AUTOMATIC CARDIOVERTING CIRCUIT

• US 3,805,795 A
• Filed: 03/17/1972
• Issued: 04/23/1974
• Est. Priority Date: 03/17/1972
• Status: Expired due to Term

• Current Assignee: Rollin H. Denniston, Thomas E. Davis
• Original Assignee: Rollin H. Denniston, Thomas E. Davis
• Inventors: Denniston, Rollin H., Davis, Thomas E.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/235,756
• Time in Patent Office: 767 Days
• Field of Search: 128/2.5R,2.6A,26R,419D,419P,418,26F,25P,25D 338/5
• US Class Current: 607/6
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

Pulse generating apparatus which provides electrical heartstimulating pulses only in the absence of normal heart activity. If the patient'"'"''"'"'s heart has developed a life threatening arrhythmic condition the inventive apparatus automatically applies an electrical shock to the heart having sufficient magnitude to restore normal heart activity. The inventive apparatus features a redundant heartbeat sensing system which monitors two dynamic characteristics of heart function, for example, heart contraction and EKG. An electrical heart stimulating pulse is delivered to the patient'"'"''"'"'s heart following the elapse of a specified period of time since the sensing of a dynamic characteristic indicative of a normal functional heart. Sensing control is automatically regained following successful heart stimulation, thereby inhibiting the application of further electrical pulses. In the event that the patient'"'"''"'"'s heart fails to resume normal heartbeat action, the inventive apparatus will continue delivering intermittant shocks-a lower energy pulse is applied first followed by higher energy pulses.

Claims

1. Heart contraction sensing and stimulation circuit comprising:

a. first detecting means responsive to a change in a monitored electrical parameter produced by the normal beating action of the heart for providing a first identifiable electrical signal corresponding with each heart contraction;

b. second detecting means responsive to monitored heart electrical activity corresponding to heart contractions for providing a second identifiable signal corresponding with each heart contraction;

c. gating means electrically connected to receive electrical signals from said first and second detecting means, said gating means for providing an electrical output signal in response to either of said identifiable electrical signals produced by a single heart contraction;

d. electrical energy storage means capable of storing sufficient energy to cardiovert a malfunctioning heart;

e. electrical energy source means;

f. control means connected in controlling relation to said energy storage means and said energy source means and operatively connected to said gating means and responsive thereto, said control means for controlling the transmission of electrical energy from said source means to said storage means only in the absence of electrical signals from both the first and second detecting means for a predetermined period of time;

g. output means adapted for connection to the heart;

h. regulating means connected in controlling relation to said energy storage means, said regulating means for permitting energy to be transmitted from said storage means to said output means when the energy stored by said storage means becomes greater than a predetermined level.

2. Heart contraction sensing and stimulation apparatus comprising:

a. first heart monitoring means being in the form of an elastomer body means having conductive particles imbedded therein and exhibiting a change in electrical impedance upon flexing, the body means including means adapted to be positioned adjacent heart muscle so that each heart contraction causes the body means to flex thereby changing its impedance;

b. first detecting means responsive to a change in impedance of said elastomer body means for providing a first identifiable electrical signal corresponding with each heart contraction;

c. second heart monitoring means in the form of conductive electrode means being adapted for insertion within the human vascular system and positioned adjacent the heart for monitoring heart electrical activity and transmitting electrical energy to the heart, d. second detecting means responsive to the monitored heart electrical activity corresponding to heart contractions for providing a second identifiable signal corresponding with each heart contraction;

e. gating means electrically connected to receive electrical signals from said first and second detecting means, said gating means for providing an electrical output signal in response to either of said identifiable electrical signals produced by a singlE heart contraction;

f. electrical energy storage means capable of storing sufficient energy to cardiovert a malfunctioning heart;

g. electrical energy source means;

h. control means electrically connected in controlling relation to said energy storage means and said energy source means and operatively connected to said gating means and responsive thereto, said control means for controlling the transmission of electrical energy from said source means to said storage means only in the absence of both said first and second identifiable signals for a predetermined period of time;

i. regulating means electrically connected to said electrode means and further connected in controlling relation to said energy storage means, said regulating means for permitting transmission of energy from said storage means to said electrode means when the energy stored by said storage means is greater than a predetermined level; and

j. disabling means electrically connected to said first monitoring means for sensing a break in the electrical circuitry of said first monitoring means, said disabling means for preventing electrical energy from being delivered to said electrodes when such a break occurs.

