U.S. patent number RE35,779 [Application Number 08/608,410] was granted by the patent office on 1998-04-28 for post-heart surgery cardioverting system and method.
This patent grant is currently assigned to InControl, Inc.. Invention is credited to Clifton A. Alferness, Gregory M. Ayers, Jerry C. Griffin, Kenneth R. Infinger.
United States Patent |
RE35,779 |
Alferness , et al. |
April 28, 1998 |
Post-heart surgery cardioverting system and method
Abstract
A post-surgical cardioverting system and method applies
cardioverting electrical energy to the atria of the heart of a
post-surgical heart patient. The system includes a first lead
including a first elongated electrode having a proximal end and a
distal end, a second lead including a second elongated electrode
having a proximal end and a distal end, and sutures for releasably
anchoring the distal ends of the first and second electrodes to the
pericardium and disposing the first and second electrodes along the
pericardium overlying the right and left atria respectively. A
non-implantable cardiovertor is coupled to the first and second
leads for applying the cardioverting electrical energy to the first
and second electrodes. When cardioversion is no longer required,
the first and second leads may be pulled out of the patient's
chest.
Inventors: |
Alferness; Clifton A. (Redmond,
WA), Ayers; Gregory M. (Redmond, WA), Griffin; Jerry
C. (Chicago, IL), Infinger; Kenneth R. (Issaquah,
WA) |
Assignee: |
InControl, Inc. (Redmond,
WA)
|
Family
ID: |
22280039 |
Appl.
No.: |
08/608,410 |
Filed: |
February 28, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
100492 |
Jul 30, 1993 |
05403353 |
Apr 4, 1995 |
|
|
Current U.S.
Class: |
607/5;
607/10 |
Current CPC
Class: |
A61N
1/05 (20130101); A61N 1/0587 (20130101); A61N
1/3918 (20130101); A61N 1/395 (20130101); A61N
1/3904 (20170801) |
Current International
Class: |
A61N
1/05 (20060101); A61N 1/39 (20060101); A61N
001/36 () |
Field of
Search: |
;607/4,5,6,7,8,10 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Dr. K. Westermann, `A New External Pacemaker` Medicamundi, vol. 21,
No. 2, 1976, pp. 91-94..
|
Primary Examiner: Kamm; William E.
Assistant Examiner: Getzow; Scott M.
Attorney, Agent or Firm: Gray, Jr.; Richard O.
Claims
What is claimed is:
1. A post-surgical cardioverting system for applying cardioverting
electrical energy to the heart of a post-surgical heart patient,
said system comprising:
a first lead including a first elongated electrode, said first
electrode having a proximal end and a distal end;
a second lead including a second elongated electrode, said second
electrode having a proximal end and a distal end;
first anchor means for releasably anchoring the distal ends of said
first and second electrodes to body tissue external to but in close
proximity to the heart beneath the skin of the patient to dispose
said first and second electrodes in electrical contact with the
heart; and
non-implantable cardioverting means coupled to said first and
second leads for applying said cardioverting electrical energy to
said first and second electrodes.
2. A system as defined in claim 1 wherein said first anchor means
comprises suture means for releasably suturing the distal ends of
said first and second electrodes to said body tissue external to
but in close proximity to the heart.
3. A system as defined in claim 1 further including second anchor
means for releasably anchoring the proximal ends of said first and
second electrodes to body tissue external to but in close proximity
to the heart beneath the skin of the patient.
4. A system as defined in claim 3 wherein said second anchor means
comprises suture means for releasably suturing the proximal ends of
said first and second electrodes to said body tissue external to
but in close proximity to the heart.
5. A system as defined in claim 1 further including sensing means
for sensing R waves of the heart, and wherein said cardioverting
means is coupled to said sensing means and responsive to R waves
sensed by said sensing means for applying said cardioverting
electrical energy to said first and second electrodes in timed
relation to a sensed R wave.
6. A system as defined in claim 5 wherein said cardioverting means
is further responsive to said sensed R waves for applying said
cardioverting electrical energy to said first and second electrodes
when the time between immediately successive R waves is greater
than a preselected minimum time interval.
7. A system as defined in claim 5 wherein said sensing means
comprises third and fourth electrodes and attachment means for
releasably attaching said third and fourth electrodes to a
ventricle of the heart.
8. A system as defined in claim 7 wherein said cardioverting means
further includes pacing means coupled to said third and fourth
electrodes for applying pacing electrical energy pulses to said
third and fourth electrodes.
