In 49 young people who died suddenly and inexplicably at an average age of 14, conventional autopsies found no cause of death. But when Mayo Clinic researchers conducted a sophisticated form of postmortem genetic testing, known as a molecular autopsy, they found that more than one-third died due to potentially heritable genetic defects that impair the heart's rhythm center.

The defects were caused by mutations, which can be thought of as spelling errors in the genetic code. The defects produced one of two abnormal heart rhythm conditions: long QT syndrome ( LQTS ) and catecholaminergic polymorphic ventricular tachycardia ( CPVT ). Both syndromes can declare their presence silently and catastrophically with a sudden death episode as the first symptom. Because they leave no structural or physical clues, the defects can't be detected with conventional autopsy methods.

Mayo Clinic's molecular autopsy is a detailed examination at a molecular level of heart function. Molecular autopsies can help lessen grief burden of families because data show that they exposed the lethal mutations as the cause of death in 35 percent of cases in which conventional autopsies could not ascertain cause of death. " The fact that conventional autopsy fails to provide an answer is, in fact, a key clue that the killer may be LQTS or CPVT, " says Michael J. Ackerman, at Clinic Windland Smith Rice Sudden Death Genomics Laboratory.

" To prevent further tragic, premature deaths, the standard of care for the evaluation of sudden unexplained death must now change. Surviving members in a family in which there's been this tragedy should receive medical attention that is equal to a ‘full-court press,'" Ackerman says. " It must involve a careful and sleuth-like search for these inherited glitches in the heart's electrical system."

The Mayo Clinic report is published in the Journal of the American College of Cardiology.

Spurce: Mayo Clinic, 2007

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