Concealed Conduction
Concealed conduction occurs when an impulse enters part of the conduction system but does not produce a visible ECG deflection, yet alters the refractoriness of the tissue so that subsequent impulses conduct differently.
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
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