Left bundle area pacing: Guiding implant depth by ring measurements

Background: Criteria for successful left bundle area pacing (LBAP) are in flux and currently guided by lead tip measurements. Lead ring measurements during LBAP have not been well studied.

Objective: The purpose of this study was to investigate dynamics in pacing parameters during successful and unsuccessful lead implant attempts.

Methods: SelectSecure 3830 pacing leads (Medtronic, Inc) guided by C315 sheaths for LBAP were placed for standard pacing indications in 73 patients. Retrospective review of procedural, echocardiographic, and standard pacing data were performed. Depth and lead-septal angle of implanted electrodes were determined from fluoroscopy with septal contrast delineation. Depth was graded in 4 categories according to the degree of ring penetration into the septum. Successful implant was defined by the ability to advance the lead deep into the septum and achieve LBAP criteria (ventricular activation time, QRS width/shape).

Results: Ring impedance increased stepwise during successful attempts as opposed to unsuccessful attempts (P = .039). A wider lead-septal angle at implant position correlated with higher ring impedance (P = .036), whereas no association was found with tip impedance. Unipolar ring threshold correlated with depth of lead implant (P = .029). Tip impedance measurements at implant position were less predictive of lead depth and did not correlate with septal thickness.

Conclusion: Ring pacing parameters are more predictive of lead progress than tip measurements. Lead depth and lead-septal angle can be determined from ring impedance measurements. These measurements may provide determination of lead depth and could obviate the need for contrast injection.