Discussion
Double drainage of TAPVC is a rare variant of a mixed type TAPVC, which occurs when all the pulmonary veins form a confluence and then drain to both the coronary sinus and the left innominate vein. [3]. [4]
Recently however, other variants of TAPVCs with double drainage have been reported. [5]. [6]
In our 2 cases, the pulmonary veins formed a confluence and drained into the systemic venous system via two vertical veins. The first of the vertical veins drained through the innominate vein, and the second originated from the proximal side of the ascending vertical vein.
Preoperative identification of TAPVC with double drainage has important surgical implications. Although in both cases we performed echocardiography and contrast CT before the initial surgery so as not to miss the diagnosis, we did not detect this anomaly.
Because the first ascending vertical vein was more prominent and blood flowed without obstruction, the second vertical vein had less perfusion and a smaller vessel diameter. However, after the initial surgery, perfusion to the dominant vertical vein decreased, causing an increase in blood flow to the second vertical vein. Pulmonary venous obstruction, with or without confluence stenosis, is a well-known complication occurring in approximately 8–15% of patients after surgical correction of TAPVC. [7]
It was reported that with smaller left-sided chambers and a noncompliant left atrium, an un-ligated vertical vein may improve survival by preventing a pulmonary hypertensive (PH) crisis. [8]
An un-ligated vertical vein has been reported to atrophy spontaneously.
However, if it remains patent, it may cause right cardiac failure due to left-to-right shunting. [9]
PVS did not occur after surgery in either of the cases, and on follow-up, using chest X-rays and echocardiography for diagnostic imaging, this complication was not detected. In our institution, a follow-up diagnostic catheterization for post TAPVC surgery patients is performed 1 year after the operation routinely. If this catheterization is not performed, this anomaly can go undetected. While echocardiography is sufficient for diagnosing most TAPVC cases, cardiac catheterization is essential in a mixed variety to adequately assess drainage and possible obstruction of all 4 pulmonary veins. [10]
We performed angiography and contrast CT again in another patient who underwent repair of a supracardiac TAPVC 10 years ago in our institution; this patient did not present with the same anomaly. The left-to-right shunting persisted, and we did not identify right heart volume overload early as was done in Case 1. The hemodynamics in this patient however mimicked an atrial septal defect, and the right heart volume load gradually increased as he became an adult.
On the other hand, in Case 2, there was significant right heart volume overload and it caused an exacerbation of the tricuspid regurgitation, resulting in an increase of the mean pulmonary artery pressure. Coil embolization of the second vertical vein was therefore appropriate in this case.
Previously, it was recommended that the vertical vein was deliberately not operated on in order to prevent a PH crisis, with embolization with a coil or plug to be performed if the right heart volume load increased. [11], [12]
If we could ligate vertical vein near the pulmonary vein, these results might not be occur.
To our knowledge, this is the first case of a coil embolization for a vessel that originated from the proximal ligated vertical vein and drained into the superior vena cava through an accessory hemiazygos vein-azygos vein after a TAPVC repair.
TAPVC of mixed type is often misdiagnosed if left-to-right shunting is present like in our case. This procedure proved to be safe and provided an alternative noninvasive treatment that did not involve surgery.