Evaluation of atrial conduction time at various sites of right atrial pacing and influence on atrioventricular delay optimization by surface electrocardiography

Cardiac function and electrical stability may be improved by programming of optimal AV delay in DDD pacing. This study tested the hypothesis if the global atrial conduction time at various pacing sites can be derived from the surface ECG to achieve an optimal electromechanical timing of the left heart. Data were obtained from 60 patients following dual chamber pacemaker implantation. Right atrial septal pacing was associated with significantly shorter atrial conduction time (P < 0.0005) and P wave duration (P < 0.005), compared to standard right atrial pacing sites at the right atrial appendage or at the right free wall. The last two pacing sites showed no significant difference. In a group of 31 patients with AV block, optimal AV delay was achieved by programming a delay of 100 ms from the end of the paced P wave to peak/nadir of the paced ventricular complex. Optimization of AV delay resulted in a relative increase of echocardiographic stroke volume (SV) (10.9 +/- 13.7%; 95% CI: 5.9-15.9%) when compared to nominal AV delay (170 ms). Optimized AV delay was highly variable (range 130-250 ms; mean 180 +/- 35 ms). The hemodynamic response was characterized by a weak significant relationship between SV increase and optimized AV delay (R2 = 0.196, R = 0.443, P = 0.047). The study validated that septal pacing is advantageous for atrial synchronization compared to conventional right atrial pacing. Tailoring the AV delay with respect to the surface ECG improved systolic function significantly and was superior to nominal AV delay settings in the majority of patients.