker.
Breathing regulator 40 may comprise one or more electrodes for
supplying electrical current to the phrenic nerve to control
breathing during vagal and/or cardiac stimulation and/or
destimulation. Electrodes used to stimulate the phrenic nerve may
be, for example, non-invasive, e.g., clips, or invasive, e.g.,
needles or probes. The application of an electrical stimulus to the
phrenic nerve may include, but is not limited to bipolar and/or
monopolar techniques. Different electrode positions are accessible
through various access openings, for example, in the cervical or
thorax regions. Nerve stimulation electrodes may be positioned
through a thoracotomy, sternotomy, endoscopically through a
percutaneous port, through a stab wound or puncture, through a
small incision, placed on the skin or in combinations thereof. The
present invention may include various electrodes, catheters and
electrode catheters suitable for phrenic nerve stimulation to
control breathing.
[0055] Phrenic nerve stimulation electrodes may be intravascular,
patch-type, balloon-type, basket-type, umbrella-type, tape-type,
cuff-type, suction-type, screw-type, barb-type, bipolar, monopolar,
metal, wire, endotracheal, endoesophageal, intravascular,
transcutaneous or intracutaneous electrodes. Guided or steerable
catheter devices comprising electrodes may be used alone or in
combination with the nerve stimulation electrodes. For example, a
catheter comprising one or more wire, metal strips or metal foil
electrodes or electrode arrays may be used. The catheter may
comprise, for example, a balloon, which may be inflated with air,
or liquid to press the electrodes firmly against a vessel wall that
lays adjacent the phrenic nerve.
[0056] Phrenic nerve stimulation electrodes may be oriented in any
fashion along the catheter device, including longitudinally or
transversely. Various techniques such as ultrasound, fluoroscopy
and echocardiography may be used to facilitate positioning of the
electrodes. If desired or necessary, avoidance of obstruction of
blood flow may be achieved with notched catheter designs or with
catheters which incorporate one or more tunnels or passageways.
[0057] In another embodiment, the breathing regulator 40 may
comprise a connector which interfaces with a patient's respirator,
and sends a logic signal to activate or deactivate the respirator
to control breathing during vagal and/or cardiac stimulation and/or
destimulation.
[0058] As indicated above, FIG. 2 shows one embodiment of the
present invention at 200. In this embodiment, the elements named
above may be combined or connected to a control unit along with
other components. The unit 200 may be used to coordinate the
various elements. Unit 200 may incorporate a controller or any
suitable processor 230.
[0059] Unit 200 may incorporate a cardiac contraction sensor 206 as
described above. As seen in FIG. 2, the sensor 206 may be or may
incorporate one or more sensing electrodes 226. Such an electrode
may also be attached to a display component 216. Sensing electrodes
226 incorporated with sensor 206 may be, for example, non-invasive,
e.g., clips, or invasive, e.g., needles or probes. Electrodes 226
may be positioned through a thoracotomy, sternotomy, endoscopically
through a percutaneous port, through a stab wound or puncture,
through a small incision in the chest, placed on the chest or in
combinations thereof. The present invention may also use various
electrodes, catheters and electrode catheters suitable for pacing
the heart, e.g., epicardial, patch-type, intravascular,
balloon-type, basket-type, umbrella-type, tape-type,
transcutaneous, intracutaneous, screw-type, barb-type, bipolar,
monopolar, metal, wire, cuff-type or suction-type. Guided or
steerable catheter devices comprising electrodes may be used alone
or in combination with the electrodes. Although FIG. 2 shows a
separate sensor 206 and cardiac stimulator 220, one
sensing/stimulating electrode may serve both functions in one
embodiment of the invention.
[0060] Unit 200 may also incorporate a separate cardiac stimulator
and sensing electrode. For example, FIG. 2 shows an electrode for
stimulation of the heart at 220 separate from sensing electrode
226. Cardiac electrodes 220 used to stimulate the heart may be, for
example, non-invasive, e.g., clips, or invasive, e.g., needles or
probes. Electrodes 220 may be positioned through a thoracotomy,
sternotomy, endoscopically through a percutaneous port, through a
stab wound or puncture, through a small incision in the chest,
placed on the chest or in combinations thereof. The present
invention may also use various electrodes, catheters and electrode
catheters suitable for pacing the heart, e.g., epicardial,
patch-type, intravascular, balloon-type, basket-type,
umbrella-type, tape-type electrodes, suction-type, pacing
electrodes, endotracheal electrodes, endoesophageal electrodes,
transcutaneous electrodes, intracutaneous electrodes, screw-type
electrodes, barb-type electrodes, bipolar electrodes, monopolar
electrodes, metal electrodes, wire electrodes and cuff electrodes.
Guided or steerable catheter devices comprising electrodes may be
used alone or in combination with the electrodes.
[0061] Unit 200 may also incorporate a nerve stimulator. For
example, FIG. 2 shows an electrode for nerve stimulation at 210.
