Is the Measurement of Accessory Pathway Refractory Period Reproducible?

Abstract

IntroductionShort accessory pathway (AP) effective refractory period (ERP) is one of the risk factors in Wolff-Parkinson-White syndrome (WPW). The purpose of study was to evaluate the reproducibility of APERP measurement during a same electrophysiological study (EPS). MethodsEPS consisted of 2 APERP measurements performed prospectively in 77 patients for a WPW in control state (CS) at a cycle length of 400ms (n=76) and after isoproterenol (n=56). ResultsIn CS, 18 patients (24 %) had the same APERP at both measurements; 41 (54.6 %) had differences from 10 to 40ms, 17 (22.4 %) had differences >40ms. Among 45 patients with initial APERP>240ms, 7 had an APERP≤240ms at 2nd study. Among 31 patients with initial APERP≤240ms, 5 had an APERP>240ms at 2nd study. Pearson’s productmoment correlation was 0.75. After isoproterenol, 5 patients (9 %) had the same APERPs; 37 (66 %) had differences from 10 to 40ms and 14 had differences >40ms. Among 38 patients with initial APERP>200ms, 12 had an AP ERP≤200ms at 2nd study. Among 18 patients with initial APERP≤200ms, 10 had still APERP≤200ms at 2nd study. Pearson’s productmoment correlation was 0.54. ConclusionsThere are important variations of APERPs during EPS mainly after isoproterenol infusion. Therefore the values of APERPs should be interpreted cautiously.