Treatment of severe pulmonary artery atresia – unifocalization operation
Unifocalization operation (UF) is the direct coupling of large somatic pulmonary collateral vessels (MAPCAs) or by various methods to the main pulmonary artery trunk to unifocalize the source of pulmonary blood, i.e., to be supplied by the central pulmonary artery.
This procedure was first adopted by Haworth et al. in 1981, and its early results were very unsatisfactory, partly because of neglecting to choose the right size at the time of hilar vascular fusion, creating difficulties for connection to the right ventricle at later radical surgery.
Early monogenization procedures used a lateral open thoracotomy, including ligation and grafting of collateral vessels, and patching to enlarge the collateral vessels. When one or more lung segments are dual blood supply, the collateral vessels should be closed. Preoperative catheter embolization is also possible if collateral vessels are not necessary to ensure satisfactory somatic arterial oxygenation.
The management of somatic pulmonary collateral vessels in monogenic surgery has been a difficult surgical task due to the complex pathophysiology and variable anatomic location of somatic pulmonary collateral vessels.
Origin and classification of MAPCAs
In normal early embryonic development, the vascular plexus forming the pulmonary buds is connected to the segmental arteries emanating from the dorsal aorta. At day 40, the intrapulmonary vascular plexus differentiates into several segmental arteries, at which point the pulmonary blood supply originates from the 6th pair of aortic arches (pulmonary artery trunk) and the segmental arteries (which should normally die out by day 50). Later, the vessels in the lung parenchyma are connected to the right ventricle by the main pulmonary artery trunk. In some severe cases of congenital heart disease with pulmonary hyperaemia, such as pulmonary atresia combined with ventricular septal defect and tetralogy of Fallot combined with pulmonary atresia, the normal developmental process is arrested and the segmental arteries that should have disappeared are present, while the main pulmonary artery trunk can be present or absent at the same time. The so-called large somatic pulmonary collateral arteries (MAPCAs) refer to these segmental arteries.
According to their diameter, somatic pulmonary artery collateral branches can be divided into two main categories: large collateral branches (originating proximally from the aorta or its main branches and connecting distally to the pulmonary arteries in the hilum) and diffuse small collateral branches (generally originating proximally from the small intercostal arteries and connecting distally to the pulmonary arteries in the parenchyma). The two types of collateral branches differ significantly in their ontogeny, with large collateral branches forming as described above; diffuse small collateral branches are born as a secondary compensatory response of the body due to persistent cyanosis and pulmonary blood deficiency after birth. Its formation is mainly the collateral circulation of the bronchi, which is distributed along the tracheal ramus and bronchial tree.
Therefore, larger collateral vessels may be the cause of pulmonary atresia and pulmonary artery dysplasia, while diffuse small collateral vessels may be secondary to pulmonary atresia or pulmonary artery dysplasia. Surgical procedures are usually able to deal with only the large collateral vessels.
Hazards of MAPCAs
There are 4 main hazards as follows.
(1) The blood supplied by the collateral vessels of the corporal pulmonary artery is mainly from the corporal artery, which has a relatively high oxygen content. The long-term impact of these arterial blood on the pulmonary vascular bed will cause pulmonary hypertension and eventually cause cardiac failure; (2) When performing correction of intracardiac malformations, if the collateral vessels of the corporal pulmonary artery are not treated beforehand, a large amount of blood from the corporal circulation will flow back to the left heart via MAPCAs after the establishment of extracorporeal circulation, resulting in the operation (3) if the MAPCAs are not monogenized and the intracardiac malformation and right ventricular outflow tract reconstruction are performed directly, the increased source of pulmonary blood (reconstructed right ventricular outflow tract and MAPCAs) will often lead to congestive left heart failure after surgery, causing death of the sick child in the near postoperative period; (4) the follow-up results of children operated on with TOF combined with PAA and somatic pulmonary collateral vessels found that the postoperative distant morbidity and mortality rates were significantly higher in those without monogenic surgery for MAPCAs, indicating that MAPCAs are an important risk factor.
Monogenic surgery for MAPCAs is an important way to avoid and reduce these risks, and monogenic surgery can also promote the development of the pulmonary vascular bed and create a good condition for later surgery.
Evaluation of MPCAs before monogenization surgery
1, the method of evaluation, mainly applies right ventriculography + arch descending or ascending aortography and right ventriculography + arch descending or ascending aorta + selective body pulmonary collateral angiography aortography can comprehensively understand the distribution of body pulmonary collateral vessels, selective collateral angiography is necessary for preoperative embolization. In addition, coronary artery malformations can be understood.