Electrodes used to stimulate a nerve such as the vagal nerve may
be, for example, non-invasive, e.g., clips, or invasive, e.g.,
needles or probes. The application of an electrical stimulus to the
right or left vagal nerve may include, but is not limited to
bipolar and/or monopolar techniques. Different electrode positions
are accessible through various access openings, for example, in the
cervical or thorax regions. Nerve stimulation electrodes 210 may be
positioned through a thoracotomy, sternotomy, endoscopically
through a percutaneous port, through a stab wound or puncture,
through a small incision in the neck or chest, through the internal
jugular vein, the esophagus, the trachea, placed on the skin or in
combinations thereof. Electrical stimulation may be carried out on
the right vagal nerve, the left vagal nerve or to both nerves
simultaneously or sequentially. The present invention may include
various electrodes, catheters and electrode catheters suitable for
vagal nerve stimulation to temporarily stop or slow the beating
heart alone or in combination with other heart rate inhibiting
agents.
[0062] Nerve stimulation electrodes 210 may be endotracheal,
endoesophageal, intravascular, transcutaneous, intracutaneous,
patch-type, balloon-type, cuff-type, basket-type, umbrella-type,
tape-type, screw-type, barb-type, metal, wire or suction-type
electrodes. Guided or steerable catheter devices comprising
electrodes may be used alone or in combination with the nerve
stimulation electrodes 210. For example, a catheter comprising one
or more wire, metal strips or metal foil electrodes or electrode
arrays may be inserted into the internal jugular vein to make
electrical contact with the wall of the internal jugular vein, and
thus stimulate the vagal nerve adjacent to the internal jugular
vein. Access to the internal jugular vein may be via, for example,
the right atrium, the right atrial appendage, the inferior vena
cava or the superior vena cava. The catheter may comprise, for
example, a balloon, which may be inflated with air or liquid to
press the electrodes firmly against the vessel wall. Similar
techniques may be performed by insertion of a catheter-type device
into the trachea or esophagus. Additionally, tracheal tubes and
esophageal tubes comprising electrodes may be used.
[0063] Nerve stimulation electrodes 210 may be oriented in any
fashion along the catheter device, including longitudinally or
transversely. Various techniques such as ultrasound, fluoroscopy
and echocardiography may be used to facilitate positioning of the
electrodes. If desired or necessary, avoidance of obstruction of
blood flow may be achieved with notched catheter designs or with
catheters which incorporate one or more tunnels or passageways.
[0064] In one embodiment of the present invention, the location of
the electrodes 210 is chosen to elicit maximum bradycardia
effectiveness while minimizing current spread to adjacent tissues
and vessels and to prevent the induction of post stimulation
tachycardia. Furthermore, a non-conductive material such as plastic
may be employed to sufficiently enclose the electrodes of all the
configurations to shield them from the surrounding tissues and
vessels, while exposing their confronting edges and surfaces for
positive contact with the vagal nerve or selected tissues.
[0065] Controller 230 may be used to gather information from nerve
stimulation electrodes 210 and cardiac stimulation electrodes 220.
Controller 230 may also be used to control the stimulation levels
and stimulation duration from nerve stimulation electrodes 210 and
cardiac stimulation electrodes 220. Controller 230 may also gather
and process information from sensor 206. This information may be
used to adjust stimulation levels and stimulation times from nerve
stimulation electrodes 210 and cardiac stimulation electrodes
220.
[0066] Unit 200 may incorporate one or more switches to facilitate
regulation of the various components by the surgeon. One example of
such a switch is shown as foot pedal 250. The switch may also be,
for example, a hand switch, or a voice-activated switch comprising
voice-recognition technologies. The switch may be incorporated in
or on one of the surgeon's instruments, such as surgical site
retractor, or any other location easily and quickly accessed by the
surgeon.
[0067] Unit 200 may also include a display 260. Unit 200 may also
include other means of indicating the status of various components
to the surgeon such as a numerical display, gauges, a monitor
display or audio feedback. Unit 200 may also include one or more
visual and/or audible signals used to prepare a surgeon for the
start or stop of nerve stimulation and/or cardiac stimulation.
[0068] FIG. 3 shows a flow diagram of one embodiment of the present
invention. The patient is prepared for a medical procedure at 500.
In one embodiment of the invention, the patient's initial heart
rate may be measured (Block 505). This initial reading is then used
as a gauge to compare with the electrical signals detected by
sensor 6 during the procedure. In one embodiment, the sensor alerts
the surgeon if the sensed electrical (or depolarization) signals
reach a predetermined level.
[0069] At Block 510, a nerve that controls the beating of the heart
is stimulated. Such a nerve may be for example a vagal nerve. At
Block 510, one or more of a variety of pharmacological agents or
drugs may be delivered. These drugs may produce reversible asystole
of a heart while maintaining the ability of the heart to be
electrically paced.
[0070] A variety of pharmacological agents or drugs may also be
delivered at other times during the procedure 500. These drugs may
also produce reversible asystole of a heart while maintaining the
ability of the heart to be electrically paced. Other drugs may be
administered for a variety of functions and purposes as described
below. Drugs may be delivered at any appropriate time during the
medical procedure, for example, at the beginning of the procedure,
intermittently during the procedure, continuously during the
procedure or following the procedure.