9. A system as defined in claim 1 wherein said first and second
elongated electrodes each have a length dimension for extending
across a substantial portion of a respective chamber of the
heart.
10. A system as defined in claim 1 wherein said first and second
elongated electrodes each have a length dimension for extending
across a substantial portion of the right and left atria
respectively.
11. A system as defined in claim 1 wherein said first and second
elongated electrodes each have a length dimension of approximately
six centimeters.
12. A system as defined in claim 1 wherein said first and second
leads each have an impedance of one ohm or less.
13. A method of cardioverting the heart of a heart surgery patient
subsequent to a heart surgery procedure, said method comprising the
steps of:
providing a first lead having a first elongated electrode, said
first electrode having a distal end and a proximal end;
providing a second lead having a second elongated electrode, said
second electrode having a distal end and a proximal end;
following said heart surgery procedure and before closing the chest
of the patient, releasably anchoring said distal ends of said first
and second electrodes to body tissue external to but in close
proximity to the heart beneath the skin of the patient to dispose
said first and second electrodes in electrical contact with the
heart;
providing a non-implanted cardioverting means for providing
cardioverting electrical energy;
coupling said non-implanted cardioverting means to said first and
second electrodes; and
causing said cardioverting means to apply said cardioverting
electrical energy to said first and second electrodes when the
heart of the patient is in need of cardioversion.
14. A method as defined in claim 13 wherein said anchoring step
includes releasably suturing said distal ends of said first and
second electrodes to body tissue external to but in close proximity
to the heart beneath the skin of the patient.
15. A method as defined in claim 13 wherein said anchoring step
includes releasably anchoring said distal ends of said first and
second electrodes to the pericardium.
16. A method as defined in claim 15 wherein said anchoring step
includes disposing said first and second electrodes along the
inside of the pericardium.
17. A method as defined in claim 15 wherein said anchoring step
includes disposing said first and second electrodes along the
outside of the pericardium.
18. A method as defined in claim 15 wherein said anchoring step
includes releasably anchoring said proximal ends of said first and
second electrodes to the pericardium.
19. A method as defined in claim 18 wherein said anchoring step
includes releasably suturing said distal ends and said proximal
ends of said first and second electrodes to the pericardium.
20. A method as defined in claim 13 wherein said method is for
applying cardioverting electrical energy to the atria of the heart
and wherein said anchoring step includes disposing said first
electrode to overlie the right atrium and disposing said second
electrode to overlie the left atrium.
21. A method as defined in claim 20 wherein said anchoring step
includes releasably anchoring said distal ends of said first and
second electrodes to the pericardium, disposing said first
electrode along the pericardium to overlie the right atrium, and
disposing said second electrode along the pericardium to overlie
the left atrium.
22. A method as defined in claim 21 wherein said anchoring step
includes disposing said first and second electrodes along the
inside of the pericardium.
23. A method as defined in claim 21 wherein said anchoring step
includes disposing said first and second electrodes along the
outside of the pericardium.
24. A method as defined in claim 21 wherein said anchoring step
includes releasably anchoring said proximal ends of said first and
second electrodes to the pericardium.
25. A method as defined in claim 24 wherein said anchoring step
includes releasably suturing said distal ends and said proximal
ends of said first and second electrodes to the pericardium.
26. A method as defined in claim 13 including the further steps
of;
providing sensing means for sensing R waves of the heart,
sensing R waves of the heart with said sensing means; and
causing said cardioverting means to apply said cardioverting
electrical energy to said first and second electrodes in timed
relation to a sensed R wave.
27. A method as defined in claim 26 wherein said last recited
causing step includes causing said cardioverting means to apply
said cardioverting electrical energy to said first and second
electrodes when the time between immediately successive sensed R
waves is greater than a preselected minimum time period.
28. A method as defined in claim 26 wherein said step of providing
said sensing means includes providing third and fourth electrodes,
releasably attaching said third and fourth electrodes to a
ventricle of the heart, and coupling said third and fourth
electrodes to said cardioverting means.
29. A method as defined in claim 28 including the further steps of
providing said cardioverting means with pacing means for providing
pacing electrical energy pulses, coupling said pacing means to said
third and fourth electrodes, and causing said pacing means to apply
said pacing electrical energy pulses to said third and fourth
electrodes.
