Conduction properties of accessory atrioventricular pathways: Importance of the accessory pathway location and normal atrioventricular conduction

Objective-The objective of this study was to determine the conduction properties of the normal atrioventricular (AV) conduction system in relation to accessory pathway (AP) location in patients with symptomatic Wolff-Parkinson-White syndrome. Design-The conduction properties of the AP and the AV node were studied in 356 patients with single manifest AP who underwent successful ablation. Results-Sixty-three percent of the APs were located on the left free wall (226) and the remaining 37% were posteroseptal, anteroseptal and right free wall. AV block (PRgreater than or equal to220 ms) was observed in 15 patients, 8 cases being associated with the right free wall (15%) compared with 7 on the left free wall (3%, p=0.002) and none on the anteroseptal (p=0.02) or posteroseptal (p=0.007). The PR (182+/-30 ms) and AH (102+/-25 ms) intervals associated with right free wall AP were longer than left free wall (166+/-23, 88+/-21 ms, p<0.0001, respectively), anteroseptal (155 +/- 11, 79 +/- 12 ms, p<0.0001) and posteroseptal AP (155+/-16, 79+/-13 ms, p<0.0001), whereas the PR and AH intervals associated with posteroseptal and anteroseptal AP were shorter than left free wall AP (p<0.05). When patients with AV block were excluded from the analysis, the PR intervals in patients with right free wall AP were still longer than in those with left free wall (p<0.005), anteroseptal (p<0.001) and posteroseptal AP (p<0.0001), as were the PR intervals associated with left free wall AP compared with data of posteroseptal (p<0.01) and anteroseptal AP (p<0.05). Significant differences in AV nodal effective refractory period, anterograde and retrograde AV block cycle length were also observed in relation to AP location. Conclusion-The conduction properties of the normal AV conduction system are associated with specific AP location in patients with Wolff-Parkinson-White syndrome.