[0071] Drugs, drug formulations or compositions suitable for
administration to a patient during a medical procedure may include
a pharmaceutically acceptable carrier or solution in an appropriate
dosage. There are a number of pharmaceutically acceptable carriers
that may be used for delivery of various drugs, for example, via
direct injection, oral delivery, suppository delivery, transdermal
delivery, epicardial delivery and/or inhalation delivery.
Pharmaceutically acceptable carriers include a number of solutions,
preferably sterile, for example, water, saline, Ringer's solution
and/or sugar solutions such as dextrose in water or saline. Other
possible carriers that may be used include sodium citrate, citric
acid, amino acids, lactate, mannitol, maltose, glycerol, sucrose,
ammonium chloride, sodium chloride, potassium chloride, calcium
chloride, sodium lactate, and/or sodium bicarbonate. Carrier
solutions may or may not be buffered.
[0072] Drug formulations or compositions may include antioxidants
or preservatives such as ascorbic acid. They may also be in a
pharmaceutically acceptable form for parenteral administration, for
example to the cardiovascular system, or directly to the heart,
such as intracoronary infusion or injection. Drug formulations or
compositions may comprise agents that provide a synergistic effect
when administered together. A synergistic effect between two or
more drugs or agents may reduce the amount that normally is
required for therapeutic delivery of an individual drug or agent.
Two or more drugs may be administered, for example, sequentially or
simultaneously. Drugs may be administered via one or more bolus
injections and/or infusions or combinations thereof. The injections
and/or infusions may be continuous or intermittent. Drugs may be
administered, for example, systemically or locally, for example, to
the heart, to a coronary artery and/or vein, to a pulmonary artery
and/or vein, to the right atrium and/or ventricle, to the left
atrium and/or ventricle, to the aorta, to the AV node, to the SA
node, to a nerve and/or to the coronary sinus. Drugs may be
administered or delivered via intravenous, intracoronary and/or
intraventricular administration in a suitable carrier. Examples of
arteries that may be used to deliver drugs to the AV node include
the AV node artery, the right coronary artery, the right descending
coronary artery, the left coronary artery, the left anterior
descending coronary artery and Kugel's artery. Drugs may be
delivered systemically, for example, via oral, transdermal,
intranasal, suppository or inhalation methods. Drugs also may be
delivered via a pill, a spray, a cream, an ointment or a medicament
formulation.
[0073] Drugs may be delivered via a drug delivery device that may
comprise a catheter, such as a drug delivery catheter or a guide
catheter, a patch, such as a transepicardial patch that slowly
releases drugs directly into the myocardium, a cannula, a pump
and/or a hypodermic needle and syringe assembly. A drug delivery
catheter may include an expandable member, e.g., a low-pressure
balloon, and a shaft having a distal portion, wherein the
expandable member is disposed along the distal portion. A catheter
for drug delivery may comprise one or more lumens and may be
delivered endovascularly via insertion into a blood vessel, e.g.,
an artery such as a femoral, radial, subclavian or coronary artery.
The catheter can be guided into a desired position using various
guidance techniques, e.g., flouroscopic guidance and/or a guiding
catheter or guide wire techniques.
[0074] Drugs may be delivered via an iontophoretic drug delivery
device placed on the heart. In general, the delivery of ionized
drugs may be enhanced via a small current applied across two
electrodes. Positive ions may be introduced into the tissues from
the positive pole, or negative ions from the negative pole. The use
of iontophoresis may markedly facilitate the transport of certain
ionized drug molecules. For example, lidocaine hydrochloride may be
applied to the heart via a drug patch comprising the drug. A
positive electrode could be placed over the patch and current
passed. The negative electrode would contact the heart or other
body part at some desired distance point to complete the circuit.
One or more of the electrodes may also be used as nerve stimulation
electrodes 210, as cardiac stimulation electrodes 220 or as sensing
electrodes 226.
[0075] The two divisions of the autonomic nervous system that
regulate the heart have opposite functions. First, the adrenergic
or sympathetic nervous system increases heart rate by releasing
epinephrine and norepinephrine. Second, the parasympathetic system
also known as the cholinergic nervous system or the vagal nervous
system decreases heart rate by releasing acetylcholine.
Catecholamines such as norepinephrine (also called noradrenaline)
and epinephrine (also called adrenaline) are agonists for
beta-adrenergic receptors. An agonist is a stimulant biomolecule or
agent that binds to a receptor.
[0076] Beta-adrenergic receptor blocking agents compete with
beta-adrenergic receptor stimulating agents for available
beta-receptor sites. When access to beta-receptor sites are blocked
by receptor blocking agents, also known as beta-adrenergic
blockade, the chronotropic or heart rate, inotropic or
contractility, and vasodilator responses to receptor stimulating
agents are decreased proportionately. Therefore, beta-adrenergic
receptor blocking agents are agents that are capable of blocking
beta-adrenergic receptor sites.
[0077] Since beta-adrenergic receptors are concerned with
contractility and heart rate, stimulation of beta-adrenergic
receptors, in general, increases heart rate, the contractility of
the heart and the rate of conduction of electrical impulses through
the AV node and the conduction system.
[0078] Drugs, drug formulations and/or drug compositions that may
be used according to this invention may include any naturally
occurring or chemically synthesized (synthetic analogues)
beta-adrenergic receptor blocking agents. Beta-adrenergic receptor
blocking agents or .quadrature.-adrenergic blocking agents are also
known as beta-blockers or .quadrature.-blockers and as class II
antiarrhythmics.
