Cardiac defibrillator with high energy storage antiferroelectric capacitor

• US 5,545,184 A
• Filed: 04/19/1995
• Issued: 08/13/1996
• Est. Priority Date: 04/19/1995
• Status: Expired due to Term

• Current Assignee: Penn State Research Foundation
• Original Assignee: Penn State Research Foundation
• Inventors: Dougherty, Joseph P.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US08/423,500
• Time in Patent Office: 482 Days
• Field of Search: 607/5, 607/7, 607/34, 252/62.9, 361/313, 361/320, 361/321.4, 361/321.5, 501/134, 501/135
• US Class Current: 607/5
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A cardiac defibrillator which incorporates the invention hereof includes a multilayer capacitor with a plurality of conductive electrodes and interspersed dielectric layers, each dielectric layer composed of constituents which cause the dielectric layer to exhibit antiferroelectric characteristics. The defibrillator includes a charging circuit for applying to the capacitor an electric field across each dielectric layer that is at least equal to E_f, where E_f is a field value that enables the dielectric layer to transition to a ferroelectric phase. A preferred dielectric material comprises lead, lanthanum, zirconium and titanium, all at constituent values which cause the resulting ceramic material to lie within the antiferroelectric region.

Claims

1. A cardiac defibrillator for applying a high energy, short duration electrical pulse to the heart muscle, said defibrillator comprising:

capacitor means comprising plural dielectric layers, each layer composed of constituents which exhibit both an antiferroelectric phase and a ferroelectric phase in dependence upon an applied electric field; and

charging circuit means for applying to said capacitor means, a voltage which causes an electric field at least equal to E_f to appear across said dielectric layers, where E_f is a field value which causes said dielectric layers to transition at least partially from said anti-ferroelectric phase to said ferroelectric phase; and

discharge means for applying energy stored in said capacitor means to a heart muscle.

2. A cardiac defibrillator as recited in claim 1, wherein each said dielectric layer comprises lead, lanthanum, zirconium and titanium (PLZT) constituents.

3. The cardiac defibrillator as recited in claim 2 wherein the lanthanum, zirconium and titanium constituents are present in the PLZT in molar percentages as follows:

La;

from approximately 2 to approximately 10,

Zr;

from approximately 90 to approximately 95, and

Ti;

from approximately 5 to approximately 10.

4. The cardiac defibrillator as recited in claim 2 wherein the zirconium and titanium constituents are present in the PLZT in molar percentages of approximately 95 and 5, respectively.

5. The cardiac defibrillator as recited in claim 2 wherein the zirconium and titanium constituents are present in the PLZT in molar percentages of approximately 90 and 10, respectively.

6. A cardiac defibrillator as recited in claim 1, wherein each said dielectric layer comprises lead, lanthanum, tin and titanium constituents.

7. A cardiac defibrillator as recited in claim 1, wherein each said dielectric layer comprises barium, lanthanum, zirconium and titanium constituents.

8. The cardiac defibrillator as recited in claim 7 wherein the barium constituent molar percentage does not exceed approximately 10%.