Evaluating right ventricular septal implantation ratio of Micra TPS using post-procedural CT and predictive factors

A septal implantation of the Micra Transcatheter Pacing System (TPS) is recommended to avoid myocardial injury. However, there are no reports to evaluate the actual Micra device implantation site using post-procedural Computed tomography (CT) scans. This study aimed to identify the right ventricular (RV) septal implantation ratio and factors regarding successful RV septal implantation of Micra device.

A cohort of 110 consecutive patients who underwent Micra TPS implantation were enrolled. CT scans after procedure were performed to evaluate the actual implantation site of the Micra device. RV septal implantation was defined as not being positioned in the non-septal region such as RV apex, the free wall, or the inferior wall of the RV. Delivery catheter positioning, specifically maintaining an adequate distance from the RV free wall and/or forming an α-loop shape during the procedure were evaluated (Figure A and B).

Post-procedural CT scans revealed RV septal implantation in 74 patients (67.3%) and non-septal positioning in 36 patients (32.7%). Compared to cases with non-RV septal implantation, in those with RV septal implantation, the distance between the Micra device and the RV walls was maintained more than half the size of the Micra device in the right anterior oblique view, as well as formation of the α-loop shape in the left anterior oblique view. Multivariate analysis revealed that "adequate distance and the α-loop shape" was the independent predictor of successful RV septal implantation (OR:20.1 [4.68-86.6], p <0.001, Figure C).

Successful ratio of RV septal implantation was slightly lower than expectation. Maintaining a distance between the tip of Micra and RV free wall and the forming an α-loop shape of the delivery catheter are important factors for successful implantation.