U.S. patent application number 10/011533 was filed with the patent office on 2002-08-08 for power supply for a subcutaneous implantable cardioverter-defibrillator.
This patent application is currently assigned to Cameron Health, Inc.. Invention is credited to Bardy, Gust H., Cappato, Riccardo, Rissmann, William J..
Application Number | 20020107545 10/011533 |
Document ID | / |
Family ID | 25474894 |
Filed Date | 2002-08-08 |
United States Patent
Application |
20020107545 |
Kind Code |
A1 |
Rissmann, William J. ; et
al. |
August 8, 2002 |
Power supply for a subcutaneous implantable
cardioverter-defibrillator
Abstract
A power supply for an implantable cardioverter-defibrillator for
subcutaneous positioning between the third rib and the twelfth rib
and for providing cardioversion/defibrillation energy to the heart,
the power supply comprising a capacitor subsystem for storing the
cardioversion/defibrillation energy for delivery to the patient's
heart; and a battery subsystem electrically coupled to the
capacitor subsystem for providing electrical energy to the
capacitor subsystem.
Inventors: |
Rissmann, William J.; (Coto
de Caza, CA) ; Bardy, Gust H.; (Seattle, WA) ;
Cappato, Riccardo; (Ferrara, IT) |
Correspondence
Address: |
BROBECK, PHLEGER & HARRISON LLP
12390 EL CAMINO REAL
SAN DIEGO
CA
92130
US
|
Assignee: |
Cameron Health, Inc.
|
Family ID: |
25474894 |
Appl. No.: |
10/011533 |
Filed: |
November 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10011533 |
Nov 5, 2001 |
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09663607 |
Sep 18, 2000 |
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10011533 |
Nov 5, 2001 |
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09663606 |
Sep 18, 2000 |
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Current U.S.
Class: |
607/5 |
Current CPC
Class: |
A61N 1/3968 20130101;
A61N 1/3956 20130101; A61N 1/3906 20130101; A61N 1/3756 20130101;
A61N 1/3975 20130101; A61N 1/375 20130101; A61N 1/378 20130101 |
Class at
Publication: |
607/5 |
International
Class: |
A61N 001/39 |
Claims
What is claimed is:
1. A power supply for an implantable cardioverter-defibrillator for
subcutaneous positioning between the third rib and the twelfth rib
and for providing cardioversion/defibrillation energy to the heart,
the power supply comprising: a capacitor subsystem for storing the
cardioversion/defibrillation energy for delivery to the patient's
heart; and a battery subsystem electrically coupled to the
capacitor subsystem for providing electrical energy to the
capacitor subsystem.
2. The power supply of claim 1 , wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 350 joules.
3. The power supply of claim 2, wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 20 joules.
4. The power supply of claim 2, wherein the
cardioversion/defibrillation energy is approximately 20 to
approximately 40 joules.
5. The power supply of claim 2, wherein the
cardioversion/defibrillation energy is approximately 210 to
approximately 250 joules.
6. The power supply of claim 2, wherein the
cardioversion/defibrillation energy is approximately 250 to
approximately 300 joules.
7. The power supply of claim 2, wherein the
cardioversion/defibrillation energy is approximately 300 to
approximately 350 joules.
8. The power supply of claim 1, wherein the capacitor subsystem has
an effective capacitance of approximately 25 microfarads to
approximately 200 microfarads.
9. The power supply of claim 1, wherein the capacitor subsystem
comprises one or more film capacitor(s).
10. The power supply of claim 1, wherein the capacitor subsystem
comprises one or more aluminum electrolytic capacitor(s).
11. The power supply of claim 1, wherein the capacitor subsystem
comprises one or more wet tantalum capacitor(s).
12. The power supply of claim 1, wherein the battery subsystem
comprises one or more LiSVO battery(ies).
13. The power supply of claim 1, wherein the battery subsystem
comprises one or more LiMnO.sub.2 battery(ies).
14. The power supply of claim 1, wherein the battery subsystem
comprises one or more LiI.sub.2 battery(ies).
15. The power supply of claim 1, wherein the battery subsystem
comprises one or more LICF.sub.x battery(ies).
16. The power supply of claim 1, wherein the battery subsystem
comprises one or more thin film battery(ies).
17. A power supply for an implantable cardioverter-defibrillator
for subcutaneous positioning outside the ribcage and between the
third rib and the twelfth rib within a patient and using a lead
system that does not directly contact the patient's heart or reside
in the intrathoracic blood vessels, and for providing
cardioversion/defibrillation energy to the heart, the power supply
comprising: a capacitor subsystem for storing the
cardioversion/defibrillation energy for delivery to the patient's
heart; and a battery subsystem electrically coupled to the
capacitor subsystem for providing electrical energy to the
capacitor subsystem.
18. The power supply of claim 17, wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 350 joules.
19. The power supply of claim 18, wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 20 joules.
20. The power supply of claim 18, wherein the
cardioversion/defibrillation energy is approximately 20 to
approximately 40 joules.
21. The power supply of claim 18, wherein the
cardioversion/defibrillation energy is approximately 210 to
approximately 250 joules.
22. The power supply of claim 18, wherein the
cardioversion/defibrillation energy of approximately 250 to
approximately 300 joules.
23. The power supply of claim 18, wherein the
cardioversion/defibrillation energy is approximately 300 to
approximately 350 joules.
24. The power supply of claim 17, wherein the capacitor subsystem
has an effective capacitance of approximately 25 microfarads to
approximately 200 microfarads.
25. The power supply of claim 17, wherein the capacitor subsystem
comprises one or more film capacitor(s).
26. The power supply of claim 17, wherein the capacitor subsystem
comprises one or more aluminum electrolytic capacitor(s).
27. The power supply of claim 17, wherein the capacitor subsystem
comprises one or more wet tantalum capacitor(s).
28. The power supply of claim 17, wherein the battery subsystem
comprises one or more LiSVO battery(ies).
29. The power supply of claim 17, wherein the battery subsystem
comprises one or more LiMnO.sub.2 battery(ies).
30. The power supply of claim 17, wherein the battery subsystem
comprises one or more LiI.sub.2 battery(ies).
31. The power supply of claim 17, wherein the battery subsystem
comprises one or more LiCF.sub.x battery(ies).
32. The power supply of claim 17, wherein the battery subsystem
comprises one or more thin film battery(ies).
33. A voltage output system for an implantable heart stimulator for
subcutaneous positioning between the third rib and the twelfth rib
within a patient and employing a lead system that does not directly
contact the patient's heart or reside in the intrathoracic blood
vessels, comprising: an energy storage system for storing
electrical energy to generate an electrical stimulation pulse for
delivery to the patient's heart; and an energy source system
operably connected to the energy storage system for providing the
electrical energy to the energy storage system.
34. The voltage output system of claim 33, wherein the electrical
stimulation pulse is approximately 40 to approximately 210
joules.
35. The voltage output system of claim 34, wherein the electrical
stimulation pulse is approximately 0.5 to approximately 20
joules.
36. The voltage output system of claim 34, wherein the electrical
stimulation pulse is approximately 20 to approximately 40
joules.
37. The voltage output system of claim 34, wherein the electrical
stimulation pulse is approximately 210 to approximately 250
joules.
38. The voltage output system of claim 34, wherein the electrical
stimulation pulse is approximately 250 to approximately 300
joules.
39. The voltage output system of claim 34, wherein the electrical
stimulation pulse is approximately 300 to approximately 350
joules.
40. The voltage output system of claim 34, wherein the energy
storage system has an effective capacitance of approximately 25
microfarads to approximately 200 microfarads.
41. The voltage output system of claim 33, wherein the capacitor
subsystem comprises one or more film capacitor(s).
42. The voltage output system of claim 33, wherein the capacitor
subsystem comprises one or more aluminum electrolytic
capacitors(s).
43. The voltage output system of claim 33, wherein the capacitor
subsystem comprises one or more wet tantalum capacitor(s).
44. The voltage output system of claim 33, wherein the battery
subsystem comprises one or more LiSVO battery(ies).
45. The voltage output system of claim 33, wherein the battery
subsystem comprises one or more LiMnO.sub.2 battery(ies).
46. The voltage output system of claim 33, wherein the battery
subsystem comprises one or more LiI.sub.2 battery(ies).
47. The voltage output system of claim 33, wherein the battery
subsystem comprises one or more LiCF.sub.x battery(ies).
48. The voltage output system of claim 33, wherein the battery
subsystem comprises one or more thin film battery(ies).
49. An implantable cardioverter-defibrillator for subcutaneous
positioning outside the ribcage and between the third rib and the
twelfth rib within a patient, the implantable
cardioverter-defibrillator comprising: a housing having an
electrically conductive surface on an outer surface of the housing;
a lead assembly electrically coupled to the housing and having an
electrode, wherein the lead assembly does not directly contact the
patient's heart or reside in the intrathoracic blood vessels; a
capacitor subsystem located within the housing and electrically
coupled to the electrically conductive surface and the electrode
for storing cardioversion/defibrillation energy and for delivering
the cardioversion/defibrillation energy to the patient's heart
through the electrically conductive surface and the electrode; and
a battery subsystem electrically coupled to the capacitor subsystem
for providing the cardioversion/defibrillation energy to the
capacitor subsystem.
