Flecainide for Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a genetic arrhythmia
syndrome characterized by frequent ventricular ectopy and polymorphic, classically
bidirectional ventricular tachycardia with physical or emotional stress, which also carries
a risk of ventricular fibrillation and sudden death, despite no structural heart
abnormality. Treatment consists of beta-blockers and/or calcium channel blockers, but up to
30% of patients require implantable cardioverter-defibrillators (ICDs) due to recurrent
symptoms on medical therapy. In an animal model, flecainide was found to directly target the
molecular defect in CPVT. In a retrospective clinical study in patients with CPVT we have
seen improvement of ventricular ectopy on exercise tests when flecainide is added to
standard therapy. We propose a prospective trial of flecainide added to standard therapy in
CPVT patients to test the hypothesis that flecainide will reduce ventricular ectopy on
exercise testing compared to placebo plus standard therapy.

This will be a single-blind (blinded subjects) randomized cross-over study, in which each
patient will receive treatment A (flecainide or placebo) for at least 3 months and, after a
1 week wash-out, treatment B (placebo or flecainide) for at least 3 months.

Inclusion Criteria:

1. Clinical diagnosis of CPVT, based on:

A. reproducible polymorphic or bidirectional ventricular tachycardia with exercise OR
B. Ventricular ectopy on exercise test with RYR2 or CASQ2 mutation

2. Functioning ICD in place

3. On stable dose of standard therapy defined as the maximal tolerated dose of
beta-blocker and may include a calcium channel blocker

Patients on flecainide or mexiletine are also eligible for enrollment after a 1 week
"washout" period during which flecainide or mexiletine is discontinued, and standard
therapy alone is used.

Exclusion Criteria:

1. Females who are pregnant or plan to be pregnant during the study period

2. Children < 5 years of age

3. Patients unable to perform treadmill exercise

4. Patients with significant structural heart disease

5. Patients with features consistent with Andersen-Tawil syndrome A. Periodic paralysis
or unexplained weakness B. Dysmorphic facies C. Known KCNJ2 mutation

6. Patients with known hypersensitivity to flecainide

7. Patients on amiodarone

8. Patients not expected to comply with follow-up