[0079] The term "beta-blocker" appearing herein may refer to one or
more agents that antagonize the effects of beta-stimulating
catecholamines by blocking the catecholamines from binding to the
beta-receptors. Examples of beta-blockers include, but are not
limited to, acebutolol, alprenolol, atenolol, betantolol,
betaxolol, bevantolol, bisoprolol, carterolol, celiprolol,
chlorthalidone, esmolol, labetalol, metoprolol, nadolol,
penbutolol, pindolol, propranolol, oxprenolol, sotalol, teratolo,
timolol and combinations, mixtures and/or salts thereof.
[0080] The effects of administered beta-blockers may be reversed by
administration of beta-receptor agonists, e.g., dobutamine or
isoproterenol.
[0081] The parasympathetic or cholinergic system participates in
control of heart rate via the sinoatrial (SA) node, where it
reduces heart rate. Other cholinergic effects include inhibition of
the AV node and an inhibitory effect on contractile force. The
cholinergic system acts through the vagal nerve to release
acetylcholine, which, in turn, stimulates cholinergic receptors.
Cholinergic receptors are also known as muscarinic receptors.
Stimulation of the cholinergic receptors decreases the formation of
cAMP. Stimulation of cholinergic receptors generally has an
opposite effect on heart rate compared to stimulation of
beta-adrenergic receptors. For example, beta-adrenergic stimulation
increases heart rate, whereas cholinergic stimulation decreases it.
When vagal tone is high and adrenergic tone is low, there is a
marked slowing of the heart (sinus bradycardia). Acetylcholine
effectively reduces the amplitude, rate of increase and duration of
the SA node action potential. During vagal nerve stimulation, the
SA node does not arrest. Rather, pacemaker function may shift to
cells that fire at a slower rate. In addition, acetylcholine may
help open certain potassium channels thereby creating an outward
flow of potassium ions and hyperpolarization. Acetylcholine also
slows conduction through the AV node.
[0082] Drugs, drug formulations and/or drug compositions that may
be used according to this invention may include any naturally
occurring or chemically synthesized (synthetic analogues)
cholinergic agent. The term "cholinergic agent" appearing herein
may refer to one or more cholinergic receptor modulators or
agonists. Examples of cholinergic agents include, but are not
limited to, acetylcholine, carbachol (carbamyl choline chloride),
bethanechol, methacholine, arecoline, norarecoline and
combinations, mixtures and/or salts thereof.
[0083] Drugs, drug formulations and/or drug compositions that may
be used according to this invention may include any naturally
occurring or chemically synthesized cholinesterase inhibitor. The
term "cholinesterase inhibitor" appearing herein may refer to one
or more agents that prolong the action of acetylcholine by
inhibiting its destruction or hydrolysis by cholinesterase.
Cholinesterase inhibitors are also known as acetylcholinesterase
inhibitors. Examples of cholinesterase inhibitors include, but are
not limited to, edrophonium, neostigmine, neostigmine
methylsulfate, pyridostigmine, tacrine and combinations, mixtures
and/or salts thereof.
[0084] There are ion-selective channels within certain cell
membranes. These ion selective channels include calcium channels,
sodium channels and/or potassium channels. Therefore, other drugs,
drug formulations and/or drug compositions that may be used
according to this invention may include any naturally occurring or
chemically synthesized calcium channel blocker. Calcium channel
blockers inhibit the inward flux of calcium ions across cell
membranes of arterial smooth muscle cells and myocardial cells.
Therefore, the term "calcium channel blocker" appearing herein may
refer to one or more agents that inhibit or block the flow of
calcium ions across a cell membrane. The calcium channel is
generally concerned with the triggering of the contractile cycle.
Calcium channel blockers are also known as calcium ion influx
inhibitors, slow channel blockers, calcium ion antagonists, calcium
channel antagonist drugs and as class IV antiarrhythmics. A
commonly used calcium channel blocker is verapamil.
[0085] Administration of a calcium channel blocker, e.g.,
verapamil, generally prolongs the effective refractory period
within the AV node and slows AV conduction in a rate-related
manner, since the electrical activity through the AV node depends
significantly upon the influx of calcium ions through the slow
channel. A calcium channel blocker has the ability to slow a
patient's heart rate, as well as produce AV block. Examples of
calcium channel blockers include, but are not limited to,
amiloride, amlodipine, bepridil, diltiazem, felodipine, isradipine,
mibefradil, nicardipine, nifedipine (dihydropyridines), nickel,
nimodinpine, nisoldipine, nitric oxide (NO), norverapamil and
verapamil and combinations, mixtures and/or salts thereof.
Verapamil and diltiazem are very effective at inhibiting the AV
node, whereas drugs of the nifedipine family have a lesser
inhibitory effect on the AV node. Nitric oxide (NO) indirectly
promotes calcium channel closure. NO may be used to inhibit
contraction. NO may also be used to inhibit sympathetic outflow,
lessen the release of norepinephrine, cause vasodilation, decrease
heart rate and decrease contractility. In the SA node, cholinergic
stimulation leads to formation of NO.
