Pulmonary artery atresia with intact ventricular septum (PA/IVS) is one of the rare forms of cyanotic congenital heart disease, accounting for approximately 1% of congenital heart malformations. More than 50% of untreated cases die in the neonatal period and 85% die within 6 months of age. Lesions include septal atresia with fusion of the pulmonary valve junction, varying degrees of stenosis of the annulus, and mild or moderate narrowing of the common pulmonary artery trunk. The tricuspid valve and right ventricle are hypoplastic, the ventricular septum is intact with secondary foramen ovale septal defect or patent foramen ovale, and an arteriovenous ductus arteriosus is necessary for survival of the child. Cardiac macrovascular connections are normal.
Pathologic anatomy
The main pathological features are the absence of direct right ventricle-pulmonary artery continuity and intact ventricular septum, both combined with secondary foramen ovale septal defect or patent foramen ovale. Pulmonary atresia usually occurs in the valve or valve and funnel. In the former case, the pulmonary valve is septal-like atresia with complete fusion of the triple leaflet junction, and the pulmonary valve annulus and pulmonary trunk can be near normal in diameter; in the latter case, the pulmonary valve base is muscular with only shallow concave changes, and the funnel is atretic or severely dysplastic with a poorly developed pulmonary valve annulus and pulmonary trunk. In 45% of children, a right ventricular-coronary fistula is present, especially in children with severe right ventricular hypoplasia and small tricuspid valve openings, with a unique anatomic pattern of dependence on the coronary circulation of the right ventricle. Less than 10% of children have a combined inferior tricuspid valve malformation (Ebstein’s malformation), in which the right ventricle may be normal in size or even enlarged. Aortopulmonary collateral circulation is rare.
Clinical classification
No uniform clinical classification has been developed nationally or internationally, and PA-IVS has been classified according to right ventricular and tricuspid valve development due to surgical options.
Bull and de Leval et al. classified PA-IVS into three types according to the different development of the right ventricular input, trabeculation, and funnel parts: type I, in which all parts of the right ventricle are present but with some degree of dysplasia; type II, in which only the input and funnel parts are present and the trabeculation part is occluded; and type III, in which only the input part is present and neither the funnel nor the trabeculation part is developed.
Billingsley and colleagues classified PA/IVS as mild, moderate, or severe by combining the classification of Bull and Hanley et al. Hanley, Agnoletti et al. suggested that the diameter of the tricuspid valve and the size of the right ventricular cavity are positively correlated and that the diameter of the tricuspid annulus (Z value) is a determinant of right ventricular development and the choice of procedure, which can be determined by right ventriculography or two-dimensional The correction of the tricuspid orifice diameter (Z value) measured by right ventriculography or two-dimensional echocardiography can be applied to evaluate the surgical indications and guide clinical procedures. Mild dysplasia: The right ventricle is well developed, with the input and funnel sections and trabeculation sections present, and the outflow tract is well developed. The size of the right ventricular cavity is approximately 2/more than that of the normal control. The tricuspid valve Z value was between 0–2. Moderately dysplastic type: the right ventricular cavity and tricuspid valve size were approximately 1/–2/ of normal controls. Three parts of the right ventricle are present, all hypoplastic. The degree of right ventricular outflow tract development allows for pulmonary valvuloplasty. Tricuspid valve Z value between -2 and 4; severe dysplasia type: right ventricular cavity and tricuspid valve size less than 1/ of normal control. Only the inflow tract or three parts of the right ventricle are present and unrecognizable; the outflow tract is absent or the degree of development does not allow for pulmonary valvuloplasty. Tricuspid valve Z-values between -4 and 6. It is often combined with a right ventricular coronary fistula or even a coronary circulation dependent on the right ventricle.
