Initial experience, feasibility and safety of permanent left bundle branch pacing; a retrospective single centre study
Authors: Van Den Broek JLPM , Bracke FALE , Stranders I , Op "T Hof MNJ , Rademakers LM 
Published: May 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.
Background
Physiologic pacing by left bundle branch pacing (LBBP) is characterized by direct stimulation of the intrinsic His-Purkinje system and results in physiologic ventricular depolarization and repolarization. This technique has emerged as an alternative to both traditional right ventricular pacing for bradycardia and classic cardiac resynchronization therapy (CRT). High success rates and low complication rates are reported, however the majority of literature is reported by relatively few, highly experienced centres.
Purpose
This retrospective study aims to describe success rate, feasibility and safety of LBBP for both bradycardia and CRT indications in a high volume referral centre, performed by three physicians without previous experience with LBBP.
Methods
100 patients who underwent attempted LBBP from January 2020 to September 2020 were analysed. LBBP was performed using the Medtronic SelectSecure 3830 pacing lead and the Medtronic C315HIS delivery sheath. The primary end points are acute LBBP success rates and LBBP related complications within 3-6 months from implantation. Success was defined as a paced QRS with QR or RSr’ in V1 and left ventricular activation time (LVAT) &lt;90ms. Device follow-up data was acquired at 1 month and 3-6 months after implantation.
Results
The mean age was 70 ± 11.4 years and 67% were men. 57% had a left ventricular ejection fraction &lt;0.50 and QRS was 146 ± 33.7ms. Pacing indication was CRT in 48, bradycardia in 42 and planned AV node ablation in 9. LBBP was successful in 83/100 patients (83%), with paced QRS of 121 ± 19.7ms and LVAT of 81 ± 13.8ms. A learning curve could not be demonstrated; the success rates in the first and latter half were 78% and 88% respectively (p = 0.183). Pacing parameters at implantation were satisfactory; R-wave 11.9 ± 5.9mV, impedance 736 ± 153Ω and capture threshold 0.7 ± 0.4V. R-wave increased to 14.6 ± 6.3mV at 1 month (p &lt; 0.001) and remained stable at 13.6 ± 5.5mV after 3-6 months (p = 0.829). Impedance decreased to 572 ± 82Ω at 1 month (p &lt; 0.001) and further decreased to 536 ± 81Ω after 3-6 months (p &lt; 0.001). Capture threshold remained stable at 1 and 3-6 months (0.7 ± 0.2V (p = 0.287) and 0.8 ± 0.2V (p = 0.055), respectively). No LBBP related complications, e.g. lead perforation or dislodgement, occurred during the follow-up of 249 ± 64 days. The main reasons for unsuccessful implantation (n = 17) were insufficient reach of the delivery sheath (n = 8) and inability to penetrate the septum due to fibrosis (n = 5).

Conclusion
This study shows that LBBP is a safe and feasible method for delivering physiological pacing. Without previous experience, our initial success rate is comparable to highly experienced centres. Pacing parameters remained stable after 6 months and no LBBP complications occurred. Success rate of implantation could further improve with dedicated LBBP delivery sheaths. Large randomized controlled trials are needed to further confirm safety and efficacy of LBBP.