Left ventricular lead implantation in an unusual anatomy of the proximal coronary sinus.

A 62-year-old man with Class III heart failure and left bundle branch block underwent cardiac resynchronization therapy. Because prior implantation attempts from the left side were unsuccessful, the right side approach was attempted. However, it was still impossible to advance the pre-shaped sheaths into the distal coronary sinus (CS) because the CS was abnormal with a posterior vertical take off followed by a sharp sigmoid curve before the AV groove. Ultimately, a straight sheath was adjusted to fit the sigmoid curve with the guidance of an electrophysiologic catheter and a left ventricular lead was then passed into the anterolateral vein.