3. The apparatus of claim 2 further comprising flexible enclosure means substantially inert in living body fluids and tissue, the enclosure means being adapted for insertion within the vascular system of a living animal, the enclosure means further for enclosing, at least some of, the apparatus elements, thereby sealing them from living body fluids and tissues.

4. The apparatus of claim 2 wherein the second monitoring means includes two conductive electrode means, one of the electrode means being adapted to be positioned within the heart and the other electrode means being adapted to be positioned outside the heart to monitor heart electrical activity produced by the natural beating action of the heart.

5. The apparatus of claim 2 wherein the second detecting means includes discrimination means, said discrimination means for responding to the heart electrical activity produced by the natural beating action of the heart while discriminating against the heart electrical signals produced by an abnormally functioning heart and those artificially induced by a heart pacing device.

6. The apparatus of claim 2 wherein said gating means includes a conforming means, said conforming means for transforming the pulses having varying amplitudes and widths into pulses having substantially the same pulse amplitude and pulse width.

7. The apparatus of claim 2 wherein said control means has a transmitting and a non-transmitting state and includes a timing means for maintaining said control means in the non-transmitting state for a predetermined time interval following each signal received from said gating means.

8. The apparatus of claim 7 wherein the timing means includes capacitive means for switching said control means from the non-conductive state to the conductive state when said capacitive means becomes charged above a predetermined level, said capacitive means being operatively connected to said gating means so that a signal from said gating means causes the capacitive means to discharge rendering said control means non-conductive.

9. The apparatus of claim 2 further comprising a counting means operatively connected to said energy storage means for disabling the transmission of electrical pulses from said energy storage means to said electrode means after a predetermined number of electrical pulses have been transmitted without an intervening heart contraction having been detected by said first or second detecting means.

10. The apparatus of claim 2 wherein the regulating means includes multiple level control means, said level control means being constructed and arranged such that energy will begin being transmitted from said energy storage means to said electrodes when the energy stored by said storage means is above a certain first predetermined level and Will cease being transmitted when the stored energy becomes less than a second lesser predetermined level, thereby causing the energy stored by said storage means to be transmitted to said electrodes in a truncated capacitive discharge electrical pulse waveform.

11. The apparatus of claim 2 wherein the regulating means includes means for setting the time interval between the generation of the latest pulse from said gate means and the generation of the first electrical pulse transmitted to said electrode means so that said time interval is substantially greater than the time interval between each of the succeeding electrical pulses transmitted to said electrodes, during the time interval in which no pulses are provided by said gate means.

12. The apparatus of claim 2 wherein the regulating means includes means for increasing the energy content of all but the first electrical pulse of the series of pulses transmitted to said electrodes during the time interval in which there is an absence of normal heart contractions.

13. In an automatic cardioverting system comprising intravascular electrical lead means having electrodes adapted for transmitting electrical pulses to the heart of a living animal, sensing means including electrically conductive means within said lead means and flexible therewith for sensing the action of a heart contration upon said lead means, means electrically connected with and responsive to said sensing means for continuously monitoring heart activity and producing an identifiable electrical signal corresponding to each sensed heart contraction, and stimulation means responsive to the identifiable signal and operatively connected to said intravascular lead for providing cardioverting shocks to said electrodes, the improvement comprising:

disabling means electrically connected to said sensing means for sensing a break in said electrically conductive means and its electrical connection with said monitoring means, said disabling means for preventing cardioverting shocks from being transmitted from said stimulating means to said electrode upon sensing a break in said electrically conductive means or its electrical circuitry.