PO-05-043 RIGHT VENTRICULAR POSITIONING OF LEADLESS PACEMAKER MAY INFLUENCE LEFT VENTRICULAR ELECTROMECHANICAL SYNCHRONY

Abstract

Leadless pacemakers (LP) reduce certain complications of conventional pacemakers, yet limitations of single chamber right ventricular (RV) pacing remain, including pacing-induced dyssynchrony. The Micra LP is positioned in RV septum, avoiding the free wall to minimize perforation, and the location is primarily determined by capture threshold and sensitivity. Whether positioning of the LP in the mid to upper septum vs. apical septum affects the degree of left ventricular (LV) synchrony is yet to be determined. We sought to establish whether the Micra position on the RV septum affects LV synchrony, using strain imaging by speckle-tracking echocardiography. Between May 2019 and February 2022, 53 consecutive patients implanted with Micra LP were screened. Of those, eleven patients were found to be 100% paced and have an adequate quality transthoracic echocardiogram (TTE) for strain analysis. Chest imaging and 12-lead electrocardiogram (EKG) were used to identify the implantation site (apical vs. mid to high RV septum). The LV focused apical views were processed with Tomtec software to acquire strain variables including left ventricle mechanical dispersion (LVMD) and maximal opposing wall delays from an 18 segment LV model. QRS duration (QRSd) was obtained from the paced EKG. The Mann-Whitney U test and Fisher’s exact test were used to compare the independent groups. All analyses were performed using SPSS Ver 29.0 (IBM Corporation, Armonk, NY). Electrical dyssynchrony measured by QRSd showed a tendency of longer QRSd in the apical septal group (n= 5) compared to higher septal group (n= 6), but it was not statistically significant (159.6 +/- 13.8 vs. 148.33 +/- 16.15, p = 0.302). Ejection fraction showed no significant difference between two groups (median 64 vs. 60, p = 0.879). Degree of mitral regurgitation also showed no significant difference (U = 11.5, p = 0.537). Higher septal placement resulted in improved mechanical LV synchrony compared to the apical placement as measure by lower LVMD and shorter opposing wall delay (U = 2 and 3, p = 0.017 and 0.03 respectively). The Implantation site of a Micra LP displays a difference in speckle tracking derived LV mechanical strain, which was improved with higher septal positioning. This may have consequences on cardiac mechanical function in patients requiring continuous pacing. Larger studies are needed to determine whether these preliminary findings may be generalized to a larger population.