Coherence between body surface ECG leads and intracardiac signals increases during the first 10 s of ventricular fibrillation in the human heart

Ventricular fibrillation (VF) in the human heart is not well understood. Th e aim of this study was to measure changes in the phase relationship betwee n the body surface ECG and intracardiac electrograms recorded during the fi rst 10 s of human VE We studied 11 episodes of VF and measured the coherenc e of (a) ECG lead I and ECG lead V1, (b) ECG lead V1 and the right ventricu lar apex (RVA) electrogram, and (c) ECG lead V1 and the smoothed RVA electr ogram. Each coherence measurement was the average of the magnitude squared coherence function in the range 0-60 Hz, and measurements were made 1, 3, 5 , 7 and 9 s after the onset of VE Overall, the mean (SD) coherence was 31(6 )% between ECG leads I and V1, 17(3)% between ECG lead V1 and the RVA elect rogram, and 20(4)% between ECG lead V1 and the smoothed RVA electrogram. Al l three measurements of coherence increased significantly between 1 and 9 s with mean (SD) rates of 0.97(1.01)% s(-1), 0.8(1.18)% s(-1) and 0.82(1.19) % s(-1) respectively. These results show that propagation in human VF becom es more organized during the first 10 s of VE This may be an optimal window for defibrillation.