THE man was 40 years old and seemed perfectly healthy — he had just run a 10-kilometer race. But he fainted after the race and was rushed to a hospital. There, in the emergency room, his blood was tested. His levels of a heart protein, troponin, were sky-high. It looked as if he was having a heart attack.
The runner ended up in the coronary intensive care unit at Hadassah-Hebrew University Medical Center in Jerusalem. He was in the hospital for four days, undergoing test after test. Yet nothing appeared to be wrong, his doctors — Lior Tolkin, Beth Goldstein and David Rott — report in a recent issue of Cardiology. He had no other symptoms of a heart attack; every test of his heart’s function was normal. And his soaring troponin levels, which can be an indicator of heart muscle damage, went down to normal.
A false alarm or a heart attack averted or maybe a lab error? Researchers say the most likely explanation is that the man had been caught up in a poorly understood but surprisingly common phenomenon: blood tested shortly after a long or strenuous bout of exercise is likely to show abnormalities, maybe even indicators of a heart attack or liver failure. But usually the patient is not in danger. Instead, those results are normal and are not a reason for concern.
While it is unusual to find such effects after a race as short as 10 kilometers, researchers say they are well aware of the general problem.
“I can tell you several stories like that,” said Dr. Fred Apple, a professor of laboratory medicine and pathology at the University of Minnesota School of Medicine.
In one, in fact, he is the center of the story.
Dr. Apple likes to experiment on himself, so one day, when he was a medical resident at Washington University in St. Louis, he drew his own blood and sent it to the hospital lab for routine tests.
The next thing he knew, he was being paged and escorted to the coronary intensive care unit. His blood test results were terrifying, with levels of an enzyme, creatine kinase MB, 10 times higher than normal. Like the runner in Israel, it looked as if Dr. Apple was having a heart attack.
His heart was fine. But Dr. Apple had just gone for a long run (he was running 50 to 60 miles a week in those days).
That experience, in the 1980s, made Dr. Apple curious about lab tests after strenuous exercise, and led him to systematically study the problem, documenting the exercise effect.
“I’d say that 5 percent of people who stress their bodies with exercise could bump up some of these levels above the level that signals a heart attack,” Dr. Apple said.
To avoid false alarms, he suggests that patients avoid lab tests within 24 hours of exercise. If not, he said, “you are asking for abnormalities to be detected.”
Dr. Malissa Wood, a cardiologist at the Massachusetts General Hospital who is a marathon runner, goes further. “I think it’s a really bad idea to have blood work unless something is wrong,” she said.
Dr. Wood and her colleagues have studied runners in the Boston Marathon, testing their blood before and after the race for proteins that can indicate a stroke risk or a heart attack.
“Almost everything we looked at went up,” she said.
And it may not take hours of exercise to do it.
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