U.S. patent application number 09/843511 was filed with the patent office on 2001-08-23 for implantable defibrillator apparatus.
This patent application is currently assigned to Sorin Biomedica Cardio S.p.A.. Invention is credited to Gaggini, Guido, Garberoglio, Bruno, Marcelli, Emanuela, Plicchi, Gianni.
Application Number | 20010016758 09/843511 |
Document ID | / |
Family ID | 8243245 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016758 |
Kind Code |
A1 |
Plicchi, Gianni ; et
al. |
August 23, 2001 |
Implantable defibrillator apparatus
Abstract
An implantable defibrillator apparatus having a plurality of
defibrillation electrodes which can be applied to the heart muscle
in order to apply electric defibrillation shocks thereto, and
defibrillation-control means for selectively applying respective
electric defibrillation shocks to the electrodes preferably
sequentially in time and in synchronism with the QRS.
Inventors: |
Plicchi, Gianni; (Bologna,
IT) ; Garberoglio, Bruno; (Torino, IT) ;
Gaggini, Guido; (Milano, IT) ; Marcelli,
Emanuela; (Macerata, IT) |
Correspondence
Address: |
Thomas E. Popovich, Esq.
Popovich & Wiles, PA
IDS Center, Suite 1902
80 South 8th Street
Minneapolis
MN
55402
US
|
Assignee: |
Sorin Biomedica Cardio
S.p.A.
|
Family ID: |
8243245 |
Appl. No.: |
09/843511 |
Filed: |
April 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09843511 |
Apr 25, 2001 |
|
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|
09299699 |
Apr 26, 1999 |
|
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|
6226550 |
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Current U.S.
Class: |
607/5 |
Current CPC
Class: |
A61N 1/3956 20130101;
A61N 1/3918 20130101; A61N 1/395 20130101 |
Class at
Publication: |
607/5 |
International
Class: |
A61N 001/39 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 1999 |
EP |
99830034.7 |
Claims
What is claimed is:
1. An implantable defibrillator apparatus comprising: a plurality
of defibrillation electrodes adapted to be applied to the heart
muscle and to deliver electric defibrillation shocks thereto; the
plurality of electrodes in communication with
defibrillation-control means capable of selectively supplying
voltage pulses to the electrodes; and wherein the defibrillation
control means controls the duration and interval of the voltage
pulses and further wherein the voltage pulses produce electric
defibrillation shocks sufficient to produce defibrillation.
2. The implantable defibrillator apparatus of claim 1 wherein the
electric defibrillation shocks are sufficient to produce
defibrillation synchronized with the heart's QRS.
3. An apparatus according to claim 1, wherein the control unit is
adapted to deliver defibrillation shocks to the electrodes in a
desired time sequence.
4. An apparatus according to claim 1, wherein the control unit is
adapted to selectively vary at least one characteristic of the
electric defibrillation shocks, the at least one characteristic
selected from the group of waveform of the defibrillation shock,
the duration of the defibrillation shock, the interval between
successive defibrillation shocks, and the electrodes to which a
defibrillation shock is applied at any particular time.
5. An apparatus according to claim 1, wherein the apparatus further
comprises sensor means for detecting the occurrence of a
fibrillation phenomenon, the sensor means being connected to the
control unit and adapted to activate the application of
defibrillation shocks.
6. An apparatus according to claim 5, wherein the sensor means
comprise respective sensing lines that connect the plurality of
electrodes to the control unit to enable the electrodes to act both
as defibrillation electrodes and as sensing electrodes.
7. An apparatus according to claim 1, wherein the apparatus further
comprises sensor means capable of detecting a ventricular
electrogram, and wherein the control unit synchronizes the
application of defibrillation shock during the QRS of the
electrogram.
8. An implantable defibrillator apparatus comprising: a plurality
of defibrillation electrodes adapted to be applied to the heart
muscle and to deliver electric defibrillation shocks thereto; the
plurality of electrodes in communication with electronic switches;
the electronic switches in communication with a power stage capable
of supplying voltage pulses to the electrodes; and wherein the
power stage is connected to a control unit that controls the
duration and interval of the voltage pulses and further wherein the
voltage pulses are applied for a time sufficient to produce
defibrillation.
9. An apparatus according to claim 8, wherein the control unit is
adapted to deliver defibrillation shocks to the electrodes in a
desired time sequence.
10. An apparatus according to claim 8, wherein the control unit is
adapted to selective vary at least one characteristic of the
electric defibrillation shocks, the at least one characteristic
selected from the group of waveform of the defibrillation shock,
the duration of the defibrillation shock, the interval between
successive defibrillation shocks, and the electrodes to which a
defibrillation shock is applied at any particular time.
11. An apparatus according to claim 8, wherein the successive
defibrillation shocks are applied at intervals of approximately 100
microseconds.
