Discussion:
There has been attention to the neo-pulmonary artery stenosis after
arterial switch operation as it is the commonest reason for
reintervention3-5. Therefore, several techniques to
reconstruct the pulmonary artery during arterial switch procedures have
been developed, including pantaloon pericardial patch, limited buttons
resection, and extended pericardial patch to pulmonary branches.
The use of pantaloon pericardial patch compared to synthetic patch was
associated with lower neo-pulmonary artery stenosis (7% versus 40%)
and reintervention rate (4% versus 14%), respectively. However,
complex anatomy increased risk for neo-pulmonary
reintervention4.
Regarding Limited buttons resection technique, a data of 120 patients
and follow up 66±46
Months revealed that (5%) of the patients required neo-pulmonary
reintervention5.
A report by Wervovsky and colleagues was in favor of extended
pericardial patch technique due to the result of gradual recognition of
the necessity to avoid tension on the anastomosis of the neo-pulmonary
artery. This led to the more extensive mobilization of the distal
pulmonary arteries and the use of more generous pericardial patches
(single or double), not only for filling in the defects created by
coronary arteries dissection but also to add length to the proximal
neo-pulmonary root7.
Pulmonary artery reconstruction with quadrangular fresh autologous
pericardial patch represents a practical, simple and reproducible option
during the arterial switch operation with all positions of the great
vessels. The incidence of postoperative pulmonary stenosis is low, and
there may be considerable potential for unlimited tissue growth. The
peak pressure gradient across the neo-pulmonary valve and pulmonary
artery branches as determined by transthoracic echocardiography is the
most common clinical tool to assess the outcome of the surgical repair.
Ideal results would show laminar flow across the proximal pulmonary tree
with no significant pressure gradient. However, there is almost always
an element of flow acceleration and measured pressure gradient that
could be attributed to stretching of the pulmonary arteries secondary to
Lecompte maneuver and the reconstruction technique of the neo-pulmonary
artery. The value of that residual pressure gradient is ill-defined in
the literature. This paper is focused on examining the value of the
residual pressure gradient, its behavior over time, and its relationship
with the need for reintervention.
In this report, 309 patients were included with all echocardiographic
measurements that were performed in standardized fashion (n=1844). The
rate of reintervention was 5%, which is at the lowest part of the
published ranges5,8-11. There was no difference in the
pressure gradient in the presence or absence of an associated
ventricular septal defect. It was not surprising to find the residual
pressure gradient more in patients with complex anatomy and longer
bypass time as compared to those without.
Our institutional repair strategy is based on using a fresh autologous
redundant pericardial patch for the reconstruction of the neo-pulmonary
artery. Furthermore, the impact of the surgeon was not significant in
predicting the pressure gradient or reintervention in multivariable
testing. The most notable difference in pressure gradient was seen in
the first postoperative transthoracic echocardiogram (pre-discharge).
Using the longitudinal data analysis with stratification based on
intervention, it showed clear demarcation of the behavior of the
pressure gradient. We propose if the pressure gradient as measured in
the first postoperative transthoracic echocardiogram is 55 mmHg or more
will likely increase over time and subsequently require re-intervention.
The threshold for reintervention was a clinical decision was based on
the observed increase in the pressure gradient across the pulmonary
arteries. The sustainability of laminar flow in the main pulmonary
artery and its branches is the main component of maintaining low
longitudinal averaged mean line of the total peak gradient following
surgery for the entire follow up time (17-year), and we believe that
enough dissection of right and left pulmonary arteries and tension-free
anastomosis with redundant fresh pericardial patch for the
reconstruction of the neo-pulmonary artery are crucial to achieving this
result.
Additional statistical techniques were used to determine the best
cut-off point of the “high gradient” that will persist, get higher and
predict reintervention. The best cut-off point was a total peak gradient
across the neo-pulmonary artery, right pulmonary artery and left
pulmonary artery as measures in the first postoperative echocardiography
of 55 mmHg or higher.
The association between the transposition of the great arteries and
pulmonary artery growth has been suggested in published reports relating
it to accelerated pulmonary vasculopathy and asymmetric distribution of
the pulmonary blood flow12,13.