30. A method of cardioverting the atria of the heart of a heart
surgery patient subsequent to an opened chest heart surgery
procedure, said method comprising the steps of:
providing a first lead having a first elongated electrode, said
first electrode having a distal end and a proximal end;
providing a second lead having a second elongated electrode, said
second electrode having a distal end and a proximal end;
following said heart surgery procedure and prior to closing the
chest of the patient, releasably anchoring said distal ends of said
first and second electrodes to the pericardium;
disposing said first electrode along the pericardium adjacent to
the right atrium of the heart;
disposing said second electrode along the pericardium adjacent to
the left atrium of the heart;
providing a non-implanted cardioverting means for providing
cardioverting electrical energy;
coupling said cardioverting means to said first and second
electrodes through said first and second leads; and
applying said cardioverting electrical energy with said
cardioverting means to said first and second electrodes when the
atria are in need of cardioversion.
31. A post-surgical defibrillating system for applying
defibrillating electrical energy to the heart of a post-surgical
heart patient, said system comprising:
a first lead including a first elongated electrode, said first
electrode having a proximal end and a distal end;
a second lead including a second elongated electrode, said second
electrode having a proximal end and a distal end;
first anchor means for releasably anchoring the distal ends of said
first and second electrodes to body tissue external to but in close
proximity to the heart beneath the skin of the patient to dispose
said first and second electrodes in electrical contact with the
heart; and
non-implantable defibrillator coupled to said first and second
leads for applying said defibrillating electrical energy to said
first and second electrodes. .Iadd.
32. A post-surgical cardioverting system for applying cardioverting
electrical energy to the heart of a post-surgical heart patient,
said system comprising:
a first lead including a first elongated electrode, said first
electrode having a proximal end and a distal end;
a second lead including a second elongated electrode, said second
electrode having a proximal end and a distal end;
said first and second electrodes adapted to be in electrical
contact with the heart;
at least one anchor at the distal end of said first and second
electrodes releasably connected beneath the skin of the patient;
and
a non-implantable cardioverter electrically coupled for
cardioversion by said first and second leads to the
heart..Iaddend..Iadd.33. A system as defined in claim 32 in which
said anchor is adapted to be connected to body tissue external to
but in close proximity to the heart beneath the skin of the
patient..Iaddend..Iadd.34. A system as defined in claim 32 in which
said anchor is adapted to be attached to the pericardium of the
heart..Iaddend..Iadd.35. A system as described in claim 32 in which
said
anchor is a suture..Iaddend..Iadd.36. A system as defined in claim
32 in which said anchor is a suture adapted to be attached to the
pericardium of the heart..Iaddend..Iadd.37. A post-surgical
cardioverting system for applying cardioverting electrical energy
to the heart of a post-surgical heart patient, said system
comprising:
a first lead including a first elongated electrode;
a second lead including a second elongated electrode;
anchor means for releasably anchoring the first and second
electrodes to body tissue beneath the skin of the patient to
dispose said first and second electrodes in electrical contact with
the heart; and
non-implantable cardioverting means coupled to said first and
second leads for applying said cardioverting electrical energy to
said first and second
electrodes for cardioversion of the heart..Iaddend..Iadd.38. A
system as defined in claim 37 in which said anchor means is adapted
to be connected to body tissue external to but in close proximity
to the heart beneath the skin of the patient..Iaddend..Iadd.39. A
system as defined in claim 37 in which said anchor means is adapted
to be attached to the pericardium of the heart..Iaddend..Iadd.40. A
system as described in claim 37 in which
said anchor means is a suture..Iaddend..Iadd.41. A system as
described in claim 37 in which said anchor means is a suture
adapted to be attached to the pericardium of the
heart..Iaddend..Iadd.42. A method of cardioverting the heart of a
heart surgery patient subsequent to a heart surgery procedure, said
method comprising the steps of:
providing a first lead having a first elongated electrode, said
first electrode having a distal end and a proximal end;
providing a second lead having a second elongated electrode, said
second electrode having a distal end and a proximal end;
placing said first and second electrodes in electrical contact with
the heart;
following said heart surgery procedure, releasable anchoring said
distal ends of said first and second electrodes to body tissue
beneath the skin of the patient;
providing a non-implanted cardiovertor for providing cardioverting
electrical energy;
coupling said non-implantable cardioverting means to said first and
second electrodes; and
causing said cardioverting means to apply said cardioverting
electrical energy to said first and second electrodes for