[0086] Other drugs, drug formulations and/or drug compositions that
may be used according to this invention may include any naturally
occurring or chemically synthesized sodium channel blocker. Sodium
channel blockers are also known as sodium channel inhibitors,
sodium channel blocking agents, rapid channel blockers or rapid
channel inhibitors. Antiarrhythmic agents that inhibit or block the
sodium channel are known as class I antiarrhythmics, examples
include, but are not limited to, quinidine and quinidine-like
agents, lidocaine and lidocaine-like agents, tetrodotoxin,
encainide, flecainide and combinations, mixtures and/or salts
thereof. Therefore, the term "sodium channel blocker" appearing
herein may refer to one or more agents that inhibit or block the
flow of sodium ions across a cell membrane or remove the potential
difference across a cell membrane. For example, the sodium channel
may also be totally inhibited by increasing the extracellular
potassium levels to depolarizing hyperkalemic values, which remove
the potential difference across the cell membrane. The result is
inhibition of cardiac contraction with cardiac arrest
(cardioplegia). The opening of the sodium channel (influx of
sodium) is for swift conduction of the electrical impulse
throughout the heart.
[0087] Other drugs, drug formulations and/or drug compositions that
may be used according to this invention may include any naturally
occurring or chemically synthesized potassium channel agent. The
term "potassium channel agent" appearing herein may refer to one or
more agents that impact the flow of potassium ions across the cell
membrane. There are two major types of potassium channels. The
first type of channel is voltage-gated and the second type is
ligand-gated. Acetylcholine-activated potassium channels, which are
ligand-gated channels, open in response to vagal stimulation and
the release of acetylcholine. Opening of the potassium channel
causes hyperpolarization, which decreases the rate at which the
activation threshold is reached. Adenosine is one example of a
potassium channel opener. Adenosine slows conduction through the AV
node. Adenosine, a breakdown product of adenosine triphosphate,
inhibits the AV node and atria. In atrial tissue, adenosine causes
the shortening of the action potential duration and causes
hyperpolarization. In the AV node, adenosine has similar effects
and also decreases the action potential amplitude and the rate of
increase of the action potential. Adenosine is also a direct
vasodilator by its actions on the adenosine receptor on vascular
smooth muscle cells. In addition, adenosine acts as a negative
neuromodulator, thereby inhibiting release of norepinephrine. Class
III antiarrhythmic agents also known as potassium channel
inhibitors lengthen the action potential duration and
refractoriness by blocking the outward potassium channel to prolong
the action potential. Amiodarone and d-sotalol are both examples of
class III antiarrhythmic agents.
[0088] Potassium is the most common component in cardioplegic
solutions. High extracellular potassium levels reduce the membrane
resting potential. Opening of the sodium channel, which normally
allows rapid sodium influx during the upstroke of the action
potential, is therefore inactivated because of a reduction in the
membrane resting potential. The present invention may be combined
with conventional CPB. Alternatively, the induced asystole as
described by this invention may serve as a substitute for
conventional cardioplegic arrest. For example, the combination of
drugs and vagal stimulation may be used as a cardioplegic agent in
a variety of medical procedures.
[0089] Drugs, drug formulations and/or drug compositions that may
be used according to this invention may comprise one or more of any
naturally occurring or chemically synthesized beta-blocker,
cholinergic agent, cholinesterase inhibitor, calcium channel
blocker, sodium channel blocker, potassium channel agent,
adenosine, adenosine receptor agonist, adenosine deaminase
inhibitor, dipyridamole, monoamine oxidase inhibitor, digoxin,
digitalis, lignocaine, bradykinin agents, serotoninergic agonist,
antiarrythmic agents, cardiac glycosides, local anesthetics and
combinations or mixtures thereof. Digitalis and digoxin both
inhibit the sodium pump. Digitalis is a natural inotrope derived
from plant material, while digoxin is a synthesized inotrope.
Dipyridamole inhibits adenosine deaminase, which breaks down
adenosine. Drugs, drug formulations and/or drug compositions
capable of reversibly suppressing autonomous electrical conduction
at the SA and/or AV node, while still allowing the heart to be
electrically paced to maintain cardiac output may be used according
to this invention.
[0090] In one embodiment, the cardiac asystole produced in
accordance with the present invention is reversible, e.g.,
chemically such as by the administration of atropine or by natural
forces. Beta-adrenergic stimulation or administration of calcium
solutions may be used to reverse the effects of a calcium channel
blocker such as verapamil. Agents that promote heart rate and/or
contraction may be used in a preferred embodiment of the present
invention. For example, dopamine, a natural catecholamine, is known
to increase contractility. Positive inotropes are agents that
specifically increase the force of contraction of the heart.
Glucagon, a naturally occurring hormone, is known to increase heart
rate and contractility. Glucagon may be used to reverse the effects
of a beta-blocker since its effects bypass the beta receptor.
Forskolin is known to increase heart rate and contractility. As
mentioned earlier, epinephrine and norepinephrine naturally
increase heart rate and contractility. Thyroid hormone,
phosphodiesterase inhibitors and prostacyclin, a prostaglandin, are
also known to increase heart rate and contractility. In addition,
methylxanthines are known to prevent adenosine from interacting
with its cell receptors.