12. An apparatus according to claim 8, wherein the electrodes have
a surface area ranging from about 50 mm.sup.2 to about 100
mm.sup.2.
13. An apparatus according to claim 8, wherein the apparatus
further comprises a sensor for detecting the occurrence of a
fibrillation phenomenon, the sensor being connected to the control
unit and adapted to activate the application of defibrillation
shocks.
14. An apparatus according to claim 13, wherein the sequence of
defibrillation shocks has a duration no greater than approximately
50 milliseconds.
15. An apparatus according to claim 13, wherein the sensor
comprises respective sensing lines that connect the plurality of
electrodes to the control unit to enable the electrodes to act both
as defibrillation electrodes and as sensing electrodes.
16. An apparatus according to claim 8, wherein the apparatus
further comprises a sensor capable of detecting a ventricular
electrogram, and wherein the control unit synchronizes the
application of defibrillation shock during the QRS of the
electrogram.
17. A method of treating atrial fibrillation comprising: providing
a stimulating device having a plurality of electrodes; inserting
the plurality of electrodes at desired locations in the heart; and
applying defibrillation shocks to the plurality of electrodes in a
desired sequence, thereby creating an electric field having a
geometry designed for the patient's anatomy.
18. The method of claim 17 further comprising the step of sensing
atrial fibrillation by means of the plurality of electrodes.
19. The method of claim 17 further comprising the step of sensing
atrial fibrillation by means of a specialized sensor.
20. The method of claim 17 wherein the step of applying
defibrillation shocks further comprises a control unit in
communication with plurality of electrodes, the control unit
controlling the characteristics of the defibrillation shocks by
means of one of the waveform, the duration, the interval between
shocks, and the sequence of activating shocks to various
electrodes.
Description
[0001] This is a continuation of application Ser. No. 09/299,699,
filed Apr. 26, 1999, the contents of which are hereby incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to defibrillation techniques,
and in particular relates to atrial defibrillation.
BACKGROUND OF THE INVENTION
[0003] Atrial fibrillation (often referred to simply as AF), in its
chronic and paroxysmal forms, constitutes the arrhythmia that is
most frequent in the population, with a particularly high incidence
(10%) in adults aged over 65 years. There is no pharmacological
treatment which is sure to be effective and, as for all
antiarrhythmic drugs, there is an increased probability of inducing
serious ventricular proarrhythmia. In patients who are suffering
from this condition to an incapacitating extent and who do not
respond to the use of an average of two to three antiarrhythmia
drugs, the subject of an alternative solution becomes
important.
[0004] An implantable atrial defibrillator with an associated
ventricular stimulation/sensing capability constitutes a recent
treatment which is currently at the clinical evaluation stage. A
defibrillator of this type is usually implanted by the insertion in
the heart of two electrodes (leads) having large active surface
areas and constituted by metal coils which are positioned along the
outer wall of the right atrium and in the coronary sinus, whilst
the metal container of the defibrillator can also operate as an
active pole during discharge.
[0005] The basic object of defibrillation is to produce an electric
field adequate to involve, anatomically, a significant portion of
the myocardium of both atria, in order to depolarize, by means of
the electric shock, a predominant number of myocardial cells which
are subject to spontaneous, chaotic and non-synchronized electrical
activity. Recent tests have shown the great importance of the
distribution of the electric field in minimizing defibrillation
energy and consequently voltage, muscle-stimulation and perception
of pain, which constitutes the most important factor limiting the
use of these devices.
SUMMARY OF THE INVENTION
[0006] The object of the present invention is to provide a
defibrillator which can achieve an effective action antagonistic to
fibrillation.
[0007] In one aspect, this invention is an implantable
defibrillator apparatus comprising a plurality of defibrillation
electrodes adapted to be applied to the heart muscle and to deliver
electric defibrillation shocks thereto, the plurality of electrodes
in communication with defibrillation-control means capable of
selectively supplying voltage pulses to the electrodes, wherein the
defibrillation control means controls the duration and interval of
the voltage pulses and further wherein the voltage pulses produce
electric defibrillation shocks sufficient to produce
defibrillation. Preferably, the electric defibrillation shocks are
sufficient to produce defibrillation synchronized with the heart's
QRS, and the control unit can deliver defibrillation shocks to the
electrodes in a desired time sequence. The control unit may
selectively vary at least one characteristic of the electric
defibrillation shocks, including the waveform of the defibrillation
shock, the duration of the defibrillation shock, the interval
between successive defibrillation shocks, and the electrodes to
which a defibrillation shock is applied at any particular time. The
apparatus may also comprise sensor means for detecting the
occurrence of a fibrillation phenomenon, the sensor means being
connected to the control unit and adapted to activate the
application of defibrillation shocks. The sensor means may comprise
respective sensing lines that connect the plurality of electrodes
to the control unit to enable the electrodes to act both as
defibrillation electrodes and as sensing electrodes. The apparatus
may also comprise sensor means capable of detecting a ventricular
electrogram. The control unit may synchronize the application of
defibrillation shock during the QRS of the electrogram.
