CASPER may identify relatives at risk

The CASPER Registry¹ was a multicentre study of 63 patients (mean age 43 years, 29 women) successfully resuscitated from an apparently unexplained SCA who had a normal ejection fraction (EF), non-diagnostic electrocardiogram, normal echocardiogram, normal coronary arteries, and no reversible cause of SCA. Noninvasive testing included cardiac magnetic resonance imaging, signal-averaged electrocardiogram, exercise testing, and provocative testing with adrenaline and procainamide. Electrophysiological testing and genetic testing were only performed in selected patients.

After testing, 28/63 patients (44%) were diagnosed with idiopathic ventricular fibrillation, and a specific cause of SCA was identified in the other 35 patients (56%). Among these 35 patients, 23% had long QT syndrome (LQTS), 23% had catecholaminergic polymorphic ventricular tachycardia (CPVT), 17% had arrhythmogenic right ventricular cardiomyopathy (ARVC), 14% had early repolarization, 11% had coronary spasm, 9% had Brugada syndrome, and 3% had myocarditis. The diagnostic test with the highest yield was provocative drug testing, which led to a diagnosis of LQTS, CPVT, or ARVC in 18/35 patients (51%). A causative mutation was found in 9/19 patients (47%) who underwent genetic testing. Genetic screening of 64 family members identified 15 genotype-positive individuals.
An internal cardiac defibrillator is usually the appropriate first-line therapy for SCA without a reversible or preventable cause. However systematic testing identifies a specific cause of SCA in approximately 50% of patients. This approach assists in directing genetic testing to diagnose genetically mediated arrhythmia syndromes which results in a cascade of family screening and appropriate counseling, and also guides adjunctive therapy.

Reference

1. Krahn AD et al. Circulation 2009 120(4):278-285