50. The implantable cardioverter-defibrillator of claim 49, wherein
the cardioversion/defibrillation energy is approximately 0.5 to
approximately 350 joules.
51. The implantable cardioverter-defibrillator of claim 50, wherein
the cardioversion/defibrillation energy is approximately 0.5 to
approximately 20 joules.
52. The implantable cardioverter-defibrillator of claim 50, wherein
the cardioversion/defibrillation energy is approximately 20 to
approximately 40 joules.
53. The implantable cardioverter-defibrillator of claim 50, wherein
the cardioversion/defibrillation energy is approximately 210 to
approximately 250 joules.
54. The implantable cardioverter-defibrillator of claim 50, wherein
the cardioversion/defibrillation energy of approximately 250 to
approximately 300 joules.
55. The implantable cardioverter-defibrillator of claim 50, wherein
the cardioversion/defibrillation energy is approximately 300 to
approximately 350 joules.
56. The implantable cardioverter-defibrillator of claim 50, wherein
the capacitor subsystem has an effective capacitance of
approximately 25 microfarads to approximately 200 microfarads.
57. The implantable cardioverter-defibrillator of claim 49, wherein
the capacitor subsystem comprises one or more film
capacitor(s).
58. The implantable cardioverter-defibrillator of claim 49, wherein
the capacitor subsystem comprises one or more aluminum electrolytic
capacitor(s).
59. The implantable cardioverter-defibrillator of claim 49, wherein
the capacitor subsystem comprises one or more wet tantalum
capacitor(s).
60. The implantable cardioverter-defibrillator of claim 49, wherein
the battery subsystem comprises one or more LiSVO battery(ies).
61. The implantable cardioverter-defibrillator of claim 49, wherein
the battery subsystem comprises one or more LiMnO.sub.2
battery(ies).
62. The implantable cardioverter-defibrillator of claim 49, wherein
the battery subsystem comprises one or more LiI.sub.2
battery(ies).
63. The implantable cardioverter-defibrillator of claim 49, wherein
the battery subsystem comprises one or more LiCF.sub.x
battery(ies).
64. The implantable cardioverter-defibrillator of claim 49, wherein
the battery subsystem comprises one or more thin film
battery(ies).
65. A method of supplying power for an implantable
cardioverter-defibrilla- tor for subcutaneous positioning outside
the ribcage and between the third rib and the twelfth rib within a
patient and using a lead system that does not directly contact the
patient's heart or reside in the intrathoracic blood vessels, the
method comprising: generating cardioversion/defibrillation energy;
storing the cardioversion/defibrilla- tion energy; and delivering
the cardioversion/defibrillation energy to the patient's heart.
66. The method of claim 65, wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 350 joules.
67. The method of claim 66, wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 20 joules.
68. The method of claim 66, wherein the
cardioversion/defibrillation energy is approximately 20 to
approximately 40 joules.
69. The method of claim 66, wherein the
cardioversion/defibrillation energy is approximately 210 to
approximately 250 joules.
70. The method of claim 66, wherein the
cardioversion/defibrillation energy of approximately 250 to
approximately 300 joules.
71. The method of claim 66, wherein the
cardioversion/defibrillation energy is approximately 300 to
approximately 350 joules.
72. The method of claim 65, wherein the energy storage system has
an effective capacitance of approximately 25 microfarads to
approximately 200 microfarads.
73. The method of claim 65, wherein the capacitor subsystem
comprises one or more film capacitor(s).
74. The method of claim 65, wherein the capacitor subsystem
comprises one or more aluminum electrolytic capacitor(s).
75. The method of claim 65, wherein the capacitor subsystem
comprises one or more wet tantalum capacitor(s).
76. The method of claim 65, wherein the battery subsystem comprises
one or more LiSVO battery(ies).
77. The method of claim 65, wherein the battery subsystem comprises
one or more LiMnO.sub.2 battery(ies).
78. The method of claim 65, wherein the battery subsystem comprises
one or more LiI.sub.2 battery(ies).
79. The method of claim 65, wherein the battery subsystem comprises
one or more LiCF.sub.x battery(ies).
80. The method of claim 65, wherein the battery subsystem comprises
one or more thin film battery(ies).
81. A power supply for an implantable cardioverter-defibrillator
for subcutaneous positioning outside the ribcage and between the
third rib and the twelfth rib within a patient and using a lead
system that does not directly contact the patient's heart or
resided in the intrathoracic blood vessels, and for providing
cardioversion/defibrillation energy to the heart, the method
comprising: means for storing the cardioversion/defibrillation
energy and delivering the cardioversion/defibrillation energy to
the patient's heart; means for providing
cardioversion/defibrillation energy to the means for storing the
cardioversion/defibrillation energy.
82. The power supply of claim 81, wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 350 joules.
83. The power supply of claim 82, wherein the
cardioversion/defibrillation energy is approximately 0.5 to
approximately 20 joules.
84. The power supply of claim 82, wherein the
cardioversion/defibrillation energy is approximately 20 to
approximately 40 joules.
85. The power supply of claim 82, wherein the
cardioversion/defibrillation energy is approximately 210 to
approximately 250 joules.
86. The power supply of claim 82, wherein the
cardioversion/defibrillation energy of approximately 250 to
approximately 300 joules.
87. The power supply of claim 82, wherein the
cardioversion/defibrillation energy is approximately 300 to
approximately 350 joules.
88. The power supply of claim 81, wherein the means for storing the
cardioversion/defibrillation energy has an effective capacitance of
approximately 25 microfarads to approximately 200 microfarads.
89. The power supply of claim 81, wherein the capacitor subsystem
comprises one or more film capacitor(s).
90. The power supply of claim 81, wherein the capacitor subsystem
comprises one or more aluminum electrolytic capacitor(s).
91. The power supply of claim 81, wherein the capacitor subsystem
comprises one or more wet tantalum capacitor(s).
92. The power supply of claim 81, wherein the battery subsystem
comprises one or more LiSVO battery(ies).
93. The power supply of claim 81, wherein the battery subsystem
comprises one or more LiMnO.sub.2 battery(ies).
94. The power supply of claim 81, wherein the battery subsystem
comprises one or more LiI.sub.2 battery(ies).
95. The power supply of claim 81, wherein the battery subsystem
comprises one or more LiCF.sub.x battery(ies).
96. The power supply of claim 81, wherein the battery subsystem
comprises one or more thin film battery(ies).
97. The power supply of claim 81, wherein the implantable
cardioverter-defibrillator is positioned subcutaneously between the
third and fifth ribs.
98. The power supply of claim 81, wherein the implantable
cardioverter-defibrillator is positioned subcutaneously between the
fourth and sixth ribs.
99. The power supply of claim 81, wherein the implantable
cardioverter-defibrillator is positioned subcutaneously between the
sixth and eighth ribs.
100. The power supply of claim 81, wherein the implantable
cardioverter-defibrillator is positioned subcutaneously between the
eighth and tenth ribs.
101. The power supply of claim 81, wherein the implantable
cardioverter-defibrillator is positioned subcutaneously between the
tenth and twelfth ribs.
102. The power supply of claim 81, wherein the implantable
cardioverter-defibrillator provides anti-tachycardia pacing energy
to the heart for treatment of atrial fibrillation.
103. The power supply of claim 81, wherein the implantable
cardioverter-defibrillator provides anti-tachycardia pacing energy
to the heart for treatment of ventricular tachycardia.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of U.S.
patent application entitled "SUBCUTANEOUS ONLY IMPLANTABLE
CARDIOVERTER-DEFIBRILLATOR AND OPTIONAL PACER," having Ser. No.
09/663,607, filed Sep. 18, 2000, pending, U.S. patent application
entitled "UNITARY SUBCUTANEOUS ONLY IMPLANTABLE
CARDIOVERTER-DEFIBRILLATO- R AND OPTIONAL PACER," having Ser. No.
09/663,606, filed Sep. 18, 2000, pending, and U.S. patent
application entitled "POWER SUPPLY FOR AN IMPLANTABLE SUBCUTANEOUS
CARDIOVERTER-DEFIBRILLATOR," filed Aug. 27, 2001, pending, of which
all applications are assigned to the assignee of the present
application, and the disclosures of all applications are hereby
incorporated by reference.
FIELD OF THE INVENTION method for performing electrical
cardioversion/defibrillation and optional pacing of the heart via a
totally subcutaneous non-transvenous system.
BACKGROUND OF THE INVENTION
[0002] Defibrillation/cardioversion is a technique employed to
counter arrhythmic heart conditions including some tachycardias in
the atria and/or ventricles. Typically, electrodes are employed to
stimulate the heart with electrical impulses or shocks, of a
magnitude substantially greater than pulses used in cardiac pacing.
Shocks used for defibrillation therapy can comprise a biphasic
truncated exponential waveform. As for pacing, a constant current
density is desired to reduce or eliminate variability due to the
electrode/tissue interface.
[0003] Defibrillation/cardioversion systems include body
implantable electrodes that are connected to a hermetically sealed
container housing the electronics, battery supply and capacitors.
