What will you learn?
- what is gap phenomenon
- how to explain reappearing AV conduction
- appreciation of interactions between supra- and infra-his conduction
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
![](https://cdn.prod.website-files.com/6556498c64dd04b09862251a/65e8b264e6829380304d5115_65e8b1ea252e752d1fc5e30a_63b441a7cbfcf989b92bf53c_L-FHbaVI30z7JxJjGnmaXa0mFktPcbnt8f4tsST3BvI.jpeg)