When you do aerobic exercise, you not only work muscles in your lower extremities, you also give another important muscle a workout, your heart. Some athletes and people who exercise on a regular basis develop a condition called athlete’s heart where the heart becomes larger in size and the walls of the heart become thickened. You may have heard that enlarged hearts can be a sign of heart disease or uncontrolled high blood pressure. Is athlete’s heart a cause for concern?
What Causes Athlete’s Heart?
When you exercise, your muscles require more oxygen. It’s the heart’s job to deliver oxygen to the hard-working muscles. In response to the challenges of increased oxygen requirements, the heart has to work harder to deliver blood and oxygen. As a result, the heart enlarges and the left ventricle that pumps blood to the body thickens. This happens so it can more easily supply blood to the muscles and the rest of the body. This is a normal response to the increased demands exercise places on the heart. At the same time, an athlete’s heart may become slower, because the heart can now eject more blood with each heartbeat. This reduces the number of times the heart needs to beat.
Enlarged Hearts in Athletes: Is Athlete’s Heart Dangerous?
Athlete’s heart causes no symptoms and is usually found incidentally as an enlarged heart on chest x-ray or an echocardiogram, a test that uses sound waves to look at the structure of the heart. The problem is a small number of athletes with an enlarged heart have a genetic condition called hypertrophic cardiomyopathy that puts them at high risk for sudden death. This condition affects up to 1 in 500 people and is the most common cause of sudden death among young, apparently healthy, athletes. Some well-known athletes including Boston Celtic player Reggie Lewis died suddenly from hypertrophic cardiomyopathy while playing basketball.
The good news is most athletes who have an enlarged heart don’t have hypertrophic cardiomyopathy. If they have athlete’s heart, in most cases, they’re not at greater risk for sudden death. In 80% of cases, if an athlete stops training, their heart size will return to normal. Twenty-percent of athletes with enlarged hearts will have persistent enlargement even after they stop working out. It’s not clear whether this sub-group of people is at greater risk for heart problems, although most evidence suggests they aren’t.
Because athlete’s heart can be difficult to distinguish from hypertrophic cardiomyopathy, most doctors will want to run further tests and monitor athletes with an enlarged heart until they’re convinced that the heart enlargement and thickening of the ventricle is only a result of training. Hypertrophic cardiomyopathy doesn’t always cause symptoms. When it does, it may cause fainting, chest pain, dizziness, shortness of breath, lightheadedness, and palpitations. Sadly, many athletes don’t report these symptoms, and the results can be tragic.
The Bottom Line?
Enlarged hearts in athletes isn’t uncommon and if hypertrophic cardiomyopathy and other heart conditions that cause heart enlargement can be ruled out, it doesn’t increase the risk of heart problems or sudden death. In the 20% of people who have heart enlargement due to athlete’s heart that doesn’t return to normal after training is stopped, the long-term picture isn’t as clear. Most evidence suggests they’re not at greater risk. In the majority of athletes, athlete’s heart is a normal adaptation to training.
References:
Exercise Physiology. Fifth edition. McArdle, Katch and Katch. 2001.
Medscape. “Hypertrophic Cardiomyopathy”
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