The value of a detailed clinical history cannot be overstated. Details of the circumstances preceding the cardiac arrest are crucial and witnesses may need to be interviewed. Cardiac arrest associated with exertion is suggestive of CAD, but is also a well-recognized trigger in the less common inherited arrhythmic syndromes (eg: long QT syndrome [LQTS] and catecholaminergic polymorphic ventricular tachycardia [CPVT]) and some cardiomyopathies. Febrile illness should raise suspicion of myocarditis, particularly if associated with features of heart failure. Ventricular arrhythmias may also be precipitated by febrile illness in patients with Brugada syndrome.
The family history is vital in the diagnostic evaluation of possible heritable arrhythmic syndromes. A simple inquiry restricted to premature deaths in first-degree relatives risks missing all but the most conspicuous patterns of phenotypic transmission of heritable conditions. A detailed inquiry should ideally include a three-generation pedigree of not only premature deaths, but also individuals with syncope, neuromuscular disorders, learning difficulties, unexplained single vehicle accidents, sudden infant deaths and even sensorineural deafness (Jervell Lange-Nielsen syndrome). Multidisciplinary team support from clinical geneticists and genetic counselors is invaluable in the diagnosis of potential heritable arrhythmic syndromes, particularly if genetic assessment is considered.
The association between drugs and fatal ventricular arrhythmias is well documented. The use of QT prolonging drugs in susceptible individuals, or pharmacokinetic and pharmacodynamic drug interactions can increase the risk of ventricular arrhythmia. A detailed drug history should include the use of all drugs, whether prescribed, over the counter or recreational/illicit and supplements. A history suggestive of drug use should prompt toxicology screening in addition to routine biochemistry.