Duplicated coronary sinus with a connecting branch.

A 48-year-old woman with class III heart failure and left bundle branch block underwent an implantation for cardiac resynchronization therapy. Right anterior oblique (RAO) view coronary sinus (CS) venography suggested the antero- and postero-lateral branches appeared to arise from the same vessel of a duplicated CS, but the antero-lateral branch arising from a different vessel was visualized via a connecting branch by the contrast injected into the vessel with the postero-lateral branch, and the distal parts of the two vessels were superimposed in the RAO view. This unusual anomaly may have the potential risk for complications such as perforations.