The angiographic evaluation includes.
1) The condition of the pulmonary artery trunk, its relationship to the right ventricular connection, the source and path of the blood supply and the extent of the supply of pulmonary blood.
(2) Pressure measurement to understand whether there is restrictive stenosis in the collateral vessels is also an important part of preoperative diagnosis.
2. The most important index to determine the survival of the patient after surgery is the ratio of peak postoperative left and right ventricular pressures. If right ventricular outflow tract stenosis is excluded, the factor that determines P(Rv)/(Lv) is the thickness of the pulmonary artery, or the size of the cross-sectional area of the pulmonary artery.
(1) The most commonly used simple method is the McGoon ratio, which takes the sum of the diameters of the proximal ends of the right and left pulmonary arteries outside the pericardium and divides it by the diameter of the descending thoracic aorta at the level of the diaphragm. The general determination is.
a ratio greater than 2, the pulmonary artery is considered well developed and free of stenosis.
A ratio equal to 1 predicts a P(Rv)/(Lv) of approximately 0.7.
If the ratio is equal to 0.8, then the predicted P(Rv)/(Lv) is slightly higher than 0.8.
Predicted P(Rv)/(Lv) ≤ 0.7, stage I radical treatment can be considered; predicted P(Rv)/(Lv) between 0.7 and 1.0, staged radical treatment can be considered; predicted P(Rv)/(Lv) > 1, then radical surgery should not be performed.
(2) Another method of predicting postoperative P(Rv)/(Lv) is the pulmonary artery index PAI index, which is the sum of the left and right pulmonary artery cross-sectional areas divided by the body surface area (normal value is 330 mm2 /m2).
The preoperative determination of the total new pulmonary artery index (TNPAI), pulmonary artery index (PAI) and the ratio of pulmonary blood supplied by the pulmonary artery to pulmonary blood supplied by the collateral circulation (Spa:Sca) is of great significance. ＜If the TNPAI is less than 100 mm2/m2 , but the Spa:Sca is >1, it is recommended to first reconstruct the right ventricular outflow tract, and then perform complete monogenic surgery and correction of intracardiac malformation in the second stage.
Development of a monogenic surgical plan
The treatment plan depends on the thickness of the pulmonary artery, the presence or absence of pulmonary artery fusion, and the length and location of the atretic segment.
The central pulmonary artery is classified into four types according to its development, as follows.
Type I (medium sized): the central pulmonary artery is well developed.
Type II (small sized): poorly developed pulmonary artery, but its diameter is greater than 2 mm.
Type III (Vesigial): the central pulmonary artery is present, but its diameter is less than 2 mm.
Type IV (Absent): the absence of a central pulmonary artery is confirmed by imaging, and both lungs are mainly supplied by collateral blood.
First-stage monogenic surgery for radical treatment
In the literature, early stage monogenic surgery combined with right ventricular outflow tract reconstruction and septal defect repair has been reported to have good results, with no significant increase in long-term mortality compared with staged surgery and avoiding the high cost of staged surgery.
In 1997, Christo et al. reported 12 patients with PAA combined with MAPCAs in which the first 7 cases were staged radically, with UF surgery to fuse the lateral branch of the body lung and second stage surgery to repair the VSD; the second 5 cases were staged radically with median open-heart UF surgery + VSD repair. The postoperative P(Rv)/(Lv) was 0.49 (staged) and 0.45 (stage I) in the two groups, respectively. Therefore, the authors concluded that one-stage surgical radical treatment was the best surgical option.
In 1997, at the 70th Annual Meeting of the AHA, Dr. Mohan Reddy of the University of California reported a case study of 85 cases with a mean age of 7 months and 56 cases of complete stage I UF + VSD repair. The survival rate was 80% at three years of follow-up. The authors analyzed more than 90% of cases with complete stage I UF, and more than 2/3 of patients were able to achieve radical stage I UF + VSD repair. The authors concluded that this result was much better than the 65% one-year survival rate and the 50% two-year survival rate of the natural course of the disease.
