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.