The entire system is referred to as implantable
cardioverter/defibrillators (ICDs). The electrodes used in ICDs can
be in the form of patches applied directly to epicardial tissue,
or, more commonly, are on the distal regions of small cylindrical
insulated catheters that typically enter the subclavian venous
system, pass through the superior vena cava and into one or more
endocardial areas of the heart. Such electrode systems are called
intravascular or transvenous electrodes. U.S. Pat. Nos. 4,603,705,
4,693,253, 4,944,300, 5,105,810, the disclosures of which are all
incorporated herein by reference, disclose intravascular or
transvenous electrodes, employed either alone, in combination with
other intravascular or transvenous electrodes, or in combination
with an epicardial patch or subcutaneous electrodes. Compliant
epicardial defibrillator electrodes are disclosed in U.S. Pat. Nos.
4,567,900 and 5,618,287, the disclosures of which are incorporated
herein by reference. A sensing epicardial electrode configuration
is disclosed in U.S. Pat. No. 5,476,503, the disclosure of which is
incorporated herein by reference.
[0004] In addition to epicardial and transvenous electrodes,
subcutaneous electrode systems have also been developed. For
example, U.S. Pat. Nos. 5,342,407 and 5,603,732, the disclosures of
which are incorporated herein by reference, teach the use of a
pulse monitor/generator surgically implanted into the abdomen and
subcutaneous electrodes implanted in the thorax. This system is far
more complicated to use than current ICD systems using transvenous
lead systems together with an active can electrode and therefore it
has no practical use. It has in fact never been used because of the
surgical difficulty of applying such a device (3 incisions), the
impractical abdominal location of the generator and the
electrically poor sensing and defibrillation aspects of such a
system.
[0005] Recent efforts to improve the efficiency of ICDs have led
manufacturers to produce ICDs which are small enough to be
implanted in the pectoral region. In addition, advances in circuit
design have enabled the housing of the ICD to form a subcutaneous
electrode. Some examples of ICDs in which the housing of the ICD
serves as an optional additional electrode are described in U.S.
Pat. Nos. 5,133,353, 5,261,400, 5,620,477, and 5,658,321 the
disclosures of which are incorporated herein by reference.
[0006] ICDs are now an established therapy for the management of
life threatening cardiac rhythm disorders, primarily ventricular
fibrillation (V-Fib). ICDs are very effective at treating V-Fib,
but are therapies that still require significant surgery.
[0007] As ICD therapy becomes more prophylactic in nature and used
in progressively less ill individuals, especially children at risk
of cardiac arrest, the requirement of ICD therapy to use
intravenous catheters and transvenous leads is an impediment to
very long term management as most individuals will begin to develop
complications related to lead system malfunction sometime in the
5-10 year time frame, often earlier. In addition, chronic
transvenous lead systems, their reimplantation and removals, can
damage major cardiovascular venous systems and the tricuspid valve,
as well as result in life threatening perforations of the great
vessels and heart. Consequently, use of transvenous lead systems,
despite their many advantages, are not without their chronic
patient management limitations in those with life expectancies of
>5 years. The problem of lead complications is even greater in
children where body growth can substantially alter transvenous lead
function and lead to additional cardiovascular problems and
revisions. Moreover, transvenous ICD systems also increase cost and
require specialized interventional rooms and equipment as well as
special skill for insertion. These systems are typically implanted
by cardiac electrophysiologists who have had a great deal of extra
training.
[0008] In addition to the background related to ICD therapy, the
present invention requires a brief understanding of a related
therapy, the automatic external defibrillator (AED). AEDs employ
the use of cutaneous patch electrodes, rather than implantable lead
systems, to effect defibrillation under the direction of a
bystander user who treats the patient suffering from V-Fib with a
portable device containing the necessary electronics and power
supply that allows defibrillation. AEDs can be nearly as effective
as an ICD for defibrillation if applied to the victim of
ventricular fibrillation promptly, i.e., within 2 to 3 minutes of
the onset of the ventricular fibrillation.
[0009] AED therapy has great appeal as a tool for diminishing the
risk of death in public venues such as in air flight. However, an
AED must be used by another individual, not the person suffering
from the potential fatal rhythm. It is more of a public health tool
than a patient-specific tool like an ICD. Because >75% of
cardiac arrests occur in the home, and over half occur in the
bedroom, patients at risk of cardiac arrest are often alone or
asleep and can not be helped in time with an AED. Moreover, its
success depends to a reasonable degree on an acceptable level of
skill and calm by the bystander user.
[0010] What is needed therefore, especially for children and for
prophylactic long term use for those at risk of cardiac arrest, is
a combination of the two forms of therapy which would provide
prompt and near-certain defibrillation, like an ICD, but without
the long-term adverse sequelae of a transvenous lead system while
simultaneously using most of the simpler and lower cost technology
of an AED. What is also needed is a cardioverter/defibrillator that
is of simple design and can be comfortably implanted in a patient
for many years.
SUMMARY OF THE INVENTION
[0011] A power supply for an implantable cardioverter-defibrillator
for subcutaneous positioning between the third rib and the twelfth
rib and for providing cardioversion/defibrillation energy to the
heart, the power supply comprising a capacitor subsystem for
storing the cardioversion/defibrillation energy for delivery to the
patient's heart; and a battery subsystem electrically coupled to
the capacitor subsystem for providing electrical energy to the
capacitor subsystem.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For a better understanding of the invention, reference is
now made to the drawings where like numerals represent similar
objects throughout the figures where:
[0013] FIG. 1 is a schematic view of a Subcutaneous ICD (S-ICD) of
the present invention;
[0014] FIG. 2 is a schematic view of an alternate embodiment of a
subcutaneous electrode of the present invention;
[0015] FIG. 3 is a schematic view of an alternate embodiment of a
subcutaneous electrode of the present invention;
[0016] FIG. 4 is a schematic view of the S-ICD and lead of FIG. 1
subcutaneously implanted in the thorax of a patient;
[0017] FIG. 5 is a schematic view of the S-ICD and lead of FIG. 2
subcutaneously implanted in an alternate location within the thorax
of a patient;
[0018] FIG. 6 is a schematic view of the S-ICD and lead of FIG. 3
subcutaneously implanted in the thorax of a patient;
[0019] FIG. 7 is a schematic view of the method of making a
subcutaneous path from the preferred incision and housing
implantation point to a termination point for locating a
subcutaneous electrode of the present invention;
[0020] FIG. 8 is a schematic view of an introducer set for
performing the method of lead insertion of any of the described
embodiments;
[0021] FIG. 9 is a schematic view of an alternative S-ICD of the
present invention illustrating a lead subcutaneously and
serpiginously implanted in the thorax of a patient for use
particularly in children;
[0022] FIG. 10 is a schematic view of an alternate embodiment of an
S-ICD of the present invention;
[0023] FIG. 11 is a schematic view of the S-ICD of FIG. 10
subcutaneously implanted in the thorax of a patient;
[0024] FIG. 12 is a schematic view of yet a further embodiment
where the canister of the S-ICD of the present invention is shaped
to be particularly useful in placing subcutaneously adjacent and
parallel to a rib of a patient; and
[0025] FIG. 13 is a schematic of a different embodiment where the
canister of the S-ICD of the present invention is shaped to be
particularly useful in placing subcutaneously adjacent and parallel
to a rib of a patient.
[0026] FIG. 14 is a schematic view of a Unitary Subcutaneous ICD
(US-ICD) of the present invention;
[0027] FIG. 15 is a schematic view of the US-ICD subcutaneously
implanted in the thorax of a patient;
[0028] FIG. 16 is a schematic view of the method of making a
subcutaneous path from the preferred incision for implanting the
US-ICD.
[0029] FIG. 17 is a schematic view of an introducer for performing
the method of US-ICD implantation; and
[0030] FIG. 18 is an exploded schematic view of an alternate
embodiment of the present invention with a plug-in portion that
contains operational circuitry and means for generating
cardioversion/defibrillation shock waves.
[0031] FIG. 19 is a block diagram showing the power supply of an
implantable cardioverter/defibrillator in an embodiment according
to the present invention.
[0032] FIG. 20 is a table that shows several examples of
embodiments of the present invention comprising various numbers of
capacitors and pulse widths.
[0033] FIG. 21 is a graph that shows several examples of
embodiments of the present invention comprising various numbers of
capacitors and pulse widths.
[0034] FIG. 22 is a table that shows several examples for the
battery subsystem comprising two battery cells, as well as varying
efficiencies and charge times in an embodiment of the present
invention.
[0035] FIG. 23 is a table that shows several examples for the
battery subsystem comprising various numbers of battery cells,
efficiencies and charge times in an embodiment of the present
invention.
[0036] FIG. 24 is a diagram that shows one example of a physical
layout for the battery subsystem and the capacitor subsystem in an
embodiment of the present invention.
[0037] FIG. 25 shows one example of a physical layout for the
battery subsystem 102 and the capacitor subsystem 104 in an
embodiment of the present invention.
[0038] FIG. 26 is a table that shows various examples of sizes for
the combined capacitor subsystem and the battery subsystem in an
embodiment of the present invention.
[0039] FIG. 27 is a table that shows several examples of the
capacitor subsystem and the battery subsystem at different energy
levels in an embodiment of the present invention.