In 2000, Lofland et al. of the University of Missouri, Children’s Mercy Hospital reported that they began performing stage I UF + VSD repair in March 1997 and performed a total of 11 cases in 18 months, aged 5 days to 5 months, weighing 2.2 kg to 5.6 kg. A total of 11 cases were done during 18 months, with ages ranging from 5 days to 5 months and weights ranging from 2.2 kg to 5.6 kg. Postoperative ultrasound confirmed P(Rv)/(Lv) >0.5 in two cases; balloon angioplasty was performed in two patients, and in one case a stent was placed at the end of the thoracic pulmonary artery. Therefore, the authors conclude that the results of a stage I UF procedure + VSD repair in small infants and children are superior to staged surgery, and that the combination of balloon dilation and stenting of partially stenosed pulmonary artery segments would be highly desirable.
There is still controversy as to whether staged radical treatment should be performed, and in 2005 Dr. Yves d’Udekem of the Royal Children’s Hospital in Melbourne reported at the 85th Annual Meeting of the AATS a case study of 82 cases of UF with an in-hospital mortality rate of 4%. 53 cases (65%) had complete surgical radical treatment (UF + VSD repair) with an in-hospital mortality rate of 8% and 9 cases of distant death. All patients survived to 30 years of age in 58% ± 7%, with a 12-year survival rate of 51% ± 14% after complete radical treatment. Moreover, angiographic results showed that central bypass surgery promoted the development of the central pulmonary artery in all patients (29), while only 31 of the 60 patients who underwent UF were confirmed, and after a mean of 3.2 years, 26 had thrombosis and 12 had stenosis of more than 50%. Serial measurements showed no further development of the large somatic pulmonary collateral in 29 branches. Therefore, this author concluded that the follow-up results of such patients surviving into adulthood showed that staged surgery was the key factor. Moreover, the patients’ long-term survival was entirely dependent on the development of their own pulmonary arteries, whereas the somatic pulmonary collateral vessels after UF surgery did not develop even without embolization.
Reviewing the literature, we believe that the ability to complete a staged radical surgery requires meeting relatively stringent requirements.
1. The child has relatively well developed pulmonary arteries, most of which belong to types I and II of the pulmonary artery typology. Having their own intrinsic pulmonary arteries, or relatively well-developed right and left pulmonary arteries.
2, the proportion of blood supplying pulmonary segments accounted for by somatic pulmonary collateral branches is less than 30%, i.e., the pulmonary artery supply area is at least 70%.
3, the body-pulmonary collateral of UF is a protected collateral vessel (imaging shows stenosis at the beginning of the segment after the aorta emanates from MACPAs) rather than an unprotected vessel (imaging shows no stenosis at the beginning of the segment after the aorta emanates from MACPAs, with possible obstructive pathological changes).
4. P(Rv)/(Lv) ≤ 0.7 is measured at the end of the procedure, and if it is higher than 0.8, the VSD patch should be removed and replaced by a staged procedure.
Staged surgery
In cases of type III or type IV pulmonary atresia with relatively poor pulmonary vascular development, complete radical treatment with stage I surgery is very difficult, and staged surgery can be considered for radical treatment. In early stage, some or all of the lateral branches of the body lung are monogenized and combined with central shunt to improve the pulmonary vascular bed, and then the right ventricular outflow tract is reconstructed and the VSD defect is repaired in the second stage according to the pulmonary vascular development shown on the imaging. The postoperative morbidity and mortality rate was reduced with good results.
In 2003, Dr. Duncan of the Children’s Hospital of Corryvallan reported a case study of 46 staged procedures. Complete cure was achieved in 28 patients (61%), who underwent an average of 3 surgeries. The mean P(Rv)/(Lv) for patients who were able to achieve definitive cure was 0.36 (0.19 to 0.58). There were no in-hospital deaths in all patients, and only one premature infant died distally due to severe bronchial asthma after completion of VSD repair.
In 2006, Nobuyuki Ishibashi et al. of Tokyo Women’s University reported the staged surgical results of 113 cases of UF surgery and second-stage VSD repair at the 20th Annual European Thoracic Surgery Conference and the 14th Annual ESTS Conference, in which the surgical approach was to UF all body pulmonary collaterals in stage 1 and to establish right ventricular-pulmonary artery access and repair the VSD in stage 2. The overall survival rates at 5, 10, and 15 years after stage 1 UF surgery were 80.9%, 73.8%, and 69.9%, respectively. The authors concluded that the outcome of staged surgery was relatively satisfactory. However, poor central pulmonary artery development is a significant risk factor for the disease, and the rise in right ventricular pressure after VSD repair affects long-term survival.
Based on the comprehensive literature, staged surgery is indicated for patients with relatively poor pulmonary vascular development in.
1, type III and type IV pulmonary atresia with MAPCAs supplying >30% of the innervated pulmonary segments after monogenization.
