Hypertrophic cardiomyopathy is “the most common cause of sudden death in young athletes,” according to Tamara Horwich, M.D., a cardiologist at the Ahmanson-UCLA Cardiomyopathy Center.

It accounts for 35 to 40 percent of all pediatric cardiomyopathies, and has caused the in-game deaths of numerous college and high school athletes. Characterized by thick left ventricle walls, hypertrophic cardiomyopathy prevents the heart from filling with and pumping a healthy amount of blood.

“With a cardiomyopathy, almost any kind of cardiomyopathy, the heart and the patient are at risk of arrhythmias and sudden cardiac death and it can happen at any time,” Horwich said. “It’s not inevitable, but anything can trigger it.”

Cardiomyopathy, the disease of the heart muscle that preliminary autopsy results said affected Justin Carr ’14, is a problem for one in every 100,000 children in the U.S., according to the Pediatric Cardiomyopathy Registry and it is not a single disease, but a whole group of them.

Children and teenagers suffer from nonischemic cardiomyopathy, or cardiomyopathy unrelated to coronary artery disease.

There are four main types of nonischemic cardiomyopathy: dilated, hypertrophic, restrictive and arrhythmogenic right ventricular dysplasia.

Family history plays a big role in cardiomyopathy.

Hypertrophic and arrhythmogenic right ventricular cardiomyopathy are known to be genetic; dilated and restrictive cardiomyopathies can be genetic, but also can be caused by severe infection, alcoholism, chemotherapy and autoimmune disorders.

“We’re finding out more and more each year how important genetics and family history are,” Horwich said.

Cardiomyopathy’s symptoms can include fatigue, swelling in the legs and  chest pains,  but others may be asymptomatic their whole lives.

And for some, sudden cardiac death is the first and only symptom. Because symptoms do not necessarily correlate with arrhythmia risk, doctors rely more on risk factors for sudden death when they form a treatment plan, Horwich said.

“The major risk factors are syncope, or fainting, family history of hypertrophic cardiomyopathy with sudden cardiac death, a stress test to see if blood pressure drops with exercise, a very thick heart and scarring on the heart as detected by an MRI,” Horwich said. “If you see one or two or two or more you would move in a more aggressive approach by putting in a defibrillator.”

Cardiologists often perform echocardiograms, or sonograms of the heart, on patients suspected of having cardiomyopathy.

One common test that is not always useful, though, is the EKG, or electrocardiogram. While EKGs are able to detect arrhythmias, they are limited in their ability to identify most forms of cardiomyopathy. Treatment depends on the patient’s specific type of cardiomyopathy, age and symptoms. Treatment may include medication, surgically implanted devices such as Pacemakers and in some, cases, heart transplant. Transplants may extend the life of the patient by an average of 10 years, but the need for donor organs outpaces the supply.