Gap phenomenon in AV conduction
Acknowledgement
Laura Vitali Serdoz
Electrophysiologist
What will you learn?
- what is gap phenomenon
- how to explain reappearing AV conduction
- appreciation of interactions between supra- and infra-his conduction
Your task for this lesson
- Note at which CL the block occurs for the first time, where conduction is reappearing and when it finally blocks
- Write down what was the last signal at His channel for those events.
About this scenario
- The Gap phenomenon is observed during atrial extrastimulation in which AV block at longer coupling intervals is followed by restored AV conduction at shorter coupling intervals. Meaning that paradoxically a faster pace improves conduction.
- It appears only when the initial site of block is in the distal conduction system (infra-his) and as the coupling interval is further decreased, a further (decremental) delay occurs in the proximal conducting site (supra-his). This "extra" time caused by the supra-his delay gives the distal site time to recover and conduct again
- Key condition for occurrence of the gap phenomenon is that the effective refractory period of the distal site is longer than the functional refractory period of the proximal site
What can be interesting
