Genetic testing for sudden cardiac death

Sudden Cardiac Death (SCD) is a major contributor to mortality in industrialized nations, affecting around 500,000 individuals annually in the Western World, and causing more deaths than AIDS, lung and breast cancer and stroke together.

Frequently, autopsy becomes the principal diagnostic tool when macro and microscopic analyses provide a conclusive diagnosis in cardiomyopathies. However, on average one third of autopsies do not identify a pathologically defined cause of death and these deaths are classified as "natural" or arrhythmogenic. In the athlete, the most common causes of sudden cardiac death are of inherited origin. This represents a tremendous burden to families, community and health care.

There has been considerable progress in the understanding of these genetic components thanks to research in familial forms of sudden death. Because these inherited diseases may remain undetected by conventional clinical investigations, genetic testing has been recently added to the clinical tools, improving significantly the detection of those individuals at risk. With that new information the physician, the proband and his family members can make an informed decision regarding their care and in the case of athletes, regarding continuation of competitive training.

While genetic technology has become essential to the diagnosis and subsequent prevention strategies in carriers with borderline or abnormal phenotypes, the use of this technology to guide clinical decisions in asymptomatic genetic carriers with normal phenotype is not without controversy.

These diseases have a low penetrance, indicating that only a small percentage of individuals with the genetic defect will develop the clinical features of the disease. Though to the physician genetic data are compelling evidence of having a risk for the development of the disease, and in several instances they tend to be overly aggressive with therapies. Genetic technology is useful to identify those at risk and those spared, but the clinical decisions have to be based on the clinical parametres and not solely on genetic testing.