Coronary sinus aneurysm and left ventricular-coronary sinus fistula. Implantation of CRT device.

We describe a 72-year-old man referred for implantation of a cardiac resynchronization therapy device who had previously undergone repeated operations to replace the mitral valve. Retrograde venography of the coronary sinus (CS) to implant the left ventricular (LV) pacing lead revealed aneurysmal dilatation of the CS with LV-CS fistula that hindered-but did not prevent-complete implantation of the system.