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).