[0008] In another aspect, this invention is an implantable
defibrillator apparatus comprising a plurality of defibrillation
electrodes adapted to be applied to the heart muscle and to deliver
electric defibrillation shocks thereto; the plurality of electrodes
in communication with electronic switches; the electronic switches
in communication with a power stage capable of supplying voltage
pulses to the electrodes, wherein the power stage is connected to a
control unit that controls the duration and interval of the voltage
pulses and further wherein the voltage pulses are applied for a
time sufficient to produce defibrillation.
[0009] In yet another aspect, this invention is a method of
treating atrial fibrillation comprising providing a stimulating
device having a plurality of electrodes; inserting the plurality of
electrodes at desired locations in the heart; and applying
defibrillation shocks to the plurality of electrodes in a desired
sequence, thereby creating an electric field having a geometry
designed for the patient's anatomy. Sensing atrial fibrillation may
be done by means of the plurality of electrodes or by means of a
specialized sensor.
BRIEF DESCRIPTION OF THE DRAWING
[0010] FIG. 1 shows a block diagram of the circuit structure of a
multi-pole defibrillator according to the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0011] Basically, the solution according to the invention enables
the atrial defibrillation shock to be split up physically and over
time so as to reduce the energy delivered.
[0012] In a preferred embodiment, the implantable atrial
defibrillator of this invention comprises at least two electrodes
that can be inserted permanently in the heart chambers. Each
electrode has a surface area ranging from 50 to 100 mm.sup.2. The
electrodes permit the delivery of electric shocks in a programmable
manner, sequentially in time, between any electrode or pole or
group of electrodes or poles belonging to the same or to different
leads, in order to defibrillate the fibrillating atria in an
optimal manner.
[0013] The electrical characteristics of the shock and, in
particular, the waveforms (single-phase, symmetric two-phase and
asymmetric two-phase, etc.), the duration, and the interval between
successive shocks (on the order of about 100 microseconds) can be
programmed.
[0014] When atrial fibrillation has been confirmed by sensing of
the chaotic atrial activity detectable by one or more poles of the
same leads or by means of a specialized sensor, the sequence of
defibrillation discharges is activated by sensing of the
ventricular electrogram, detected by a suitable lead located in the
right ventricle. This activation takes place in synchronism with
the so-called QRS of the electrocardiograph signal to prevent
dangerous proarrhythmia. The sequence has a programmable duration,
by way of indication, no longer than 50 milliseconds, such that it
is sure to be included within in the absolute refractory period of
the ventricular myocardium.
[0015] Since the functional relationship between impedance and
surface area of a conductor pole immersed in blood is hyperbolic,
for surface areas greater than about 50 to 100 mm.sup.2, reduced
variations occur in impedance as a function of surface area. In the
currently preferred solution for implementing the invention, a low
shock voltage thus suffices to produce, at each of the
above-described poles, a current density equal to that which
requires voltages even three to four times greater in the single
poles of large surface area which are used predominantly at the
moment. It is consequently possible to achieve effective atrial
defibrillation with reduced perception of pain, which is caused
mainly by the voltage. The multi-pole configuration also permits
the creation of an electric field of variable geometry designed for
the patient's anatomy, which can further reduce the need for high
voltages.
[0016] The invention will now be described with reference to FIG.
1, which shows a plurality of electrodes (or "poles"), indicated 1,
2, 3, . . . n, that can be fitted in sites of the heart suitable
for bringing about an effect antagonistic to fibrillation
(defibrillation), particularly with regard to atrial fibrillation
(AF), by the application of electric signals (shocks).
[0017] The structural characteristics of these electrodes, for
example, the selection of constituent materials, any surface
treatment, etc., are those currently used in known implantable
defibrillators.
[0018] In particular, the term "electrode" or "pole" as used herein
is intended to define any electrically-conductive member which can
be associated with the heart muscle in a relationship suitable for
the transmission of an electrical signal. Consequently, the
electrodes or poles in question may either be configured as
physically separate members which are thus intended to be fitted in
distinct and separate respective myocardial sites, or may be
associated in groups or sets with respective supporting structures
(so-called "leads") so as to be fitted in respective myocardial
sites separately (in the sense that each electrode or pole can
transfer--and detect--a respective signal to-- and from--the
myocardium) but not independently, since the electrodes or poles of
each group disposed on a respective lead are implanted
simultaneously as a result of the implantation of the respective
supporting element.
