Reproducibility of bipolar endocavitary electrogram measurements at sites of radiofrequency energy delivery in patients with the Wolff-Parkinson-White syndrome

Background: Radiofrequency ablation of atrioventricular accessory pathway i s widely used to cure patients with the Wolff-Parkinson-White syndrome. The site of successful ablation is determined using electrophysiological param eters, endocavitary bipolar electrogram measurements being the most commonl y used. Interobserver reproducibility of these measurements may limit the r eliability of ablation criteria based upon bipolar measurements only but, t o our knowledge, this reproducibility has not been evaluated so far. Such w as the aim of this study. Methods: Three independent observers reviewed the bipolar electrograms reco rded at sites were radiofrequency energy was delivered (successfully or not ) in 28 consecutive patients with the Wolff-Parkinson-White syndrome. In ea ch tracing, 4 intervals were measured: (1) A(0)V(0) (onset of the atrial el ectrogram to onset of the ventricular electrogram), (2) A(a)V(a) (activatio n time of the atrial electrogram to activation time of the ventricular elec trogram), (3) V-0-QRS (onset of the ventricular electrogram to onset of del ta wave on the surface ECG) and (4) V-a-QRS (activation time of the ventric ular electrogram to onset of delta wave on the surface EGG). Results: The interobserver reproducibility was low since only 50% of A(0)V( 0) intervals were measured with an interobserver difference lower than 10ms and up to 43% of V-a-QRS intervals were measured with an interobserver dif ference greater than 30ms. The reproducibility of interval measurement was graded from the highest to the lowest as follows: A(0)V(0), A(a)V(a), V-0-Q RS and V-a-QRS (Chi-square statistic, chi(2) = 71.72, p < 0.0001). Kappa va lues were lower than 0.40, indicating a poor interobserver reproducibility. Conclusions: Our study suggests that interobserver reproducibility of only bipolar electrograms interval measurements at sites of radiofrequency ablat ion of atrioventricular accessory pathway is poor, which limits the reliabi lity of bipolar criteria to predict a successful ablation site.