gap phenomenon
The resumption of conduction at shorter coupling intervals after conduction block has occurred at longer coupling intervals.
Full Definition
The gap phenomenon refers to an apparent paradox in cardiac electrophysiology where conduction resumes at very short coupling intervals after being blocked at intermediate coupling intervals. This occurs when two structures in series have different recovery characteristics, such as the AV node and His-Purkinje system. At intermediate coupling intervals, the faster-recovering proximal structure (AV node) conducts but the slower-recovering distal structure (His-Purkinje) blocks. At very short intervals, concealed conduction into the proximal structure causes sufficient delay for the distal structure to recover, allowing conduction to resume. This phenomenon is important for understanding complex conduction patterns and supraventricular tachycardia mechanisms.
Usage
Usage note: Classic electrophysiologic phenomenon; important for understanding paradoxical conduction patterns.
In Context
- "The gap phenomenon was demonstrated when atrial extrastimuli at 300 ms blocked in the His-Purkinje system, but conducted normally at 250 ms." — Electrophysiology study report
- "Understanding the gap phenomenon helped explain the patient's intermittent AV conduction patterns during rapid atrial pacing." — Clinical correlation note