[0019] The apparatus may comprise two electrodes, or in more
complex configurations, the number n may equal, for example, ten
electrodes. Preferred numbers of electrodes typically range from
three to five. Electrodes 1 to n may either be identical to one
another or may have different shapes according to the sites in
which they are to be positioned.
[0020] In general, electrodes 1 to n preferably have a surface area
typically of the order of 50 mm.sup.2 or more, for example, 100
mm.sup.2. Since, as mentioned above, the functional relationship
between impedance and surface area of a conductor pole immersed in
blood is typically hyperbolic, with surface-area values of the type
indicated, a low shock voltage (for example 50 to 100 volts)
suffices to produce a current density in each of the electrodes
equal to that which required the application of voltages even three
to four times greater in the (single) electrodes of known
implantable defibrillators.
[0021] The apparatus comprises defibrillation control means having
power stage 4; electrodes 1, 2, 3, . . . to n; electronic enabling
switches 11, 12, 12, . . . , in; and timing and control unit 37,
whose operation is described as follows.
[0022] Power stage (the "high voltage" stage) 4 of the implantable
defibrillator generates voltage pulses which are applied to
electrodes 1, 2, 3, . . . to n, via respective electronic enabling
switches or control gates 11, 12, 13, . . . , 1n.
[0023] Switches or control gates 11 to 1n are connected to
respective enabling lines 21, 22, 23, . . . , 2n, thus allowing the
signals generated in power stage 4 to pass selectively towards
electrodes 1, 2, . . . n). Switches or control gates 11 to 1n
communicate with and are controlled by timing and control unit 37,
preferably provided with telemetering interface 37a of generally
known type.
[0024] The control performed by control unit 37 by means of lines
21, 22, 23, . . . 2n enables the characteristics of the
defibrillation signals applied to the myocardium to be programmed,
in particular with regard to the following characteristics:
[0025] the waveform: single-phase, symmetric two-phase and
asymmetric two-phase, etc.,
[0026] the duration of each shock,
[0027] the interval between successive shocks, and
[0028] the ability to activate the defibrillation pulses in the
various electrodes 1, 2, 3, . . . , n sequentially in time (in
accordance with a typical time-sharing scheme).
[0029] As a result, the above-described multi-pole configuration
permits, in particular, the creation of an electric defibrillation
field of variable geometry designed for the patient's anatomy, by
virtue of the ability to program the emission of the control
signals by control unit 37. This permits a further reduction in the
intensity (in practice, the voltage) of the signals applied; this
results in an ability to achieve effective atrial defibrillation
with low pain perception since the latter is caused mainly by the
voltage.
[0030] The defibrillation may be activated by sensing of the
chaotic atrial activity in the presence of fibrillation, which may
be detected by means of specialized sensor 5 of generally known
type. However, in a particularly preferred embodiment of the
invention, it is possible to replace and/or to supplement this
conventional sensing with sensing performed by the electrodes 1, 2,
3, . . . n themselves. Respective sensing lines, generally
indicated 6, are provided for this purpose and enable the
electrical signals indicative of the local myocardial activity at
the respective implant site to be detected by the respective
electrode so as to supply to control unit 37 a set of signals which
enables control unit 37 to see and to identify the occurrence of a
fibrillation phenomenon.
[0031] The block diagram of FIG. 1 shows multiplexer 7, that
enables the signal coming from one or more of electrodes 1, 2, 3, .
. . n, to be detected selectively by the respective sensing line 6.
After anti-noise filtering performed in filter 8 and automatic gain
control performed in automatic gain-control circuit (AGC) 9
controlled by control unit 37 by means of line 10, the sensing
signals thus detected reach comparator circuit 30. Here, the
sensing signals are compared with a threshold level, which may be
adaptively modifiable, and which is supplied by control unit 37 by
means of line 31.
[0032] Finally, a sensor (of known type), indicated 32, can detect
ventricular activity and can supply to the unit a corresponding
synchronization signal such that control unit 37 can synchronize
the application of the shock sequence by the electrodes 1 to n with
the ventricular QRS.
[0033] Moreover, the various electronic components shown in the
drawing (or at least those of low power) clearly may either be in
the form of discrete blocks or components, or may be integrated in
a single circuit.
[0034] According to known criteria, the sensing operation is
regulated in a manner such as to prevent a sensing signal from
being picked up from an electrode which is being used at the time
in question for the application of a defibrillation signal. In
particular, as already mentioned, the sequence of defibrillation
discharges is activated by sensing of the ventricular electrogram
detected by sensor 32, preferably located in the right ventricle,
so as to have a programmable duration, by way of indication, no
greater than 50 milliseconds, which is sure to be included within
the absolute refractory period of the ventricular myocardium.
[0035] Naturally, the principle of the invention remaining the
same, the details of construction and forms of embodiment may be
varied widely with respect to those described and illustrated,
without thereby departing from the scope of the present invention,
as defined by the following claims.
* * * * *