Electrophysiological characteristics of septal perforation during left bundle branch pacing

BACKGROUND Left bundle branch pacing (LBBP) provides a low and stable threshold by direct capture of left bundle fibers on the left ventricular subendocardium. As the procedure involves the deployment of the pacing lead deep inside the septum, septal perforation is a potential complication. OBJECTIVES The purpose of this study was to analyze the morphology of intracardiac electrograms and unipolar pacing parameters to identify septal perforation in patients undergoing LBBP. METHODS Patients who had undergone successful LBBP between January 2020 to November 2021 were retrospectively included in the study. RESULTS LBBP was attempted in 219 patients and was successful in 212 (96.8% success rate). Septal perforation during lead deployment was identified in 30 patients (14.1%). Peak troponin release was 188 +/- 162 pg/mL. Mean unipolar impedance during septal perforation was 404.6 +/- 19.9 Omega (400-450 Omega in 16 patients [53.3%]; < 400 id in 14 patients [46.7%]). A cutoff < 450 Omega for diagnosing septal perforation had high sensitivity (100%) and specificity (96.6%). Current of injury amplitude reduced from 15.4 +/- 11.6 mV just before perforation to 0.9 +/- 0.6 mV after perforation. Based on morphology, unfiltered unipolar electrograms were classified into 2 patterns: (1) type I (QS) seen in 20 patients (67%) due to complete perforation (mean unipolar impedance 402.5 +/- 20.4 Omega); and (2) type II (RS/rS) seen in 10 patients (33%) due to partial perforation, with 80% showing capture (mean impedance 411 +/- 21.3 Omega). All 30 patients underwent successful reimplantation at a new site. No patient developed lead dislodgment during mean follow-up of 9.9 +/- 6.7 months. CONCLUSION Although considered one of the concerns of LBBP, septal perforation, when recognized promptly during implantation by unipolar parameters and treated by reimplantation, would be benign and not associated with an unfavorable outcome.