Calcium channel blockers and beta-blockers versus beta-blockers alone for preventing exercise-induced arrhythmias in catecholaminergic polymorphic ventricular tachycardia

Background: The mainstay of therapy for catecholaminergic polymorphic ventricular tachycardia (CPVT) is maximal doses of β-blockers. However, although β-blockers prevent exercise-induced ventricular tachycardia (VT), most patients continue to have ventricular ectopy during exercise, and some studies report high mortality rates despite β-blockade. Objective: The purpose of this study was to investigate whether combining a calcium channel blocker with β-blockers would prevent ventricular arrhythmias during exercise better than β-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 β-blocker therapy were studied. Symptom-limited exercise was first performed during maximal β-blocker therapy and repeated after addition of oral verapamil. Results: When comparing exercise during β-blockers with exercise during β-blockers + verapamil, exercise-induced arrhythmias were reduced: (1) Three patients had nonsustained VT on β-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 β-blocker therapy (14 ICD shocks over 6 months while on β-blockers) has remained free of arrhythmias (for 7 months) since the addition of verapamil therapy. Conclusions: This preliminary evidence suggests that β-blockers and calcium blockers could be better than β-blockers alone for preventing exercise-induced arrhythmias in CPVT.