What is a capture beat in VT?

• A. A normal-looking QRS complex occurring during VT due to intermittent sinus conduction capturing the ventricle
• B. A QRS complex that is a fusion of VT and normal conduction
• C. A QRS complex that is always VT morphology
• D. A QRS not preceded by a P wave during VT

Answer: (A)

The concept being tested is recognizing a capture beat during ventricular tachycardia. A capture beat is a normal-looking QRS that appears during VT when a normal sinus impulse momentarily conducts to the ventricles and “captures” them, producing a beat that resembles the patient’s baseline rhythm. This happens because, at times, the ventricles are excitable enough for the impulse from the atria to get through the conduction system despite the VT circuit. It shows that ventricular conduction is not completely blocked.

This is why the described option is the best: it specifically describes a normal QRS during VT caused by intermittent sinus conduction capturing the ventricle. It does not describe a fusion beat, which would produce a QRS with a hybrid morphology, nor a QRS that always has VT morphology, which would not be a capture. It also isn’t about AV dissociation (a QRS not preceded by a P wave) in VT, which is a different phenomenon.