Wilson, W.M., University of Melbourne Australia
Burchill, L., Finch, S., Grigg, L. et al
ACC Adv 2026 10 Pt 2 103276
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.