cardioversion of the
heart..Iaddend..Iadd.43. A method as defined in claim 42 wherein
said anchoring step includes anchoring said first and second
electrodes to body tissue external to but in close proximity to the
heart..Iaddend..Iadd.44. A method as defined in claim 42 wherein
said anchoring step includes anchoring said first and second
electrodes to the pericardium of the heart..Iaddend..Iadd.45. A
method as defined in claim 42 wherein said anchoring step includes
suturing..Iaddend..Iadd.46. A method as defined in claim 42 wherein
said anchoring step includes suturing the first and
second electrodes to the pericardium of the
heart..Iaddend..Iadd.47. A method of cardioverting the heart of a
heart surgery patient subsequent to a heart surgery procedure, said
method comprising the steps of:
providing a first lead having a first elongated electrode;
providing a second lead having a second elongated electrode;
following said heart surgery procedure releasably disposing said
first and second electrodes in electrical contact with the
heart;
providing a non-implanted cardioverting means for providing
cardioverting electrical energy;
coupling said non-implanted cardiovertor to said first and second
electrodes; and
causing said cardioverting means to apply said cardioverting
electrical energy to said first and second electrodes for
cardioversion of the heart..Iaddend..Iadd.48. A method as defined
in claim 47 wherein said disposing step includes releasably
anchoring said first and second electrodes to body tissue external
to but in close proximity to the heart..Iaddend..Iadd.49. A method
as defined in claim 47 wherein said disposing step includes
releasably anchoring said first and second electrodes to the
pericardium of the heart..Iaddend..Iadd.50. A method as defined in
claim 47 wherein said disposing step includes
suturing..Iaddend..Iadd.51. A method as defined in claim 47 wherein
said anchoring step includes releasably suturing the first and
second electrodes to the pericardium of the heart..Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention is generally directed to a cardioverting
system and method for providing temporary cardioversion of the
heart of a heart surgery patient following a heart surgery
procedure. The present invention is more particularly directed to
such a system and method for providing post-surgery cardioversion
of the atria of the heart.
There are approximately four hundred thousand (400,000) heart
surgery procedures performed annually in the United States. The
types of such surgical procedures vary from coronary artery bypass
grafts to valve replacements, to repair of congenital heart
defects. In order to gain access to the heart, these surgeries
require the chest to be opened in the middle of the sternum. An
incision is then made in the pericardial sac (pericardium) to
expose the heart and permit the required surgical procedure to be
performed. Following the surgical procedure, the pericardial
incision is reapproximated (closed except for a drain opening) with
sutures and the chest cavity is closed.
Often, following such heart surgical procedures, the patients'
hearts during recovery experience bradycardia or slow heart rates.
In the prior art, to overcome such maladies, the hearts of
post-surgical heart patients are temporarily paced for a few days
following surgery, when required, to maintain the heart rates at a
normal rate. This is accomplished by releasably attaching heart
wires to the heart before the pericardium is sutured and the chest
cavity is closed. First and second heart wires are attached to the
myocardium of one of the ventricles such as the left ventricle. The
heart wires are then brought outside of the chest. Thereafter, the
pericardium is sutured and the chest cavity is closed. The proximal
ends of the heart wires are then coupled to a temporary pacemaker
to permit the heart to be paced. After the patient has recovered
sufficiently wherein pacing is no longer required, the heart wires
are pulled out of the patient.
Unfortunately, twenty to thirty percent of all heart surgical
patients experience an arrhythmia called atrial fibrillation during
the immediate or early post-surgical period. When this occurs, the
heart beats rapidly and irregularly. According to reports, this
constitutes a major clinical problem resulting in hypotension,
heart failure, pneumonia and/or stroke, due to thromboembolism.
Hence, such a condition is of great concern to the physician and it
is therefore in the best interest of the patient to terminate this
arrhythmia as soon as possible.
The development of post-surgical atrial fibrillation has not been
associated with preoperative or postoperative events. Further, the
specificity and sensitivity of age and other possible relevant
factors for prediction of atrial fibrillation after heart surgery
is low. No effective prophylactic regimen has yet been
established.
When atrial fibrillation of a surgical patient's heart occurs
during surgery, the physician terminates the fibrillation by
cardioverting the heart. In this cardioversion procedure, the
physician contacts each atria with a spoon-sized conductive paddle
which is coupled to an external defibrillator. The external
defibrillator includes a storage capacitor which is charged to a
selected voltage. When the storage capacitor is fully charged, the
stored energy is discharged into the atria of the heart through the
paddles.
