Background: The mainstay of therapy for catecholaminergic polymorphic ventricular tachycardia (CPVT) is maximal doses of beta-blockers. However, although beta-blockers prevent exercise-induced ventricular tachycardia (VT), most patients continue to have ventricular ectopy during exercise, and some studies report high mortality rates despite beta-blockade.
Objective: The purpose of this study was to investigate whether combining a calcium channel blocker with beta-blockers would prevent ventricular arrhythmias during exercise better than beta-blockers alone since the mutations causing CPVT lead to intracellular calcium overload.
Methods: Five patients with CPVT and one with polymorphic VT (PVT) and hypertrophic cardiomyopathy who had exercise-induced ventricular ectopy despite beta-blocker therapy were studied. Symptom-limited exercise was first performed during maximal beta-blocker therapy and repeated after addition of oral verapamil.
Results: When comparing exercise during beta-blockers with exercise during beta-blockers + verapamil, exercise-induced arrhythmias were reduced: (1) Three patients had nonsustained VT on beta-blockers, and none of them had VT on combination therapy. (2) The number of ventricular ectopics during the whole exercise test went down from 78 +/- 59 beats to 6 +/- 8 beats; the ratio of ventricular ectopic to sinus beats during the 10-second period recorded at the time of the worst ventricular arrhythmia went down from 0.9 +/- 0.4 to 0.2 +/- 0.2. One patient with recurrent spontaneous VT leading to multiple shocks from her implanted cardioverter-defibrillator (ICD) despite maximal beta-blocker therapy (14 ICD shocks over 6 months while on beta-blockers) has remained free of arrhythmias (for 7 months) since the addition of verapamil therapy.
Conclusions: This preliminary evidence suggests that beta-blockers and calcium blockers could be better than beta-blockers alone for preventing exercise-induced arrhythmias in CPVT.