Characterization of tricuspid regurgitation in patients following left bundle branch pacing

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Abstract Background Pacemakers placed in the right ventricle apex can lead to mechanical and electrical dyssynchrony. There is a growing interest in more physiologically stimulating techniques, and in this context, left bundle branch pacing (LBBP) emerges as an option. In this pacemaker, the lead is positioned perpendicular to the septum approximately 15-20 mm below the tricuspid valve annulus, and the helix is advanced towards the left side (Image 1). There is limited data on the incidence of new-onset tricuspid regurgitation (TR) or deterioration of pre-existing TR following the implantation of this type of pacemaker. Purpose To characterize the incidence of TR or deterioration of pre-existing TR after LBBP and to determine if there are predictors of a higher degree of TR. Methods All patients who received a pacemaker with LBBP between January and October 2023 were consecutively recruited. A transthoracic echocardiogram following the implantation of the pacemaker was performed to assess the size and function of right heart chambers, degree of TR and position of pacemaker lead. Continuous variables are expressed as mean ± SD or median [IQR] and categorical variables as absolute (%). Results There were 31 implants with a mean age of 73.4±8.7 years and 42% women. Nine patients (22.5%) had atrial fibrillation, and 7 patients (23%) had known coronary artery disease. The main indication for implant was a complete AV block (63.3%). Two patients had TR greater than moderate before the implantation of the pacemaker. Mean time elapsed between implantation and follow-up echocardiogram was 5.8 months. The distance between the lead-implanted site to the tricuspid annulus (Lead-TA distance) was 26.7±10.5 mm, mean lead depth in the interventricular septum (IVS) was 7.7±1.8mm and the IVS thickness at the lead-implanted site was 10.6±2.1 mm. Overall, TR worsed less than 1 degree after the lead implant (table 2) and was significantly related with the Lead-TA distance (TR worsed 0.3 degrees in Lead-TA distances shorter than 26.7mm and TR reduced 0.2 degrees in Lead-TA distances longer than 26.7mm, p=0.037). Conclusions In the short term following the implantation of an LBBP pacemaker the distance from the lead to the tricuspid annulus has an acute impact on tricuspid regurgitation, with TR worsening at short Lead-TA distances and TR improving at longer distances.