Determinants of spontaneous occurrence of sustained monomorphic ventricular tachycardia in right ventricular dysplasia.

OBJECTIVES: We sought to demonstrate the determinants of spontaneous onset of ventricular tachycardia in right ventricular dysplasia. BACKGROUND: Sudden death during athletic activities has been described in patients 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 monomorphic ventricular tachycardia was recorded during ambulatory electrocardiographic (Holter) monitoring in 12 patients. RESULTS: The ventricular tachycardia usually occurred without a significant immediate precipitating arrhythmic event: Atrial arrhythmia was never present, and long-short cycle sequences by postextrasystolic pauses or runs of polymorphic extrasystoles were also unusual (four episodes of ventricular tachycardia each). Finally, no arrhythmia was present immediately before the tachycardia in 36 (84%) of the 43 episodes and in 8 of 12 patients. Examination of the sinus rate before the initial episode of tachycardia in each patient showed a continuous increase from 30 min to the few cycles before the tachycardia (mean RR decrease from 876 +/- 778 to 830.5 +/- 189 ms, with a mean slope of approximately 8.4 ms/min; both p = 0.01 by Wilcoxon test). A within-patient comparison showed that the first cycle of the ventricular tachycardia was shorter than that of runs or couplets (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 shorter than that of runs (383 +/- 96 vs. 435 +/- 120 ms, p = 0.03). Sinus 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 shortening of the coupling intervals of the first cycles before the tachycardia are due to a change in the vagosympathetic balance with an increased sympathetic tone. This increase appears to be the main determinant of the ventricular tachycardia in this disease in contrast to the multifactorial origin of ventricular tachycardia due to coronary heart disease. It should be considered in patients participating in strenuous athletic activities.