Sudden arrhythmic death syndrome: familial evaluation identifies inheritable heart disease in the majority of families

AIMS: At least 4% of sudden deaths are unexplained at autopsy sudden arrhythmic death syndrome (SADS) and a quarter may be due to inherited cardiac disease. We hypothesized that comprehensive clinical investigation of SADS families would identify more susceptible individuals and causes of death. METHODS AND RESULTS: Fifty seven consecutively referred families with SADS death underwent evaluation including resting 12 lead, 24 h and exercise ECG and 2D echocardiography. Other investigations included signal averaged ECG, ajmaline testing, cardiac magnetic resonance imaging, and mutation analysis. First-degree relatives 184/262 (70%) underwent evaluation, 13 (7%) reporting unexplained syncope. Seventeen (30%) families had a history of additional unexplained premature sudden death(s). Thirty families (53%) were diagnosed with inheritable heart disease: 13 definite long QT syndrome (LQTS), three possible/probable LQTS, five Brugada syndrome, five arrhythmogenic right ventricular cardiomyopathy (ARVC), and four other cardiomyopathies. One SCN5A and four KCNH2 mutations (38%) were identified in 13 definite LQTS families, one SCN5A mutation (20%) in five Brugada syndrome families and one (25%) PKP2 (plakophyllin2) mutation in four ARVC families. CONCLUSION: Over half of SADS deaths were likely to be due to inherited heart disease; accurate identification is vital for appropriate prophylaxis amongst relatives who should undergo comprehensive cardiological evaluation, guided and confirmed by mutation analysis.