The potential gradient field created by epicardial defibrillation electrodes in dogs.

Abstract

Knowledge of the potential gradient field created by defibrillation electrodes is important for the understanding and improvement of defibrillation. To obtain this knowledge by direct measurements, potentials were recorded from 60 epicardial, eight septal, and 36 right ventricular transmural electrodes in six open-chest dogs while 1 to 2 V shocks were given through defibrillation electrodes (1) on the right atrium and left ventricular apex (RA. V) and (2) on the right and left ventricles (RV.LV). The potential gradient field across the ventricles was calculated for these low voltages. Ventricular fibrillation was electrically induced, and ventricular activation patterns were recorded after delivering high-voltage shocks just below the defibrillation threshold. With the low-voltage shocks, the potential gradient field was very uneven, with the highest gradient near the epicardial defibrillation electrodes and the weakest gradient distant from the defibrillation electrodes for both RA.V and RV.LV combinations. The mean ratio of the highest to the lowest measured gradient over the entire ventricular epicardium was 19.4 + 8. 1 SD for the RA.V combination and 14.4 ± 3.4 for the RV.LV combination. For both defibrillation electrode combinations, the earliest sites of activation after unsuccessful shocks just below the defibrillation threshold were located in areas where the potential gradient was weak for the low-voltage shocks. We conclude that (1) there is a markedly uneven distribution of potential gradients for epicardial defibrillation electrodes with most of the voltage drop occurring near the electrodes, (2) the potential gradient field is significant because it determines where shocks fail to halt fibrillation, and (3) determination of the potential gradient field should lead to the development of improved electrode locations for defibrillation. Circulation 74, No. 3, 626-636, 1986.

Spatiotemporal complexity of ventricular fibrillation revealed by tissue mass reduction in isolated swine right ventricle. Further evidence for the quasiperiodic route to chaos hypothesis.

“…2 C ), and found that the results are comparable. To be consistent with our previous study (13), we report only the interactivation intervals selected with peak-picking method. The interactivation interval is defined by the time difference between adjacent peaks.…”

Transmural and endocardial Purkinje activation in pigs before local myocardial activation after defibrillation shocks

“…10 This rapid firing may lead to multiple wavefronts on the heart at one time, which may degenerate back into VF. 11 While mapping studies have demonstrated that first myocardial activation emerges from the low field gradient region after near DFT shocks, 31,32 activation could originate in the conduction system in high gradient areas from rapidly firing Purkinje fibers and then spread to the low gradient areas. The rapid activation rate of the Purkinje fibers in the high gradient regions of the heart may be spreading through the specialized conduction system, but may not spread through the myocardial tissue because it is still refractory from the defibrillation shock.…”

Virtual Sources and Sinks During Extracellular Field Shocks in Cardiac Cell Cultures

“…7 Recent studies on the effect of short defibrillation pulses have demonstrated the importance of intramyocardial virtual electrodes caused by the coronary vasculature. 9 While membrane potential sources close to the extracellular electrodes are mostly produced by the macroscopic boundaries of the heart itself, 10 "far-field" virtual sources 11,12 most likely are caused by the bidomain nature 5,13 and the structural organization of myocardial tissue. 14,15 Theoretically, structural discontinuities may occur in both intra-and extracellular domains.…”