Regular physical exercise improves an individual's CV risk profile and reduces CVD morbidity and mortality. Paradoxically, vigorous exercise increases the short-term risk of coronary events and sudden death by 5- to 7-fold compared to rest.

Chest pain may grab an older athlete's attention. Assuming it's not ignored (an all-too-common response), it may be nothing more than an indication of underlying ischemic heart disease. Paul Thompson, MD, notes that angina has to start sometime and it need not be unstable angina just because it's activity-related. Indeed, he says, athletes can "hide their angina" by exercise training. Their heart rate slows enough that during exercise they do not feel any angina. Often, it is "revealed" when their activity is interrupted: an athlete will get sick or suffer an injury, experience short-term detraining, and when they return to their usual regimen, angina informs them of underlying heart disease. They may think it's brand new, but in fact it is probably not a new problem. They had "trained themselves out of it," but now it has become apparent.

Dr. Thompson sees his share of middle-aged patients referred with recent exercise test results, but often he suspects the report is misleading if the test is given at high speed and the patient is holding on to the treadmill for dear life to keep from flying off. He reminds his fellows that this is meant to be an exercise test and not a hand-grip test. When he sees a patient for the first time, Dr. Thompson said, "I like to repeat the [exercise] test in my own lab to determine whether they did the test with their feet or their hands." It's an important test: exercise duration (what Dr. Thompson calls the individual's "external work rate") predicts survival. "Excellent exercise tolerance, regardless of other results of the exercise test, is the best predictor of survival," he said.

He is also interested in the heart rate response, or "internal work rate." If pulse tops out at 140 or 150 bpm, that's a good indicator because it correlates with myocardial oxygen demand. It also suggests room for medical therapy, such as beta-blockers that can help keep the patient relatively asymptomatic.

For older patients, Dr. Thompson advises they use the "talk test" to determine the proper intensity for threshold workouts. The old adage that 220 minus your age is how to calculate maximum heart rate is wrong. This age-adjusted maximum heart rate formula (also known as the "age regression formula") was used to determine a target zone of 70-80% of that maximum heart rate. However it was developed a half-century ago, at a time when the science of exercise physiology was in its infancy.

History Should Not Be Rushed
In a recent review article on managing older athletes,¹ Dr. Thompson noted that asymptomatic athletes may seek a physician's advice regarding exercise because clearance is required before a specific event or because of personal concern about exercise-related events.

An effective evaluation requires a history and a physical examination to detect possible cardiac risk factors. It should not be rushed: history should include inquiry into why the patient sought medical attention and, specifically:

• Did subtle symptoms prompt the visit?
• Has there been any change in exercise performance?
• Have there been any exercise-related symptoms?

What are causes for concern? Particular attention should be paid in athletes to the presence of "warm-up angina" or dyspnea. Also, reports of exhaustion are worrisome. Without knowledge of coronary anatomy, a patient reporting a sense of exhaustion may indicate possible left main disease or, in the presence of high coronary artery calcium score, perhaps a "widow-maker" type lesion. Any drop in systolic BP during activity raises a red flag, too. There is obligatory vasodilatation in the legs during exercise and if cardiac output cannot keep up with it, then systolic BP will fall.

What Does an Exercise Test Predict?
The answer to that question is not MI or sudden cardiac death. The rupture of a nonstenotic vulnerable plaque is most commonly implicated in exercise-related CAD events in previously asymptomatic individuals. Exercise testing detects stable, flow-limiting stenosis, meaning negative findings may be falsely reassuring. Positive exercise test results are most predictive of angina but poorly predictive of acute events, such as sudden death or myocardial infarction.

In patients who have suffered an acute event, there may be benefit in taking time away from competitive athletics to allow for stabilization of CAD with cholesterol-lowering therapy and, therefore, reduction of future risk. Exercise testing is important for defining risk before the return to participation for athletes who have sustained a cardiac event. Many athletes will ultimately be able to return to full participation provided they have received aggressive therapy and understand the residual risk associated with vigorous physical exertion in the setting of CAD.

Dr. Thompson's specific advice:

• When advising patients, it is important to know how essential exercise is to the individual patient. "Some people are hooked on it and it is very important to their lives."
• Tell them the facts; we know their risk of coronary events increases during intense activity. It's not possible to precisely determine this increased risk, but it is greater than at rest.
• And, he added, "Treat the dickens out of their risk factors, especially their lipids." Hopefully, intensive lipid-lowering will stabilize their plaques and permit them to continue their chosen activity. Warning: some patients think that because they are in good shape and run marathons, they do not have to take cholesterol-lowering therapy. You are most likely to see this in people with risk factors who want to ignore them.

Reference

1. Parker MW, Thompson PD. Prog Cardiovasc Dis. 2012;54:416-22.

Take-aways Routine physical exercise is associated with reduced morbidity and mortality from CAD, but vigorous physical exertion also transiently increases the risk of both acute MI and sudden cardiac death. In most cases, the risk to asymptomatic individuals without prior atherosclerotic disease is small. However, athletes with established CAD remain at some increased risk of sudden cardiac death or MI and any CAD risk factors should be vigorously treated.

To listen to an interview with Paul D. Thompson, MD, about CAD in older athletes, visit youtube.cswnews.org. The interview was conducted by Alfred A. Bove, MD, PhD.

Keywords: Exercise Tolerance, Athletes, Myocardial Infarction, Vasodilation, Cardiac Output, Risk Factors, Constriction, Pathologic, Dyspnea, Heart Rate, Calcium, Cholesterol, Middle Aged, Coronary Vessels, Oxygen, Physical Exertion, Death, Sudden, Cardiac

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