Silent misplacement: leadless pacemaker in the left ventricle discovered over a year later—How did it end up there? Could it explain the stroke?

Introduction: Leadless intracardiac pacemakers (LICPs) reduce lead-related complications but may be malpositioned in patients with unrecognized structural defects. We report a 69-year-old man with high-grade AV block whose LICP, intended for right ventricular placement, was found in the left ventricle via an undiagnosed ostium secundum ASD after presenting with multifocal embolic strokes 16 months later. Case Presentation: Stroke workup for acute right-sided symptoms revealed the LICP in the LV and a large, previously undiagnosed ASD with bidirectional shunting and severe pulmonary hypertension. Embolic infarcts were attributed to either paradoxical embolism or device-related thromboembolism. Due to high surgical risk, the device was left in place; heparin was started with plans to bridge to warfarin. The patient later declined percutaneous ASD closure. Conclusion: This case highlights the risk of LICP misplacement via an unrecognized ASD and underscores the need for structural evaluation before implantation, even without clinical suspicion.