When Patent Foramen Ovale (PFO) Can Cause Trouble-A Misplacement of Pacemaker Lead Into the Left Ventricle

Misplacement of pacemakers lead into the left ventricle (LV) is a rare but clinically important complication, often facilitated by unrecognized intracardiac shunts such as a patent foramen ovale (PFO). Early recognition is essential to avoid systemic embolization and ensure safe device function. We report a man in his 70s with a background of bioprosthetic aortic valve replacement, coronary bypass grafting, hypertension, chronic kidney disease, Parkinson's disease, and prostate cancer, who underwent permanent pacemaker implantation for symptomatic sinus pauses. Follow-up echocardiography 1 year later, performed as part of surveillance of his aortic valve prosthesis, unexpectedly revealed that the ventricular lead had crossed a PFO and was positioned in the LV via the mitral valve. His 12-lead ECG demonstrated a right bundle branch block-like paced morphology, raising suspicion of LV pacing. The patient remained asymptomatic with no evidence of systemic embolization. He was anticoagulated with apixaban and subsequently underwent successful lead extraction and repositioning into the right ventricle (RV). Correct RV placement was confirmed using multiple fluoroscopic views, particularly the left anterior oblique (LAO) projection and by postprocedure ECG, chest x-ray, and echocardiogram. This case underlines the importance of careful assessment of paced ECG morphology, fluoroscopic views during implantation (especially LAO), and postimplant imaging to confirm lead location. Suspicion should be raised when an RBBB-like QRS morphology is observed during RV pacing. Timely recognition and management with anticoagulation, followed by extraction and repositioning, can prevent potentially devastating complications. Operators should remain vigilant for inadvertent LV lead placement, particularly in patients with unrecognized PFO. Routine use of multiple fluoroscopic projections and correlation with ECG and echocardiography can aid early diagnosis and improve procedural safety.