Conclusion
We encountered two rare cases of mixed type TAPVC with double drainage, where the second vertical vein enlarged rather than atrophied after surgery. Echocardiography is a useful diagnostic tool in the follow-up of PVS, however, contrast enhanced CT or diagnostic catheterization should be performed to exclude a second veno-venous shunt post-surgery. Cases of left-to-right shunting that is not recognized before surgery, it can be treated with catheterization as demonstrated by our case.