Complete ectopic pulmonary venous drainage (TAPVC) is a relatively rare intracardiac malformation that accounts for about 2% of precordial disease. In the last decade, with the improvement of preoperative diagnosis, intraoperative surgery and postoperative monitoring techniques, surgical correction of TAPVC has achieved satisfactory results [1]. Since the symptoms of obstructive TAPVC appear early and most sick infants die within the first month of life, it is advisable to perform this type of surgery within the first month of life, often as an emergency procedure [2]. In this paper, we summarize and review the results of acute corrective TAPVC surgery and evaluate the risk factors associated with the postoperative period in our hospital.
Materials and methods
A total of 386 cases of pediatric TAPVC were admitted to our hospital from March 1999 to May 2011, including 68 cases of neonatal obstructive TAPVC, accounting for 16% of the total group. The preoperative examination of transcutaneous oxygen saturation was 0.71-0.89, with a mean of 0.79±0.2. Echocardiography was performed to assess left ventricular function in all cases, and CT was added in 12 cases. 17 children with cardiac insufficiency and severe internal environmental The rest of the children were operated within 24 hours of admission after echocardiographic diagnosis and emergency surgery.
In this group, there were 21 cases of supracardiac type, 8 cases of intracardiac type, 36 cases of subcardiac type, and 3 cases of mixed type (supracardiac combined with intracardiac type or subcardiac combined with intracardiac type). The supracardiac type obstruction occurred at the junction of the vertical vein and the left innominate vein in 7 cases, the junction of the left and right innominate veins in 3 cases, and the oval hole type in 9 cases, with diameters of 0.13-0.21; the intracardiac type were all oval hole type atrial defects; the subcardiac type obstruction occurred at the junction of the left and right pulmonary veins forming the vertical vein across the diaphragm and the hepatic vein, and the blood flow velocity in the vertical vein reached 2.3-2.6 m/s.
All children were operated under shallow to medium hypothermic extracorporeal circulation, except for 6 children operated with deep hypothermic stop circulation (DHCA) technique from 1999 to 2002. Before the start of extracorporeal circulation diversion, the arterial catheter and ligament were routinely separated, and after aortic block, the root was injected with 20 ml/kg of 4°C blood-containing myocardial protective fluid, and thereafter one infusion was made every 20 min.
The surgical route for supracardiac TAPVC is dissected through the top of the atrium between the aorta and superior vena cava, and four pulmonary veins are isolated to converge into the venous coaptation located behind the left atrium, the common pulmonary vein and the vertical venous return to the left innominate vein. The posterior wall of the left atrium is incised parallel to the direction of the summary vein, cut upward to the top of the left auricle and downward to about 3-5 mm from the mitral valve annulus, and the common pulmonary vein is incised longitudinally to the beginning of the vertical vein before the common pulmonary vein is incised, and the incision between the posterior wall of the left atrium and the common pulmonary vein and the vertical vein is closed with 7-0 prolene continuous sutures. If the common pulmonary vein is narrow, the anastomosis can be extended to the upper and lower branches of the left and right pulmonary veins If the pulmonary vein coaptation is narrow, the anastomosis can be extended to the upper and lower branches of the right and left pulmonary veins. In most children, a pericardial slice is used to close the atrial septal defect or foramen ovale to expand the left atrial volume. The vertical veins are ligated at the end of the procedure.
Pulmonary venous return at the intracardiac level in the intracardiac TAPVC was achieved in 6 cases to the coronary sinus and in 2 cases directly to the right atrium, with unclosed foramen ovale for traffic in both atria. In patients with coronary sinus reflux, coronary sinus decortication connects the coronary sinus opening to the atrial septal defect, creating a large opening between the left atrium and the coronary sinus. The atrial septal defect is closed using a patch and the coronary sinus orifice is also encircled within it. In patients with direct pulmonary vein connection to the right atrium, blood flow can be directed into the left atrium by using a plate barrier to cut through the foramen ovale into the atrial septal defect.
In subcardiac TAPVC, the pulmonary veins often enter the common confluence of the pulmonary veins behind the left atrium, separating the vertical veins down to the mediastinum. The posterior wall of the left atrium is incised parallel to the direction of the vertical vein, cut upward to the top of the left atrium and downward to about 3-5 mm from the mitral annulus, and after the vertical vein is incised longitudinally, the incision between the posterior wall of the left atrium and the vertical vein is closed with 7-0 prolene continuous sutures, and the vertical vein is ligated at the level of the diaphragm.
