Electrophysiology Unit (EPU) Practice Exam

The key idea is that these intervals measure how long different parts of the conduction system take to pass the impulse. The HV interval specifically reflects conduction from the His bundle to the ventricles, i.e., through the infra-Hisian/His–Purkinje pathway. In a healthy system, this is typically about 35–55 ms. An HV interval of 80 ms is longer than normal, showing a delay below the AV node. This points to infranodal conduction disease and can be a sign of potential progression to higher-grade block, which is clinically important and may require further evaluation or pacing. The PR interval at 153 ms is well within the usual 120–200 ms range, indicating normal atrial-to-ventricular conduction time. The AH interval at 79 ms sits in the expected range for atrial-to-His conduction (roughly 50–130 ms), so it’s normal. The QT interval at 350 ms is also typically normal for many heart rates (QTc considerations aside), indicating normal overall ventricular depolarization and repolarization timing.