Which interval measures conduction from His to the ventricles?

• A. PR interval
• B. QRS
• C. AH interval
• D. HV interval

Answer: (D)

The main idea is that the HV interval specifically tracks the time it takes for electrical impulse to travel from the His bundle down through the His‑Purkinje system to activate the ventricular myocardium. In practice, this interval is measured from the His bundle electrogram to the onset of the QRS complex on the ECG. It directly reflects conduction through the His–Purkinje pathway into the ventricles, and a normal value is typically around 35–55 ms in adults. Prolongation suggests block or slowing within the infra-Hisian system.

The other intervals measure different stages: the PR interval covers atrial activation to ventricular depolarization (including AV nodal delay and His conduction); the AH interval reflects conduction from the high atrium through the AV node to the His bundle; and the QRS duration represents how long ventricular depolarization lasts, not the conduction time from His to ventricles.