Heart Disease Health Center

Shocking Heart Deaths: Why They Happen

Causes of Sudden Cardiac Arrest

You probably know that high blood pressure, high cholesterol, diabetes, and other problems can lead to heart disease in older people. But you may not know about the rare heart disorders that can cause sudden cardiac arrest in young people.

"The underlying conditions in young people are very different from the underlying conditions in somebody who is 50 or 60 years old," Lawless says. "In the younger people, we're looking for inherited diseases of the myocardium [the heart's muscular tissue], of the electrical system, and then of course, congenital [heart] diseases." 

The No. 1 culprit: hypertrophic cardiomyopathy (HCM), a disorder marked by abnormal thickening of the heart muscle. "Their heart is thick," Lawless says. "The inner layers of the heart maybe are not getting enough blood supply with exercise."

But remember, HCM is rare. It has been estimated to affect only 0.05% to 0.2% of the population.

Congenital abnormalities of the coronary arteries pose another risk for sudden cardiac arrest. The arteries may be positioned improperly -- or, as in basketball star Pete Maravich's case, a person may be born with only one coronary artery, instead of the usual two.

Other conditions that can trigger sudden cardiac arrest include an inherited electrical disorder of the heart called long QT syndrome; an inflammatory heart condition called acute myocarditis; and Marfan syndrome, which led to Flo Hyman's cardiac arrest.

Marfan syndrome is a genetic disorder of the connective tissue that can have fatal cardiovascular effects. People with Marfan syndrome "tend to be tall and lanky," Lawless says. They are at risk for tears in their blood vessels (such as the aorta). That risk rises with sudden increases in blood pressure, as may happen during intense sporting activity.

Some athletes die after being struck in the chest, a trauma called commotio cordis.

"When the chest is hit at the vulnerable period of the cardiac cycle, the heart goes into this terrible rhythm, the ventricular fibrillation," Lawless says. The window of time is miniscule, she says. "It's got to happen within forty-thousandths of a second."

Screening for Sudden Cardiac Arrest Risk

Sudden cardiac arrest occurs without previous symptoms in some cases.

But sometimes, there are red flags. For example, Reggie Lewis fainted during a basketball game a few months before his death.

The American Heart Association recommends a 12-step screening for high school and college athletes. It includes a careful family and medical history and a physical exam. The assessment asks about chest pain on exertion, unexplained fainting, a family history of premature death from heart disease, and other relevant issues. The physical exam includes a check for heart murmurs, pulses, blood pressure, and physical signs of Marfan syndrome.

But the assessment isn't applauded across the board, and how to best identify patients at risk remains debatable. Not all doctors use the assessment -- or even know that it exists -- and there are various issues involved.