High-intensity exercise does not significantly increase the risk of sudden cardiac death in individuals with congenital long-QT syndrome (LQTS), a genetic heart disorder, according to findings from a recent multicenter study published in Circulation.

“The most important takeaway message of this study is that current therapies for long-QT syndrome, when they are taken as prescribed, are highly effective to prevent sudden death,” said Gregory Webster, MD, ’13 MPH, assistant professor of Pediatrics in the Division of Cardiology and a co-author of the study.

LQTS is an inherited cardiac arrhythmia disorder in which the lower chambers of the heart take too long to electrically reset; it affects one in every 2,500 people. While current medications are effective in treating LQTS, patients have historically been restricted from vigorous physical activity due to concerns that it may increase the risk of sudden cardiac death.

In the current study, the National Institutes of Health–funded LIVE-LQTS study (Lifestyle and Exercise in Genetic Cardiovascular Conditions), more than 1,400 individuals between the ages of 8 and 60 years who were diagnosed with LQTS were enrolled across five countries (the U.S., U.K., Canada, Australia and New Zealand) from May 2015 to February 2019.

At the time of enrollment, ninety-one percent of participants were being treated with beta-blockers, left cardiac sympathetic denervation, or an implantable cardioverter defibrillator.

Participants (or their guardians) answered physical activity and clinical event surveys every six months for three years with a follow-up exam completed in February 2022. More than half reported participating in vigorous physical activity.

By the end of the study period, 37 participants experienced the composite end point, which included one sudden cardiac arrest and one sudden death in the non-vigorous exercise group and one sudden cardiac arrest in the vigorous exercise group.

Overall, event rates over three years were similar between both groups: 2.6 percent in the vigorous exercise group and 2.7 percent in the non-vigorous exercise group.

“Most of the more than 1,400 people were following effective management strategies with their physicians, and there was no detectable difference between doing vigorous exercise, doing moderate exercise and being sedentary in relation to the death rate or in the major event rate (passing out while you’re on therapy or getting a shock from your implantable cardiac device),” Webster said.

The findings can help inform care decision-making conversations between patients and their healthcare providers, however more research is needed to help inform care strategies for patients who fall in between being low-risk and high-risk, according to Webster.

“One of the key messages is that Dr. Lampert’s team defined low-risk patients for whom sports probably carry very little increased risk of sudden death. Future work will need to better define the line between high risk and low risk,” Webster said.

This study was funded by National Heart Lung and Blood Institute grant 1R01HL125918.