| 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 ryhthmic 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 Atrial defibrillation is achieved with an internal esophageal electrode and an external chest electrode placed approximately on a line between the two nipples and part way between the sternum and the left nipple. This provides a precise path for the defibrillating pulse and consequently a very efficient path, so that defibrillation is accomplished with very low power of 30 to 70 joules (average 50 joules) compared to what is normally used, namely, 100 to 360 joules. n Also in accordance with this invention, ventricular defibrillation is achieved with an internal esophageal electrode and an external chest electrode placed approximately over the apex of the left ventricle. This provides a precise path for the defibrillating pulse, and consequently a very efficient path so that the power of the same magnitude as those used for atrial defibrillation are used for ventricular defibrillation. |