Pathophysiology
Cyanosis is present in the neonatal period due to right ventricular hypertension and right-to-left shunting at the atrial level. The open arterial duct is the only source of pulmonary blood, and the child’s pulmonary blood flow and oxygen saturation after birth are completely dependent on the shunt from the arterial duct. If the arterial duct is constricted or functionally closed after birth, this will result in pulmonary blood deficiency, progressively increasing hypoxemia and metabolic acidosis, and even death. In right ventricular hypertension, blood entering the right ventricle flows back into the right atrium via the tricuspid valve or retrogradely into the coronary circulation through the myocardial sinusoidal gap, leading to severe consequences of coronary underperfusion and myocardial ischemia once right ventricular decompression is performed. Blood returning from the body vein enters the left ventricle and aorta through the foramen ovale or atrial septal defect to mix with pulmonary venous blood. However, the diameter of the foramen ovale or atrial septal defect may limit the amount of right-to-left shunt, and if it is small, it may lead to right atrial hypertension and result in body vein stasis and low cardiac output in the body circulation.
Incidence PA/IVS is one of the rare cyanotic congenital heart diseases, which accounts for about 1%-% of congenital heart malformations as reported by different cardiac centers abroad. More than 50% of untreated cases die in the neonatal period and 85% die within 6 months of age.
The embryologic mechanism of ventricular septal atresia is unknown, but it has been hypothesized that it is caused by a significant reduction in blood flow through the tricuspid valve and the right ventricle. In contrast, the mechanism of right ventricle-coronary artery fistulae is due to direct return of normal coronary venous return from the right ventricle into the right ventricle itself via the minimal cardiac vein (Thebesian), rather than into the coronary sinus. In the right ventricle, due to high pressure from pulmonary atresia, the return blood flows backwards through the Thebesian vein into the coronary artery.
Clinical manifestations
Symptoms: Most children present with cyanosis of the cheeks, lips, and fingertips a few days after birth, pauses in breastfeeding, excessive sweating, short periods of shortness of breath, increased cyanosis, dyspnea, progressive hypoxemia, and moderate metabolic acidity. The degree of cyanosis depends on the amount of blood flow from the ductus arteriosus to the pulmonary artery, if accompanied by a large ductus arteriosus the degree of cyanosis, metabolic acidosis can be mild.
Signs: cyanotic face, inspiratory trismus, poor peripheral perfusion of the extremities. Most of the tricuspid regurgitant all-systolic murmurs can be heard at the left edge of the sternum, or systolic-dominated continuous murmurs of the arterial duct can be heard, and the first and second heart sounds are single, and the heart murmurs are more variable.
Ancillary tests.
Electrocardiogram: Characteristic manifestations are left-sided electrical axis, left ventricular predominance, right ventricular hypovoltage, and right atrial enlargement due to tricuspid atresia and double inlet of the left ventricle. ST-T segment changes often suggest varying degrees of subendocardial ischemia.
Imaging examinations.
1. Chest X-ray: The child’s heart is not large or mildly enlarged at birth, with depressed or flattened pulmonary artery segments and varying degrees of reduced pulmonary blood. When the tricuspid valve is not closed, the right atrium is enlarged, and if the tricuspid valve is severely regurgitated, the heart is enlarged significantly.
2.64-row spiral CT cardiovascular reconstruction: It has unparalleled diagnostic value and can visually show right ventricular outflow tract atresia, right ventricular dysplasia, unclosed arterial duct alignment, size, right ventricular size, whether combined with right ventricular coronary fistula and other intracardiac and macrovascular malformations.
Cardiac catheterization: Cardiac catheterization and cardiovascular angiography should be performed before surgery or transcatheter right ventricular decompression to determine whether there is coronary artery stenosis or interruption. Hemodynamics shows that the diastolic pressure of the right ventricle is equal to or greater than the pressure of the body circulation. It is rare to find a pressure lower than that of the body circulation, but it is common to find severe tricuspid regurgitation due to tricuspid dysplasia, Ebstein’s malformation, and right ventricular stenosis. Right ventricular end-systolic pressures are elevated and compliance is reduced. The right and left mean arterial pressures are similar due to the presence of nonrestrictive interventricular traffic. Ortho-lateral right ventriculography films show tricuspid valve activity function, size, and right ventricular morphology, as well as the presence of right atrial coronary artery traffic. If no right ventricular coronary artery traffic is present, there is no right ventricle-dependent coronary circulation, and conversely, it does not indicate the presence of a right ventricle-dependent coronary circulation. The presence or absence of coronary stenosis or disruption can be confirmed by a cisplane balloon closure or by retrograde ascending aortography. In some patients, coronary angiography is required to clarify the coronary artery course.
