Ivabradine Use and Exercise Capacity Post-Atrial Switch Repair for Transposition of Great Arteries.

BACKGROUND: There are few proven therapies for improving exercise capacity in patients with transposition of the great arteries who have undergone an atrial switch repair. OBJECTIVES: The objective of the study was to evaluate the effect of heart rate lowering using ivabradine on exercise capacity and quality of life in this cohort. METHODS: In this single-center, randomized, double-blind, crossover study, patients were randomized to ivabradine or placebo for 4 weeks then crossover treatment for 4 weeks. A cardiopulmonary stress test and quality of life assessment were performed at baseline then at weeks 4 and 8. Estimates of difference were described using a mixed effects model. RESULTS: A total of 19 patients were eligible and 10 patients completed the study. Compared to placebo, ivabradine treatment was associated with lower heart rate at baseline (65 ± 3 beats/min on ivabradine vs 79 ± 5 beats/min on placebo, difference -14.6 [-24, -5]; P = 0.008) and at peak exercise (131 ± 7 beats/min vs 146 ± 7 beats/min, difference -15.3 [-24, -6]; P = 0.003). Peak oxygen consumption was 20.4 ± 1.2 mL/kg/min on ivabradine vs 19.2 ± 1.2 mL/kg/min on placebo (difference +1.2 [-0.09, 2.6]; P = 0.06). Peak oxygen pulse was higher on ivabradine compared to placebo (12.5 ± 1.2 vs 10.7 ± 1.2 mL/beat, difference +1.7 [0.9, 2.6]; P = 0.002). Visual analog score was 73.5 ± 5.6 on ivabradine vs 62.5 ± 5.6 on placebo (mean difference 11.0 [-1.6, 23.6]; P = 0.08). One patient developed symptomatic bradycardia and one patient experienced phosphenes. CONCLUSIONS: Ivabradine use in patients with transposition of the great arteries and atrial switch repair lowered peak heart rate with exercise and was associated with a higher oxygen pulse. (Effect of Ivabradine use on exercise capacity in patients with transposition of the great arteries [TGA] post atrial switch repair; ACTRN12621000196842).