In three cases of mixed TAPVC, three pulmonary veins formed a common confluence to the intracardiac coronary sinus, and the fourth pulmonary vein returned independently to the left innominate vein. the treatment of the three pulmonary veins draining to the coronary sinus was similar to that of intracardiac TAPVC, in which the distal pulmonary vein draining to the left innominate vein alone was cut and turned down and redirected or reanastomosed to the left auricular position.
The extracorporeal circulation was diverted from 65 to 156 min (, mean (88.9±12.0) min); the aortic block was 21 to 116 min, (mean (48.9±7.0) min); 6 patients with DHCA were circulated for 46 to 72 min extracorporeally and stopped circulation for 31 to 44 min. 56 cases had esophageal ultrasound after surgery, and 2 cases had pulmonary venous flow velocity >1.6 m/s, After re-transfer, the pulmonary venous flow velocity was <1.4m/s after enlargement of the anastomosis by pericardial slices.
Results
The operation was successful in the whole group, but there were 2 postoperative deaths (2.9%), all of them were children with subcardiac TAPVC, who died of postoperative hypovolemic syndrome and hemorrhage respectively. 6 cases had postoperative cardiac swelling and were given delayed chest closure, and the average chest closure was 2-5 days later. The surviving children were ventilator-assisted for 2 to 13 days postoperatively (, mean (6.0±3.5) days). 7 of them had pulmonary hypertension crisis, which improved after treatment with sedation, nitric oxide (NO), vancomycin and bosentan; 5 had hypocapnia syndrome with anuria or oliguria, which improved after 2 to 5 days with peritoneal dialysis. Other complications included 3 cases of pulmonary infection, 1 case of suspected mycobacterial infection, 3 cases of pulmonary edema, 2 cases of pleural effusion, and 2 cases of pneumothorax.
The children were followed up for 6 months to 3 years after surgery. In two cases, the right pulmonary venous flow velocity increased by 2.2 m/s on the first review six months after surgery, and it did not decrease to normal three years after surgery. 58 cases showed significant improvement in cardiac function, with significant reduction in cardiac shadow and disappearance of pulmonary congestion during the follow-up. Pulmonary venous flow velocity decreased to (0.9±0.2)m/s at 3 years postoperative follow-up.
Discussion
I. Preoperative diagnosis and preparation
Because TAPVC can be combined with most other congenital heart lesions, early diagnosis is particularly difficult because of the variability of symptoms [3]. Echocardiography is the most commonly used tool for definitive diagnosis of TAPVC and can clarify its anatomical staging. Echocardiography is safe and accurate, and for many children, cardiac catheterization is not necessary, and CT can be performed to provide the type of TAPVC if necessary. All cases in our group were clarified by cardiac ultrasound and then operated directly, and in 12 cases the course of the pulmonary veins was clarified by CT. Children with pulmonary venous obstruction may have progressive hypoxia, hypoperfusion and progressive hemodynamic failure, and often have progressive metabolic acidosis, with a mortality rate of up to 50% within the first 3 months of life. Once diagnosed, surgery can be performed immediately. Congestive heart failure often occurs in the neonatal period due to obstruction and is not a risk factor for surgical death.
Fifteen children were intubated preoperatively with mechanical hyperventilation and 100% oxygen, which reduced pulmonary vascular resistance and maximized oxygen transport. The use of prostaglandins keeps the arterial catheter open, and the arterial catheter can serve as a protective right-to-left shunt. Prompt and early correction of metabolic acidosis to improve sensitivity to catecholamine drugs. If these measures do not improve oxygenation and perfusion of the body circulation, emergency or subemergency surgery should be considered. In patients with severe preoperative metabolic disturbances that cannot be corrected, preoperative staged use of ECMO is very useful [4] to correct and stabilize organ function and may improve the prognosis of such critically ill infants.
II. Discussion of surgical methods and techniques
Different surgeons use different surgical techniques, some use the deep hypothermic stop circulation technique (DHCA), while others try to avoid DHCA. all technical steps aim to connect the pulmonary veins to the left atrium, eliminate all abnormal connections, and correct any combined other malformations, including atrial septal defects.
