12-12: Ventricular Tachycardia

ESSENTIALS OF DIAGNOSIS

GENERAL CONSIDERATIONS

Ventricular tachycardia is defined as three or more consecutive ventricular premature beats. It is classified as either nonsustained (lasting less than 30 seconds and terminating spontaneously) or sustained with a heart rate greater than 100 beats/min. In individuals without heart disease, nonsustained ventricular tachycardia is generally associated with a benign prognosis. In patients with structural heart disease, nonsustained ventricular tachycardia is associated with an increased risk of subsequent symptomatic ventricular tachycardia and sudden death, especially when seen more than 48 hours after MI.

Ventricular tachycardia is a frequent complication of acute MI and dilated cardiomyopathy but may occur in chronic coronary disease, HCM, myocarditis, and in most other forms of myocardial disease. It can also be a consequence of atypical forms of cardiomyopathies, such as arrhythmogenic RV cardiomyopathy. However, idiopathic ventricular tachycardia can also occur in patients with structurally normal hearts. Accelerated idioventricular rhythm is a regular wide-complex rhythm with a rate of 60–120 beats/min, usually with a gradual onset (eFigure 12–16). It occurs commonly in acute infarction and following reperfusion with thrombolytic medications. Treatment is not indicated unless there is hemodynamic compromise or more serious arrhythmias. Torsades de pointes, a form of ventricular tachycardia in which the QRS morphology twists around the baseline, may occur in the setting of severe hypokalemia, hypomagnesemia, or in the setting of a prolonged QT interval (inherited or medication-induced) (eFigure 12–17). In nonacute settings, most patients with ventricular tachycardia have known or easily detectable cardiac disease, and the finding of ventricular tachycardia is an unfavorable prognostic sign.