While the above-mentioned cardioverting process is very effective
in terminating atrial fibrillation occurring during surgery, this
procedure is not available to the physician for terminating atrial
fibrillation occurring after the heart surgery is completed and the
patient's chest cavity has been closed. It has been observed that
the peak incidence of atrial fibrillation is during the second or
third postoperative day. While external cardioversion is an option,
because the patient's chest cavity at this time is closed, much
larger paddles and much greater cardioverting energies must be used
as compared to the paddle size and cardioverting energies employed
during surgery. Such energies, generally between 50 and 360 joules,
would also require that the patient be briefly anesthetized or very
heavily sedated prior to attempted external cardioversion. Hence,
while external cardioversion, using much larger paddles and much
higher cardioverting energies, is available to the physician as an
option, most physicians are reluctant to use such external
cardioversion because of the likely trauma and tissue damage it
would cause the patient during a time in which the patient is in
initial recovery from serious open heart surgery.
Drug therapy is also an available option. Its use however is often
attended with significant side effects. In addition, there is a
substantial potential interaction of such drugs with the many
different types and amounts of other drugs the patient is already
being given during this initial recovery period.
Hence, there remains a long felt need in the art for a
cardioverting system and method capable of arresting fibrillation,
such as atrial fibrillation, occurring during the post-heart
surgery period. More specifically, there is a need in the art for
such a system and method which does not cause prolongation of the
patient's recovery period due to trauma and tissue damage and which
avoids the need for drug therapy to treat such a condition.
SUMMARY OF THE INVENTION
The present invention therefore provides a post-surgical
cardioverting system for applying cardioverting electrical energy
to the heart of a post-surgical heart patient. The system includes
a first lead including a first elongated electrode having a
proximal end and a distal end, a second lead including a second
elongated electrode having a proximal end and a distal end, and
first anchor means for releasably anchoring the distal ends of the
first and second electrodes to body tissue external to but in close
proximity to the heart beneath the skin of the patient to dispose
the first and second electrodes in electrical contact with the
heart. The system further includes a non-implantable cardiovertor
coupled to the first and second leads for applying the
cardioverting electrical energy to the first and second
electrodes.
The present invention further provides a method of cardioverting
the heart of a heart surgery patient subsequent to a heart surgery
procedure. The method includes the steps of providing a first lead
having a first elongated electrode and a second lead having a
second elongated electrode, the first and second electrodes each
having a distal end and a proximal end. The method further includes
the steps of, following the heart surgery procedure and before
closing the chest of the patient, releasably anchoring the distal
ends of the first and second electrodes to body tissue external to
but in close proximity to the heart beneath the skin of the patient
to dispose the first and second electrodes in electrical contact
with the heart. The method further includes the steps of providing
a non-implanted cardiovertor for providing cardioverting electrical
energy, coupling the non-implanted cardiovertor to the first and
second electrodes, and causing the cardiovertor to apply the
cardioverting electrical energy to the first and second electrodes
when the heart of the patient is in need of cardioversion.
The present invention still further provides a method of
cardioverting the atria of the heart of a heart surgery patient
subsequent to an opened chest heart surgery procedure. The method
includes the steps of providing a first lead having a first
elongated electrode, the first electrode having a distal end and a
proximal end, providing a second lead having a second elongated
electrode, the second electrode having a distal end and a proximal
end, and following the heart surgery procedure and prior to closing
the chest of the patient, releasably anchoring the distal ends of
the first and second electrodes to the pericardium. The method
further includes the steps of disposing the first electrode along
the pericardium adjacent to the right atrium of the heart,
disposing the second electrode along the pericardium adjacent to
the left atrium of the heart, providing a non-implanted
cardioverting means for providing cardioverting electrical energy,
coupling the cardioverting means to the first and second electrodes
through the first and second leads, and applying the cardioverting
electrical energy with the cardioverting means to the first and
second electrodes when the atria are in need of cardioversion.
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention which are believed to be
novel are set forth with particularity in the appended claims. The
invention, together with further objects and advantages thereof,
may best be understood by making reference to the following
description taken in conjunction with the accompanying drawing, in
the several Figures of which like reference numerals identify
identical elements, and wherein:
FIG. 1 is a schematic block diagram of a cardioverting system
embodying the present invention including an atrial cardiovertor
for applying post-surgery cardioverting electrical energy to the
atria of a human heart;
FIG. 2 is a partial plan view illustrating one manner in which the
temporary cardioverting electrodes may be releasably anchored to
the pericardium of the heart in practicing the present invention;
and
FIG. 3 is another partial plan view illustrating another manner in
which the temporary cardioverting electrodes may be releasably
anchored to the pericardium in practicing the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, it illustrates a cardioverting system 30
embodying the present invention shown in association with a human
heart 10 which has undergone surgery and which may require
cardioversion of, for example, the atria, during the post-surgery
period. The portions of the heart 10 illustrated in FIG. 1 and
which will be referred to hereinafter are the right ventricle 12,
the left ventricle 14, the right atrium 16, the left atrium 18, and
the ventricular myocardium 20. The heart 10, as illustrated, is
within the pericardial sac 24 which separates the heart from the
lungs (not shown).
