Cardiac Arrest and Marathons – Don’t Take Off Your Running Shoes Just Yet

Marathon runners have been making headlines more and more in recent years. Not because of the times they put up, but rather the dramatic images of runners collapsing and in some cases, dying during or right after an event.

Should you stay out of the race? Not so fast. A study published in the New England Journal of Medicine shows that if you want to go the distance, go ahead – as long as you don’t have a pre-existing condition.

The study looked at nearly 11 million runners who took part in marathons between 2000 and 2010.

By scouring media reports and checking with medical staff of races, the researchers discovered 59 cases of cardiac arrest, where a runner became unconscious with no pulse during the race or within an hour of finishing. Unfortunately forty-two of these runners died, and 51 of the 59 cases happened in men.

The overall figures translate to 1 cardiac arrest per 184,000 participants and 1 death per 259,000 participants, the researchers said. Those numbers are low compared to other athletic activities, as shown by prior studies of deaths in college athletes, triathlon participants and previously healthy middle-aged joggers, researchers said.

“You hear about this more and more,” said Dr. Aaron Baggish, senior author of the study.

Cardiac Arrest and Marathons

One of the reasons we have seen an increase in the number of collapses is due to an increase, overall, of runners who are trying to push themselves to stay fit, giving the illusion that cardiac arrest is on the rise amongst runners.

“More cases showed up during 2005-2010 than in the preceding five-year span, but that’s just because more people are participating in the races,” Baggish said. More worrisome was the finding that among male marathoners, the rate of cardiac arrest per 100,000 runners was higher during the latter half of the decade than in the first half.

Baggish thinks that’s because of a shift in attitudes about who can run long distances. Even a decade ago, 26.2 mile marathons were considered appropriate only for very athletic people, he said. But more recently people have come to think of it as “something anyone can do,” and even as a healthy activity for lowering the risk of heart disease, he said. So it has attracted people with a family history of early heart disease or early deaths. “These are just the people who are likely to get into trouble,” says Baggish

In the 31 cardiac arrests for which researchers could find a cause, most were due to clogged hardened arteries or hypertrophic cardiomyopathy, a sometimes inherited condition in which an unusually thick heart muscle can interfere with the pumping rhythm.

According to Baggish, most of the victims were unaware of their pre-existing conditions, so he would encourage aspiring and experienced runners to talk to their doctors about heart risks associated with distance running.

American Heart Association Dr. Gordon Tomaselli, president of the , called the study “reassuring” for finding so few cardiac arrests. “For most people, running a marathon, if you are so inclined, is a reasonably safe proposition,” he said.

Tomaselli, a heart specialist at Johns Hopkins University, also said runners should pay attention if they feel chest pain, dizziness, light-headedness or unusually short breath or rapid heartbeat while running. “You should listen to your body,” he said.

“We don’t want to alarm people about marathon running. The benefits of exercise are well established” said one of that report’s authors, Dr. Navin Kapur of Tufts Medical Center in Boston. The report shows even seasoned marathon runners can have heart disease, something paramedics should keep in mind if a runner shows suggestive signs, said Kapur.

Study Looks to Predict Sudden Cardiac Arrest Risk

A promising new way to predict sudden cardiac arrest risk has been identified by medical researchers at the University of Buffalo.

For patients who are at the highest risk of sudden cardiac arrest, this is exciting news, as this research may give cardiologists an advanced screening tool to help those in the high-risk category and those most likely to benefit from receiving an implantable cardiac defibrillator (ICD).

ICDs are mainly used to prevent sudden cardiac arrest in patients with advanced heart disease, but many patients’ devices are never triggered.

New research suggests that imaging the degradation of nerve function in the heart may identify those patients at greatest risk of developing a life-threatening heart rhythm.

Using Positron Emission Tomography (PET), in the largest PET imaging study ever done on sudden cardiac arrest, researchers were able to measure the amount of nerve damage within the muscular tissue of the heart.

PET imaging is also able to show where nerves have died or become damaged due to inadequate blood flow.

Sudden cardiac arrest

“The principal question we posed with this study was whether the amount of nerve damage in the heart could predict sudden cardiac arrest,” says James A. Fallavollita, author on the study. “We found that when at least 38 percent of the heart was showed signs of nerve damage, there was a significant increase in the risk of sudden cardiac arrest.”

At this time, to determine whether an ICD is needed, doctors take a measurement of heart function called the ejection fraction; the percentage of blood pumped by the heart with each beat. An ejection fraction of 35 percent or less is a strong indicator of sudden cardiac arrest risk; these patients usually require an ICD.

This research is a prime example of translational medicine (the emerging field which focuses on using what is learned in pre-clinical studies to do smarter things in the clinic). In this case, the pre-clinical studies demonstrated that the risk of developing ventricular fibrillation (a deadly heart rhythm) was related to regional nerve damage.

“Ultimately, we wanted to develop an approach that could tackle the problem of identifying a larger portion of the patients with coronary artery disease who are at risk of developing sudden cardiac arrest,” explains John M. Canty, a principal investigator of the research. “Since many patients who suffer a cardiac arrest do not have severely depressed heart function, PET imaging may be able to identify high risk individuals who, in the future, could be considered candidates for an ICD.”