Introduction: It is important to avoid unnecessary ventricular pacing (VP) to prevent adverse cardiac events in patients undergoing pacemaker implantation. However, right atrial (RA) pacing sometimes causes prolongation of PQ interval leading to increase of VP frequency. The purpose of this study was to determine if there was any favorable atrial lead location to avoid unnecessary VP.
Methods: This study included 18 patients who had sinus rhythm and spontaneous atrio-ventricular conduction, and undergoing pacemaker implantation or electrophysiological study (11 males, mean age 62+/-18.5 years). Ventricular lead was placed in right ventricular (RV) apex or septum, and RA lead was placed in RA appendage (RAA), high RA septum (HAS) and low RA septum (LAS) in series in each patient. The following parameters were obtained from ECG and compared according to 3 atrial lead locations: P width, interval from atrial pacing (AP) spike to QRS (AP-QRS), and the shortest AV delay which enables avoidance of VP (Non-VP AVD) during AP, interval from onset of P wave to local A wave (P-AS), interval from local A wave to QRS (AS-QRS) and Non-VP AVD during atrial sensing (AS).
Results: During AP, P width (112.8+/-26.8 vs 103.8+/-19.8 vs 88.8+/-26.5[ms], p<0.05), AP-QRS (186.1+/-42.6 vs 170.5+/-36.2 vs 146.4+/-33.9[ms], p<0.05) and Non-VP AVD (231.7+/-47.4 vs 209.4+/-48.9 vs 190.6+/-52.5[ms], p<0.05) were shortest during LAS pacing. During AS, LAS lead location resulted in the longest P-AS (5.6+/-18.9 vs 7.1+/-18 vs 28.6+/-32.9[ms], p<0.05), the shortest AS-QRS (163.7+/-23.2 vs 164.2+/-24.7 vs 144.1+/-30[ms], p<0.05) and the shortest Non-VP AVD (180.6+/-31.9 vs 188.9+/-37.7 vs 157.2+/-32.7[ms], p<0.05). Non-VP AVD correlated with AP-QRS (r=0.92, p<0.0001) and AS-QRS (r=0.73, p<0.0001).
Conclusions: LAS lead location resulted in shortest Non-VP AVD due to shortening of atrio-ventricular conduction during AP, and due to prolongation of the interval from onset of atrial activation to atrial sensing during AS. LAS atrial lead positioning seems to be most favorable to avoid unnecessary ventricular pacing under the presence of spontaneous atrio-ventricular conduction.