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.