1. Supracardiac TAPVC
For supracardiac TAPVC, the branches of the right and left pulmonary arteries should be fully freed intraoperatively in order to reduce the tension on the anastomosis later [5], and care must be taken when ligating the vertical veins to avoid damaging the left phrenic nerve immediately adjacent to the vertical veins. We believe that the current ideal method is to make a wide anastomosis between the pulmonary vein coaptation and the left atrium by pathway from the aorta and superior vena cava to avoid suture load-like contraction, which can cause residual obstruction of the pulmonary vein anastomosis. The atrial septal defect or foramen ovale is closed with a pericardial slice through the right atrial incision to enlarge the left atrial volume.
2. Intracardiac TAPVC
Repair through a right atrial incision, in patients with coronary sinus reflux, the coronary sinus is de-roofed, but not too close to the tricuspid annulus, connecting the coronary sinus opening to the atrial septal defect [6]. This creates a large opening between the left atrium and the coronary sinus. The atrial septal defect is closed using a patch that should be wide enough and envelop the coronary sinus opening as well to direct pulmonary and cardiac venous blood flow to the left atrium. In 2 patients with direct pulmonary vein connection to the right atrium, a plate barrier was used to direct blood flow into the left atrium through the enlarged atrial septal defect.
3 Subcardiac TAPVC
Although the physiological and clinical manifestations of subcardiac TAPVC are very different from the other subtypes, the surgical repair is similar to that of the supracardiac type. However, preoperative pulmonary venous return in these children often passes through the hepatic vein and then into the inferior chamber to the right atrium, often with reflux obstruction, resulting in cyanosis and rapid deterioration of low cardiac output to multiple organ failure in sick infants, which must be treated surgically as soon as the diagnosis is clear [6-7]. Previously, the heart was turned upward to the right to expose the left atrium and the summary vein for anastomosis, but the exposure was difficult, and the heart was turned upward by hand, and the myocardial temperature was higher, which was not conducive to myocardial protection, so we used to free the upper and lower vena cava and separate the interatrial sulcus respectively, and came from the right side of the heart to expose the posterior wall of the atrium and the summary vein, the vertical vein, and then fully free the pulmonary vein branches and the vertical vein, and cut the distal end of the vertical vein in the , distal suture, proximal end is cut upward to anastomose with the posterior wall of the left atrium to enlarge the left atrial volume, if the vertical vein is short, the incision can be extended to the thicker side of the pulmonary vein to ensure that the anastomosis is large enough [8~9]. The management of postoperative pulmonary hypertension is very important and can be monitored continuously via pulmonary artery manometry tube if necessary. Sedation, hyperventilation, positive systolic drugs and cardiac afterload reducing drugs are available, as well as inhaled nitric oxide or vantave.
Some scholars believe that it can be left open to relieve the high pressure of the pulmonary venous anastomosis, and there is a possibility of self-closing in the long term [6], but some scholars believe that it will not close by itself [9], instead, there is a risk of heart failure due to left-to-right shunting in the long term, except for 3 cases of supracardiac TAPVC with high pulmonary venous pressure to keep it open after surgery, the rest were ligated or cut and sutured.
III. Prognosis
Extensive results reported in the literature [10] have shown that the mortality rate in patients with TAPVC has decreased dramatically, from 10% to 30% in the 1970s and early 1980s to 5% to 9% today. The incidence of postoperative pulmonary vein stenosis ranges from 6 to 11%; this is often the case with subcardiac or mixed TAPVC. Accurate preoperative ultrasound diagnosis, improved intraoperative myocardial protection, anastomosis using the pulmonary vein coaptation wall and atrial wall tissue whenever possible, avoidance of twisting of pulmonary vein branches and delayed chest closure can reduce mortality. The degree of severe preoperative pulmonary vein obstruction and the duration of emergency surgery, as well as the inferior cavity type of TAPVC, may affect the prognosis [11]. With improved surgical techniques, postoperative reoperation rates reach <5%< span=""> or less. Although recent retrospective studies have found low mortality and better outcomes after TAPVC surgery, attention should still be paid to the treatment and timing for patients with pulmonary vein restenosis and the need for reoperation.