ECG clues for diagnosing ventricular tachycardia mechanism.

Three mechanisms underlie the initiation and maintenance of ventricular tachycardia: automaticity, triggered activity, and reentry. As straightforward as these mechanisms are, assessing which mechanism is operative in a particular patient's ventricular tachycardia can be difficult. The optimal treatment strategy for ventricular tachycardia in a given patient can be influenced by the mechanism underlying the ventricular tachycardia. Appropriately counseling patients, choosing the optimal pharmacologic agent that maximizes efficacy while minimizing undesirable side effects, risks, and toxicities, as well as recommending and timing ablative therapy all hinge on identifying the probable mechanism of ventricular tachycardia. Much has been published regarding invasive electrophysiologic maneuvers that allow for correct diagnosis of ventricular tachycardia mechanism. The aim of this clinical review is to provide insight into VT mechanisms based on ECG clues of spontaneous arrhythmia events and the response to pharmacologic manipulation prior to invasive electrophysiologic evaluation.