TOPLINE:

A 12-week supervised high-intensity interval training (HIIT) programme significantly improved exercise capacity and quality of life (QOL) in patients with an implantable cardioverter defibrillator (ICD) due to coronary artery disease (CAD) or non-ischaemic dilated cardiomyopathy (DCM).

METHODOLOGY:

• Researchers conducted a single-centre randomised controlled trial to evaluate the effect of HIIT on exercise capacity and QOL in patients with an ICD due to CAD or non-ischaemic DCM.
• They included 56 patients (mean age, 68.2 years; 82% men) who underwent ICD implantation at a hospital in Norway between September 2019 and January 2022.
• Participants were stratified on the basis of the underlying cause of device implantation (CAD or DCM) and were randomly assigned to either a supervised HIIT group or a control group continuing usual activity.
• The HIIT protocol comprised treadmill sessions three times weekly for 12 weeks with four 4-minute intervals, targeting 85%-95% of maximum heart rate separated by a 3-minute recovery period under the supervision of an exercise physiologist, with safety ensured by the cardiac emergency response plan; the heart rate was monitored to ensure adherence to the prescribed intensity.
• Primary outcomes were changes in peak oxygen uptake (VO₂ peak) measured using the cardiopulmonary exercise test and QOL assessed using the RAND 36-item Short-Form (SF-36) questionnaire.

TAKEAWAY:

• HIIT increased VO₂ peak by 7.0% from baseline to follow-up, whereas no change in VO₂ peak was observed for the control group; the between-group difference was 1.7 mL/kg/min (P < .001).
• After adjustment for multiple comparisons, patients in the HIIT group showed significant improvement in QOL on the SF-36 health change domain compared with those in the control group (+14.8 vs -7.1 points; P < .001), although other SF-36 domains showed favourable but non-significant trends.
• The incidence of sustained ventricular tachycardia was lower in the HIIT group (P = .037); however, this finding had limited clinical interpretability as most patients in both the groups experienced no events, and few patients accounted for the majority of sustained ventricular tachycardia events.
• Two patients in the HIIT group experienced sustained ventricular tachycardia during the training session, with one serious event of ventricular fibrillation requiring ICD shock and exclusion, and another patient had an asymptomatic ventricular tachycardia episode, successfully managed with antitachycardia pacing.

IN PRACTICE:

"For ICD patients considering participation in HIIT, a maximal exercise test is advisable to assess functional capacity, identify those at higher risk to exercise-induced VA [ventricular arrhythmia], and determine HR_max [maximum heart rate] for potential adjustment of ICD therapy zones," the researchers of the study wrote.

SOURCE:

This study was led by Mathias Nyman, St Olavs Hospital, Trondheim University Hospital, Trondheim, Norway. It was published online on April 13, 2026, in European Heart Journal Open.

LIMITATIONS:

The single-centre design, modest sample size, and relatively short 12-week intervention period limited statistical power for safety endpoints and long-term outcome assessment. The high exclusion rate and baseline imbalances in the prevalence of atrial fibrillation may have introduced selection bias and influenced arrhythmic outcomes.

DISCLOSURES:

This study received support from the Joint Research Committee between St Olavs Hospital and the Faculty of Medicine and Health Sciences at the Norwegian University of Science and Technology and other sources. The authors reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.