Septal–Inferior Vena Cava Angle and Accurate Septal Implantation of Leadless Pacemakers: Computed Tomography‐Based Study

Background The Micra leadless pacemaker (LPM) should ideally be implanted in the septal location to enhance safety. However, the probability of accurate septal implantation and its predictive factors have not been fully elucidated. Methods Eighty‐three consecutive patients who underwent computed tomography (CT) following LPM implantation were included. The ventricular septum was targeted using a standard fluoroscopic‐guided transfemoral approach. The LPM implantation site was classified as septal or non‐septal based on CT findings. The septal–inferior vena cava (IVC) angle was evaluated as a patient‐specific anatomical parameter representing the relationship between IVC inflow and the ventricular septum. Results Accurate septal implantation was achieved in 44 patients (53.0%). The septal–IVC angle was significantly larger in the septal group than in the non‐septal group (13.1 ± 11.6° vs. 2.7 ± 10.6°, p < 0.001). Multivariate logistic regression analysis indicated that the septal–IVC angle (odds ratio, 1.09; 95% confidence interval, 1.03–1.14; p = 0.002) was independently associated with the incidence of septal implantation. The optimal cutoff value for the septal–IVC angle was 6°, with a sensitivity of 77.3% and a specificity of 66.7% for predicting septal implantation. There were no cases of cardiac tamponade or pericardial effusion. No significant differences in long‐term outcomes, including all‐cause mortality, cardiac mortality, and heart failure hospitalization, were observed between the two groups. Conclusions Accurate septal implantation was observed in 53.0% of patients who had undergone LPM implantation with the standard femoral approach. A larger septal–IVC angle was associated with accurate septal implantation.