Respective role of sympathetic tone and of cardiac pauses in the genesis of 62 cases of ventricular fibrillation recorded during Holter monitoring

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Abstract
Sixty-two Holter recordings of sudden death due to ventricular fibrillation (VF) were analysed by full disclosure and computerized processing. Thirteen sudden deaths were due to torsades de pointes in non coronary subjects (11/13), related to quinidine-like drugs and/or hypokalaemia: they were always initiated by a long RR cycle due to a post-extrasystolic pause, and announced by a progressive decrease of mean heart rate (from 77.5 ± 2.5 to 60.6 ± 2.7 beats min−1, P−1, rather than with primary VF (12 cases). A cardiac pause (RR cycle exceeding 125% of the mean five preceding cycles) was present in 22/49 cases immediately before the onset of VT/VF. The coupling interval of the extrasystole initiating VT/ VF was shorter than the shortest value encountered before: 377.6 ±± 94.5 ms vs 421.4 ± 92.3. The prematurity index (coupling interval/preceding RR cycle ratio) was lower in primary VF than in VT leading to VF. In the last hour preceding VF, ST changes were unusual (five cases), whereas heart rate increased from 82.8±20 to 92.0 ± 26.7 beats min−1, (P<0001).This acceleration was in fact present only in cases without pauses before the onset of VT/VF: from 85.0±22.8 to 99.1 + 31.1 (n = 27, P<0.001) whereas no change occurred in cases with preceding pause: from 79.8 ±15.5 to 80.8 ±16.3 (n = 22, P = NS). As a result, VT/VF without a preceding pause occurs in the setting of a higher heart rate, most probably reflecting a higher sympathetic drive. Prevention of these two main determinants by pacing and beta-blocking therapy should be more efficient than the use of antianginal or antiarrhythmic drugs.