DETAILED DESCRIPTION
[0040] Turning now to FIG. 1, the S-ICD of the present invention is
illustrated. The S-ICD consists of an electrically active canister
11 and a subcutaneous electrode 13 attached to the canister. The
canister has an electrically active surface 15 that is electrically
insulated from the electrode connector block 17 and the canister
housing 16 via insulating area 14. The canister can be similar to
numerous electrically active canisters commercially available in
that the canister will contain a battery supply, capacitor and
operational circuitry. Alternatively, the canister can be thin and
elongated to conform to the intercostal space. The circuitry will
be able to monitor cardiac rhythms for tachycardia and
fibrillation, and if detected, will initiate charging the capacitor
and then delivering cardioversion /defibrillation energy through
the active surface of the housing and to the subcutaneous
electrode. Examples of such circuitry are described in U.S. Pat.
Nos. 4,693,253 and 5,105,810, the entire disclosures of which are
herein incorporated by reference. The canister circuitry can
provide cardioversion/ defibrillation energy in different types of
waveforms. In one embodiment, a 100 uF biphasic waveform is used of
approximately 10-20 ms total duration and with the initial phase
containing approximately 2/3 of the energy, however, any type of
waveform can be utilized such as monophasic, biphasic, multiphasic
or alternative waveforms as is known in the art.
[0041] In addition to providing cardioversion/ defibrillation
energy, the circuitry can also provide transthoracic cardiac pacing
energy. The optional circuitry will be able to monitor the heart
for bradycardia and/or tachycardia rhythms. Once a bradycardia or
tachycardia rhythm is detected, the circuitry can then deliver
appropriate pacing energy at appropriate intervals through the
active surface and the subcutaneous electrode. Pacing stimuli will
be biphasic in one embodiment and similar in pulse amplitude to
that used for conventional transthoracic pacing.
[0042] This same circuitry can also be used to deliver low
amplitude shocks on the T-wave for induction of ventricular
fibrillation for testing S-ICD performance in treating V-Fib as is
described in U.S. Pat. No. 5,129,392, the entire disclosure of
which is hereby incorporated by reference. Also the circuitry can
be provided with rapid induction of ventricular fibrillation or
ventricular tachycardia using rapid ventricular pacing. Another
optional way for inducing ventricular fibrillation would be to
provide a continuous low voltage, i.e., about 3 volts, across the
heart during the entire cardiac cycle.
[0043] Another optional aspect of the present invention is that the
operational circuitry can detect the presence of atrial
fibrillation as described in Olson, W. et al. "Onset And Stability
For Ventricular Tachyarrhythmia Detection in an Implantable
Cardioverter and Defibrillator," Computers in Cardiology (1986) pp.
167-170. Detection can be provided via R-R Cycle length instability
detection algorithms. Once atrial fibrillation has been detected,
the operational circuitry will then provide QRS synchronized atrial
defibrillation/cardioversion using the same shock energy and
waveshape characteristics used for ventricular defibrillation/
cardioversion.
[0044] The sensing circuitry will utilize the electronic signals
generated from the heart and will primarily detect QRS waves. In
one embodiment, the circuitry will be programmed to detect only
ventricular tachycardias or fibrillations. The detection circuitry
will utilize in its most direct form, a rate detection algorithm
that triggers charging of the capacitor once the ventricular rate
exceeds some predetermined level for a fixed period of time: for
example, if the ventricular rate exceeds 240 bpm on average for
more than 4 seconds. Once the capacitor is charged, a confirmatory
rhythm check would ensure that the rate persists for at least
another 1 second before discharge. Similarly, termination
algorithms could be instituted that ensure that a rhythm less than
240 bpm persisting for at least 4 seconds before the capacitor
charge is drained to an internal resistor. Detection, confirmation
and termination algorithms as are described above and in the art
can be modulated to increase sensitivity and specificity by
examining QRS beat-to-beat uniformity, QRS signal frequency
content, R-R interval stability data, and signal amplitude
characteristics all or part of which can be used to increase or
decrease both sensitivity and specificity of S-ICD arrhythmia
detection function.
[0045] In addition to use of the sense circuitry for detection of
V-Fib or V-Tach by examining the QRS waves, the sense circuitry can
check for the presence or the absence of respiration. The
respiration rate can be detected by monitoring the impedance across
the thorax using subthreshold currents delivered across the active
can and the high voltage subcutaneous lead electrode and monitoring
the frequency in undulation in the waveform that results from the
undulations of transthoracic impedance during the respiratory
cycle. If there is no undulation, then the patent is not respiring
and this lack of respiration can be used to confirm the QRS
findings of cardiac arrest. The same technique can be used to
provide information about the respiratory rate or estimate cardiac
output as described in U.S. Pat. Nos. 6,095,987, 5,423,326,
4,450,527, the entire disclosures of which are incorporated herein
by reference.
[0046] The canister of the present invention can be made out of
titanium alloy or other presently preferred electrically active
canister designs. However, it is contemplated that a malleable
canister that can conform to the curvature of the patient's chest
will be preferred. In this way the patient can have a comfortable
canister that conforms to the shape of the patient's rib cage.
Examples of conforming canisters are provided in U.S. Pat. No.
5,645,586, the entire disclosure of which is herein incorporated by
reference. Therefore, the canister can be made out of numerous
materials such as medical grade plastics, metals, and alloys. In
the preferred embodiment, the canister is smaller than 60 cc volume
having a weight of less than 100 gms for long term wearability,
especially in children. The canister and the lead of the S-ICD can
also use fractal or wrinkled surfaces to increase surface area to
improve defibrillation capability. Because of the primary
prevention role of the therapy and the likely need to reach
energies over 40 Joules, a feature of the preferred embodiment is
that the charge time for the therapy, intentionally e relatively
long to allow capacitor charging within the limitations of device
size. Examples of small ICD housings are disclosed in U.S. Pat.
Nos. 5,597,956 and 5,405,363, the entire disclosures of which are
herein incorporated by reference.
[0047] Different subcutaneous electrodes 13 of the present
invention are illustrated in FIGS. 1-3. Turning to FIG. 1, the lead
21 for the subcutaneous electrode is preferably composed of
silicone or polyurethane insulation. The electrode is connected to
the canister at its proximal end via connection port 19 which is
located on an electrically insulated area 17 of the canister. The
electrode illustrated is a composite electrode with three different
electrodes attached to the lead. In the embodiment illustrated, an
optional anchor segment 52 is attached at the most distal end of
the subcutaneous electrode for anchoring the electrode into soft
tissue such that the electrode does not dislodge after
implantation.
[0048] The most distal electrode on the composite subcutaneous
electrode is a coil electrode 27 that is used for delivering the
high voltage cardioversion/defibrillation energy across the heart.
The coil cardioversion/defibrillation electrode is about 5-10 cm in
length. Proximal to the coil electrode are two sense electrodes, a
first sense electrode 25 is located proximally to the coil
electrode and a second sense electrode 23 is located proximally to
the first sense electrode. The sense electrodes are spaced far
enough apart to be able to have good QRS detection. This spacing
can range from 1 to 10 cm with 4 cm being presently preferred. The
electrodes may or may not be circumferential with the preferred
embodiment. Having the electrodes non-circumferential and
positioned outward, toward the skin surface, is a means to minimize
muscle artifact and enhance QRS signal quality. The sensing
electrodes are electrically isolated from the
cardioversion/defibrillation electrode via insulating areas 29.
Similar types of cardioversion/defibrillation electrodes are
currently commercially available in a transvenous configuration.
For example, U.S. Pat. No. 5,534,022, the entire disclosure of
which is herein incorporated by reference, disclosures a composite
electrode with a coil cardioversion/defibrillation electrode and
sense electrodes. Modifications to this arrangement is contemplated
within the scope of the invention. One such modification is
illustrated in FIG. 2 where the two sensing electrodes 25 and 23
are non-circumferential sensing electrodes and one is located at
the distal end, the other is located proximal thereto with the coil
electrode located in between the two sensing electrodes. In this
embodiment the sense electrodes are spaced about 6 to about 12 cm
apart depending on the length of the coil electrode used. FIG. 3
illustrates yet a further embodiment where the two sensing
electrodes are located at the distal end to the composite electrode
with the coil electrode located proximally thereto. Other
possibilities exist and are contemplated within the present
invention. For example, having only one sensing electrode, either
proximal or distal to the coil cardioversion/defibrillation
electrode with the coil serving as both a sensing electrode and a
cardioversion/defibrillation electrode.
[0049] It is also contemplated within the scope of the invention
that the sensing of QRS waves (and transthoracic impedance) can be
carried out via sense electrodes on the canister housing or in
combination with the cardioversion/defibrillation coil electrode
and/or the subcutaneous lead sensing electrode(s). In this way,
sensing could be performed via the one coil electrode located on
the subcutaneous electrode and the active surface on the canister
housing. Another possibility would be to have only one sense
electrode located on the subcutaneous electrode and the sensing
would be performed by that one electrode and either the coil
electrode on the subcutaneous electrode or by the active surface of
the canister. The use of sensing electrodes on the canister would
eliminate the need for sensing electrodes on the subcutaneous
electrode. It is also contemplated that the subcutaneous electrode
would be provided with at least one sense electrode, the canister
with at least one sense electrode, and if multiple sense electrodes
are used on either the subcutaneous electrode and/or the canister,
that the best QRS wave detection combination will be identified
when the S-ICD is implanted and this combination can be selected,
activating the best sensing arrangement from all the existing
sensing possibilities. Turning again to FIG. 2, two sensing
electrodes 26 and 28 are located on the electrically active surface
15 with electrical insulator rings 30 placed between the sense
electrodes and the active surface. These canister sense electrodes
could be switched off and electrically insulated during and shortly
after defibrillation/cardioversion shock delivery. The canister
sense electrodes may also be placed on the electrically inactive
surface of the canister. In the embodiment of FIG. 2, there are
actually four sensing electrodes, two on the subcutaneous lead and
two on the canister. In the preferred embodiment, the ability to
change which electrodes are used for sensing would be a
programmable feature of the S-ICD to adapt to changes in the
patient physiology and size (in the case of children) over time.