[0091] Typically, vagal nerve stimulation prevents the heart from
contracting. This non-contraction must then be followed by periods
without vagal nerve stimulation during which the heart is allowed
to contract, and blood flow is restored throughout the body. At
517, the sensor 6 may be checked to determine if an escape beat is
imminent. The sensor may be checked periodically during the
procedure, for example, as shown at 517. Alternatively, the sensor
may interrupt the procedure at any point by indicating that an
escape beat is imminent. For example, a visual and/or audible
signal, such as a flashing light or beeping tone, may be used to
alert a surgeon that an escape beat is imminent. If no contraction
is imminent, then all or a portion of the medical procedure may be
carried out (Block 520). However, if a contraction is imminent,
then a signal may indicate an escape beat is about to occur (as
seen at 523). If the sensor indicates an escape beat is imminent,
the surgeon may stop the medical procedure to allow the beat to
occur. In one embodiment, the surgeon may then proceed to Block
530, where the nerve stimulation is ceased and the heart is allowed
to contract. Alternatively, unit 200 may automatically proceed to
Block 530 to cease nerve stimulation when sensor 6 indicates that a
beat is imminent.
[0092] The output of sensor 6 may be communicated to the surgeon by
a number of suitable means. For example, the output may be
indicated on a display or monitor. A visual or audio signal may
indicate when the electrical signals from the heart reach a certain
level, e.g. a level indicating an imminent escape beat.
Alternatively, the system of the present invention may "lock" the
controls of the vagal stimulator in an "off" state when an escape
beat is sensed. Alternatively, the system of the present invention
may "lock" the controls of the surgical instruments being used to
perform the surgery to indicate to the surgeon that an escape beat
is imminent. The system may then release the controls when the
signals indicate that the heart is again appropriately stilled.
[0093] Additionally, the amount of vagal nerve stimulation used
and/or the amount of drugs administered may be adjusted based on
the output of the sensor 6. For example, the level of stimulation
may be increased if sensor 6 indicates that too many escape beats
are occurring or are likely to occur. This adjustment may be
automatic or may be controlled by the surgeon.
[0094] At Block 520, a medical procedure may be performed or begun.
Such a procedure may be for example surgery on the heart.
Alternatively, the procedure may be surgery performed on another
organ of the body. At Block 520, one or more of a variety of
pharmacological agents or drugs may be delivered or may continue to
be delivered. These drugs may produce reversible asystole of a
heart while maintaining the ability of the heart to be electrically
paced. Other drugs may be administered for a variety of functions
and purposes as described above.
[0095] The term "medical procedure" may mean any one or more
medical or surgical procedures such as, for example cardiac
surgery, performed with or without cardiopulmonary bypass (CPB)
circuits, heart valve repair, heart valve replacement, MAZE
procedures, revascularization procedures, transmyocardial
revascularization (TMR) procedures, percutaneous myocardial
revascularization (PMR) procedures, CABG procedures, anastomosis
procedures, non-surgical procedures, fluoroscopic procedures,
beating heart surgery, vascular surgery, neurosurgery, brain
surgery, electrophysiology procedures, diagnostic and therapeutic
procedures, ablation procedures, ablation of arrhythmias,
endovascular procedures, treatment of the liver, spleen, heart,
lungs, and major blood vessels, aneurysm repair, imaging procedures
of the heart and great vessels, CAT scans or MRI procedures,
pharmacological therapies, drug delivery procedures, gene
therapies, cellular therapies, cancer therapies, radiation
therapies, genetic, cellular, tissue and/or organ manipulation or
transplantation procedures, coronary angioplasty procedures,
placement or delivery of coated or noncoated stents, atherectomy
procedures, atherosclerotic plaque manipulation and/or removal
procedures, procedures where bleeding needs to be precisely
controlled, procedures that require precise control of cardiac
motion and/or bleeding.
[0096] When the medical procedure comprises one or more medical
devices, e.g., coated stents, these devices may be coated with one
or more radioactive materials and/or biological agents such as, for
example, an anticoagulant agent, an antithrombotic agent, a
clotting agent, a platelet agent, an anti-inflammatory agent, an
antibody, an antigen, an immunoglobulin, a defense agent, an
enzyme, a hormone, a growth factor, a neurotransmitter, a cytokine,
a blood agent, a regulatory agent, a transport agent, a fibrous
agent, a protein, a peptide, a proteoglycan, a toxin, an antibiotic
agent, an antibacterial agent, an antimicrobial agent, a bacterial
agent or component, hyaluronic acid, a polysaccharide, a
carbohydrate, a fatty acid, a catalyst, a drug, a vitamin, a DNA
segment, a RNA segment, a nucleic acid, a lectin, an antiviral
agent, a viral agent or component, a genetic agent, a ligand and a
dye (which acts as a biological ligand). Biological agents may be
found in nature (naturally occurring) or may be chemically
synthesized.
[0097] The medical procedure may be non-invasive, minimally
invasive and/or invasive. The medical procedure may entail a
port-access approach, a partial or total endoscopic approach, a
sternotomy approach or a thoracotomy approach. The medical
procedure may include the use of various mechanical stabilization
devices or techniques as well as various robotic or imaging
systems.
