Long-term Serial Exercise Stress Testing in RyR2-Positive Genotype Patients with Catecholaminergic Polymorphic Ventricular Tachycardia on Beta-Blocker and Flecainide Therapy.

IntroductionCatecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is a potentially life-threatening arrhythmic disorder typically treated with beta-blockers and, occasionally, with flecainide. MethodsAll patients underwent genetic testing, ECG, echocardiogram, and exercise tests. Ventricular arrhythmias were assessed using qualitative and quantitative scoring. Flecainide dosing was gradually increased, and follow-up extended from 2007 to 2024. Results235 patients were genetically positive for the RyR2 p.Gly357Ser mutation, of whom 32 required beta-blockers and flecainide (age at diagnosis 18 (1-55) years old, start of flecainide at 32 (15-66) years old, 16 (50%) male patients). 47% had an implantable cardioverter defibrillator (ICD). Flecainide was indicated for ventricular arrhythmia (97%) during the exercise test despite beta-blocker therapy and median treatment duration with flecainide was of 7.3 years. All patients were on propranolol (median dose 65 mg/day). Flecainide (median dose 100 mg/day) was well tolerated, with no syncope or stress-induced dizziness. Before flecainide, 5 patients (16%) had ventricular arrhythmic events in the ICD, with 2 requiring appropriate shocks. After flecainide, no events occurred. Both qualitative (2.07{+/-}0.77 vs. 1.22{+/-}1.08, p<0.001) and quantitative (69.78{+/-}83.17 vs. 15.29{+/-}5.53, p<0.001) arrhythmic scores improved significantly after adding flecainide. Additionally, there was a significant increase in METs (Z=-2.564, p=0.010) and a reduction in the maximum heart rate (Z=-2.870, p=0.004) and the percentage of the age-predicted maximum heart rate (Z=-3.403, p=0.001) during the exercise test with the combined therapy. ConclusionFlecainide and beta-blocker therapy in CPVT patients resulted in significant improvements in exercise capacity and a reduction in arrhythmic burden in the long-term follow-up.