Abstract 9815: Nadolol Seems to Be Superior to Selective Beta Blockers in Patients With Catecholaminergic Polymorphic Ventricular Tachycardia: Is a Smaller Arrhythmic Window Part of the Explanation?

Abstract

Introduction: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inheritable arrhythmogenic disease, and typically presents as syncope or sudden cardiac death during exercise. Beta blockers are first choice therapy but little is known about antiarrhythmic effects of different beta blockers in CPVT. Nadolol has shown superior antiarrhythmic effect in other cardiomyopathies. Hypothesis: We hypothesized that nadolol is superior to selective beta blockers in arrhythmia protection in CPVT patients. Methods: We included 34 CPVT patients (age 34±19 yrs, 44% female, 88% RYR2 mutation positive). We serially performed 2 bicycle exercise tests in each patient; 1)>6 weeks on maximum tolerated dose of selective beta blockers. 2)>6 weeks on maximum tolerated dose of nadolol. We recorded resting and maximum heart rate (HR), HR at first arrhythmia and the most severe arrhythmia occurring. Arrhythmic window was defined as the difference between maximum HR and HR at first arrhythmia. Severity of arrhythmias was scored as arrhythmic score: no arrhythmias (0point), single ventricular extra systoles (1point), bigemini (2points), couplets (3points) and nonsustained VT (4points). Results: Resting HR was similar on nadolol and selective beta blockers (54±10bpm vs. 56±14bpm, p=0.50), while maximum heart rate was lower on nadolol (122±21bpm vs. 139±24bpm, p<0.01). First arrhythmias occurred at similar HR at both exercise tests (113±21bpm vs. 113±19bpm, p=1.0). Consequently, arrhythmic window was smaller during nadolol treatment (17±10bpm vs. 32±26bpm, p=0.03) (Figure) and also the arrhythmic score was lower than on selective beta blockers (1.1±1.2 vs. 2.4±0.9, p<0.01). Conclusion: Arrhythmic score was lower on nadolol compared to selective beta blockers. Also, arrhythmic window, representing the span of heart rates where arrhythmias may occur and progress in severity, was smaller. This suggests that nadolol should be the beta blocker of choice in CPVT patients.