Electrophysiological demonstration of nonselective His-Purkinje system capture with para-Hisian pacing

Background: The adverse effects of conventional right ventricular (RV) apical pacing prompted the search for more physiological pacing sites, such as selective and nonselective His bundle pacing (HBP), a variant of nonselective HBP (para-Hisian pacing), and mid-septal pacing. However, knowledge of their true benefit on the physiology of ventricular activation, lead stability, and pacing thresholds is limited. Methods and results: We included 152 consecutive patients (mean age 61 +/- 24, 63% men) in this retrospective study. Of these, 137 patients with different bradyarrhythmias underwent active fixation lead implantation at the RV apex (n = 54), para-Hisian region (n = 66), or mid interventricular septum (n = 17). Fifteen patients with ventricular preexcitation due to an accessory pathway not undergoing pacing were included as controls. A 12-lead ECG was recorded in all patients, and cardiac electrical synchrony was assessed using the Synchromax (R) cross-correlation cardiac synchrony index (CSI). Results: QRS duration was prolonged in all pacing sites: from 114 +/- 28 to 160 +/- 29 (RV apex), from 110 +/- 28 to 122 +/- 29 (para-Hisian), and from 121 +/- 24 to 154 +/- 30 (mid interventricular septum). The CSI was significantly improved only in patients undergoing para-Hisian pacing, despite a slight widening of the QRS interval. There was no difference in pacing thresholds and sensed R-wave voltage between pacing sites. Only 1 lead, implanted at the para-Hisian region (1.5%), was dislodged towards the mid septum 48 h after implantation but did not require repositioning. Conclusions: QRS duration was not associated with changes in CSI, meaning that QRS width does not significantly affect electrical synchrony.