Broad QRS tachycardia: electrocardiographic diagnosis and management

The diagnostic difficulties between supraventricular tachyarrhythmias with intraventricular conduction delay and ventricular tachycardia have challenged the physician since the first recording of a ventricular tachycardia by Lewis in 1909. The examples selected emphasize some of the diagnostic and therapeutic dilemmas of "broad QRS tachycardias" and their major differential features from abberrancy. Multiple simultaneous surface ECG leads are valuable in showing the direction of the initial activation forces of the QRS complexes, the frontal QRS axis and the configuration of the QRS in lead V1. Vagal maneuvers and intra-atrial or esophageal leads are very useful in demonstrating the underlying atrial rhythm and atrioventricular dissociation when present. In life-threatening situations, urgent therapy or D.C. cardioversion may be required before a definitive diagnosis has been established. In recent years electrode catheter techniques for the diagnosis, for arrhythmia induction and for the selection and assessment of the effectiveness of the antiarrhythmic drug therapy have been carried out in the management of recurrent broad QRS tachycardia. In view of the inherent risks with the use of this invasive technique, it should be restricted to a carefully selected number of patients with recurrent life-threatening dysrhythmias as suggested by Scheinman.