Short HV interval in absence of delta wave and normal PR interval—What is the mechanism?

Key Teaching Points•Fasciculoventricular pathways (FVP) can be an incidental finding during electrophysiology study. They may be present in addition to a pathological atrioventricular pathway participating in tachycardia. Actually they are a breach in the insulation near the right bundle branch.•The PR interval can rarely be normal, although more often it is slightly short with subtle pre-excitation. The magnitude of pre-excitation is fixed during atrial pacing, as the pathway is completely infranodal.•Ipsilateral bundle branch block, decremental FVP, and source-sink mismatch can lead to absence of subtle pre-excitation. •Fasciculoventricular pathways (FVP) can be an incidental finding during electrophysiology study. They may be present in addition to a pathological atrioventricular pathway participating in tachycardia. Actually they are a breach in the insulation near the right bundle branch.•The PR interval can rarely be normal, although more often it is slightly short with subtle pre-excitation. The magnitude of pre-excitation is fixed during atrial pacing, as the pathway is completely infranodal.•Ipsilateral bundle branch block, decremental FVP, and source-sink mismatch can lead to absence of subtle pre-excitation.