Nadolol decreases the incidence and severity of ventricular arrhythmias during exercise stress testing compared with β1-selective β-blockers in patients with catecholaminergic polymorphic ventricular tachycardia

BACKGROUND Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inheritable cardiac disease predisposing to malignant ventricular arrhythmias. OBJECTIVE We aimed to explore the incidence and severity of ventricular arrhythmias in patients with CPVT before the initiation of beta-blocker treatment, when treated with beta(1)-selective beta-blockers, and when treated with nadolol. METHODS In this study, 34 patients with CPVT were included (mean age 34 +/- 19 years; 15 (44%) women; 30 (88%) ryanodine receptor 2 variant positive). We performed 3 bicycle exercise stress tests in each patient: (1) before the initiation of beta-blocker treatment, (2) after >6 weeks of treatment with beta(1)-selective beta-blockers and (3) after >6 weeks of treatment with nadolol. We recorded resting and maximum heart rates and the most severe ventricular arrhythmia occurring. Severity of arrhythmias was scored as 1 point for no arrhythmias or only single ventricular extrasystoles, 2 points for >10 ventricular extrasystoles per minute or bigeminy, 3 points for couplets, and 4 points for nonsustained ventricular tachycardia or sustained ventricular tachycardia. RESULTS Resting heart rate was similar during treatment with nadolol and beta(1)-selective beta-blockers (54 +/- 10 beats/min vs 56 +/- 14 beats/min; P = .50), while maximum heart rate was lower during treatment with nadolol compared with beta(1)-selective beta-blockers (122 +/- 21 beats/min vs 139 +/- 24 beats/min; P = .001). Arrhythmias during exercise stress testing were less severe during treatment with nadolol compared with during treatment with beta(1)-selective beta-blockers (arrhythmic score 1.6 +/- 0.9 vs 2.5 +/- 0.8; P < .001) and before the initiation of beta-blocker treatment (arrhythmic score 1.6 +/- 0.9 vs 2.7 +/- 0.9; P = .001); however, no differences were observed during treatment with beta(1)-selective beta-blockers compared with before the initiation of beta-blocker treatment (arrhythmic score 2.5 +/- 0.8 vs 2.7 +/- 0.9; P = .46). CONCLUSION The incidence and severity of ventricular arrhythmias decreased during treatment with nadolol compared with during treatment with beta(1)-selective beta-blockers. beta(1)-Selective beta-blockers did not change the occurrence or severity of arrhythmias compared with no medication.