Sheath shape pattern during leadless pacemaker implantation

Purpose Options for shaping the delivery sheath of leadless pacemakers (LPs) based on the cardiac anatomy of patients are limited. We predicted the shape of the LP sheath during implantation using preoperative computed tomography (CT) and intraoperative fluoroscopy. Methods Forty-eight patients with implanted LPs due to symptomatic bradyarrhythmia were divided into two groups, alpha-loop and non-alpha-loop, based on the shape of the LP delivery sheath head at implantation. Angles between the inferior vena cava (IVC) and the interventricular septum (IVST), and the IVC and right ventricular apex (RVA) were measured by CT. The relationship between the final sheath shape and position of the IVC and the right or left side of the line drawn vertically from the deflection point of the sheath in the LAO view on fluoroscopy was assessed. Results Angles between the IVC and IVST (44.4 +/- 5.9 degrees vs. 50.2 +/- 6.8 degrees) and IVC and RVA (52.5 +/- 5.3 degrees vs. 58.8 +/- 7.8 degrees) on CT were significantly (p < 0.01) smaller in the alpha-loop group. To predict the alpha-loop shape, a combined IVC-IVST angle < 50 degrees and IVC-RVA angle < 55 degrees revealed higher sensitivity (81.8%). The delivery sheath positioned right of the vertical line was more frequent in the alpha-loop group (90.9% vs. 23.1%, p < 0.01). Conclusions When the preoperatively calculated angles of IVC to IVST and RVA on CT were narrow, the right side of the sheath in the IVC from the vertical line drawn from the deflection point in the LAO view indicated the need to shape the delivery sheath head into an alpha-loop during LP implantation.