The cardioverting system 30 generally includes an external
cardiovertor or defibrillator 32 for providing cardioverting
electrical energy. This system 30 further includes a first lead 34,
a second lead 36, a third lead 38, and a fourth lead 40.
The third and fourth leads 38 and 40 preferably comprise heart
wires of the type well known in the art which are releasably
attached to the myocardium 20 of the left ventricle 14. The heart
wires 38 and 40 have electrodes 38a and 40a in contact with the
myocardium to permit bi-polar sensing of ventricular activations or
R waves of the heart 10. As will be seen hereinafter, the heart
wires 38 and 40 and their respective electrodes 38a and 40a may
also be used for temporarily pacing the heart 10.
The first lead 34 includes a first elongated electrode 42 having a
distal end 44 and a proximal end 46. The distal end 44 of electrode
42 is releasably anchored to the pericardium 24 by suture 53 which
has been given a loose suture knot to permit the electrode 42 to
extend along the pericardium 24 and disposed overlying the right
atrium 16 while permitting the lead 34 and electrode 42 to be
withdrawn from the patient, as by pulling, to disengage the loose
suture after the patient has recovered sufficiently so as to no
longer require cardioversion.
The electrode 42 may be disposed along either the inner surface or
the outer surface of the pericardium. The proximal end 46 of
electrode 42 may also be releasably anchored to the pericardium by
a suture 54 in a similar manner with a loose suture knot.
Alternatively, the electrode 42 may be inserted through the
pericardium 24 with the distal end 44 sutured to the pericardium as
described above and the proximal end 46 releasably anchored by the
point of entry into the pericardium 24.
The second lead 36 similarly includes an elongated electrode 48
having a distal end 50 and a proximal end 52. The distal end 50 of
electrode 48 is also releasably anchored to the pericardium 24 by a
suture 55 in a manner previously described. The electrode 48 is
disposed along the pericardium 24 for overlying the left atrium.
Again, the electrode 48 may be disposed along either the inner
surface or the outer surface of the pericardium 24. The proximal
end 52 of electrode 48 may also be releasably anchored to the
pericardium by suture 56 in a manner as previously described.
More specifically, and referring to FIG. 2, one of the electrodes
42 or 48, for example electrode 42, is shown disposed along the
inner surface of the pericardium 24. The distal end 44 of electrode
42 is releasably anchored by the loose suture 53 at the point of
exit 61 from the pericardium. The proximal end 46 of electrode 42
is also releasably anchored by the loose suture 54 at the point of
entry 63 into the pericardium. As previously mentioned, the
proximal end 46 of electrode 42 may be releasably anchored by the
point of entry 63, in which case, loose suture 54 may be dispensed
with.
Referring now to FIG. 3, it illustrates one of the electrodes 42 or
48, again for example electrode 42, disposed along the outer
surface of the pericardium 24. Here, the electrode 42 is first
inserted into the pericardium 24 at a first point of entry 65 and
is exited from the pericardium 24 at a first point of exit 67 to
form a first pericardial flap 69. The electrode is then extended
along the outer surface of the pericardium 24 for substantially its
entire length until it reaches a second point of entry 71 into the
pericardium 24, and then is exited from the pericardium 24 at a
second point of exit 73. This forms a second pericardial flap 75.
The distal end 44 of electrode 42 is then releasably anchored to
the pericardium with the loose suture 53 at a point beyond the
second pericardial flap 75. The second pericardial flap 75, as can
be seen in FIG. 3, lends to further assist in the releasable
anchoring of distal end 44.
At the proximal end 46 of electrode 42, the first pericardial flap
69 may be used to releasably anchor the proximal end 46. The loose
suture 54 may also be employed for this purpose.
The heart wires 38 and 40 may take the form as described in U.S.
