A reappraisal of atrioventricular nodal excitability during functional 2:1 block: what should be the gauge?
By using extrastimulation technique the effective refractory period (ERP) of the atrioventricular (AV) node is conventionally defined as the longest A1A2 interval at which conduction of A2 is blocked within the node. With the prolongation of the AV nodal transit time that is associated with this technique, the delayed AV nodal arrival of the A1 impulse will cause an overestimation of the true interval if the A1A2 interval is used as the gauge. Under this condition, the conventional approach will not accurately delineate the ERP of the AV node. However, this prolongation of the nodal transit time can be calculated by subtracting the basal conduction time from the conducted A-H interval. By subtracting out the prolongation from the longest A1A2 at which A2 impulse is blocked, not only an interval more indicative of the true AV nodal ERP can be obtained, but also the apparent discrepancies between the in vitro and human AV nodal recovery curves disappear.
Young
M L
ML
Department of Pediatrics, National Taiwan University, Taipei.
D001283:Atrioventricular Node / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004562:Electrocardiography; D004594:Electrophysiology; D006327:Heart Block / Q000503:physiopathology*; D006801:Humans; D012032:Refractory Period, Electrophysiological