Echocardiography: A mandatory diagnostic test. 2D Doppler echocardiography can show right ventricular outflow tract agenesis or narrowing as a characteristic manifestation. It can also show pulmonary atresia, dysplasia of the right ventricle and tricuspid valve, hypertrophy of the right ventricular wall and small right heart chambers, regurgitation of the tricuspid valve, the size of the atrial septal defect and the degree of development of the pulmonary trunk and its branches, and measurement of the size of the arterial duct can make a judgment on the degree of hypoxia and prognosis.
Diagnosis
Diagnosis can be made based on history and signs, combined with echocardiography, electrocardiography and X-ray chest radiographs. Cardiac catheterization is the only reliable means of assessing coronary anatomy and determining the presence of a right ventricular myocardial sinusoidal gap traffic coronary malformation. Selective cardiovascular angiography must include a right ventriculogram, which clearly demonstrates right ventricular cavity size, tricuspid regurgitation, and the blind end of the right ventricular funnel. Retrograde aortic cannulation at the site of the arterial catheter opening can satisfactorily demonstrate the blind end of the pulmonary trunk and the condition of the left and right pulmonary arteries, allowing measurement of the distance separating the funnel from the blind end of the pulmonary artery.
Treatment
PA-IVS has an aggressive onset and a high natural mortality rate. Children with PA-IVS depend on the PDA for survival after birth, and once the PDA is closed, the child quickly dies, so treatment should be provided as soon as possible.
There is no universally agreed treatment strategy that is suitable for all cases. The development of ventricular septal intact pulmonary atresia is rare, and individualized treatment experience is relatively limited. The ideal treatment plan depends on the morphologic and physiologic basis of the individual case.
(1) Preoperative preparation The neonate should be established with intravenous access as soon as possible after diagnosis, with continuous infusion of prostaglandin E1 to keep the arterial duct open, improve hypoxia, and correct metabolic acidosis. If there is inadequate perfusion, positive inotropic drugs must be maintained. In critically ill neonates with severe hypoxia, mechanical ventilation, pharmacological sedation and inotropic drugs should be given.
(2) Surgical principles: Ensure appropriate supply of pulmonary artery blood flow, improve hypoxemia and correct metabolic acidosis to maintain the survival of the child; at the same time, perform right ventricular decompression to promote the development of the right ventricle and create conditions for secondary radical surgery later. The importance of right ventricular decompression: right ventricular dysplasia in children with PA/IVS is associated with excessive right ventricular wall hypertrophy, which is mostly due to complete right ventricular outflow tract obstruction. The growth potential of the right ventricle is high after right ventricular outflow tract obstruction and right ventricular hypertension is relieved, and even a severely hypoplastic right ventricle may grow, so many authors have emphasized the importance of early right ventricular decompression in patients with right ventricular outflow tract presence. Staged palliative surgery plays a considerable role in the treatment of ventricular septal atresia with intact pulmonary arteries.
Surgical methods
1. One-stage radical surgery: mainly suitable for mild dysplasia type: well-developed right ventricle with three parts of inflow tract, apical trabecular part and outflow tract present, good development of outflow tract; right ventricular cavity and tricuspid valve diameter size is about 2/more than normal control; tricuspid valve Z value is between 0–2. The pulmonary valve annulus can be incised under extracorporeal circulation, and the right ventricular outflow tract can be enlarged with a homogeneous or heterogeneous valved patch. At the same time, the atrial septal defect is repaired and the arteriovenous ductus arteriosus is ligated.
2. Staged radical surgery: The current concept of treatment for ventricular septal intact pulmonary atresia is staged surgery combined with the principle of individualization. The principle of second-stage surgery is that if the right ventricle is well developed after the first-stage palliative surgery, the second surgery will take the form of biventricular repair; if the right ventricle is still poorly developed after palliative surgery, only physiological correction or modified Fontan surgery or 1?ventricular repair can be done.
