We thank Drs van Gelder and Bracke for their response to our paper. Their experience of 4 such cases of coronary sinus (CS) atresia during cardiac resynchronization therapy implantation emphasizes the strong association between this rare anomaly and the presence of a persistent left superior vena cava (PLSVC). They also make an important learning point about the ability of combining subclavian contrast injection and coronary angiography to confirm this diagnosis and guide planning of left ventricular (LV) lead placement during the index procedure.Although their experience has been one of successful LV lead delivery via the PLSVC in each of their 4 cases, we do not believe that would have been possible in our patient for the anatomic reasons previously stated. In particular, the absence of any posterolateral target veins would have precluded satisfactory lead positioning, whereas through the WiCS-LV system we were able to deliver targeted LV stimulation and achieve complete resynchronization. Furthermore, I would also emphasize that not all cases of atresia of the CS orifice are associated with the presence of a PLSVC, and in some the associated anomaly is direct drainage into the LA, most commonly through fenestrations in the LA floor1, 2 (unroofed CS variant), and in such cases the approach described by van Gelder et al would not have been possible.