Krahn AD et al. (2005) Diagnosis of unexplained cardiac arrest: role of adrenaline and procainamide infusion. Circulation 112: 2228–2234

Unexplained cardiac arrest (UCA) in the absence of underlying structural heart disease might be associated with a broad range of differential clinical diagnoses or genetic conditions. Correct diagnosis of the underlying etiology is important not only to determine optimal management, but also for directing genetic testing and possible prophylactic intervention in family members. Although electrocardiography alone may be useful in some patients, long-term monitoring or provocative testing might be required to diagnose latent primary electrical disease.

In this study, 18 patients with UCA but no detectable cardiac disease underwent pharmacologic challenge with epinephrine and procainamide infusion. This technique identified a latent cause for UCA in two-thirds of patients (catecholaminergic polymorphic ventricular tachycardia [CPVT] 56%, Brugada syndrome 11%); idiopathic ventricular fibrillation was diagnosed in the remaining 33% of patients. Of the 55 (8 symptomatic and 47 asymptomatic) family members tested, 9 affected individuals from two families were detected. In all, seven cases of CPVT (five symptomatic and two asymptomatic individuals) and one case of Brugada syndrome (asymptomatic individual) were identified.

Epinephrine and procainamide infusion can be used to unmask the underlying etiology of UCA, helping to diagnose primary electrical diseases such as CPVT and Brugada syndrome. Detection of latent disease in asymptomatic family members using this technique could support genetic testing and might allow early intervention.