Contrasting anatomical challenges in the implantation of tine-fixed and helix-fixed leadless pacemakers in a single patient: A case report.

Patient-specific anatomical variations can significantly influence the implantation technique of different types of leadless pacemakers (LPMs). A 74-year-old man with complete atrioventricular block initially underwent successful implantation of a tine-fixed LPM. Three years later, an elevated pacing threshold caused premature battery depletion, and a helix-fixed LPM was selected for reimplantation. Unlike the tine-fixed LPM implantation procedure, this implantation proved technically challenging. The catheter developed a sigmoid deformation while crossing the tricuspid valve, which subsequently made manipulation at the interventricular septum difficult. This deformation was resolved by alternating retraction and advancement of the protective sleeve, leading to successful device implantation. We considered that the technical challenges were attributable to the inferior vena cava axis being oriented toward the posterior atrial wall and interatrial septum-directing the delivery catheter away from the tricuspid valve-in combination with the larger curvature of the helix-fixed LPM delivery system. Learning objective: Compared with tine-fixed leadless pacemakers, helix-fixed systems may be more susceptible to anatomical challenges during implantation. Pre-implantation assessment of anatomical features might be helpful for the procedures.