| abstract |
When the heart is in ventricular fibrillation, the heart cells that stimulate the heart muscles produce rapid repetitive excitation without coordinated contraction of the ventricle. There is no effective simultaneous action to make the heart beat in a rhythmic fashion. A defibrillator delivers to the heart cells and muscles, enough voltage to override the erratic voltages in the heart (called repolarization) so they can rearrange themselves with order. The heart can then start over to deliver a regular rhythm. n In accordance with the present invention, two small intimately located electrodes, one in the lower esophagus where it is intimate to the posterior section of the heart and the other small electrode on the chest over the sternum where it is close to the anterior portion of the heart, provide a precise electrical path between the two electrodes. A regulated power supply is turned on, and a relatively small voltage builds from zero over a period of approximately three-tenths of a second to its peak of approximately 150 volts. During this period, gentle repolarizing of the heart takes place. When the heart is repolarized, the heart cells become neutral. They are vulnerable to a stimulas. In accordance with a second embodiment of this invention, the defibrillation pulse is immediately followed by a stimulas in the form of pacing pulses that are at the rate of approximately 70 to 100 pulses per minute and of a magnitude of approximately 75 to 150 milliamps. The switch from one mode to the other is made without changing the location of the electrodes. |