Ventricular fibrillation (VF) in the human heart is not well understood. The aim of this study was to measure changes in the phase relationship between the body surface ECG and intracardiac electrograms recorded during the first 10 s of human VF.
We studied 11 episodes of VF and measured the coherence of (a) ECG lead 1 and ECG lead V1, (b) ECG had V1 and the right ventricular apex (RVA) electrogram, and (c) ECG lead V1 and the smoothed RVA electrogram. 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 VF.
Overall, the mean (SD) coherence was 31(6)% between ECG leads 1 and V 1, 17(3)% between ECG lead V1 and the RVA electrogram, and 20(4)% between ECG lead V 1 and the smoothed RVA electrogram. All 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 becomes more organised during the first 10 s of VF. This may be an optimal window for defibrillation.
Clayton RH, Murray A. Coherence between body surface ECG leads and intracardiac signals increases during the first 10 s of ventricular fibrillation in the human heart. Physiol. Meas. 20 (1999) 159-166.
Professor Alan Murray, Freeman Unit, Newcastle upon Tyne. Tel: +44 (0)191-223-6161.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
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