To the Editor – Cardiac resynchronization therapy in coronary sinus atresia delivered using leadless endocardial pacing

We read with great interest the report by Thomas et al describing the use of leadless left ventricular (LV) endocardial pacing in a patient with coronary sinus (CS) atresia. The technique they used was highly sophisticated but necessitated, besides implantation of the LV receiver-electrode, an ultrasound source for energy transmission and a separate battery pack for the ultrasound source. In our 17-year experience with cardiac resynchronization therapy, we have encountered CS ostial atresia in 4 patients. In the first patient we performed a left coronary artery angiogram to visualize the venous phase and the anatomy of the CS. This angiogram revealed a coronary venous system but with runoff in an upward direction toward the pectoral area. Subsequent contrast injection into the subclavian vein showed a persistent left superior vena cava (PLSVC) that gave access to the CS. It is therefore our opinion that if the CS cannot be intubated from the right atrium, a contrast injection in the proximal subclavian vein can elucidate the presence of a PLSVC; flow of contrast from the PLSVC toward the subclavian vein confirms the atresia of the CS. CS anatomy can be visualized by a selective angiogram and the decision can be made to proceed to a CS implant or to use an alternative implantation as described by Thomas et al. In our experience so far, all 4 patients had a successful CS lead implantation via the PLSVC with standard equipment and a more complicated approach could be avoided. Two of our patients have been described in case reports.