Which statement best differentiates ventricular tachycardia from supraventricular tachycardia?

• A. VT originates in the ventricles with a wide QRS
• B. SVT originates in the ventricles
• C. VT has a narrow QRS
• D. SVT has a wide QRS

Answer: (A)

The key difference lies in where the rhythm starts and how that affects the QRS width. Ventricular tachycardia begins in the ventricular myocardium, so the impulse spreads through the ventricles in an abnormal, slower pattern. This produces a wide, often bizarre-appearing QRS complex because depolarization is not conducted through the normal His-Purkinje system. You may also see signs like AV dissociation or fusion/capture beats that point to a ventricular origin.

Supraventricular tachycardia starts above the ventricles—in the atria or AV node. The ventricles are activated via the normal conduction pathways, resulting in a narrow QRS complex most of the time. Only when there is aberrant conduction or a preexisting block would the QRS widen, but the typical differentiator is the origin with a wide QRS indicating VT.