3.One-stage palliative surgery: When the arterial duct is functionally closed or small in newborns or small infants of ~6 months old, hypoxia is aggravated and metabolic acidosis appears, palliative surgery must be performed as early as possible. The purpose is to reduce right ventricular hypertension, reduce myocardial hypertrophy, improve myocardial compliance, provide adequate pulmonary blood perfusion, promote the development of the right ventricle and pulmonary vasculature, and prepare for second-stage radical treatment. The primary palliative procedures include modified B-T shunt, intra-arterial catheter stenting, interventional pulmonary valvuloplasty, extracorporeal or non-extracorporeal pulmonary valvotomy ± right ventricular outflow tract patch enlargement.
(1) Modified body-pulmonary shunt (Blalock-Taussing shunt): Modified B-T shunt is suitable for children with moderate to severe hypoplasia of the right ventricle and tricuspid valve, small arterial ducts or tend to be closed. The procedure is usually performed in an emergency, using a median sternal The procedure is relatively easy to perform, but there are many postoperative complications and poor long-term results.
(2) Intraductal stent placement: In PDA-dependent congenital heart disease, keeping the arterial duct open is the basis for survival of the child, thus Alwi et al. have been trying to use adult coronary stenting since 1992, and percutaneous intraductal stenting keeps the arterial duct open to replace B-T shunt and improves the success rate of the procedure as well as the prognosis. The advantages of percutaneous placement of intra-arterial catheter stents include.
(i) Avoidance of open-heart surgery.
(ii) Continuation of the blood flow status of the child after birth without causing distortion and deformation of the pulmonary vessels.
(iii) The possibility to expand the stent or replace it according to the size needed.
④Prostil is no longer used. If the arterial catheter blood supply can meet the pulmonary blood demand at this stage in small infants, does not produce severe hypoxemia, and the right ventricle is still developing, they can be followed up until about 1 week of age for direct stage II radical surgery.
(3) Interventional pulmonary valvuloplasty: It has been reported that about 70% of pulmonary atresia in children with PA-IVS is fibrous, and therefore some scholars have considered the use of interventional techniques as an alternative to surgical decompression of the right ventricle. 1991 Qureshi et al. first used interventional catheter valve perforation + balloon dilatation for palliative treatment of PA-IVS, although the first 2 children died, however, with the continued efforts of many scholars and the use of interventional techniques, the right ventricle can be decompressed. continuous efforts of many scholars and improvements in interventional devices and delivery techniques, preoperative diagnosis, and postoperative monitoring techniques, the success rate of the procedure has improved significantly and this method is being used by more and more cardiac centers. The interventional methods for this disease include guided wire valve perforation ± balloon dilation; laser valve perforation ± balloon dilation; and radiofrequency valve perforation ± balloon dilation.
(4) Extracorporeal or non-extracorporeal circulation pulmonary valvotomy ± right ventricular outflow tract patch enlargement: suitable for moderate right ventricular dysplasia type: right ventricular cavity and tricuspid valve size is about 1/-2/ of normal control, three parts of right ventricle exist, all dysplasia, the degree of right ventricular outflow tract development allows pulmonary valvuloplasty, tricuspid valve Z value is between -2 –4. Pulmonary valvuloplasty can be followed by simultaneous ligation of the ductus arteriosus, or by natural closure.
The reason for not treating other combined malformations at the same time is that although the pulmonary valve has been cut as wide as possible during surgery, it is difficult to achieve ideal blood flow in the early postoperative period due to pulmonary valve edema and right ventricular outflow tract hypertrophy, and closing the ductus arteriosus can lead to perioperative hypoxemia, so keeping the ductus arteriosus open is beneficial for early postoperative recovery and can ensure a certain level of oxygen saturation. In addition, this type of patients may have small right ventricular volume, right ventricular wall hypertrophy, and reduced compliance of the ventricular wall, so the early postoperative right ventricular pressure is in the higher range. Preservation of patent foramen ovale or atrial septal defect can play a role in decompression of the right heart, otherwise it is very likely to lead to severe right heart failure. With the disappearance of tissue edema and improvement of ventricular wall compliance, right ventricular pressure and pulmonary artery transvalvular pressure differential are usually significantly reduced 1 to 2 weeks after surgery, and tricuspid regurgitation and right-to-left shunt at the atrial level disappear or are reduced.
