Exercise lends vitality to almost all hearts. But Dr. Paul Thompson, director of cardiology at Hartford Hospital in Hartford, Conn., and a former competitive marathon racer, long has been fascinated with the rare cases when exercise kills seemingly healthy young athletes.
Professional sports teams increasingly share his interest and concern.
Still reeling from the sudden death last summer of San Francisco 49ers offensive lineman Thomas Herrion after a preseason game in Denver, National Football League officials invited Thompson last week to talk about sudden cardiac death to team officials who were in Indianapolis for the league scouting combine.
Thompson delivered a simple message.
"We always tell people that symptoms (of heart problems) in athletes should not be ignored," Thompson said. "If you have an underlying problem with the heart, exertion can kill you."
While the message was simple, screening young athletes for unusual heart conditions turns out to be trickier than it seems.
For one thing, the odds of a young athlete dying from a cardiac problem are minute. One study estimated that between 1983 and 1993, there was one exercise-related death for every 133,000 male high school or college athletes. For women, the estimate was only one per every 769,000 athletes.
Yet when a death occurs, it has the power to stun an entire community, and when the athlete is famous, the death becomes a national story. In New England, the sudden death in 1993 of Reggie Lewis - a basketball star with the Boston Celtics - still resonates among the region's sports fans.
After the age of 40, heart attacks become increasingly common, and the cause is almost always coronary artery disease. While the benefits of exercise in preventing heart attacks are well known, sudden exertion among usually sedentary people with artery-clogging plaques can be deadly.
In people younger than 35, the cause of sudden death is almost always a genetic abnormality of the heart and is often triggered by exercise.
The most common type of abnormality, Thompson said, is the one that killed Lewis - a condition called HCM, or hypertropic cardiomyopathy - literally a heart that has grown too fast.
"A lot of American kids die of muscle-bound heart," Thompson said.
Cardiologists like Thompson say they know how to identify young athletes at high risk for sudden death from HCM and many other heart abnormalities. However, the most definitive test - an echocardiogram that uses ultrasound to take images of the heart - "would break the bank" if it were given to every young athlete, Thompson noted.
Results of a less expensive screening test - the electrocardiogram, or EKG, which measures electrical activity of the heart - can be misleading, said Dr. Adolph M. Hutter Jr., a cardiologist at Massachusetts General Hospital in Boston and longtime medical adviser to the New England Patriots and the National Hockey League's Boston Bruins.
Nearly half of the college athletes who show up for the NFL combine, where top college football players spend a weekend participating in drills trying to impress scouts, will have an abnormal EKG, Hutter said.
Intense physical training in top athletes seems to produce different patterns of electrical activities in the heart than in their less conditioned peers. Also, black athletes tend to have thicker hearts, which leads to higher rates of abnormal EKG results, Hutter explained.
Experts in sports cardiology can usually tell the difference between EKG readings that might need further investigation and those that don't, Hutter said. Still, at the NFL combine, as many as one in six professional athletes who attend may be referred for more definitive echocardiogram tests.
Thompson said there is only one thing he can tell an athlete when extensive screening tests reveal a dangerous heart defect.
"I'm not going to let you play," Thompson said.
Some cardiologists have argued that widespread screening can prevent the death of many young athletes. Hutter is part of a committee formed by the American Heart Association to investigate whether it should recommend EKGs for all high school and college athletes.
Yet while screenings may save some lives, "false-positive" screening tests will inevitably raise unnecessary concerns - and medical bills - for many more athletes and their parents, Hutter and Thompson say.
"What you will see is a lot of 'Oh, no, this boy or this girl can't play,"' Hutter said.
Thompson argues that a family history of heart attacks at a young age or symptoms of heart problems should trigger preliminary tests. Athletes who have died suddenly often exhibit early warning signs, such as lightheadedness, chest pain or a rapid heartbeat.
The problem, of course, is that these symptoms can have many causes, and a dangerous cardiac abnormality may be the least likely explanation.
Still, Thompson said if young athletes complain, that should at least prompt screening with a stress test or EKG to rule out problems or to suggest further tests.
Thompson also acknowledges that, as the level of competition increases, so does the likelihood that athletes won't report those symptoms at all.