Inheritance of Sudden Arrhythmic Death Syndrome

Abstract & Commentary

Synopsis: Families of SADS victims should be referred for assessment at centers with experience in inherited cardiac diseases.

Source: Behr E, et al. Lancet. 2003;362:1457-1459.

A United Kingdom survey of sudden arrhythmic death syndrome (SADS) in 32 victims aged 4-64 with normal hearts at autopsy and a negative toxicologic screening test evaluated first-degree relatives of these victims. Death in the victims occurred during inactivity or sleep in most (72%) but in 28% occurred during exercise. A total of 109 first-degree relatives were assessed.

Familial cardiac disease was diagnosed in 7 of the 32 families (22%), and long QT syndrome was the most common suspected cause (4 of 7 families). Also, these families had a higher incidence of sudden unexplained death in other family members as compared to those without evidence of an inherited cardiac disease. Behr and colleagues concluded that families of SADS victims should be referred for assessment at centers with experience in inherited cardiac diseases.

Comment by Michael H. Crawford, MD

The conclusions of this study are supported by data and common sense. Unfortunately, we have no information as to whether the identification of an inherited cause of SADS by family evaluations actually saves lives or just creates a lot of cardiac cripples. Also, genetic testing is not universally embraced. In fact, only 74% of the first-degree relatives agreed to be evaluated, and few had sophisticated testing beyond an ECG and an echocardiogram. Consequently, other conditions such as Brugada syndrome and catecholaminergic polymorphic ventricular tachycardia and more subtle long QT cases were probably underdetected. What genetic testing that was done was disappointing since in only 2 of the 7 families were known disease-causing mutations found. However, even in well-documented clinical cases, genetic testing is not always fruitful in long QT syndrome (successful in two-thirds) and Brugada syndrome (successful in 10-20%). Finally, this type of research is difficult to do because grief-stricken families are not always agreeable, nor are institutional research boards supportive. Thus, Behr et al are to be congratulated for deriving any meaningful data from this small cohort. Although not ideal, this study clearly shows that inherited disease can be discovered in about 1 of 5 families of SADS victims. Whether such efforts will be rewarded by future lives saved is currently unclear, but I believe most families would want such information, and efforts to inform and evaluate them seem reasonable.

Dr. Crawford, Associate Chief of Cardiology for Clinical Programs, University of California, San Francisco, is Editor of Clinical Cardiology Alert.