Is the measurement of accessory pathway refractory period reproducible?
BACKGROUND
Short 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).


METHODS
EPS consisted of 2 APERP measurements performed prospectively in 77 patients for a WPW in control state (CS) at a cycle length of 400 ms (n=76) and after isoproterenol (n=56).


RESULTS
In CS, 18 patients (24 %) had the same APERP at both measurements; 41 (54.6 %) had differences from 10 to 40 ms, 17 (22.4 %) had differences > 40 ms. Among 45 patients with initial APERP > 240 ms, 7 had an APERP ≤ 240 ms at 2nd study. Among 31 patients with initial APERP ≤ 240 ms, 5 had an APERP > 240 ms at 2nd study. Pearson's product-moment correlation was 0.75. After isoproterenol, 5 patients (9 %) had the same APERPs; 37 (66 %) had differences from 10 to 40 ms and 14 had differences > 40 ms. Among 38 patients with initial APERP > 200 ms, 12 had an AP ERP ≤ 200 ms at 2nd study. Among 18 patients with initial APERP ≤ 200 ms, 10 had still APERP ≤ 200 ms at 2nd study. Pearson's product-moment correlation was 0.54.


CONCLUSIONS
There are important variations of APERPs during EPS mainly after isoproterenol infusion. Therefore the values of APERPs should be interpreted cautiously.
Department of cardiology, University Hospital of Brabois, Vandoeuvre, France.
Celine
C
Oliver
Beatrice
B
Brembilla-Perrot