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What Causes Runners To Drop Dead During A Marathon?

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You love running and are thinking about finally pulling the trigger and signing up for that marathon. But after all the news stories about athletes dropping dead at the end of a race, you're a little worried. What could cause a runner to suddenly drop dead?

Typically, sudden death during a marathon is due to a condition called hypertrophic cardiomyopathy.

What is hypertrophic cardiomyopathy?

To understand hypertrophic cardiomyopathy—HCM for short—it's helpful to have a basic understanding of the heart's anatomy. The heart has four chambers—the right atrium, the right ventricle, the left atrium, and the left ventricle. Muscle separates the left side from the right, and arteries and veins bring blood to and from the heart. Blood that flows in to the right atrium is pumped into the right ventricle and distributed to the lungs. The lungs enrich the blood with oxygen, and it is then pumped in to the left atrium. Blood flows from the left atrium to the left ventricle, and is then distributed throughout the body.

The most common form of HCM causes a thickening of the heart muscle in between the left and right ventricle. This can prevent the left ventricle from pumping enough blood out of the heart.

Are there any symptoms?

In many cases, there are no symptoms of HCM. Those who do experience symptoms may notice dizziness, chest pain, and lightheadedness during exercise, and your doctor may be able to detect a heart murmur.

Is HCM life threatening?

Hypertrophic cardiomyopathy can be fatal. It is the leading cause of death during a marathon. When cardiac arrest is due to HCM, there is only a very small window in which the condition can be reversed. Making resuscitation even more difficult is the fact that a defibrillator is the only effective way to restore normal heart function with HCM. CPR doesn't work.

HCM is present in one in 500 people but it is not usually fatal for marathon runners. The risk of dying during or immediately after a race is about .75 in 100,000 people.

How can it be diagnosed?

HCM is usually diagnosed through an echocardiogram. During an echocardiogram, a doctor or technician will place a metal device against the chest. The device is able to pick up sounds and create a map of the heart on a nearby screen.

Because HCM frequently occurs without any symptoms, it is important for athletes to receive yearly physicals, such as at Physicians Immediate Care Centers PS, particularly if there is a family history of heart disease.  

Is HCM treatable?

If HCM is detected, a doctor may recommend abstaining from strenuous exercise such as running. They may also simply recommend monitoring the condition if it's still in the early stages. Medication may be used, and if the condition is particularly serious, surgery to remove excess muscle may be necessary.

While running is generally a healthy activity, it's important to know the potential risks. If you are concerned about HCM, be sure to discuss it with your doctor.