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.