[Differential diagnosis of tachycardias with a widened QRS complex]

The differential diagnosis of tachycardias with a widened QRS complex is a frequent problem that cardiologists and emergency room physicians must face. Ventricular tachycardias, supraventrical tachycardias with aberration of ventricular conduction and supraventricular tachycardias conducted by accessory routes (pre-exited or antidromic) are the three mechanisms that cause tachycardias with a widened QRS complex, whose clinical significance and treatments are different. Recently, intracardiac electrophysiological studies allowed the identification of efficient electrocardiographic criteria to distinguish each of these mechanisms. Several reports have indicated these criteria based on the careful analysis of the surface electrocardiogram.