Cardiac Death During Triathlon 'Not Rare'

Debra L Beck

September 29, 2017

MINNEAPOLIS, MN — Over a 30-year period, 135 triathlon participants died or suffered cardiac arrest during USA Triathlon (USAT)–sanctioned events, a new study shows. The vast majority were men over 40 years of age, and two-thirds of deaths occurred during the swim segment[1].

"Deaths and cardiac arrests during the triathlon are not rare" and exceed the one fatal event per 100,000 participants reported for marathon racing, the researchers, led by Dr Kevin Harris (Minneapolis Heart Institute Foundation, MN) conclude.

Their findings were published September 19, 2017 in the Annals of Internal Medicine.

From 2006 to 2015, the period for which the researchers had the most complete data, the incidence of fatal events was 1.74 per 100,000 participants.

The researchers reviewed data assembled from multiple sources, including USAT, the governing body for multisport disciplines in the US, personal reports from interested parties, and the US National Registry of Sudden Death in Athletes, which uses news media, internet searches, LexisNexis archival databases, and news clipping services to find cases.

The number of finishers was used as a surrogate for the number of participants. The researchers made a "conservative projected estimate" that there were more than 9 million race finishers during the study period that was based on the actual number of finishers calculated using USAT records covering the 2006–2015 period, Harris said in an interview. Additional information on victims and race conditions was obtained through contact with next of kin and race directors.

"I think that our data going back to the 1980s and our denominator information [of more than 9 million finishers] allows us to be relatively precise in determining who are the people at greatest risk," Harris told | Medscape Cardiology.

Harris presented preliminary data from this study at the American College of Cardiology annual meeting in 2016.

From 135 total events, 120 were cardiac-related (107 sudden deaths and 13 resuscitated cardiac arrests) and 15 were related to blunt trauma. All of the trauma-related deaths were incurred during the bike segment—10 involved motor vehicles and five were related to falls or collisions with stationary objects, such as guard rails and trees.

Autopsy reports were available for 61 racers and showed cardiovascular abnormalities in 27 (44%). Of those, 18 were found to have significant atherosclerotic coronary artery disease, defined as >50% narrowing in the left main coronary artery or >70% in the other major coronary arteries.

"Was it coronary disease that caused these deaths, or did the athletes drown or have an arrhythmia and drown?" asked Harris. "Autopsy is really good for showing anatomic lesions, but it doesn't tell us if the patient had, say, an arrhythmia that led to the death. I think in most cases, we really don't know for sure why the athlete died."

Three decedents were found to have evidence of hypertrophic cardiomyopathy and two additional athletes had mitral-valve prolapse (one of whom had a history of Wolff-Parkinson-White syndrome).

Other relevant findings included (one each): a congenital coronary anomaly, an ascending aortic dissection with rupture, a spontaneous renal-artery dissection, and an arrhythmogenic right ventricular cardiomyopathy.

The majority of events (85%) occurred in men, with the risk increasing incrementally with each decade. Of the 115 deaths or cardiac arrests in men, 103 occurred in racers over the age of 40.

The rate of deaths and cardiac arrests per 100,000 participants was more than threefold higher for men aged 40 years or older than for those younger than 40 years (8.25 vs 2.49 events per 100,000 participants). Risk topped out at 18.6 events per 100,000 male participants in the >60 years  category.

Whether screening might save lives in this population is an open question, but Dr Reginald Ho (Thomas Jefferson University Hospital, Philadelphia, PA), who with Dr Karen Glanz (University of Pennsylvania, Philadelphia) wrote an accompanying editorial[2], thinks mandated preparticipation screening might "not be popular."

"When you get beyond a certain age, you kind of do what you want to do, and a lot of people don't realize there is an inherent risk with exercise or they don't realize they themselves are at risk, particularly if they have never had any problems before," he said in an interview.

He does feel that greater efforts should be made to educate older athletes, "especially men over 40 years of age," about the signs and symptoms of cardiovascular disease and the possible risks of participating in strenuous sports like the triathlon.

"They should at least get checked and make sure that if they have any cardiovascular symptoms that those are not ignored," he said.

For his part, Harris thinks it is reasonable for clinicians to use these data as part of a discussion on risk with an older patient who wants to participate in an endurance sport and may or may not have established coronary artery disease.

"One group is those with established disease, but the bigger group is those at risk who don't know they are at risk because they think that since they exercise and are relatively healthy, they haven't been laying down plaque in their arteries."

Is Swimming More Dangerous?

Ninety of 135 deaths and cardiac arrests (67%) occurred during the swim segment, which is the first event in the triathlon. Harris offered several causative hypotheses to explain this finding.

"We don't really understand why the swim was associated with more events, but one thought is that your adrenalin is probably going to be higher at the very beginning of the race, when you're first entering the water, but also adverse conditions, the very close proximity of other swimmers can make it hard to get into your usual endurance-sport groove," said Harris.

Although it's a possibility that has not been tested, Ho doubts swimming is an inherently riskier activity than biking or running in this "very heterogeneous population." Rather, he suspects the increased event rate seen during the swim could be related to logistical issues around detecting, reaching, rescuing, and treating an athlete who runs into trouble in the water.

"If someone collapses during the run, you may be able to get them defibrillated pretty quickly," he said. "In the water, first of all there is the risk of drowning, but even when you get to them and drag them out of the water, you can't immediately put a defibrillator on them until they are on land and dried off. It might be just a few seconds or minutes, which could make a big difference in outcome."

Interestingly though, the length of the swim segment (ranging from ≤750 m to one mile or more) did not appear to affect the risk of sudden death or cardiac arrest. Almost half (49%) of events occurred in shorter-swim events, 24% in intermediate events, and 17% in the swim segment of long-distance triathlons.

The current study is an expansion of an earlier effort that examined sudden death in USA Triathlon–sanctioned event over a 3-year period, from January 2006 to September 2008[3]. In that study, Harris's group identified 14 deaths in 14 triathlons among 922,810 finishers, 11 of which were in men and 13 of which occurred during the swim.

Since the triathlon's first appearance as an Olympic sport in 2000, the event has surged in popularity. According to data from USAT, the governing body for the sport in the US, more than 4300 sanctioned multisport events involving more than 470,000 participants took place in 2015 alone[4].

Members ages 40 to 49 comprise the largest sector of USAT annual membership at more than 30% of the overall membership base.

The study was funded by the Minneapolis Heart Institute Foundation. Harris reports no relevant financial relationships.  Disclosures for the coauthors are listed in the paper. Ho and Glanz report no relevant financial relationships.

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