Electrophysiologic Properties of Aberrant Ventricular Conduction Induced by Atrial Extrastimulation

Song, Jae Kwan; Lee, Woo Seung; Jeon, Eun Seok; Kim, Cheol Ho; Oh, Byung Hee; Park, Young Bae; Choi, Youn Shik; Seo, Jung Don; Lee, Young Woo

Abstract

In order to determine the electrophysiologic properties of aberrant ventricular conduction we analyzed the electrophysiologic studies done for various reasons in SNUH(1983.3 -1987.8). All patients did not have underlying heart disease and were in sinus rhythm with normal PR intervals & no intraventricular conduction delay at the time of study. The patients of preexcitation syndrome were excluded. Only aberrant ventricular conduction induced by premature atrial stimulation at the high right atrium or(HRA) during sinus rhythm or HRA pacing was analyzed. 1) Aberrant ventricular conuction was induced by premature atrial extrastimulation in 34 subjects of 156 cases reviewed(21.8%). The patients were 16 to 70 years old(sixteen males and eighteen females). 2) The longest atrial coupling(A1S2) interval resulting in aberrant ventricular conduction approximated 45%(600-280) of the basic cycle length(450-1550 msec). 3) As a prerequisite for aberrant ventricular conduction, the functional refractory period(FRP) of the AV node should be less than the relative refractory period(RRP) of the His Purkinje System and the most important determinant of aberrant ventricular conduction by atrial extreastimulation was resultant H1H2 interval, which should be between RRP and effective refractory period(ERP) of HPS. 4) There was good linear correlation between the basic cycle length(BCL) and RRP of the HPS(RRP=0.247xBCL+247.048, r=0.885, p-value<0.001). 5) 155 different configurations of aberrant ventricular conduction were recorded during atrial extrastimulation till atrial ERP. The pattern frequencies were as follows : left anterior hemiblock, 6(3.9%) ; right bundle brach block, 92(59.4%) ; left bundle branch block, 28(18.0%) ; left anterior hemiblock combined with right bundle branch block, 14(9.0%) ; left posterior hemiblock combined with right bundle branch block, 9(5.8%) ; unclassified intraventricular conduction disturbances, 6(3.9%). 6) As the atrial coupling intervals were further shortened, aberrant conduction persisted up to the point of atrial ERP at 19/41 BCL's(46.3%). Other patterns of atrioventricular conduction were as follows : atrio-His block, 7(17.1%) ; His-ventricular block, 6(14.6%) ; normal conduction due to prolonged A2H2, 9(22.0%). But there was no statistical significance between the pattern of A-V conduction and the longest S2H2 & H2V2 intervals during VAB (p-value=0.235>0.050). In conclusion, atrial extrastimulation which is routinely done during clinical EPS is an effective method to induce aberrant ventricular conduction and to study the electrophysiologic characteristics of atrioventricular conduction. Further study with recording of bundle branch electrogram, after infusion of cardioactive drugs and pacing of HRA at fixed rate should be done to determine the electrophysiologic properties of VAB more completely.