Analysis of registry information on patients with arrhythmogenic right ventricular dysplasia, known to be a major cause of sudden cardiac death in young athletes, may decrease future mortality from the condition, according to an article published online December 12 by Circulation.

American scientists analyzed characteristics of 100 patients, including 69 diagnosed while still alive and 31 diagnosed postmortem. The men and women came from many ethnic backgrounds; median age was 31 years. The subjects were part of the US registry at Johns Hopkins University.

Accumulation of excess fatty tissue in the right ventricle can lead to a weakened and scarred right ventricle and a dramatic increase in risk for ventricular arrhythmias and possible sudden cardiac death.

Estimates from researchers and the Heart Rhythm Society suggest that the condition accounts for up to 5 percent of the 300,000 sudden cardiac deaths each year in the United States. A family history of sudden cardiac death at a young age is considered a major risk factor for the disorder. Athletes are also at particular risk, but the precise biological reasons for this remain unknown.

According to senior study investigator and cardiac electrophysiologist Hugh Calkins, MD, “physicians need to know that this is a serious disease, and they should be on the lookout for its early signs and symptoms because it is an important cause of sudden cardiac death in apparently healthy young individuals. Preventive treatment with an implantable defibrillator appears to eliminate the risk of sudden death.”

The disease frequently strikes people who are relatively young and symptoms may appear up to 15 years before diagnosis. Initial symptoms include palpitations, dizziness and fainting.

Researchers found that symptoms usually appear after puberty and before age 50 years. Of the 31 patients who died before diagnosis, 8 had shown signs of the disease when alive, including 5 who had syncopal episodes, suggesting they could have been treated and saved.

“Our results are a sobering reminder that if a young person faints, especially in association with exercise, their physicians should evaluate them carefully for cardiac diseases, including arrhythmogenic right ventricular dysplasia,” said study lead author Darshan Dalal, MD, MPH.

Diagnosis is based on a four-point scale, and up to 10 cardiac tests are required to confirm a diagnosis. Electrocardiograms and echocardiograms are performed to verify the origins of arrhythmia, and magnetic resonance imaging - backed up by tissue biopsy - are done to confirm the accumulation of fat and fibrous tissue in the right ventricle.

According to Calkins, who founded the registry in 1998 and is also director of arrhythmia programs, these confirmatory tests are important because the illness is often misdiagnosed if physicians rely on a single diagnostic test, such as magnetic resonance imaging.

His earlier research, in 2004, showed that more than half of patients are misdiagnosed, with physicians correctly diagnosing only 27 percent of true cases.

In the new study, of 47 patients who were diagnosed early and implanted with defibrillators, only one died of cardiac arrest. Twenty-nine of the patients’ defibrillators were activated within two years. This was, said Dalal, “the good news that most patients do quite well if protected by a defibrillator.”

Of 22 patients without defibrillators and maintained on drug therapy alone, 2 died of cardiac arrest, in addition to the 31 who died before diagnosis.

While the exact cause remains unknown, scientists believe it to be an inherited syndrome and that improved awareness and better diagnosis are steps toward their goal of developing a screening test for those at risk.