Pat. No. 4,010,756. The heart wire described in that patent
includes a needle-shaped proximal end and a distal end having an
electrode with attachment means. The needle shape permits the
proximal end to pierce body tissue for bringing the wire proximal
end outside of the chest. The needle shape includes a weakened
shank portion for breaking off the needle. The shank portion which
is left forms a connector for connecting the wire to an external
heart stimulating device. The attachment means may include a suture
for releasably suturing the distal end electrode. The leads 34 and
36 may be similarly constructed. However, as contemplated by the
present invention, certain modifications are preferred. First,
while the electrodes of the referenced heart wire are approximately
one centimeter in length, it is preferred that the electrodes of
leads 34 and 36 be approximately six centimeters in length.
Further, it is preferred that the electrodes 42 and 48 be flexible
to permit the electrodes to conform to the shape or contour of the
pericardium and the heart to assure continuous electrical contact
between the electrode and the body tissue. In addition, it is
preferred that the impedance of the leads 42 and 48 be made
substantially lower than the impedance of prior art heart wires.
Such wires may have an impedance of fifteen ohms or more whereas an
impedance on the order of one ohm is preferred for leads 34 and 36.
Such a low impedance may be achieved by forming the conductor of
leads 34 and 36 with stranded wire of stainless steel and providing
the conductor with a continuous central core of silver. The
conductor may then be provided with insulation up to the
electrodes.
Referring again to FIG. 1, the cardiovertor 32 includes a sense
amplifier 60 and an R wave detector 62. The output of the sense
amplifier 60 is coupled to the R wave detector 62. The sense
amplifier 60 and the R wave detector 62 form a detecting means
which, together with the heart wires 38 and 40 to which sense
amplifier 60 is coupled, senses ventricular activations or R waves
of the heart. The R wave detector 62 is of the type well known in
the art which provides an output pulse upon the occurrence of an R
wave being sensed during a cardiac cycle of the heart.
The cardiovertor 32 further includes a microprocessor 64. The
implementation of the microprocessor 64 in accordance with this
embodiment of the present invention results in a plurality of
functional stages. The stages include a timer 66, an interval set
stage 68, a comparator stage 70, and a charge delivery and energy
control stage 72.
The microprocessor 64 is arranged to operate in conjunction with a
memory (not shown) which may be coupled to the microprocessor by a
multiple-bit address bus (not shown) and a bi-directional
multiple-bit databus (not shown). This permits the microprocessor
62 to address desired memory locations within the memory for
executing write or read operations. During a write operation, the
microprocessor stores data, such as time intervals or operating
parameters in the memory at the addresses defined by multiple-bit
addresses conveyed over the address bus and conveys the data to the
memory over the multiple-bit data bus. During a read operation, the
microprocessor 64 obtains data from the memory at the storage
locations identified by the multiple-bit addresses provided over
the address bus and receives the data from the memory over the
bi-directional data bus.
The cardiovertor 32 further includes a charger and storage
capacitor circuit 74 of the type well known in the art which
charges a storage capacitor to a peak voltage level determined by a
voltage setting control 78 and a discharge circuit 76 for
discharging the storage capacitor within circuit 74 for a
predetermined time period to provide a controlled discharge output
of electrical energy when enabled by an enable switch 84. To that
end, the discharge circuit 76 is coupled to the first electrode 42
of the first lead 34 and the second electrode 48.of the second lead
36 for applying the cardioverting electrical energy to the
atria.
Associated with the charger and delivery control 72 is a manually
operated charge switch 80 and a charge indicator 82. When it is
desired to charge the capacitor of circuit 74, the switch 80 is
actuated. When the capacitor is charged to a desired peak voltage
selected with setting control 78, the indicator, such as an LED,
will provide a suitable indication.
The defibrillator 32 further includes a pacemaker circuit 86 of the
type well known in the art for providing pacing electrical energy
pulses. The pacemaker circuit is preferably operable in a demand
mode (VVI) and is coupled to the heart wires 38 and 40 for
providing demand pacing of the heart. Alternatively, the pacer 86
may be operative in a dual chamber pacing mode, such as the DDD
mode. This however would require another pair of heart wires to be
attached to one of the atria.
Lastly, the cardiovertor 32 includes a power source 88 for
providing power to the electrical components of the atrial
cardiovertor 32. The power source 88 may be an AC power supply
since the cardiovertor 32 is intended for external use, or it may
be a battery if portability of the cardiovertor 32 is
preferred.
After the heart surgery is completed, the heart wires 38 and 40 and
leads 34 and 36 are attached to the heart as previously described,
and the patient's chest is closed, the cardiovertor 32 is coupled
to the heart wires 38 and 40 and leads 34 and 36 as illustrated.