[0098] In one method, the heart may be temporarily slowed or
intermittently stopped for short periods of time to permit the
surgeon to accomplish the required surgical task and yet still
allow the heart itself to supply blood circulation to the body. For
example, stimulation of the vagus nerve in order to temporarily and
intermittently slow or stop the heart is described in U.S. Pat. No.
6,006,134 entitled "Method and Device for Electronically
Controlling the Beating of a Heart Using Venous Electrical
Stimulation of Nerve Fibers," Dec. 21, 1999, to inventors Hill and
Junkman. This patent is assigned to Medtronic, Inc. and is
incorporated herein by reference.
[0099] During this medical procedure, cardiac contractions or
cardiac signals may be monitored constantly or intermittently as
described above. An assessment of the likelihood of a contraction
may again be taken at Block 525. If no contraction is imminent, the
physician may continue with the medical procedure that is in
progress. However, if a contraction is likely to occur, the surgeon
may increase nerve stimulation and/or the administration of drugs.
Alternatively, the surgeon may choose to proceed to Block 530 and
allow the heart to beat normally for a period of time. The heart
will therefore be allowed to contract and thus blood will again be
allowed to flow to the brain and vital organs.
[0100] After a time, the medical procedure or one phase of the
procedure is completed at 520. After some phase of the medical
procedure is performed, cardiac contractions are allowed to occur
(Block 530). Cardiac contractions may need to occur intermittently
during the procedure to ensure adequate blood flow. In one
embodiment, the stimulation from the nerve stimulator 10 is stopped
or slowed enough to allow the heart to contract. For example, the
vagal nerve stimulation is removed, thereby allowing cardiac
contractions to occur.
[0101] In another embodiment, it may be determined if the heart is
contracting as desired (532). If appropriate, the heart may be
stimulated to ensure that cardiac contractions occur (Block 535).
For example, cardiac stimulator 20 may be used to apply pacing
pulses to the heart to encourage the heart to contract normally. In
particular, the pacing pulses may be applied to the ventricle as is
well known in the field. Additionally, the amount of cardiac
stimulation used may be adjusted based on the output of the sensor
6. For example, the level of stimulation may be decreased or the
duration of stimulation may be decreased if the sensor 6 indicates
that too many escape beats are occurring or are likely to occur at
such a level of stimulation.
[0102] The present invention permits the heart to be stilled or
quiescent for selected and controllable periods of time in order to
permit a medical procedure to be performed. While such a period of
quiescence is desired, it must not last too long, otherwise
insufficient blood and oxygen is delivered to organs. Thus, it is
necessary to have the periods when the heart is beating (Blocks
530, 535). At Blocks 530, 535, one or more of a variety of
pharmacological agents or drugs may be delivered or may continue to
be delivered. These drugs may produce reversible asystole of a
heart while maintaining the ability of the heart to be electrically
paced. Particularly at Blocks 530, 535, drugs may be administered
to encourage heart contractions. Other drugs may be administered
for a variety of functions and purposes as described above
[0103] Sensor 6 may also be used to determine whether the heart is
beating as desired at Block 532. Such output may be communicated to
the surgeon by a number of suitable means. For example, the output
may be indicated on a display or monitor. A visual or audio signal
may also indicate output. Alternatively, the system of the present
invention may "lock" the controls of the cardiac stimulator in an
"on" state after an escape beat has occurred in order to return the
heart to a normal rate. Alternatively, the system of the present
invention may "lock" the controls of the cardiac stimulator in an
"off" state to prevent an escape beat. The system may then release
the controls when the electrical signals sensed by the sensor are
again as desired.
[0104] At 539, it may be determined if additional medical
procedures or additional stages of medical procedures need to be
performed. If so, the heart may again be stilled using the methods
of stilling the heart described above. The method may then be
repeated (as in the loop designated by 540). For example, the heart
may again be prevented from contracting by stimulation of the vagal
nerve (510). Additional drugs may be delivered or the drugs
previously administered may continue to be administered.
[0105] This cycle may be repeated until the procedure, such as
surgery, is completed. As the cycle continues, sensor 6 enables
monitoring of heart rate and, if necessary, appropriate adjustment
of nerve stimulation and cardiac stimulation to ensure the heart is
beating appropriately.
[0106] For example, a surgical procedure at 520 may require several
stitches to be made by the surgeon. The surgeon may stimulate the
vagal nerve at 510 to stop the heart. Then the surgeon may make the
first stitch at 520. The surgeon may then reduce or halt
stimulation at 530 and allow the heart to contract. The surgeon may
also pace the heart at 535. Then at 540, the surgeon may return to
510 to inhibit contractions of the heart. At 520, the surgeon will
then make the second stitch. This process may be repeated (the loop
designated by 540 may be repeated) until all the required stitches
have been made. Meanwhile, the heart's electrical signals are
monitored continuously or, for example at Blocks 517, 525 by sensor
6. The procedure may proceed uninterrupted if no contractions are
imminent.
