Effect of high-intensity interval training on peak oxygen uptake, quality of life, and ventricular arrhythmias in patients with an implantable cardioverter defibrillator: a randomized controlled trial

Abstract Aims Exercise is effective in preventing and treating cardiovascular disease. High-intensity interval training (HIIT) has shown promising effects on cardiorespiratory fitness and quality of life (QoL). However, evidence of risks and beneficial effects of HIIT in patients at high risk of ventricular arrhythmias (VA) is limited. This study evaluated the effects of HIIT on peak oxygen uptake (VO2peak), QoL, and the burden of VA in patients with an implantable cardioverter defibrillator (ICD). Methods and results Fifty-six ICD patients with coronary artery disease (CAD) or non-ischaemic dilated cardiomyopathy (DCM) were randomized to a 12-week supervised HIIT programme with intervals at 85–95% of maximum heart rate, or to usual activity (control). Primary outcomes were changes in VO2peak and QoL. Secondary outcomes included changes in VA burden, with or without ICD therapy. High-intensity interval training increased VO2peak by 7.0% vs. no change in the control group, with a between-group difference of 1.7 mL/kg/min (95% confidence interval, 0.7–2.6; P < 0.001). After correction for multiple testing, HIIT improved QoL on the SF-36 health change domain, while most other domains showed favourable but non-significant trends. Clinically relevant VA occurred in two patients during baseline exercise testing and in two patients during HIIT. Sustained ventricular tachycardia incidence was lower in the HIIT group (P = 0.037), although the number of events was small and unevenly distributed. Conclusion In ICD patients with CAD or non-ischaemic DCM, a supervised 12-week HIIT programme significantly improved exercise capacity and QoL. However, its overall impact on VA remains inconclusive, and the risk of exercise-induced arrhythmias remains a concern.