CHICAGO — Just because you're a well-conditioned marathon runner doesn't mean you can't have a diseased heart. This may be especially true if you're in the fifth decade of life — not an uncommon situation, according to Stefan Möhlenkamp, MD, PhD, cardiologist and principal investigator of a study of marathon runners and the use of MRI to detect coronary artery disease (CAD).

Making a press conference presentation at the annual meeting of the Radiological Society of North America (RSNA; Oak Brook, Illinois), Möhlenkamp described a familiar scenario in which a person has successfully completed a professional career, the children likely have left the nest, and so the person is looking for the next big challenge.

Aha! — why not run marathons?

And that's the challenge being targeted by an increasing number of those in the middle to later stages of life, according to Möhlenkamp.

But these stages, in terms of taking on such duty, shouldn't be marked in years or apparent physical accomplishment, he noted, since: "You're as old as your arteries."

Hence, even if the person has been running marathons and so assumes considerable health because of it, asymptomatic heart disease is altogether possible.

This reality lies in the findings of Möhlenkamp and Torleif Sandner, MD, radiologist at University Hospital, Munich University (Munich, Germany): that MRI studies showed that cardiovascular disease is a fairly common occurrence among seemingly healthy endurance athletes over the age of 50, and this may be difficult to distinguish from the common effects of training on the heart muscle.

The good news, according to Sandner, is that "radiologists can use MRI to identify cardiovascular disease that is not yet causing symptoms."

This becomes even more important when one realizes that coronary atherosclerosis is the main cause of death in individuals older than 35 years of age, a fact Möhlenkamp pointed out.

The paradox of exercise is sometimes a "two-edged sword," he said, in that it can occur in the well-trained athlete as well as the weekend warrior type of runner.

And this understanding is a wide departure from the thinking of the 1970s, when one researcher held that "marathon running provides immunity to CAD." It was not until the 1980s when researchers first began to agree that runners frequently suffer from atherosclerosis and its effects.

The study presented at RSNA was performed at University Hospital (Essen, Germany) and involved 110 male volunteers between the ages of 50 and 72, all of whom had completed at least five marathons in the last three years. The athletes had no symptoms and no known history of cardiovascular disease or diabetes.

The MRI scans revealed that, although cardiac chambers were not enlarged, left ventricular mass (LVM) in the marathon runners was significantly higher than in the general population. LVM is the weight of the muscle of the left ventricle. The marathon runners had an average LVM weight of 141 grams compared to a normal weight of about 77.5 grams.

Currently, pre-training screening of marathoners might include a blood pressure check, questions about heart disease or diabetes in one's family history or any history of chest pain — all things the researchers say could still not uncover existing heart disease.

The researchers stopped short of suggesting that all marathon runners get an MRI before beginning endurance training, saying that they will have to wait for the long-term outcome of more advanced trials before making or not making such a recommendation.

And Möhlenkamp emphasized that the study should not be taken as a clarion warning that runners should abandon their sport. He said that a key message remains that, overall, running is healthy and "a good thing."

"Exercise is the best thing anyone can do to prolong and improve the quality of life," he said.

Rather, he said that a key point of the study is targeted to clinicians who see healthy runners. "As physicians, we need to determine how to safely declare an individual of advanced age fit for marathon running."

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