Ventricular Tachycardia

Excerpt

Ventricular tachycardia (VT) is a wide complex tachycardia, defined as three or more consecutive beats at a rate of more than 100 per minute, arising from the ventricle. Ventricular tachycardia is a potentially life-threatening arrhythmia, and it is responsible for the majority of sudden cardiac deaths in the United States. It is classified by duration as non-sustained or sustained ventricular tachycardia. Non-sustained ventricular tachycardia is defined as ventricular tachycardia of fewer than 30 seconds duration that does not lead to hemodynamic instability, while sustained VT lasts more than 30 seconds or requires intervention within 30 seconds due to hemodynamic compromise.

On the basis of QRS morphology, VT is divided into monomorphic and polymorphic ventricular tachycardia. Monomorphic VT is characterized by a single, stable QRS morphology with no beat-to-beat variation, while polymorphic VT has beat-to-beat variation in QRS shape and multiple QRS morphologies. Torsades de Pointes is a form of polymorphic ventricular tachycardia (occurs in the setting of the long QT interval), characterized by waxing and waning of QRS amplitude, giving it the name "twisting of the points." Bidirectional ventricular tachycardia is another form of polymorphic ventricular tachycardia and has a characteristic beat-to-beat change in the QRS axis. It is commonly seen in the setting of digitalis toxicity and patients with catecholaminergic polymorphic ventricular tachycardia (CPVT).

Ischemic heart disease is the most common cause of ventricular tachycardia, and 5 to 10% of patients with acute coronary syndrome are found to have ventricular arrhythmias. Ventricular tachycardia in acute coronary syndrome is usually polymorphic, while monomorphic ventricular tachycardia is a sign of a myocardial scar. Accelerated atrioventricular rhythm (AIVR) is a monomorphic ventricular tachycardia, referred to as a sign of successful reperfusion, and it has a strong association with infarct size.

Ventricular tachycardia is a major contributor to sudden cardiac death in patients with ischemic and non-ischemic cardiomyopathy. Ventricular tachycardia in cardiomyopathy is usually monomorphic due to scar-related reentry, and its degeneration into ventricular fibrillation may result in cardiac arrest or even sudden cardiac death. The clinical presentation of ventricular tachycardia varies from palpitation to sudden cardiac death. For appropriate management of VT and prevention of sudden cardiac death, it is essential to understand the pathophysiology of ventricular tachycardia and underlying structural heart disease. In this chapter, we summarize the etiology and epidemiology of ventricular tachycardia and discuss the evaluation and management of patients present with ventricular tachycardia.