Elsevier

Heart Rhythm

Volume 20, Issue 1, January 2023, Pages 55-60
Heart Rhythm

Clinical
Devices
Left bundle area pacing: Guiding implant depth by ring measurements

https://doi.org/10.1016/j.hrthm.2022.09.013Get rights and content

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.

Introduction

Left bundle area pacing (LBAP) is becoming a popular method of conduction system pacing.1 LBAP has been successful for a variety of pacing indications2,3 and more recently as an alternative to cardiac resynchronization therapy.4,5 The initial lead implantation recommendations have been published.6,7 However, the procedure is novel, has a minimal number of dedicated tools, and procedural “tricks” are still being refined. The standard 3830 lead (SelectSecure, Medtronic, Inc, Dublin, Ireland) initially used for LBAP remains the most widely used, although attempts with stylet-driven leads were recently reported.8 New procedural recommendations for stylet-driven leads based on this initial experience have been proposed.9 Both types of leads must be implanted fairly deep into the interventricular septum in order to reach the branching left bundle on the left side of the septum and to achieve the reported hemodynamic benefit. Current implant recommendations provide guidance on the depth of lead implantation and avoidance of perforations.7,10 These recommendations are primarily based on lead tip impedance measurements, electrocardiographic characteristics of the paced QRS complex, unipolar tip electrogram polarity, and recording of the left bundle branch potential whenever possible. Much less data have been reported on lead ring (anode) pacing thresholds and impedance measurements during LBAP. Given the known distance between lead tip and ring, these ring measurements may provide additional guidance on the depth and direction of lead implantation and the achievement of an adequate implant position. To investigate this concept, we retrospectively analyzed the procedural records at a tertiary referral center, active in LBAP, with the focus on lead tip and ring pacing characteristics.

Section snippets

Methods

This study was a retrospective analysis of 73 consecutive patients (between September 2020 and October 2021) who were successfully implanted with LBAP leads for standard bradycardia or cardiac resynchronization therapy indications. The research reported here adhered to the Helsinki Declaration guidelines. The data extraction protocol was approved by the local institutional review board. Patient demographic characteristics are listed in Table 1. The majority of patients had bradycardia

Results

Patient demographic characteristics are listed in Table 1. The majority of patients had bradycardia indications and received a pacemaker. Implant pacing data, procedural characteristics, and electrocardiographic measurements are given in Table 2.

Discussion

This retrospective study is the first to call attention to detailed ring impedance measurements during LBAP implant procedures. A fixed distance between the tip and the ring electrode (10.8 mm in the 3830 lead) may facilitate determining the depth of lead implantation. This study demonstrated that ring impedance measurements increase in stepwise fashion during a successful lead advancement process. Tip impedance measurements are less predictive of lead depth. Tip impedance monitoring is

Conclusion

Ring pacing parameters are more informative of lead implantation progress than tip measurements. Lead implant depth and lead-septal angle are associated with the dynamics of ring impedance and threshold measurements. Lead implantation guided by these observations may be achieved without contract injection for septal delineation. Unipolar ring pacing measurements should be incorporated into the lead implant procedure.

References (20)

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Funding Sources: The authors have no funding sources to disclose.

Disclosures: Dr Orlov has received a research grant from Boston Scientific. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

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