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15-01-2012 | Cardiology | Article

Cardiac arrest risk in runners low, but incidence has increased over past decade


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MedWire News: Cardiac arrest occurs primarily among male marathon runners and has become more common over the past decade, US researchers have found.

However, overall, marathons and half-marathons are associated with a low risk for cardiac arrest and sudden death, report Jonathan Kim (Harvard Medical School, Boston, Massachusetts) and colleagues in The New England Journal of Medicine.

They assessed the incidence and outcomes of cardiac arrest associated with marathon (26.2 miles) and half-marathon (13.1 miles) races in the USA between January 2000 and May 2010.

They interviewed survivors (patients who were successfully resuscitated and subsequently discharged from hospital) and the next of kin of nonsurvivors (patients who were not successfully resuscitated or died before hospital discharge), reviewed medical records, and analyzed postmortem data to determine the clinical characteristics of the arrests.

Of 10.9 million runners, 59 experienced a cardiac arrest, corresponding to an incidence rate of 0.54 per 100,000 participants. The incidence was significantly higher among marathon runners, at 1.01 per 100,000, than half-marathon runners, at 0.27 per 100,000.

It was also significantly higher among men, at 0.90 per 100,000 than among women, at 0.16 per 100,000.

In addition, male marathon runners had a higher incidence of cardiac arrest from 2005 through 2010 at 2.03 per 100,000 participants, than from 2000 through 2004, at 0.71 per 100,000 participants.

Of the 31 runners for whom complete clinical data were obtained, 23 died. Hypertrophic cardiomyopathy and possible hypertrophic cardiomyopathy were the most common causes of death, accounting for eight and seven of 23 deaths, respectively.

Among the eight runners who survived, ischemic heart disease was the predominant cause of cardiac arrest and accounted for five of the cases.

The strongest predictors for survival after cardiac arrest were initiation of bystander-administered CPR and an underlying diagnosis other than hypertrophic cardiomyopathy.

Multivariate analysis excluding these two factors showed that an initial cardiac rhythm of ventricular fibrillation or tachycardia and the number of previous long-distance running races completed were independently associated with survival after cardiac arrest, at respective odds ratios of 0.040 and 0.533.

"We calculated that the incidence rates of cardiac arrest and sudden cardiac death during long-distance running races were 1 per 184,000 and 1 per 259,000 participants, respectively," write the authors.

They say that this corresponds to 0.2 cardiac arrests and 0.14 sudden deaths per 100,000 runner-hours at risk, demonstrating that the incidence of cardiac arrest among marathon and half-marathon runners is relatively low compared with other athletes, including collegiate and triathlon participants as well as previously healthy middle-aged joggers.

"Clinicians evaluating potential race participants should be aware of the risks of hypertrophic cardiomyopathy and atherosclerotic disease in this patient population," conclude Kim et al.

By Piriya Mahendra

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