Second-stage radical surgery
1, biventricular repair: close follow-up after palliative surgery, two-dimensional echocardiography to observe right ventricular development and tricuspid annulus size, if the development has been significantly improved, cardiac catheterization to confirm. One to four years after early palliative surgery, right ventricular dysplasia has turned mild to moderate, and right-to-left shunts at the atrial level become mild or bidirectional; tricuspid regurgitation shifts from severe to mild. Surgery includes medical intervention to close the secondary foramen ovale septal defect, or extracorporeal circulation to release the right ventricular outflow tract obstruction together.
2. 1 Ventricular repair: After phase I palliation or in infants without palliation followed to late infancy, the right ventricular septal inflow, trabecular and outflow portions are present, the ventricular cavity remains small, and tricuspid regurgitation is moderate or greater. The atretic pulmonary valve and right ventricular outflow tract can be evacuated by cutting the atretic pulmonary valve and enlarging the patch, arterial catheter ligation, bidirectional cavopulmonary shunt between superior vena cava and right pulmonary artery, and preservation of small atrial defect in the atrium. In the early postoperative period, the right ventricular pressure was high and the hypertrophied myocardium was insufficiently compliant. The restrictive ASD allowed a right-to-left shunt to gradually increase the right ventricular volume and antegrade flow, which was conducive to right ventricular development and improvement of cyanosis Follow-up When the right ventricular development and function improved, the atrial septal defect umbilical piece closure treatment was performed with cardiac catheter intervention. Bilateral cavopulmonary shunts allow the blood that accounts for 1/1 of the body vein to enter the pulmonary artery directly, which satisfies the pulmonary blood flow and reduces the pressure in the right ventricle. Clinical follow-up revealed that even in children with right ventricle and tricuspid valve dysplasia at the time of palliative surgery and without right ventricular decompression, the right ventricle was well developed and could fully meet the needs of pulmonary circulation after the second-stage 1?ventricular repair.
3. Bidirectional cavopulmonary and shunt modified Fontan operation: Children with right ventricular hypoplasia even after palliation, or children with combined coronary circulation dependent on the right ventricle, or tricuspid valve subluxation malformation. In children with severe consequences due to inadequate perfusion of the right ventricle-dependent coronary arteries after right ventricular patch enlargement and decompression or tricuspid valvuloplasty, only body-lung shunts can be performed in the neonatal period. If the RVDCC is seen to be distributed on the surface of the heart after open chest, with no stenosis proximal to the normal coronary circulation intact, the coronary-right ventricular end can be tied. If the RVDCC is indistinguishable, only single ventricle correction can be performed, Greene’s procedure at -6 months of age and Fontan’s procedure at 2-4 years of age, while enlarging the atrial septum and oxygenated blood with high oxygen content entering the right ventricle through the atrial septal defect to supply the coronary arteries.
Prognosis
The neonate is in critical condition early in life and the long-term outcome is not yet satisfactory according to a survey of two medical centers. The Society of Congenital Heart Surgeons prospective study showed that in 71 neonates from 1987-1990, surgical valvotomy with or without body-pulmonary shunt and transannular patch (RVOT), or body-pulmonary shunt only, had a survival rate of 81% at 1 month and 64% at 4 years. Low birth weight and right ventricle-dependent coronary shunts are risk factors for death. A smaller Z index was a risk factor only when the initial treatment was valvotomy or transmural patching and not when the initial treatment was a shunt. In the UK study with the Eire Collaborative Study of Ventricular Septal Integrity Pulmonary Atresia data, they investigated 18 infants born in 1991-1995. In the North American study of this disease, the initial palliative care was transcatheter treatment in only 22% of those investigated in the UK, but both had similar survival rates. In recent years, Jahangirc et al. from Boston reported significant advances in postoperative survival. They stratified patients to receive either partial biventricular or total biventricular repair alone, depending on right ventricular size and the presence of right ventricle-dependent coronary circulation, with an overall survival rate of 98%, and gained much experience with transcatheter treatment. Reports in recent years have also been encouraging. The use of laser or radiofrequency ablation-assisted valvotomy and balloon dilatation is now considered a definitive treatment option.