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Hypertrophic Cardiomyopathy: A Cause of Athlete Sudden Death

Jan 19, 2012

Written by Martha Pyron, M.D.

Hypertrophic cardiomyopathy is a genetic disorder that causes a progressive, abnormal thickening of the heart muscle. This thickening of the muscle may be minor and slowly progressive or severe and can lead to a variety of symptoms and long-term outcomes, including sudden death. In fact, hypertrophic cardiomyopathy is the leading cause of sudden death in young athletes.

What is actually wrong with the heart?
People with hypertrophic cardiomyopathy have a large and thick heart muscle. It sounds like a good thing; however, the thickened heart muscle is so large that it decreases the cavity size of the heart, which means the heart holds and pumps less blood. The thickened muscle can also cause obstruction to the flow of blood as it is pumped out of the heart. The large muscle literally gets in the way and blocks the blood from flowing out of the heart to the rest of the body. When the muscle gets large enough, it functions poorly, and can start to quiver in ventricular fibrillation, which is the cause of sudden death.

Incidence
This disorder occurs in 0.05 to 0.2 percent of the population, and is more likely in relaties of people with the disease. This disease is slightly more common in males, but does occur in females as well, and usually appears at an earlier age in females. There is no ethnic group more likely to have the disease and it has been found in all races. All age groups can be affected, from newborns to the elderly.

Symptoms
The disease is progressive, meaning a person may: A) have it and experience no symptoms; B) may develop advanced thickening of the heart muscle to the point of having chest pain, shortness of breath,dizziness,and/or palpitations; or C) may suddenly collapse and die without any previous symptoms. This type of sudden death is more likely to occur during sports or vigorous activity. The overall risk of death from this disease is 2 to 4 percent per year for the general population. Younger individuals are more likely to have sudden death, with a rate of 4 to 6 percent per year.

Physical exam
Patients with hypertrophic cardiomyopathy may have a completely normal physical exam in early stages of the disease, but also may develop a heart murmur or arrhythmia. A heart murmur is a sound made in the heart as blood is flowing through an abnormal valve or abnormal heart muscle. Just like rapids make more noise than a deep wide river, blood flowing through a narrow heart area will make more noise, which is called a murmur. Arrhythmias are abnormal rhythms of the heart. In hypertrophic cardiomyopathy, several different abnormal rhythms are possible, with the worst being ventricular fibrillation, the most common cause of sudden death.

Diagnosis
Hypertrophic cardiomyopathy can be hard to detect since the patient in question may not have any symptoms and may have a normal physical exam. Luckily, there are some tests that can help diagnose this disease. An electrocardiogram, or heart tracing, may show an abnormal electrical current flowing through the heart, due to thickened heart muscle causing changes in the current. A chest x-ray may be done, which will show an enlarged heart, but this is not specific to hypertrophic cardiomyopathy.

The best tool for making the diagnosis of the disease is an ultrasound of the heart, known as an echocardiogram. This test uses sound waves to create an image of the heart, just like an image of a baby can be seen in a pregnant woman. The echocardiogram will show thickening of the heart muscle in an asymmetric manner and abnormal changes in blood flow.

There are several criteria used to diagnose hypertrophic cardiomyopathy and several different subtypes of the disease. In some cases, genetic testing can be done to see if other family members will develop the condition. Family members should be screened for this disease if possible so that their medical care is instituted as soon as possible.

Treatment
Patients with hypertrophic cardiomyopathy have a chance of sudden death during exercise, and are therefore likely to be held from all athletic activity. They may also be given an implantable defibrillator, which is a device that can jump-start the heart if arrhythmia occurs. Sometimes, if the heart muscle is too large, surgery can be performed to remove some of the heart muscle.

Summary
Hypertrophic cardiomyopathy is a disease condition that can cause sudden death during exercise. Early detection and diagnosis can reduce the risk for sudden death. Appropriate medical management is required to ensure the health and safety of individuals with the disease condition.

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