The programming could be done via the use of physical switches on
the canister, or as presently preferred, via the use of a
programming wand or via a wireless connection to program the
circuitry within the canister.
[0050] The canister could be employed as either a cathode or an
anode of the S-ICD cardioversion/defibrillation system. If the
canister is the cathode, then the subcutaneous coil electrode would
be the anode. Likewise, if the canister is the anode, then the
subcutaneous electrode would be the cathode.
[0051] The active canister housing will provide energy and voltage
intermediate to that available with ICDs and most AEDs. The typical
maximum voltage necessary for ICDs using most biphasic waveforms is
approximately 750 Volts with an associated maximum energy of
approximately 40 Joules. The typical maximum voltage necessary for
AEDs is approximately 2000-5000 Volts with an associated maximum
energy of approximately 200-360 Joules depending upon the model and
waveform used. The S-ICD of the present invention uses maximum
voltages in the range of about 350 to about 3500 Volts and is
associated with energies of about 0.5 to about 350 Joules. The
capacitance of the S-ICD could range from about 25 to about 200
micro farads.
[0052] The sense circuitry contained within the canister is highly
sensitive and specific for the presence or absence of life
threatening ventricular arrhythmias. Features of the detection
algorithm are programmable and the algorithm is focused on the
detection of V-FIB and high rate V-TACH (>240 bpm). Although the
S-ICD of the present invention may rarely be used for an actual
life threatening event, the simplicity of design and implementation
allows it to be employed in large populations of patients at modest
risk with modest cost by non-cardiac electrophysiologists.
Consequently, the S-ICD of the present invention focuses mostly on
the detection and therapy of the most malignant rhythm disorders.
As part of the detection algorithm's applicability to children, the
upper rate range is programmable upward for use in children, known
to have rapid supraventricular tachycardias and more rapid
ventricular fibrillation. Energy levels also are programmable
downward in order to allow treatment of neonates and infants.
[0053] Turning now to FIG. 4, the optimal subcutaneous placement of
the S-ICD of the present invention is illustrated. As would be
evidence to a person skilled in the art, the actual location of the
S-ICD is in a subcutaneous space that is developed during the
implantation process. The heart is not exposed during this process
and the heart is schematically illustrated in the figures only for
help in understanding where the canister and coil electrode are
three dimensionally located in the left mid-clavicular line
approximately at the level of the inframammary crease at
approximately the 5th rib. The lead 21 of the subcutaneous
electrode traverses in a subcutaneous path around the thorax
terminating with its distal electrode end at the posterior axillary
line ideally just lateral to the left scapula. This way the
canister and subcutaneous cardioversion/defibrillation electrode
provide a reasonably good pathway for current delivery to the
majority of the ventricular myocardium.
[0054] FIG. 5 illustrates a different placement of the present
invention. The S-ICD canister with the active housing is located in
the left posterior axillary line approximately lateral to the tip
of the inferior portion of the scapula. This location is especially
useful in children. The lead 21 of the subcutaneous electrode
traverses in a subcutaneous path around the thorax terminating with
its distal electrode end at the anterior precordial region, ideally
in the inframammary crease. FIG. 6 illustrates the embodiment of
FIG. 1 subcutaneously implanted in the thorax with the proximal
sense electrodes 23 and 25 located at approximately the left
axillary line with the cardioversion/defibrillatio- n electrode
just lateral to the tip of the inferior portion of the scapula.
[0055] FIG. 7 schematically illustrates the method for implanting
the S-ICD of the present invention. An incision 31 is made in the
left anterior axillary line approximately at the level of the
cardiac apex. This incision location is distinct from that chosen
for S-ICD placement and is selected specifically to allow both
canister location more medially in the left inframammary crease and
lead positioning more posteriorly via the introducer set (described
below) around to the left posterior axillary line lateral to the
left scapula. That said, the incision could be anywhere on the
thorax deemed reasonably by the implanting physician although in
the preferred embodiment, the S-ICD of the present invention will
be applied in this region. A subcutaneous pathway 33 is then
created medially to the inframmary crease for the canister and
posteriorly to the left posterior axillary line lateral to the left
scapula for the lead.
[0056] The S-ICD canister 11 is then placed subcutaneously at the
location of the incision or medially at the subcutaneous region at
the left inframmary crease. The subcutaneous electrode 13 is placed
with a specially designed curved introducer set 40 (see FIG. 8).
The introducer set comprises a curved trocar 42 and a stiff curved
peel away sheath 44. The peel away sheath is curved to allow for
placement around the rib cage of the patient in the subcutaneous
space created by the trocar. The sheath has to be stiff enough to
allow for the placement of the electrodes without the sheath
collapsing or bending. Preferably the sheath is made out of a
biocompatible plastic material and is perforated along its axial
length to allow for it to split apart into two sections. The trocar
has a proximal handle 41 and a curved shaft 43. The distal end 45
of the trocar is tapered to allow for dissection of a subcutaneous
path 33 in the patient. Preferably, the trocar is cannulated having
a central Lumen 46 and terminating in an opening 48 at the distal
end. Local anesthetic such as lidocaine can be delivered, if
necessary, through the lumen or through a curved and elongated
needle designed to anesthetize the path to be used for trocar
insertion should general anesthesia not be employed. The curved
peel away sheath 44 has a proximal pull tab 49 for breaking the
sheath into two halves along its axial shaft 47. The sheath is
placed over a guidewire inserted through the trocar after the
subcutaneous path has been created. The subcutaneous pathway is
then developed until it terminates subcutaneously at a location
that, if a straight line were drawn from the canister location to
the path termination point the line would intersect a substantial
portion of the left ventricular mass of the patient. The guidewire
is then removed leaving the peel away sheath. The subcutaneous lead
system is then inserted through the sheath until it is in the
proper location. Once the subcutaneous lead system is in the proper
location, the sheath is split in half using the pull tab 49 and
removed. If more than one subcutaneous electrode is being used, a
new curved peel away sheath can be used for each subcutaneous
electrode.
[0057] The S-ICD will have prophylactic use in adults where chronic
transvenous/epicardial ICD lead systems pose excessive risk or have
already resulted in difficulty, such as sepsis or lead fractures.
It is also contemplated that a major use of the S-ICD system of the
present invention will be for prophylactic use in children who are
at risk for having fatal arrhythmias, where chronic transvenous
lead systems pose significant management problems. Additionally,
with the use of standard transvenous ICDs in children, problems
develop during patient growth in that the lead system does not
accommodate the growth. FIG. 9 illustrates the placement of the
S-ICD subcutaneous lead system such that he problem that growth
presents to the lead system is overcome. The distal end of the
subcutaneous electrode is placed in the same location as described
above providing a good location for the coil
cardioversion/defibrillation electrode 27 and the sensing
electrodes 23 and 25. The insulated lead 21, however is no longer
placed in a taught configuration. Instead, the lead is
serpiginously placed with a specially designed introducer trocar
and sheath such that it has numerous waves or bends. As the child
grows, the waves or bends will straighten out lengthening the lead
system while maintaining proper electrode placement. Although it is
expected that fibrous scarring especially around the defibrillation
coil will help anchor it into position to maintain its posterior
position during growth, a lead system with a distal tine or screw
electrode anchoring system 52 can also be incorporated into the
distal tip of the lead to facilitate lead stability (see FIG. 1).
Other anchoring systems can also be used such as hooks, sutures, or
the like.
[0058] FIGS. 10 and 11 illustrate another embodiment of the present
S-ICD invention. In this embodiment there are two subcutaneous
electrodes 13 and 13' of opposite polarity to the canister. The
additional subcutaneous electrode 13' is essentially identical to
the previously described electrode. In this embodiment the
cardioversion/defibrillation energy is delivered between the active
surface of the canister and the two coil electrodes 27 and 27'.
Additionally, provided in the canister is means for selecting the
optimum sensing arrangement between the four sense electrodes 23,
23', 25, and 25'. The two electrodes are subcutaneously placed on
the same side of the heart. As illustrated in FIG. 6, one
subcutaneous electrode 13 is placed inferiorly and the other
electrode 13' is placed superiorly. It is also contemplated with
this dual subcutaneous electrode system that the canister and one
subcutaneous electrode are the same polarity and the other
subcutaneous electrode is the opposite polarity.
[0059] Turning now to FIGS. 12 and 13, further embodiments are
illustrated where the canister 11 of the S-ICD of the present
invention is shaped to be particularly useful in placing
subcutaneously adjacent and parallel to a rib of a patient. The
canister is long, thin, and curved to conform to the shape of the
patient's rib. In the embodiment illustrated in FIG. 12, the
canister has a diameter ranging from about 0.5 cm to about 2 cm
without 1 cm being presently preferred. Alternatively, instead of
having a circular cross sectional area, the canister could have a
rectangular or square cross sectional area as illustrated in FIG.
