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Think ARVC in sudden cardiac death in athletes.

MIAMI -- Arrhythmogenic right ventricular cardiomyopathy is a diagnostically challenging condition that is often overlooked as the cause of sudden cardiac death in athletes.

Family history, skin manifestations, and histology aid diagnosis, but some cases are missed even on autopsy, according to a presentation at the annual meeting of the American Medical Society for Sports Medicine.

The prevalence of arrhythmogenic right ventricular cardiomyopathy (ARVC) in the general population is an estimated 1:1,000 to 1:5,000, though it is often confused with the more common hypertrophic cardiomyopathy (prevalence of 1:500) as a cause of sudden cardiac death in young athletes. As such, high clinical suspicion is warranted, Dr. William J. McKenna said. "We do miss ARVC clinically and post mortem--you miss what you don't look for. That is why ARVC has only been diagnosed in the last 25 years."

ARVC is an autosomal, dominant condition with fibrofatty replacement of myocytes in the right and left ventricles. These deposits cause structural, functional, and electrophysiologic changes. Arrhythmias and sudden death are typical presenting symptoms. There is age-related penetrance, which suggests the need for serial evaluations because an adolescent could have a normal examination one year and not the next.

"The vast majority do not know they have the condition. There are a lot of people who carry these genes and have some disease manifestation," said Dr. McKenna, clinical director at the Heart Hospital at University College, London.

No single clinical test is diagnostic. Even after multiple examinations--including electrocardiography, signal-averaged electrocardiography, echocardiography, exercise testing, and Holter monitoring--"we are left telling the patients we don't know," Dr. McKenna said. "The criteria for early disease are not specific."

Phase I, or the early phase, is typically silent, can feature sporadic ventricular ectopic beats, subtle ECG changes, morphologic abnormalities, and sudden death.

"The real problem is in people who are asymptomatic and picked up during family evaluation or routine screening," he said. Even after risk assessment with exercise testing or Holter monitoring, many remain asymptomatic. "The challenge is to predict the 'hot phase.' Currently, this is not feasible."

Ventricular arrhythmias and recurrent syncope are signs of a "hot phase" and may be associated with active inflammation. "This phase should be treated as a medical emergency," Dr. McKenna said.

Sustained ventricular tachycardia and diffuse right ventricular/left ventricular abnormalities are features of phase II disease. Phases III and IV characterize patients with advanced ARVC. There is increased dilatation and decreased contractility of the right and left ventricles. Left ventricular involvement can progress to heart failure.

Histology can confirm clinical suspicion. Look for myocytes in various stages of cell death, Dr. McKenna said. "If you are biopsying or just looking, you might see fat in the heart tissue, but it's not diagnostic--it comes with normal aging."

Recent advances in imaging may help, he said. MRI has a role in the measurement of accurate right and left ventricular volumes, he noted, and he suggested that a four-chamber view be used to detect wall-motion abnormalities.

Researchers have identified seven genetic loci to date. ARVC is a disease of the desmosome, so skin manifestations--including palmar keratosis--are a clue that it may be present.

Molecular diagnosis has "a major potential role for mutation analysis," Dr. McKenna said. Such diagnosis would help researchers define the specific genetic defects, identify sporadic cases, confirm diagnosis in borderline cases or neonates, and rule out some patients for future testing and evaluation.

BY DAMIAN MCNAMARA

Miami Bureau
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Title Annotation:Cardiovascular Medicine; arrhythmogenic right ventricular cardiomyopathy
Author:McNamara, Damian
Publication:Internal Medicine News
Geographic Code:1USA
Date:Sep 15, 2006
Words:573
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