DETERMINANTS OF SPONTANEOUS OCCURRENCE OF SUSTAINED MONOMORPHIC VENTRICULAR-TACHYCARDIA IN RIGHT-VENTRICULAR DYSPLASIA

Objectives. We sought to demonstrate the determinants of spontaneous o nset of ventricular tachycardia in right ventricular dysplasia. Backgr ound. Sudden death during athletic activities has been described in pa tients with right ventricular dysplasia, but few data are available on the clinical circumstances of well tolerated ventricular tachycardias . Methods. The spontaneous occurrence of 43 episodes of sustained mono morphic ventricular tachycardia Was recorded during ambulatory electro cardiogaphic (Holter) monitoring in 12 patients. Results. The ventricu lar tachycardia usually occurred without a significant immediate preci pitating arrhythmic event: Atrial arrhythmia was never present, and lo ng-short cycle sequences by postextrasystolic pauses or runs of polymo rphic extrasystoles were also unusual (four episodes of ventricular ta chycardia each). Finally, mo arrhythmia was present immediately before the tachycardia in 36 (84%) of the 43 episodes and in 8 of 12 patient s. Examination of the sinus rate before the initial episode of tachyca rdia in each patient showed a continuous increase from 30 min to the f ew cycles before the tachycardia (mean RR decrease from 876 +/- 778 to 830.5 +/- 189 ms, with a mean slope of -8.4 ms/min; both p = 0.01 by Wilcoxon test). A within-patient comparison showed that the first cycl e of the ventricular tachycardia was shorter than that of runs or coup lets (389 +/- 88 vs. 453 +/- 121 and 520 +/- 133 ms, p = 0.03 and p < 0.01, respectively, by paired t test) and that the second cycle was sh orter than that of runs (383 +/- 96 vs. 435 +/- 120 ms, p = 0.03). Sin us rate measured 15 beats before the event was higher for ventricular tachycardia than for isolated beats (mean RR interval 835 +/- 184 vs, 908 +/- 153 ms, p < 0.01). Conclusions. Increased heart rate and short ening of the coupling intervals of the first cycles before the tachyca rdia are due to a change in the vagosympathetic balance with an increa sed sympathetic tone, This increase appears to be the main determinant of the ventricular tachycardia in this disease in contrast to the mul tifactorial origin of ventricular tachycardia due to coronary heart di sease. It should be considered in patients participating in strenuous athletic activities.