13 without falling outside of the scope of the present invention.
The length of the canister can vary depending on the size of the
patient's thorax. Currently the canister is about 5 cm to about 15
cm long with about 10 being presently preferred. The canister is
curved to conform to the curvature of the ribs of the thorax. The
radius of the curvature will vary depending on the size of the
patient, with smaller radiuses for smaller patients and larger
radiuses for larger patients. The radius of the curvature can range
from about 5 cm to about 35 cm depending on the size of the
patient. Additionally, the radius of the curvature need not be
uniform throughout the canister such that it can be shaped closer
to the shape of the ribs. The canister has an active surface, 15
that is located on the interior (concave) portion of the curvature
and an inactive surface 16 that is located on the exterior (convex)
portion of the curvature. The leads of these embodiments, which are
not illustrated except for the attachment port 19 and the proximal
end of the lead 21, can be any of the leads previously described
above, with the lead illustrated in FIG. 1 being presently
preferred.
[0060] The circuitry of this canister is similar to the circuitry
described above. Additionally, the canister can optionally have at
least one sense electrode located on either the active surface of
the inactive surface and the circuitry within the canister can be
programmable as described above to allow for the selection of the
best sense electrodes. It is presently preferred that the canister
have two sense electrodes 26 and 28 located on the inactive surface
of the canisters as illustrated, where the electrodes are spaced
from about 1 to about 10 cm apart with a spacing of about 3 cm
being presently preferred. However, the sense electrodes can be
located on the active surface as described above.
[0061] It is envisioned that the embodiment of FIG. 12 will be
subcutaneously implanted adjacent and parallel to the left anterior
5th rib, either between the 4th and 5th ribs or between the 5th and
6th ribs. However other locations can be used.
[0062] Another component of the S-ICD of the present invention is a
cutaneous test electrode system designed to simulate the
subcutaneous high voltage shock electrode system as well as the QRS
cardiac rhythm detection system. This test electrode system is
comprised of a cutaneous patch electrode of similar surface area
and impedance to that of the S-ICD canister itself together with a
cutaneous strip electrode comprising a defibrillation strip as well
as two button electrodes for sensing of the QRS. Several cutaneous
strip electrodes are available to allow for testing various bipole
spacings to optimize signal detection comparable to the implantable
system.
[0063] FIGS. 14 to 18 depict particular US-ICD embodiments of the
present invention. The various sensing, shocking and pacing
circuitry, described in detail above with respect to the S-ICD
embodiments, may additionally be incorporated into the following
US-ICD embodiments. Furthermore, particular aspects of any
individual S-ICD embodiment discussed above, may be incorporated,
in whole or in part, into the US-ICD embodiments depicted in the
following figures.
[0064] Turning now to FIG. 14, the US-ICD of the present invention
is illustrated. The US-ICD consists of a curved housing 1211 with a
first and second end. The first end 1413 is thicker than the second
end 1215. This thicker area houses a battery supply, capacitor and
operational circuitry for the US-ICD. The circuitry will be able to
monitor cardiac rhythms for tachycardia and fibrillation, and if
detected, will initiate charging the capacitor and then delivering
cardioversion/defibrillation energy through the two
cardioversion/defibrillating electrodes 1417 and 1219 located on
the outer surface of the two ends of the housing. The circuitry can
provide cardioversion/defibrillation energy in different types of
waveforms. In one embodiment, a 100 uF biphasic waveform is used of
approximately 10-20 ms total duration and with the initial phase
containing approximately 2/3 of the energy, however, any type of
waveform can be utilized such as monophasic, biphasic, multiphasic
or alternative waveforms as is known in the art.
[0065] The housing of the present invention can be made out of
titanium alloy or other presently preferred ICD designs. It is
contemplated that the housing is also made out of biocompatible
plastic materials that electronically insulate the electrodes from
each other. However, it is contemplated that a malleable canister
that can conform to the curvature of the patient's chest will be
preferred. In this way the patient can have a comfortable canister
that conforms to the unique shape of the patient's rib cage.
Examples of conforming ICD housings are provided in U.S. Pat. No.
5,645,586, the entire disclosure of which is herein incorporated by
reference. In the preferred embodiment, the housing is curved in
the shape of a 5th rib of a person. Because there are many
different sizes of people, the housing will come in different
incremental sizes to allow a good match between the size of the rib
cage and the size of the US-ICD. The length of the US-ICD will
range from about 15 to about 50 cm. Because of the primary
preventative role of the therapy and the need to reach energies
over 40 Joules, a feature of the preferred embodiment is that the
charge time for the therapy, intentionally be relatively long to
allow capacitor charging within the limitations of device size.
[0066] The thick end of the housing is currently needed to allow
for the placement of the battery supply, operational circuitry, and
capacitors. It is contemplated that the thick end will be about 0.5
cm to about 2 cm wide with about 1 cm being presently preferred. As
microtechnology advances, the thickness of the housing will become
smaller.
[0067] The two cardioversion/defibrillation electrodes on the
housing are used for delivering the high voltage
cardioversion/defibrillation energy across the heart. In the
preferred embodiment, the cardioversion/defibrillation electrodes
are coil electrodes, however, other cardioversion/defibrillation
electrodes could be used such as having electrically isolated
active surfaces or platinum alloy electrodes. The coil
cardioversion/defibrillation electrodes are about 5-10 cm in
length. Located on the housing between the two
cardioversion/defibrillation electrodes are two sense electrodes
1425 and 1427. The sense electrodes are spaced far enough apart to
be able to have good QRS detection. This spacing can range from 1
to 10 cm with 4 cm being presently preferred. The electrodes may or
may not be circumferential with the preferred embodiment. Having
the electrodes non-circumferential and positioned outward, toward
the skin surface, is a means to minimize muscle artifact and
enhance QRS signal quality. The sensing electrodes are electrically
isolated from the cardioversion/defibrillation electrode via
insulating areas 1423. Analogous types of
cardioversion/defibrillation electrodes are currently commercially
available in a transvenous configuration. For example, U.S. Pat.
No. 5,534,022, the entire disclosure of which is herein
incorporated by reference, discloses a composite electrode with a
coil cardioversion/defibrillation electrode and sense electrodes.
Modifications to this arrangement is contemplated within the scope
of the invention. One such modification is to have the sense
electrodes at the two ends of the housing and have the
cardioversion/defibrillation electrodes located in between the
sense electrodes. Another modification is to have three or more
sense electrodes spaced throughout the housing and allow for the
selection of the two best sensing electrodes. If three or more
sensing electrodes are used, then the ability to change which
electrodes are used for sensing would be a programmable feature of
the US-ICD to adapt to changes in the patient physiology and size
over time. The programming could be done via the use of physical
switches on the canister, or as presently preferred, via the use of
a programming wand or via a wireless connection to program the
circuitry within the canister.
[0068] Turning now to FIG. 15, the optimal subcutaneous placement
of the US-ICD of the present invention is illustrated. As would be
evident to a person skilled in the art, the actual location of the
US-ICD is in a subcutaneous space that is developed during the
implantation process. The heart is not exposed during this process
and the heart is schematically illustrated in the figures only for
help in understanding where the device and its various electrodes
are three dimensionally located in the thorax of the patient. The
US-ICD is located between the left mid-clavicular line
approximately at the level of the inframammary crease at
approximately the 5.sup.th rib and the posterior axillary line,
ideally just lateral to the left scapula. This way the US-ICD
provides a reasonably good pathway for current delivery to the
majority of the ventricular myocardium.
[0069] FIG. 16 schematically illustrates the method for implanting
the US-ICD of the present invention. An incision 1631 is made in
the left anterior axillary line approximately at the level of the
cardiac apex. A subcutaneous pathway is then created that extends
posteriorly to allow placement of the US-ICD. The incision can be
anywhere on the thorax deemed reasonable by the implanting
physician although in the preferred embodiment, the US-ICD of the
present invention will be applied in this region. The subcutaneous
pathway is created medially to the inframammary crease and extends
posteriorly to the left posterior axillary line. The pathway is
developed with a specially designed curved introducer 1742 (see
FIG. 17). The trocar has a proximal handle 1641 and a curved shaft
1643. The distal end 1745 of the trocar is tapered to allow for
dissection of a subcutaneous path in the patient. Preferably, the
trocar is cannulated having a central lumen 1746 and terminating in
an opening 1748 at the distal end. Local anesthetic such as
lidocaine can be delivered, if necessary, through the lumen or
through a curved and elongated needle designed to anesthetize the
path to be used for trocar insertion should general anesthesia not
be employed. Once the subcutaneous pathway is developed, the US-ICD
is implanted in the subcutaneous space, the skin incision is closed
using standard techniques.
