What is ventricular tachycardia (VT)?

Updated: Dec 05, 2017
  • Author: Steven J Compton, MD, FACC, FACP, FHRS; Chief Editor: Jeffrey N Rottman, MD  more...
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Answer

Ventricular tachycardia (VT) refers to any rhythm faster than 100 (or 120) beats/min arising distal to the bundle of His. It is the most common form of wide complex tachycardia, with a high associated mortality rate. [9] The rhythm may arise from the working ventricular myocardium, the distal conduction system, or both. (See Etiology.) VT can be classified as sustained or nonsustained, with a generally accepted cutoff of 30 seconds.

VT is further classified according to the electrocardiographic (ECG) appearance. If the QRS complex remains identical from beat to beat, as occurs when VT originates from a single focus or circuit, it is classified as monomorphic (see the first two images below). If the QRS morphology changes from beat to beat, the VT is classified as polymorphic (see the third image below). Further classification can be made on the basis of the substrate and the location of the earliest activation.

This electrocardiogram (ECG) shows rapid monomorph This electrocardiogram (ECG) shows rapid monomorphic ventricular tachycardia (VT), 280 beats/min, associated with hemodynamic collapse. The tracing was obtained from a patient with severe ischemic cardiomyopathy during an electrophysiologic study. A single external shock subsequently converted VT to sinus rhythm. The patient had an atrial rate of 72 beats/min (measured with intracardiac electrodes; not shown). Although ventriculoatrial dissociation (faster V rate than A rate) is diagnostic of VT, surface ECG findings (dissociated P waves, fusion or capture beats) are present in only about 20% of cases. In this tracing, the ventricular rate is simply too fast for P waves to be observed. VT at 240-300 beats/min is often termed ventricular flutter.
This electrocardiogram shows slow monomorphic vent This electrocardiogram shows slow monomorphic ventricular tachycardia (VT), 121 beats/min, from a patient with an old inferior wall myocardial infarction and well-preserved left ventricular (LV) function (ejection fraction, 55%). The patient presented with symptoms of palpitation and neck fullness. Note the ventriculoatrial dissociation, which is most obvious in leads V2 and V3. Slower VT rates and preserved LV function are associated with better long-term prognosis.
This image demonstrates polymorphic ventricular ta This image demonstrates polymorphic ventricular tachycardia.

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