Torque Transmission Failure During Leadless Pacemaker Implantation Caused by Severe Iliofemoral Venous Tortuosity.

BACKGROUND: Leadless pacemakers have demonstrated safety and efficacy comparable to those of conventional transvenou s systems. However, anatomical abnormalities of the venous system may occasionally complicate implantation. We report a case of unsuccessful implantation of the Aveir VR leadless pacemaker caused by severe iliofemoral venous tortuosity resulting in failure of rotational torque transmission. CASE SUMMARY: An 88-year-old woman developed sinus node dysfunction following catheter ablation for atrial tachycardia and underwent leadless pacemaker implantation. Although the delivery catheter successfully reached the right ventricle, severe tortuosity extending from the left femoral vein to the inferior vena cava prevented effective transmission of rotational force to the distal fixation helix. Bench simulation reproduced this phenomenon, demonstrating preserved torque transmission under mild tortuosity but marked attenuation under severe 3-dimensional tortuosity. DISCUSSION: This case highlights a previously underrecognized mechanical limitation of active-fixation leadless pacemaker systems and underscores the importance of preprocedural assessment of venous anatomy.