Direct comparison of delivery systems and electrodes with and without stylets for stimulation of the left bundle branch area in patients with indications for cardioresynchronization therapy
Authors: Karpenko I , Volkov D , Pavlinova N , Bochonko O 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Currently, there are only two commercially available systems for left bundle branch (LBB) pacing, that use fundamentally different technologies: with and without stylets electrodes. These systems have not been directly compared in patients with LBB block and CRT indication by LBB area pacing.

Purpose
The primary endpoint is the achievement of the LV subendocardium according to intraoperative echocardioscopy. Secondary endpoints: number of attempts, time of implantation, time of fluoroscopy, electrode stability, depth of implantation in the IVS, QRS duration, LV activation time (Stim-LVAT).

Methods
116 patients with LBB block and indications for CRT in the period 2020-2021 underwent electrode implantation into the LBB area. Select Secure 3830, 69 cm, 4.1 F pacing lead with delivery system C315 HIS was implanted in 60 pts (M system group). Delivery system Selectra 3 D and standard electrodes with stylet and active fixation Solia S 60 cm, 5.9 F was implanted in 56 pts (B system group). The implantation of the electrode over the interventricular septum (IVS) was carried out under constant echocardiographic control.

Results
Primary endpoint was achieved in 53 from 60 pts (88.3%) M system group and in 52 from 56 pts (92.3%) B system group (P=0.1). Septal thickness (cm) at the site of implantation was 1.16 ± 0.25 and 1.28± 0.42, lead depth (cm) - 1.3 ± 0.23 (7-16) and 1.44± 0.42 (8-27) accordingly (not strictly perpendicular in all cases). The number of lead deployment attempts (screwing) to achieve the optimal result were 4.5 ± 2.3 and 2.6 ± 0.5 (P=0.01), the number of full revolutions in each attempt - 14.3 ± 5.8 and 6.2 ± 2.7 respectively (P=0.002). The mean time of lead implantation in LBB area was 19.0 ± 6.8 minutes in M system group and 8.6 ± 4.8 min in B system group (P=0.01), fluoroscopic exposure time: 4.4 ± 2.6 min and 3.0 ± 1.3 min (P=0.03) accordingly. Acute perforation of the LV septum was noted in 1 (1.6%) pts in M system group and 3 (5,6%) patients in B system group and corrected by immediate electrode repositioning. No patient showed loss of capture nor lead dislodgment during follow-up (12.4 ± 5.6 month). A significant decrease in QRS duration was observed in patients both groups: 164±19 versus 121±18 ms (M group), and 168±21 versus 119±20 ms (B group), P=0.08. Stim-LVAT was 84±10 ms (M group) and 78±12 ms (M group), P=0.1 and met the criteria LBB area pacing in pts with LBB block.

Conclusion
Both systems have shown the ability to reach the LV endocardium and overcome LBB block. Biotronik systems were more convenient and effective at achieving LV subendocardium, especially in cases of hypertrophied and fibrotic IVS, but were associated with a high risk of IVS perforation. The development of delivery systems and electrodes specifically designed for LBB area pacing (optimally 4 F with fixed Helix and stylet) in different IVS anatomy is urgent and necessary.