[0070] As described previously, the US-ICDs of the present
invention vary in length and curvature. The US-ICDs are provided in
incremental sizes for subcutaneous implantation in different sized
patients. Turning now to FIG. 18, a different embodiment is
schematically illustrated in exploded view which provides different
sized US-ICDs that are easier to manufacture. The different sized
US-ICDs will all have the same sized and shaped thick end 1413. The
thick end is hollow inside allowing for the insertion of a core
operational member 1853. The core member comprises a housing 1857
which contains the battery supply, capacitor and operational
circuitry for the US-ICD. The proximal end of the core member has a
plurality of electronic plug connectors. Plug connectors 1861 and
1863 are electronically connected to the sense electrodes via
pressure fit connectors (not illustrated) inside the thick end
which are standard in the art. Plug connectors 1865 and 1867 are
also electronically connected to the cardioverter/defibrillator
electrodes via pressure fit connectors inside the thick end. The
distal end of the core member comprises an end cap 1855, and a
ribbed fitting 1859 which creates a water-tight seal when the core
member is inserted into opening 1851 of the thick end of the
US-ICD.
[0071] The core member of the different sized and shaped US-ICD
will all be the same size and shape. That way, during an
implantation procedures, multiple sized US-ICDs can be available
for implantation, each one without a core member. Once the
implantation procedure is being performed, then the correct sized
US-ICD can be selected and the core member can be inserted into the
US-ICD and then programmed as described above. Another advantage of
this configuration is when the battery within the core member needs
replacing it can be done without removing the entire US-ICD.
[0072] A block diagram of a power supply 100 for use in a S-ICD
device of the present invention is shown in FIG. 19. The power
supply 100 is located in canister housing 16 and comprises a
capacitor subsystem 102 electrically coupled to a battery subsystem
104. In an embodiment, the battery subsystem 104 comprises one or
more individual battery cell(s) and the capacitor subsystem 102
comprises one or more individual capacitor(s).
[0073] In certain embodiments of the present invention, it is
desirable to position the canister housing 16 in close proximity to
the patient's heart, without directly contacting the heart or the
intrathoracic blood vessels. In one embodiment, the canister
housing 16 placement is just over the patient's ribcage.
[0074] In operation, the battery subsystem 104 provides electrical
energy to charge up the capacitor subsystem 102. After charge-up,
the capacitor subsystem 102 delivers the
cardioversion/defibrillation energy to the patient's heart through
the electrodes. In one embodiment, the power supply 100 can provide
approximately 0.5 to approximately 350 joules of
cardioversion/defibrillation energy to the heart through
approximately 60 ohms of thoracic impedance.
[0075] A procedure to determine the composition of the capacitor
subsystem 102 and the battery subsystem 104 will now be described.
Generally, the approach to determine needed capacitor values
includes considerations for the internal impedance of the
capacitors. As a result of this internal impedance, not all of the
energy stored by the capacitors will be delivered due to the
inherent inefficiencies of the capacitors. Thus, it is often
necessary to work backwards from the desired energy delivered in
order to calculate the needed capacitor values.
[0076] Generally, the procedure to determine the proper capacitor
values of the present invention includes the following steps:
determine the amount of cardioversion/defibrillation energy
required to be delivered to the patient's heart; determine the
amount of energy lost due to truncation of the energy wave form;
determine the amount of energy that must be stored in the capacitor
subsystem 102 by considering the amount of energy loss from the
internal impedance of the capacitor subsystem 102; determine the
effective capacitor value of the capacitor subsystem 102 associated
with using different amounts of individual capacitors; calculate
the physical volume of the different numbers of individual
capacitors for placement on a circuit board; and determine the
pulse width for each of the effective capacitor values.
[0077] The first step is to determine the amount of energy that
must be delivered to a patient's heart to provide an effective
cardioversion/defibrillation therapy. In addition, the effective
energy levels incorporate critical information regarding the
associated voltage, current, waveform duration and tilt for
effective cardioversion/defibrill- ation. Use of the term "energy"
throughout this description automatically incorporates these other
waveform characteristics. Because this information has not been
available heretofore, this data can be acquired by performing, for
example, human or animal studies to determine the appropriate
levels of the energy.
[0078] Next, it is common industry practice to truncate the
trailing edge of a capacitor-based cardioversion/defibrillation
waveform because the trailing edge can often produce undesirable
side affects, such as creating pro-arrhythmic currents should it
persist too long. Thus, the amount of energy delivered can be
calculated by the formula:
E.sub.STORED=E.sub.DEL/T,
[0079] where E.sub.STORED is the maximum amount of energy by the
capacitor, E.sub.DEL is the amount of energy delivered to the heart
and T is the truncation percentage of the waveform.
[0080] In order to determine the amount of energy as shown above,
the amount of energy stored in the capacitors is typically
compensated for by considering the internal impedance of the
capacitor subsystem 102, which is known as the Effective Series
Resistance ("ESR"). In addition, the ratio of delivered energy to
stored energy is often expressed as the capacitor efficiency.
[0081] After calculation of the energy stored by the capacitor
subsystem 102, the actual values of the individual capacitor(s) can
be determined. The amount of energy stored by an individual
capacitor is given by the formula:
E=1/2[C(V).sup.2],
[0082] where E is the total amount of energy stored by a capacitor,
C is the amount of capacitance and V is the amount of voltage for
each individual capacitor. From this equation, it can be seen that
a number of tradeoffs exist in determining the capacitor value(s)
to achieve the desired cardioversion/defibrillation output,
including the individual capacitor value(s) and the voltage across
each individual capacitor(s). For example, considerations may
include voltages of commercially available capacitors as well as
specific capacitor values most appropriate for
cardioversion/defibrillation therapy.
[0083] It is also noted from the equation above that larger
voltages permit smaller values of capacitors in order to obtain the
same energy level. The voltage is constrained, however, by the
voltage limitation of each individual capacitor. Often, in order to
produce voltages required for cardioversion/defibrillation, a
series connection of capacitors may be implemented to allow these
higher overall output voltages, while at the same time keeping each
individual capacitors' voltage below its maximum rating. Examples
of embodiments of the present invention when considering these
factors are shown in greater detail below.
[0084] Typically, the value for each individual capacitor,
C.sub.IND is determined first for the capacitor subsystem 102.
Next, the effective capacitance of the capacitor subsystem 102,
C.sub.EFF, can be determined from the equation above. Solving for
C.sub.EFF, the equation above becomes
C.sub.EFF=2.times.E/(V).sup.2.
[0085] Finally, once the individual capacitor value(s) have been
determined, the physical volume for each of the individual
capacitor(s) can also be determined. In order to solve for volume
of the individual capacitors, the equation is used as follows:
V.sub.IND=E/volumetric density,
[0086] where V.sub.IND is the individual capacitor volume, E is the
stored energy, and the volumetric density is measured in
joules/cubic centimeters. Under multiple capacitor scenarios,
individual capacitor volumes can be summed to determine the total
volume due to the capacitors. Specifically, the total device volume
can be determined by the equation E.sub.TOTAL=(the number of
capacitors).times.V.sub.IND.
[0087] Derivation of the equation used to determine pulse width
depends on the amount of cardioversion/defibrillation energy
delivered by the capacitor subsystem 102. In addition, the pulse
width must be truncated or the pulse width will stretch
indefinitely because of the exponential nature of the components.
Specifically, the amount of energy delivered by the capacitor
subsystem 102 can be determined by the fact that the amount of
energy left in the capacitor subsystem 102, E.sub.FINAL, is equal
to the amount of the energy initially stored in the capacitor
subsystem 102, E.sub.INIT, minus the amount of energy delivered by
the shock, E.sub.DEL. In addition, the amount of energy stored in
the capacitor subsystem 102 after a shock, E.sub.FINAL, is also
defined by the equation as follows:
E.sub.FINAL=1/2[C.sub.Eff][V.sub.FINAL].sup.2=1/2[C.sub.EFF][V.sub.INIT]e.-
sup.-.tau./RC.sub.EFF].sup.2,
[0088] where .tau. is the pulse width and R is the impedance of the
body.
[0089] After calculating the makeup of the capacitor subsystem 104,
the composition of the battery subsystem 102 of the present
invention can be determined. First, the total amount of energy for
the battery subsystem 104 that is required to provide a maximum
number of energy shocks at a certain amount of energy delivered is
determined. Next, after considering th e overall efficiency of the
battery subsystem 102, the total amount of energy for this number
of energy shocks is calculated. Finally , the total physical volume
and effective lifetime of the battery subsystem 102 can be
determined.
[0090] Based on the calculations described above, several examples
of embodiments of the capacitor subsystem 102 and the battery
subsystem 104 will now be shown. As an example of an embodiment of
the present invention, the power supply 100 may provide
approximately 150 joules of energy to be delivered to the heart.
Further, in an embodiment, the waveform of the energy delivered to
the heart will be truncated at approximately 97%. Therefore, in
this example, the energy output of the capacitor, E.sub.OUT, will
equal to 150 joules divided by the truncation level 97%, or 155
joules.
[0091] In an embodiment, the efficiency of the energy stored in the
capacitor is approximately 75%. With an energy output of the
capacitor equal to 155 joules, the stored energy will be 155 joules
divided by the efficiency 75%, or 207 joules.
[0092] The effective capacitance C.sub.EFF can now be calculated
using the equation C.sub.EFF=2.times.E/(V).sup.2. In this example,
assuming E is approximately 207 joules and V is approximately 350
volts, C.sub.EFF is approximately 3,380 microfarads. Because the
individual capacitance, C.sub.IND, equals the number of capacitors
times the effective capacitance, C.sub.EFF, the individual
capacitance of the single capacitor also is approximately 3,380
microfarads.