2, predicted P(Rv)/(Lv) greater than 0.7; most patients with poor pulmonary artery development require multi-stage surgery, and there are still some patients who can never be completely surgically eradicated due to poor pulmonary artery vascular development after monogenization + body-pulmonary bypass.
Adhesions in staged surgery make the procedure more difficult and there is a risk of hemorrhage due to unclear fields. However, staged surgery allows the operator to more comfortably assess the development of the pulmonary vessels and to more precisely time the surgical radicalization, which leads to better long-term clinical outcomes.
UF surgical approach
1. Type I pulmonary artery atresia
For children with type I central pulmonary artery disease, there are four main basic single-source surgical approaches.
(1) Direct ligation of the MAPCAs at their initiation, which is mainly indicated for those with pulmonary segments supplied by MAPCAs for whom the central pulmonary artery still has an adequate public blood supply.
(2) Dissection of the MAPCAs at their origin and direct anastomosis to the central pulmonary artery with a patch to enlarge the stenosis.
(3) The MAPCAs are dissected at the beginning of the MAPCAs and the severed end is anastomosed directly to the central pulmonary artery.
(4) The MAPCAs are dissected at the beginning of the MAPCAs and the severed end is attached to a prosthetic vessel, and the other end of the prosthetic vessel is placed in an end-to-side anastomosis with the central pulmonary artery. After the MAPCAs are treated, right ventricular outflow tract reconstruction can be performed at the same time, or the right ventricular outflow tract reconstruction can be performed in the second stage after the first body-pulmonary bypass.
Type II pulmonary artery atresia
In children with type II central pulmonary artery disease, the monogenic surgical approach is.
(1) After cutting MAPCAs, the severed end is anastomosed with a section of artificial vessel, and the other end of the artificial vessel is closed, and then the artificial vessel is laterally anastomosed with the central pulmonary artery, at which time the pulmonary artery end of the body-pulmonary shunt is directly connected to the artificial vessel, and when reconstructing the right ventricular outflow tract, the severed end of the closed artificial vessel is reconnected to the reconstructed main pulmonary artery, and the body-pulmonary shunt is closed at the same time.
(2) The “double central pulmonary artery” method, in which the MAPCAs are cut off and the severed ends are end-to-end anastomosed with a section of the artificial vessel, and the artificial vessel is not laterally anastomosed with the central pulmonary artery, forming two parallel systems, called the “double central pulmonary artery method”. The pulmonary artery end of the body-pulmonary shunt should be connected to the central pulmonary artery and the artificial vessel respectively. In this case, the pulmonary artery end of the body-pulmonary shunt is connected to the central pulmonary artery and the artificial vessel.
3. For children with type III and IV central pulmonary artery disease
The procedure is more difficult and is performed by fully freeing the intrapulmonary arteries, connecting all intrapulmonary arteries to a single artificial vessel, and then performing a central shunt through this artificial vessel. The specific approach is closely related to the development of the central pulmonary artery.
One-stage surgery to reconstruct the pulmonary artery can be performed with intentional coiling to reconstruct the central pulmonary artery in cases of severe pulmonary artery dysplasia and central pulmonary artery agenesis. The intrapulmonary vascular branches can be anastomosed to the pericardial canal, and the proximal end of the pericardial canal can be drawn closer and fixed in the mediastinum. A body-pulmonary bypass is also added.
The central pulmonary artery reconstructed in stage I is connected to another pericardial tube at the same time as the radical surgery of the second stage intracardiac repair, completing the radical surgery and pulmonary artery reconstruction. The location of the pulmonary artery connecting tube can be placed anterior to the aorta: (a) where the pulmonary artery is posterior to the aorta; (b) placed anterior to the aorta.
The evaluation of the outcome of monogenization surgery lacks uniform criteria for the evaluation of the surgical outcome, generally in the early postoperative period, and the cause of death of the child is often related to a high postoperative right heart pressure to left ventricular pressure ratio and severe cardiopulmonary insufficiency due to reopening of the ventricular septal defect.
One-stage radical surgery for pulmonary atresia is more demanding on the development of one’s own pulmonary artery, so one-stage surgical radical treatment is still difficult for most patients. The current domestic and international literature reports that the results of staged surgical treatment are more satisfactory and that different surgical techniques can be used flexibly according to the different developmental conditions of the patient’s pulmonary artery and that the surgical plan can be selected according to the developmental status of the patient’s pulmonary artery.