Successful Cardiac Resynchronization Therapy Defibrillator Implantation via the Vein of Marshall in a Patient with Coronary Sinus Ostial Occlusion.

Cardiac resynchronization therapy (CRT) is a well-established treatment for patients with heart failure and wide QRS complexes. Successful left ventricular (LV) lead implantation is typically achieved through the coronary sinus (CS). However, congenital anomalies such as CS ostial atresia can complicate the procedure. We report a case of a 65-year-old man with a history of aortic valve replacement and heart failure who underwent successful CRT-defibrillator implantation. During the procedure, CS ostial atresia was unexpectedly encountered, preventing standard venous access. The LV lead was successfully implanted via the vein of Marshall.