Electrophysiologic Mechanism

An impulse may penetrate the AV node or bundle branches without fully depolarizing the ventricles.
Even though no QRS is produced, the tissue becomes partially refractory.

This explains:

• Wenckebach periodicity
• Blocked PACs
• Ashman aberrancy
• Persistent aberrancy after a premature beat
• Paradoxical conduction patterns

Concealed conduction is one of the most important — and least understood — mechanisms in clinical electrophysiology.

ECG Appearance

There is no direct ECG manifestation, but concealed conduction is inferred from:

• blocked PACs
• unexpected PR prolongation
• Wenckebach sequences
• aberrant conduction following premature beats
• persistent bundle‑branch aberrancy

Common Misinterpretations

• Mistaking blocked PACs for sinus pauses
• Mislabeling Wenckebach as Mobitz II
• Misinterpreting aberrancy as PVCs
• Assuming conduction changes are random

Clinical Implications

• Essential for interpreting AV nodal physiology
• Prevents misdiagnosis of high‑grade AV block
• Explains many forms of rate‑dependent aberrancy
• Helps differentiate supraventricular from ventricular rhythms

Related Terms

Blocked PAC

Wenckebach phenomenon

Ashman phenomenon

Aberrant conduction