Implantable cardioverter defibrillator having a smaller displacement volume

• US 5,697,953 A
• Filed: 01/11/1996
• Issued: 12/16/1997
• Est. Priority Date: 03/13/1993
• Status: Expired due to Term

• Current Assignee: Ela Medical S.A. (LivaNova Plc)
• Original Assignee: Angeion Corporation (Niterra Co., Ltd.)
• Inventors: Kroll, Mark W., Smith, Charles U., Anderson, Kenneth M., Adams, Theodore P.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US08/582,529
• Time in Patent Office: 705 Days
• Field of Search: 607/5, 607/7, 607/36, 607/34
• US Class Current: 607/5
• CPC Class Codes: A61N 1/37512 Pacemakers
• CPC Class Codes: A61N 1/3758 Packaging of the components within the casing
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion
• CPC Class Codes: H01M 16/00 Structural combinations of different types of electrochemical generators
• CPC Class Codes: H01M 6/5016 Multimode utilisation

Abstract

A capacitor-discharge implantable cardioverter defibrillator (ICD) has a relatively longer device life of greater that 5 years. The longer life of the ICD is achieved by selecting and arranging the internal components of the ICD to deliver a maximum defibrillation countershock optimized in terms of a minimum physiologically effective current (I_pe), rather than a minimum defibrillation threshold energy (DFT). As a result of the optimization in terms of a minimum effective current I_pe, there is a significant decrease in the maximum electrical charge energy (E_c) that must be stored by the capacitor of the ICD to less than about 30 Joules, even though a higher safety margin is provided for by the device. Due to this decrease in the maximum E_c, as well as corollary decreases in the effective capacitance value required for the capacitor and the net energy storage required of the battery, the overall displacement volume of the ICD is reduced to the point where subcutaneous implantation of the device in the pectoral region of human patients is practical. The size of the capacitor is reduced because the effective capacitance required can be less than about 125 μF. By optimizing both the charging time and the countershock duration for the smaller maximum E_c, the size of the battery is reduced because the total energy storage capacity can be less than about 1.0 Amp-hours. In the preferred embodiment, the charging time for each defibrillation countershock is reduced to less than about 10 seconds and the pulse duration of the countershock is reduced to less than about 6 milliseconds.

Claims

1. An implantable cardioverter defibrillator for subcutaneous positioning within a pectoral region of a human patient comprising:

a sealed housing structure constructed of a biocompatible material;

a battery source of electrical energy contained in the housing wherein the battery source has an energy storage capacity of greater than five years;

a capacitor system connected to the battery source wherein the capacitor system stores electrical energy provided by the battery source to generate high voltage electrical cardioversion/defibrillation countershocks, each electrical cardioversion/defibrillation countershock being less than 30 joules;

a pacing system connected to the battery system wherein the pacing system delivers low voltage pacing pulses; and

a control system connected to the capacitor system to control the storing of the electrical energy in the capacitor system and to control the discharge of the electric energy in the capacitor system and to the pacing system to control delivery of the pacing pulses,

wherein the energy storage capacity of the battery source is determined by the equation;

space="preserve" listing-type="equation">E.sub.t =((I.sub.b *t.sub.c)*(N.sub.p)+(I.sub.i *l)+(I.sub.2 *l)

where I_b is an average current drawn from the battery source when charging the capacitor system, t_c is a charging time for the capacitor system that is less than 10 seconds, N₂ is a number of programmed countershock discharges for the implantable cardioverter defibrillator, I_i is an average idle current drawn from the battery source to operate the control system, I₂ is an average pacing current drawn from to power the pacing system and l is an expected useful life of the implantable cardioverter defibrillator of greater than five years.

2. The implantable cardioverter defibrillator of claim 1 wherein the battery source comprises a first high current battery for charging the capacitor system and a second low current battery for powering the control system.

3. The implantable cardioverter defibrillator of claim 1 wherein the capacitor system has an effective capacitance value of less than 120 μ

F.