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 Background and 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 56 ICD patients with coronary artery disease (CAD) or non-ischemic dilated cardiomyopathy (DCM) were randomized to a 12-week supervised HIIT program 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 Results HIIT increased VO2peak by 7.0% versus no change in the control group, with a between-group difference of 1.7 mL/kg/min (95% CI, 0.7-2.6; P0.001). 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 VT incidence was lower in the HIIT group (P=0.037), although the number of events were small and unevenly distributed. Conclusions In ICD patients with CAD or non-ischemic DCM, a supervised 12-week HIIT program significantly improved exercise capacity and QoL. However, its overall impact on VA remains inconclusive, and the risk of exercise-induced arrhythmias remains a concern.