Sudden Unexplained Death: Heritability and Diagnostic Yield of Cardiological and Genetic Examination in Surviving Relatives

Abstract

Background— Sudden death mostly follows from cardiac disorders that elicit lethal ventricular arrhythmias. In young individuals, it often remains unexplained because history and/or postmortem analysis are absent or provide no clue. Because such sudden unexplained deaths (SUDs) may have heritable causes, cardiological and genetic assessment of surviving relatives of SUD victims may reveal the underlying disease and unmask presymptomatic carriers. We aimed to establish the diagnostic yield of such assessments. Methods and Results— We investigated 43 consecutive families with ≥1 SUD victim who died at ≤40 years of age. All studied relatives underwent resting/exercise ECG and Doppler echocardiography. Molecular genetic analysis was conducted to confirm the diagnosis. We identified an inherited disease and likely cause of death in 17 of 43 families (40%). Twelve families had primary electrical disease: catecholaminergic polymorphic ventricular tachycardia (5 families), long-QT syndrome (4 families), Brugada syndrome (2 families), and long-QT/Brugada syndrome (1 family). Furthermore, we found arrhythmogenic right ventricular cardiomyopathy (3 families), hypertrophic cardiomyopathy (1 family), and familial hypercholesterolemia (1 family). Molecular genetic analysis provided confirmation in 10 families. Finding the diagnosis was more likely when more relatives were examined and in families with ≥2 SUD victims ≤40 years of age. The resting/exercise ECG had a high diagnostic yield. These efforts unmasked 151 presymptomatic disease carriers (8.9 per family). Conclusions— Examination of relatives of young SUD victims has a high diagnostic yield, with identification of the disease in 40% of families and 8.9 presymptomatic carriers per family. Simple procedures (examining many relatives) and routine tests (resting/exercise ECG) constitute excellent diagnostic strategies. Molecular genetics provide strong supportive information.