[0107] After the procedure is completed, step 535 may be performed
until the heart is beating normally. Once it has been determined at
539 that the medical procedure is complete, the surgeon may
continue stimulating the heart until satisfied that the heart is
beating normally. Additionally, sensor 6 may be used to monitor
heart rate until it has reached an acceptable level. At the
procedure's end, one or more of a variety of pharmacological agents
or drugs may be delivered or may continue to be delivered for
example to alleviate pain or aid in recuperation. Other drugs may
be administered for a variety of functions and purposes as
described above.
[0108] FIG. 4 is a timeline illustrating one relationship between a
cardiac contraction sensor, a nerve stimulator and a cardiac
stimulator.
[0109] Point 610 indicates a point before the medical procedure has
begun. At this point 610, both nerve stimulation and cardiac
stimulation are off. At point 610, the heart is beating regularly.
The patient's heart rate may be measured by sensor 6 at point 610.
Thus, sensor 6 may be turned on at point 610.
[0110] Then nerve stimulation is turned on to inhibit beating of
the heart. During phase 601, the vagal nerve stimulation is on and
the cardiac stimulation is off. This is the condition of the two
types of stimulation at step 520 described above. In one
embodiment, as shown in FIG. 4, cardiac contraction sensor 6 is on
throughout the entire procedure. Alternatively, cardiac contraction
sensor 6 may be turned on during phase 601 to check whether a
contraction is imminent (as described at Block 517).
[0111] Point 611 is a representative point during phase 601. At
point 611, the contractions of the heart are stilled or
substantially slowed. In addition, at point 611, sensor 6 may be
used to determine that no contractions are imminent (as described
at Blocks 517 and 525). If no contractions are impending at point
611, then the medical procedure can proceed (as described at Block
520). However, if a contraction is impending at point 611, sensor 6
may provide a signal indicating the impending contraction. The
surgeon may then stop the medical procedure and allow the
contraction to occur. After the contraction has occurred, the
surgeon may then continue in phase 601 and finish the step of the
procedure. Alternatively, the surgeon may proceed immediately to
phase 602 after the contraction has occurred. Alternatively,
control unit 200 may automatically proceed to phase 602 after
providing the signal.
[0112] During phase 602 the vagal stimulation is turned off (as
described at step 530) and the cardiac stimulation may be turned on
(as described at 535). Point 612 is a representative point during
phase 602. At point 612, the contractions are allowed and/or may be
induced. In one embodiment, cardiac contraction sensor 6 is still
on during phase 602 and may be used to determine if the
contractions are occurring appropriately. Alternatively, the sensor
6 may be turned on during phase 602 to determine if the
contractions are occurring appropriately.
[0113] During phase 603, the vagal nerve stimulation is again
turned on and the cardiac stimulation is turned off. In one
embodiment, the cardiac contraction sensor 6 has been operating
throughout each phase and continues to operate through phase 603.
The amount or duration of vagal stimulation during phase 603 may be
different than the amount or duration of vagal stimulation during
phase 601, based on the data gathered from sensor 6 during phase
601. For example, the vagal stimulation may be increased if sensor
6 detected an undesirable number of escape beats. Alternatively,
sensor 6 may be turned on during phase 603 to again determine if an
escape beat is imminent (as described at Block 525). Point 613 is a
representative point during phase 603. If no escape beat is
imminent at 613, then the medical procedure can proceed (as
described in step 520). However, if an escape beat is impending,
sensor 6 may provide a signal indicating this. The surgeon may then
stop the medical procedure and allow the contraction to occur.
After the contraction has occurred, the surgeon may then continue
in phase 603 and finish the step of the procedure. Alternatively,
the surgeon may proceed immediately to phase 604 after the
contraction has occurred. Alternatively, control unit 200 may
automatically proceed to phase 604 after providing the signal.
[0114] During phase 604 the vagal stimulation is again turned off
and the cardiac stimulation may again be turned on. The amount or
duration of cardiac stimulation during phase 604 may be different
than the amount or duration of cardiac stimulation during phase
602, based on the data gathered from sensor 6 during the previous
phases. For example, the amount or duration of cardiac stimulation
may be decreased if too many escape beats occurred during the
previous phases. Point 614 is a representative point during phase
602. At point 614, the contractions are allowed and/or may be
induced. In one embodiment, cardiac contraction sensor 6 is still
on during phase 604 and may be used to determine if the
contractions are occurring appropriately. Alternatively, the sensor
6 may be turned on during phase 604 to determine if the
contractions are occurring appropriately.
[0115] The method of the present invention may be repeated as
necessary until a point is reached, represented by point 615, when
the necessary medical procedures are completed. At this point 615,
nerve stimulation is off although cardiac stimulation may be left
on in order to pace the heart to its normal rhythm. At point 615,
sensor 6 may be used to check the heart rate for a final time (as
described at 532).
[0116] It will be appreciated by those skilled in the art that
while the invention has been described above in connection with
particular embodiments and examples, the invention is not
necessarily so limited, and that numerous other embodiments,
examples, uses, modifications and departures from the embodiments,
examples and uses are intended to be encompassed by the claims
attached hereto. The entire disclosure of each patent and
publication cited herein is incorporated by reference, as if each
such patent or publication were individually incorporated by
reference herein.
* * * * *