Conduction system pacing (CSP)—encompassing His bundle pacing (HBP) and left bundle branch area pacing (LBBAP)—has emerged in recent years as a preferred pacing strategy to preserve ventricular synchrony and minimize the risk of pacing-induced cardiomyopathy. While HBP may represent the ideal therapeutic strategy based on its inherent ability to address biventricular synchrony, LBBAP is rapidly emerging as a more reliable and durable strategy due to its target zone being wider and embedded in muscular tissue leading to improved chronic thresholds [1]. The benefits of LBBAP include lack of need for backup right ventricular (RV) lead pacing [2], improved clinical and echocardiographic outcomes in heart failure patients with left bundle branch block (LBBB) as an alternative to traditional cardiac resynchronization therapy (CRT) [3], and lower risk for heart failure hospitalization compared to CRT [4].

Several challenges exist, however, to successful and effective LBBAP implantation technique, including inability to target the proper zone on the interventricular septum, difficulty navigating in a dilated heart, and the presence of interventricular septal fibrosis. In addition, right-sided CIED implantations present both anatomic and technical challenges. Anatomically the right subclavian vein has a shorter, more vertical course prior to reaching the heart, and technically, most commercially available delivery sheaths are designed for left-sided implants. The latter presents additional challenges as the unique course of a right-sided implant necessitates catheter manipulations opposite those of typical, left-sided ones which also oftentimes limit the ability to transmit torque effectively. At the time of this writing, the only Food and Drug Association (FDA) approved delivery sheaths for conduction system pacing are the Medtronic C304-HIS and C315HIS (Medtronic, Minneapolis, MN), which are designed for left-sided approaches.

In this issue of the Journal of Interventional Cardiac Electrophysiology, Ashur et al. present their institution’s experience with left bundle area pacing via right-sided implantation [5]. They assessed for differences in procedural characteristics between right- and left-sided implants by conducting a retrospective analysis of 180 consecutive patients undergoing LBBA pacemaker implantation. Compared to the 168 (93%) implanted via a left-sided approach, the 12 (7%) who underwent right-sided implants understandably required significantly longer fluoroscopy time (24.3 ± 13.2 vs. 16.3 ± 12.3 min; p = 0.03) and more frequent delivery system exchanges during the procedure (33% vs. 6%; p = 0.0008). Furthermore, there were also longer total procedure time, lead placement time, and greater total radiation exposure with right-sided placement, with none reaching statistical significance. Of note, there was no statistically significant difference between the two approaches on left bundle branch capture rates (55% vs. 71%; p = 0.24). One possible shortcoming of the colleagues’ study is that, by design, it did not provide clinical follow-up in terms of lead longevity, capture threshold trends, risk of cardiomyopathy development, or other clinical outcomes.

This study raises two important issues vis-à-vis right-sided CIED implantation: clinical outcomes and limitations of current hardware. Right-sided implantations are typically more technically challenging than left-sided ones, but if future larger, ideally randomized, trials reaffirm the comparable rate of LBB capture as seen in the present trial, that could minimize the barrier for operators to pursue right-sided implants. As importantly, future trials should also track clinical outcomes of these implants, such as stability of lead parameters and development of cardiomyopathy. Finally, a significant source of challenge for right-sided implants may be influenced by the design of current delivery catheters. As LBBA pacing becomes more prevalent, development of custom right-sided tools can help overcome some of these challenges.

In summary, right-sided implantation of a left bundle branch area pacing system was feasible and safe. However, there was longer fluoroscopy time and more frequent delivery system exchanges. While improved custom catheter design may improve these specific outcomes, further studies are necessary to track these implants’ clinical outcomes to reassure operators that implanting from the right side offers stability comparable to those from the left side.