Which finding would most strongly indicate ventricular tachycardia during a wide-complex tachycardia?

• A. Delta waves during tachycardia
• B. AV dissociation
• C. Short PR interval
• D. Normal QRS duration

Answer: (B)

AV dissociation is the strongest clue that a wide-complex tachycardia is ventricular in origin. When the atria and ventricles beat independently, the atrial impulses do not control the ventricular rate, so you can see P waves marching through or appearing without a fixed relationship to the QRS complexes. This dissociation shows the ventricles are driven by a ventricular focus or reentry circuit rather than by the atrioventricular node, which is what you’d expect with a supraventricular tachycardia with aberrant conduction.

Delta waves during tachycardia would point to pre-excitation (WPW) but don’t by themselves confirm VT. A short PR interval likewise suggests WPW substrate rather than ventricular origin. Normal QRS duration would argue against a wide-complex tachycardia being VT, since the scenario specifically involves wide QRS complexes from ventricular depolarization.