SIMILAR TIME-DEPENDENT RECOVERY PROPERTY OF FAST AND SLOW ATRIOVENTRICULAR NODAL PATHWAYS

The purpose of this study was to determine whether fast and slow atrio ventricular (AV) nodal pathways have the same recovery property, AV no dal recovery property is studied by delivering atrial extrastimuli cou pled to atrial beats and plotting nodal coupling intervals against nod al conduction time, in patients with dual pathways the resultant curve s will include a fast to fast (F-F) and a fast to slow (F-S) pathway c oupled curves, Although fast pathway recovery property can be represen ted by the former, dow pathway recovery property requires further asse ssment by studying slow to slow (S-S) pathways coupled curve, in 9 pat ients with dual pathways F-F, FS, S-F, and S-S curves were obtained by pacing protocols, In 8 patients (control) without dual pathways, F-F curve and atrial extrastimuli coupled to a preceding slowly conducted fast pathway beat (also designated as S-F curve) were obtained. (1) Th e S-S curve had a similar time constant as the F-F curve. (2) Although the S-S curve was markedly shifted upward and leftward from the F-F c urve, the degree of leftward and upward shifts of the S-S curve from t he F-F curve were both close to the difference of the basic fast and s low pathway conduction time (a constant). (3) Although the effective r efractory period of the fast pathway in dual pathway patients was long er than that of the control patients, the slow pathway effective refra ctory period when corrected was close to that af fast pathway in contr ol patients. These results suggest that the fast and slow AV nodal pat hways have a similar rime-dependent recovery property. (C) 1997 by Exc erpta Medica, Inc.