The pacer 86 is then activated to provide demand pacing and the
sense amplifier 60 and the R wave detector 62 begin detecting the
occurrence of ventricular activations of the heart to support the
demand pacing modality. During at least the initial recovery period
in which the post-heart surgery patient may experience an
arrhythmia such as atrial fibrillation, the patient will be coupled
to an external ECG monitor by which such arrhythmias may be
detected. If an atrial arrhythmia is detected, a desired peak
voltage from which cardioversion is to begin is manually selected
with setting control 78. The charger and delivery control switch 80
is then manually actuated. This causes the storage capacitor of
circuit 74 to begin being charged. When the voltage on the
capacitor reaches the desired peak voltage, the indicator 82 will
indicate that the capacitor is fully charged. Next, the enable
switch 84 is manually actuated to condition the discharge circuit
76 to initiate the discharge of the storage capacitor within
circuit 74 into leads 34 and 36 and electrodes 42 and 48 at the
appropriate time to cardiovert the atria The discharge circuit 76
initiates the discharge of the cardioverting electrical energy
under the control of the charger and delivery control 72.
The discharge is preferably synchronized with an R wave, detected
by sense amplifier 60 and the R wave detector 62, which establishes
the first R to R interval falling between a minimum interval and a
maximum interval previously set in the interval set stage 68. The
timer 66 determines the time between immediately successive
detected R waves. After the enable switch is actuated and with each
detected R wave, microprocessor 64 interrogates the timer 66 for
the time between the last immediately successive ventricular
activations of the heart 10.
The compare stage 70 of the microprocessor then determines if the
time between the last two immediately successive ventricular
activations is greater than the minimum time interval and less than
the maximum time interval. As soon as the microprocessor 64 finds
an R to R interval greater than the preselected minimum time
interval (I.sub.min) and less than the preselected maximum time
interval (I.sub.max), the charge delivery control stage 72 of
microprocessor 64 causes the discharge circuit 76 to immediately
initiate the discharge of the electrical energy stored in the
storage capacitor of circuit 74 for applying the cardioverting
electrical energy to electrodes 42 and 48 and thus to the atria 16
and 18 of the heart 10. Since the microprocessor 64 is able to
process the R to R interval data very quickly after the occurrence
of each detected ventricular activation, the discharge circuit 76
will apply the cardioverting electrical energy to the atria of the
heart substantially coincident or in synchronism with the detected
ventricular activation establishing the R to R interval satisfying
the discharge criteria.
The minimum and maximum R to R intervals may also be selected
automatically as fully disclosed in U.S. Pat. No. 5,207,219 which
is assigned to the assignee of the present invention and
incorporated herein by reference. As fully disclosed therein, the R
to R interval timing prior to cardioversion assures safe
cardioversion by avoiding the application of the cardioverting
energy when the heart may be vulnerable to induced ventricular
fibrillation.
The cardioverting electrical energy is preferably applied for a
fixed time period using a time symmetrical biphasic waveform.
Because the electrodes 42 and 48 are either on the inner surface or
outer surface of the pericardium, energies between only one and
five joules, depending upon the patient, are required for
successful cardioversion. These energy levels are much less than
the energy levels of fifty to three hundred and sixty joules
generally required for external cardioversion.
As can thus be seen from the foregoing, the post-surgery
cardioverting system and method of the present invention satisfies
a long felt need in the art for safe and effective treatment of
post-heart surgery fibrillation. The system and method of the
present invention avoids the need for drug therapy. Further, the
option of external cardioversion with high energy requirements no
longer need be considered. As a result, the post-heart surgery
patient suffering from atrial fibrillation is no longer required to
endure the effects of such a condition. The fibrillation, by virtue
of the present invention, may be effectively terminated without
prolonging the patient's recovery. When the patient has
sufficiently recovered so as to no longer require pacing or
cardioversion, the heart wires and cardioverting leads may be
pulled out of the patient's chest.
While a particular embodiment of the present invention has been
shown and described, modifications may be made. For example, the
system and method of the present invention may also be utilized to
advantage to terminate ventricular tachycardia or even ventricular
fibrillation during the post-surgery period. In such an
application, the elongated electrodes would be disposed along the
pericardium to overlie the ventricles. The electrodes may be
releasably anchored to the pericardium as disclosed herein to
enable the electrodes to be removed from the patient by pulling on
the leads to which the electrodes are attached. Hence, it is
therefore intended in the appended claims to cover all such changes
and modifications which fall within the true spirit and scope of
the invention.
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