Efficacy of Flecainide in the Treatment of Catecholaminergic Polymorphic Ventricular Tachycardia: A Randomized Clinical Trial

Abstract

Importance: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal genetic arrhythmia syndrome characterized by polymorphic ventricular tachycardia with physical or emotional stress, for which current therapy with β-blockers is incompletely effective. Flecainide acetate directly suppresses sarcoplasmic reticulum calcium release-the cellular mechanism responsible for triggering ventricular arrhythmias in CPVT-but has never been assessed prospectively.

Objective: To determine whether flecainide dosed to therapeutic levels and added to β-blocker therapy is superior to β-blocker therapy alone for the prevention of exercise-induced arrhythmias in CPVT.

Design, setting, and participants: This investigator-initiated, multicenter, single-blind, placebo-controlled crossover clinical trial was conducted from December 19, 2011, through December 29, 2015, with a midtrial protocol change at 10 US sites. Patients with a clinical diagnosis of CPVT and an implantable cardioverter-defibrillator underwent a baseline exercise test while receiving maximally tolerated β-blocker therapy that was continued throughout the trial. Patients were then randomized to treatment A (flecainide or placebo) for 3 months, followed by exercise testing. After a 1-week washout period, patients crossed over to treatment B (placebo or flecainide) for 3 months, followed by exercise testing.

Interventions: Patients received oral flecainide or placebo twice daily, with the dosage guided by trough serum levels.

Main outcomes and measures: The primary end point of ventricular arrhythmias during exercise was compared between the flecainide and placebo arms. Exercise tests were scored on an ordinal scale of worst ventricular arrhythmia observed (0 indicates no ectopy; 1, isolated premature ventricular beats; 2, bigeminy; 3, couplets; and 4, nonsustained ventricular tachycardia).

Results: Of 14 patients (7 males and 7 females; median age, 16 years [interquartile range, 15.0-22.5 years]) randomized, 13 completed the study. The median baseline exercise test score was 3.0 (range, 0-4), with no difference noted between the baseline and placebo (median, 2.5; range, 0-4) exercise scores. The median ventricular arrhythmia score during exercise was significantly reduced by flecainide (0 [range, 0-2] vs 2.5 [range, 0-4] for placebo; P < .01), with complete suppression observed in 11 of 13 patients (85%). Overall and serious adverse events did not differ between the flecainide and placebo arms.

Conclusions and relevance: In this randomized clinical trial of patients with CPVT, flecainide plus β-blocker significantly reduced ventricular ectopy during exercise compared with placebo plus β-blocker and β-blocker alone.

Trial registration: clinicaltrials.gov Identifier: NCT01117454.

Conflict of interest statement

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Figures

Figure 1.. Study Flowchart

Participant flow is shown for a randomized clinical crossover trial of flecainide acetate for catecholaminergic polymorphic ventricular tachycardia. ICD indicates implantable cardioverter defibrillator.

Figure 2.. Efficacy of Flecainide in Reducing Ventricular Arrhythmias During Exercise in Catecholaminergic Polymorphic Ventricular Tachycardia

A, Change in arrhythmia score for each patient between the placebo and flecainide acetate arms for the 12 patients with available data (P = .008). B, Change in arrhythmia score for each patient between baseline (β-blocker only) vs flecainide arm for the 13 patients with available data (P = .005). C, Change in arrhythmia score for each patient between baseline (β-blocker only) vs placebo arm for the 12 patients with available data (P = .70). NSVT indicates nonsustained ventricular tachycardia; PVC, premature ventricular contractions.