What do the QRS's for ventricular tachycardia and ventricular fibrillation look like?

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The important idea is that QRS duration reveals where the ventricular activation is coming from. A narrow QRS means the impulse is traveling through the normal His-Purkinje system, while a wide QRS means the activation is taking a slower, ventricular pathway rather than the normal conduction network. Ventricular tachycardia starts in the ventricles, so the depolarization spreads through ventricular muscle instead of via the fast Purkinje system, producing broad, wide QRS complexes (usually 120 ms or longer) with abnormal morphology. Ventricular fibrillation, on the other hand, lacks organized ventricular depolarization altogether, so you don’t see discrete QRS complexes at all—there are chaotic, irregular waves instead. Given that VT characteristically shows wide QRS complexes, this option captures the key feature described, even though VF does not present with recognizable QRS.