[0093] In order to solve for physical volume, the equation
V.sub.IND=E/volume metric density is used. In this example, it is
assumed that the individual capacitors have a volumetric efficiency
of approximately 7.5 joules/cubic centimeters for stored energy and
approximately 5.5 joules/cubic centimeters for delivered energy.
Therefore, in this example, individual capacitor volume,
V.sub.IND=207 joules/7.5 joules/cubic centimeters=27.6 cubic
centimeters. Further, because the capacitor volume is determined by
the number of capacitors times V.sub.IND, in this example with one
individual capacitor, the total capacitor device, V.sub.TOT=27.6
cubic centimeters.
[0094] Finally, the value of the pulse width can be determined. In
this example, E.sub.FINAL=E.sub.INIT-E.sub.DEL=155.0-150.0=5.0
joules. In addition, using the equation
E.sub.FINAL=1/2[C.sub.Eff][V.sub.FINAL].sup.-
2=1/2[C.sub.EFF][V.sub.INIT][e.sup.-.tau./RC.sub.EFF].sup.2, the
pulse width .tau. is equal to 377 milliseconds.
[0095] As shown in the table in FIG. 20, several examples of
embodiments of the power supply 100 of the present invention are
shown to depending upon the number of capacitors and the pulse
width of the energy signal delivered. In addition, FIG. 21 shows in
graphical form the tabular data shown in FIG. 20.
[0096] Next, it is desired to determine the size of the battery
subsystem 104 is required given a maximum number of energy shocks
at a certain amount of energy delivered. In this example, it is
assumed that the system is capable of delivering approximately 100
maximum energy shocks at approximately 207 joules of energy.
Accordingly, because 207 joules of energy is equal to 207
watt-seconds, 100 max energy shocks is equal to 20,700
watt-seconds, or 5.75 watt-hours. Assuming for this example that
the power supply efficiency is approximately 65%, this yields a
battery capacity requirement of 8.8 watt-hours.
[0097] In one embodiment of the present invention, the battery
cells can comprise LiSVO or LiMnO.sub.2 batteries that can operate
for both defibrillation or monitoring requirements. In another
embodiment, LiSVO or LiMnO.sub.2 batteries can be employed for
defibrillation operations, and LiI.sub.2 or LiCFx batteries can be
employed for monitoring operations.
[0098] In this example, the LiSVO batteries have a energy storage
capacity of approximately 1/2 watt-hour/cubic centimeters per
battery. Therefore, a physical volume of approximately 18 cubic
centimeters of battery is required to provide 100 maximum energy
shocks at approximately 207 joules of energy.
[0099] Another variable relates to time required for the battery
subsystem 102 to fully charge the capacitor subsystem 104. Because
batteries tend to degrade over the life of the cells, the charge
time at the beginning of battery life ("BOL") is less than the end
of the battery life ("EOL"). The amount of charge time is equal to
the power output divided by the applied battery voltage at the BOL
times the maximum current. As an example, assuming a single shock
of approximately 207 joules at a 65% efficiency that yields a power
output of approximately 318 joules, and an applied battery voltage
of approximately 5 volts at BOL and maximum current drain of
approximately 2.5 amps, the battery subsystem 102 can charge the
capacitor subsystem 104 in approximately 25 seconds. In this
example, assuming the applied battery voltage decrease to
approximately 4 volts at EOL with a current drain of approximately
2.5 amps, the battery subsystem can charge the capacitor subsystem
104 in approximately 32 seconds.
[0100] Finally, in order to determine the effective lifetime of the
battery subsystem 102 assuming no shocks and no pacing, the amount
of battery capacity (8.8 watt-hours) must be divided by the amount
of monitoring current (15 microamps) times the total voltage (10.0
volts) times the battery efficiency (90%). For this example, the
battery subsystem has an effective lifetime of approximately 65,185
hours, or 7.4 years.
[0101] In an embodiment, commercially available capacitors and
batteries meeting the specifications described above are
manufactured and sold by Wilson Greatbatch, Limited, of 10,000
Wehrle Dr., Clarence, N.Y. 14031. In an embodiment, the capacitor
subsystem 104 can comprise film, aluminum electrolytic or wet
tantalum capacitor(s). In an embodiment, the battery subsystem can
comprise LiSVO, magnesium or thin film battery(ies).
[0102] FIG. 22 is a table that shows several examples for the
battery subsystem 102 comprising two battery cells, as well as
varying efficiencies and charge times. In addition, FIG. 23 is a
table that shows several examples for the battery subsystem 102
comprising other numbers of battery cells, efficiencies and charge
times.
[0103] FIG. 24 is a diagram that shows one example of a physical
layout for the battery subsystem 102 and the capacitor subsystem
104 in an embodiment of the present invention. As shown in FIG. 24,
battery subsystem 102 may comprise battery cells 2402, 2404, 2406
and 2408. Capacitor subsystem 104 may comprise capacitors 2410,
2412, 2414, 2416, 2418 and 2420. Both the battery subsystem 102 and
the capacitor subsystem 104 are located in the canister housing 16.
In this example, it is assumed that the thickness 2424 of the
canister housing 16 will be approximately 0.2 inches. As determined
in the example above, each of the six capacitors 2410, 2412, 2414,
2416, 2418 and 2420 can occupy approximately 4.6 cubic centimeters
of physical volume. In this example, it is noted that capacitor
2410 is substantially a half-circle in shape. Because volume is
equal to area times thickness 2424 and assuming the device is 0.2
inches thick, the radius 2422 of the half-circle capacitor 16 is
approximately 0.95 inches. Next, because the width 2426 is equal to
twice the radius 2422, the width 2426 is approximately 1.9 inches.
Then, assuming the width 2426 is approximately 1.9 inches, the
thickness 2424 is approximately 0.2 inches and the volume of each
of the capacitors 2412, 2414, 2416, 2418 and 2420 is approximately
4.6 cubic centimeters, each of the individual capacitors is
approximately 0.74 inches in length. Therefore, the capacitor
subsystem 104 is approximately 4.6 inches in length.
[0104] As for the battery subsystem 102, assuming approximately 4.5
cubic centimeters of volume per battery, the same width 2426 and
thickness 2424, the length of each of the battery cells 2402, 2404,
2406 and 2408 is approximately 0.72 inches for a total of
approximately 2.9 inches. Thus, the length 2428 of the canister
housing 16 is approximately 4.6 inches (capacitor subsystem 104)
plus 2.9 inches (battery subsystem 102) or a total of approximately
7.5 inches. Similarly, multiplying the length 2428 times the width
2426 times the thickness 2424 provides a total volume in this
example of approximately 50 cubic centimeters including a provision
for the electronics.
[0105] FIG. 25 shows one example of a physical layout for the
battery subsystem 102 and the capacitor subsystem 104 in an
embodiment of the present invention. As shown in FIG. 25, battery
subsystem 102 may comprise battery cells 2502, 2504, 2506 and 2508.
Capacitor subsystem 104 may comprise capacitors 2510, 2512, 2514,
2516, 2518 and 2520. Both the battery subsystem 102 and the
capacitor subsystem 104 are located in the canister housing 16. In
this example, it is assumed that thickness 2524 of the canister
housing 16 is approximately 0.3 inches. As determined in the
example above, each of the six capacitors 2510, 2512, 2514, 2516,
2518 and 2520 will occupy approximately 4.6 cubic centimeters of
physical volume. Assuming a width 2526 of approximately 2.0 inches,
the length of each of the capacitors 2510, 2512, 2514, 2516, 2518
and 2520 is approximately 0.47 inches, and the total length of the
capacitor subsystem 104 is approximately 2.8 inches. Next, given
the same assumptions for the thickness 2524 and the width 2526, and
that the volume of each of the battery cells 2502, 2504, 2506 and
2508 is approximately 4.5 cubic centimeters (as calculated above),
each of the battery cells 2502, 2504, 2506 and 2508 is
approximately 0.46 inches. Thus, the length of the battery
subsystem 102 is approximately 1.8 inches and the length 2528 of
the combined capacitor subsystem 104 and the battery subsystem 102
is approximately 2.8 inches plus 1.8 inches, or 4.6 inches.
Further, the total volume of the capacitor subsystem 104 and the
battery subsystem 102 is approximately 50 cubic centimeters.
[0106] FIG. 26 shows a table with various examples of sizes for the
combined capacitor subsystem 104 and the battery subsystem 102.
More specifically, the table shows various thicknesses, widths and
lengths, and which all have the same volume of approximately 50
cubic centimeters. There are, of course, many variations to these
potential embodiments shown in FIG. 26.
[0107] Finally, FIG. 27 shows a table of several embodiments of the
capacitor subsystem 104 and the battery subsystem 102 at different
energy levels. In these examples, energy levels of 150, 125, 100,
75 and 50 joules are shown. Typically, the amount of delivered
energy can range from approximately 0.5 joules to approximately 350
joules. Also, in an embodiment, the peak voltage of the energy can
range from approximately 350 volts to approximately 3150 volts. In
addition, in these examples, a nominal effective capacitance of 100
microfarads is targeted to align with defibrillation chronaxie.
[0108] The S-ICD and US-ICD devices and methods of the present
invention may be embodied in other specific forms without departing
from the teachings or essential characteristics of the invention.
The described embodiments are therefore to be considered in all
respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are therefore to be
embraced therein.
* * * * *