Novel parameters for micra transcatheter pacing system implantation on the right ventricular mid-septum

Abstract Background No procedural parameters for Micra transcatheter pacing system (Micra TPS) implantation on the right ventricular mid-septum have been established though it is encouraged for safety. Purpose We aimed to investigate procedural predictors for Micra TPS implantation on the ventricular mid-septum. Methods This is a single-center, retrospective and observational study. Eighty-two patients who underwent Micra TPS implantation were enrolled. The implantation sites of the ventricular septum were classified into basal, mid and apical-septum in the right anterior oblique 35° image. Predictors for mid-septal implantation were evaluated using univariable and multivariable logistic regression analysis which involved explanatory variables considered clinically important. The explanatory variables included the angle between the axis of a device cup of a delivery catheter and the tangent of the ventricular septum in the left anterior oblique 45° image (defined as angle θ). The diagnostic cut-off value of the significant predictor for mid-septal Micra implantation was assessed using receiver operating characteristic (ROC) curve analysis. Results Micra TPS was implanted on the ventricular mid-septum in 61 patients (74.4%), the apical-septum in 21 patients (25.6%), and the basal-septum in no patients. In univariable logistic regression analysis, each angle θ and α-loop shape appearance of a delivery catheter was significantly associated with mid-septal implantation (Odds ratio [OR], 1.1; 95% confidential interval [CI], 1.02-1.10; P=0.002, and OR, 4.6; 95% CI, 1.63-13.6; P=0.005, respectively). After multivariable adjustment, both angle θ and α-loop shape appearance were independently associated with mid-septal implantation (adjusted OR, 1.1; 95% CI, 1.01-1.09; P=0.010, and adjusted OR, 3.3; 95% CI, 1.01-11.4; P=0.048, respectively). Because no Micra TPS was implanted on the basal-septum, an ROC curve for binary outcome of mid-septal and apical-septal implantation was drawn. The ROC curve showed a cut-off value of angle θ for Micra TPS implantation on the ventricular mid-septum was 22° with high sensitivity and specificity at 80.0% and 70.0% (area under the curve= 0.781). Conclusion The angle θ ≧ 22°and the α-loop shape appearance of a delivery catheter may be useful predictors for Micra TPS implantation on the ventricular mid-septum.