Left bundle branch pacing with and without anodal capture: impact on ventricular activation pattern and acute hemodynamics

Introduction Left bundle branch pacing (LBBP) can deliver physiological left ventricular activation, but typically at the cost of delayed right ventricular (RV) activation. A proposed solution is to advance RV activation through anodal capture, but there is uncertainty regarding the mechanism by which early RV activation is achieved (capture of right bundle or RV myocardial capture) and it is not known whether this produces hemodynamic benefit. Methods We recruited patients with LBBP leads in whom anodal capture eliminated the terminal R wave in lead V1. Ventricular activation pattern, timing and high precision acute hemodynamic response were studied during LBBP with and without anodal capture. Results We recruited 21 patients, mean age 67 years, 14 were males. We measured ECG timings and hemodynamics in all patients and in 15 we also performed non-invasive mapping. Ventricular epicardial propagation maps demonstrated that right ventricular septal myocardial capture, rather than right bundle capture, was the mechanism for earlier RV activation. With anodal capture, QRS duration was shorter (116 ± 12ms versus 129 ± 14ms, p < 0.01), and total ventricular activation time was shorter (83 ± 18ms versus 90 ± 15ms, p = 0.01). This required higher outputs (3.6 ± 1.9V versus 0.6 ± 0.2V, p <0.01) but did not provide additional hemodynamic benefit (mean difference −0.2 ± 3.8 mmHg compared to pacing without anodal capture, p = 0.2). Conclusion Left bundle pacing with anodal capture advances right ventricular activation as a result of stimulation of the RV septal myocardium. However, this requires higher outputs and did not improve acute hemodynamics. Aiming for anodal capture may therefore not be necessary. ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial NCT04221763 ### Funding Statement The study is funded by the British Heart Foundation grant number FS/19/4/34013 ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the health research authority (REC 19/YH/0174) I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data is available upon reasonable request.