Heart Attack and Intense Exercise

(LifeWire) - It's a well-known fact that when it comes to cardiac wellness, the benefits of exercise outweigh the risks. Can intense exercise, though, somehow increase the risk of having a heart attack?

The odds of dying during exercise are remote. Estimates range from 1 in 15,000 joggers to 1 in 50,000 marathoners. Still, with about 10 million joggers in America, the number of such deaths probably exceeds several hundred per year.

Men are stricken far more often than women, though researchers aren't sure why. Possible explanations are that men may engage in more vigorous exercise and younger (premenopausal) women may benefit from the same hormonal protection that lowers their overall risk for heart disease.

Intense exercise is rarely the cause of such exercise-related deaths. Though often attributed to "heart attacks," such deaths rarely involve myocardial infarction (the medical term for heart attack), which occurs when blood flow to the heart is blocked.

Other medical conditions, however -- which are often unrecognized -- are more likely to be involved, including:

Cardiac hypertrophy: Individuals younger than age 35 who die suddenly during vigorous exercise often had a heart defect known as hypertrophic cardiomyopathy. This condition occurs in roughly 1 in every 500 people -- often with few symptoms or warning signs -- and may only be discovered after death.  It accounts for 35 to 40% of those sudden deaths.

Atherosclerosis: Four out of five exercise-related deaths among people older than age 35 probably involve atherosclerosis, an arterial disease characterized by a narrowing of the arteries that impairs blood flow. While regular exercise can help prevent its development, exercise can't wholly prevent or reverse the condition, particularly if the person has a strong family history of heart disease or other major risk factors, such as high blood pressure or diabetes.

Cardiac arrhythmia: Another heart condition that can leave one vulnerable is cardiac arrhythmia, an irregular heartbeat, which can interfere with the heart's ability to pump blood.

Electrolyte imbalances: Occasionally, intense and protracted activities -- marathon running, for example -- can produce major shifts in the blood levels of potassium and magnesium, which can result in arrhythmia and cardiac arrest. Generally, however, athletes can avoid such problems by drinking sports drinks with electrolytes.

Enlargement of the heart: Athlete's heart, by definition, is  a benign (i.e., harmless) and relatively mild enlargement of the heart caused by chronic aerobic exercise. It does not produce death or significant arrhythmias, and reverses itself if exercise is reduced. Malignant cardiac enlargement in athletes (or anyone else) has other primary causes, such as cardiomyopathy, myocarditis or congenital heart disease.

Exercise itself is rarely life-threatening, especially when compared with the alternative (not exercising). It does make sense, though,  to ask your doctor about cardiac screening -- and not just if you're planning to start (or significantly ramp up) a personal exercise routine. Cardiac screening is important for seasoned athletes as well as for rank beginners.

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