Heat stroke more prevalent than CV events among distance runners

Long-distance runners are more likely to experience a serious case of heat stroke than a serious CV event, according to new study findings.

In a retrospective study, researchers examined all long-distance races taking place in Tel Aviv, Israel, between March 2007 and November 2013. They compared life-threatening events, defined as those requiring mechanical ventilation and hospitalization in an ICU, related to CV causes and heat stroke.

There were 137,580 runners participating in the races covered by the study. The researchers observed two serious CV events — one MI and one hypotensive supraventricular tachyarrhythmia, neither fatal — compared with 21 serious cases of heat stroke, two of which were fatal and 12 of which were life-threatening. One of the people who died of heat stroke also presented with cardiac arrest without previous warning.

“This research shows that heat stroke is the real threat to marathon and long-distance runners; however, there are no clinical studies of potential strategies to prevent heat stroke during these types of events,” researcher Sami Viskin, MD, a cardiologist at Tel Aviv Medical Center, said in a press release. “It’s important that clinicians educate runners on the ways to minimize their risk of heat stroke, including allowing 10 to 14 days to adjust to a warm climate, discouraging running if a person is ill or was recently ill because a pre-existing fever impairs the body’s ability to dissipate additional heat stress, and developing better methods of monitoring body core temperature during physical activity.”

It is unlikely that runners at risk for CV events were screened out before the races, as a survey of 513 runners at a 2013 race revealed that only 35% had an ECG screening in the previous years and 46% had it in the previous 5 years, according to the researchers. Israeli sports law does not require ECG screening for individuals in public endurance races, but it does for those in team or association sports, according to the press release.

Brian Olshansky, MD, of the University of Iowa, Iowa City, and David S. Cannom, MD, of the UCLA School of Medicine, wrote in a related editorial that “patients who develop heat stroke may rapidly develop cardiac arrest, and the diagnosis may be missed if rectal core body temperature is not measured soon after a runner collapses.”

They noted that a previous review found that the incidence of cardiac arrest in long-distance races was just 0.54 per 100,000 participants, and that hypertrophic cardiomyopathy was usually the cause of death when cardiac arrest did occur; myocardial ischemia was found in only 16% of cases.

For more information:

Olshansky B. J Am Coll Cardiol. 2014;64:470-471.

Yankelson L. J Am Coll Cardiol. 2014;64:463-469.

Disclosure: The researchers and Cannom report no relevant financial disclosures. Olshansky reports speaking for Medtronic and consulting for Amarin, Boehringer Ingelheim, BioControl, Boston Scientific, Daiichi Sankyo and Sanofi-Aventis.