| disease | Total Anomalous Pulmonary Venous Return |
Total anomalous pulmonary venous return (TAPVR) refers to the condition where all pulmonary veins do not enter the left atrium but instead directly connect to the right atrium or the systemic venous system. It is often associated with an atrial septal defect. The incidence rate accounts for 1.5-2% of congenital heart diseases.
bubble_chart Pathological Changes
The lung primordium develops from the foregut, and the pulmonary vascular plexus originates from the visceral venous plexus, draining into the cardinal veins, umbilical vein, and egg yolk veins. When the atria are not yet separated, the common pulmonary vein protrudes from the mid-posterior wall of the atrium and divides into two branches, each of which further splits into two, connecting to the left and right lungs, respectively. Subsequently, the dilated common pulmonary vein is absorbed into the enlarging left atrium, causing all four pulmonary veins to open into the left atrium and disconnect from the systemic venous channels. If the connection between the common pulmonary vein and the left atrium fails to develop, while maintaining connections with the cardinal veins, umbilical vein, or egg yolk veins, various types of anomalous pulmonary venous connections occur. The most common is drainage into the innominate vein or coronary sinus.
**Pathology:** Darling classified total anomalous pulmonary venous connection (TAPVC) into four types based on the site of abnormal drainage: 1. **Supracardiac type (55%)**: The pulmonary veins converge posterior to the left atrium and drain via a vertical vein into the left innominate vein, sometimes into the superior vena cava or azygos vein. The vertical vein passes anterior to the left pulmonary artery and left main bronchus before entering the innominate vein, where compression may cause venous obstruction. 2. **Cardiac type (30%)**: All pulmonary veins drain directly into the right atrium or via a common pulmonary vein into the coronary sinus. Obstruction may occur between the common pulmonary vein and the coronary sinus. 3. **Infracardiac type (12%)**: All pulmonary veins converge posterior to the heart and descend via a vertical vein through the diaphragmatic esophageal hiatus into the portal vein, inferior vena cava, or ductus venosus. The return blood must pass through the high-resistance hepatic vascular bed to reach the right atrium, or the descending vertical vein may be compressed, leading to pulmonary venous obstruction. 4. **Mixed type (~3%)**: All pulmonary veins drain into the right atrium via multiple pathways. Most cases of infracardiac and mixed types die in infancy. About 75% of TAPVC patients have a patent foramen ovale, and 25% have an atrial septal defect. The right atrium and ventricle are often enlarged and hypertrophied, the pulmonary artery is dilated with increased pressure, and the left atrium is smaller. Pulmonary venous obstruction is most common in the infracardiac type, followed by the supracardiac type, with an incidence as high as 50%. Other associated cardiovascular anomalies include patent ductus arteriosus, aortic coarctation, persistent truncus arteriosus, transposition of the great arteries, single ventricle, pulmonary atresia, tetralogy of Fallot, and double-outlet right ventricle.
**Pathophysiology:** In TAPVC, all pulmonary venous blood enters the right atrium. Some of this blood must then flow through a patent foramen ovale or atrial septal defect into the left atrium; otherwise, death occurs shortly after birth. The right atrium receives all systemic and pulmonary venous return, resulting in an extreme increase in blood volume. In patients with a small patent foramen ovale, only a small amount of mixed caval and pulmonary venous blood enters the left atrium and is pumped by the left ventricle into the systemic circulation, leading to **grade I cyanosis** clinically. However, due to the high flow in the right heart and pulmonary circulation, pulmonary artery pressure rises, and most patients die of **right heart failure** within months after birth. If the atrial septal defect is large, more blood flows from the right to the left atrium, resulting in **marked cyanosis**, while pulmonary hypertension develops later, allowing survival beyond one year. Patients with **pulmonary venous obstruction** exhibit severe cyanosis, pulmonary congestion, and **pulmonary edema**, usually dying within weeks after birth.In TAPVC, due to significantly elevated pulmonary pressure, all patients, regardless of age, show **obstructive pathological changes** in the small pulmonary arteries.
bubble_chart Clinical Manifestations
The symptoms of the patient depend on whether there is pulmonary venous obstruction, the size of the interatrial communication, and other coexisting cardiac anomalies. In cases with a small interatrial communication, pulmonary hypertension and right heart failure occur early after birth, with rapid progression and severe symptoms. In cases without pulmonary venous obstruction and with a large interatrial communication, pulmonary hypertension appears later, but cyanosis is pronounced, and the condition progresses more slowly. Infants exhibit slow growth, rapid breathing, accelerated heart rate, and grade I cyanosis, often leading to misdiagnosis as pneumonia or respiratory distress syndrome. Physical examination may reveal no specific murmurs, though sometimes a systolic blowing ejection murmur can be heard at the second left intercostal space near the sternum, with splitting and accentuation of the second heart sound in the pulmonary valve area. A diastolic rumbling murmur may be audible at the lower left sternal border. The cardiac dullness border is enlarged, and a heaving precordial impulse may be present. Clubbing of fingers and toes is generally mild.
(1) X-ray film shows increased pulmonary vascular shadows, prominence of the pulmonary artery trunk, enlargement of the right ventricle and right atrium. In patients with anomalous drainage into the left superior vena cava, the upper mediastinal shadow is widened, and the entire cardiac shadow appears in a "figure-8" shape.
(2) Electrocardiogram shows right axis deviation, hypertrophy of the right ventricle and right atrium, and sometimes incomplete right bundle branch block.
(3) Right heart catheterization and selective pulmonary angiography reveal elevated oxygen content at the site where pulmonary venous blood drains into systemic veins, decreased oxygen content in peripheral arterial blood, and increased or normal right atrial pressure. In cases with a small interatrial communication, the right atrial pressure gradient is higher than that of the left atrium. In patients with pulmonary venous obstruction, right ventricular and pulmonary arterial pressures are significantly elevated, and pulmonary capillary wedge pressure exceeds the mean left atrial pressure. Selective pulmonary angiography can demonstrate the course of the anomalous pulmonary venous trunk, the site of abnormal drainage, the presence of pulmonary venous obstruction, and associated cardiovascular anomalies.
(4) Two-dimensional echocardiography and Doppler examination may reveal the absence of pulmonary venous orifices in the left atrium. Right ventricular diastolic volume overload and interruption of the atrial septum echo can also be observed, along with the anomalous pulmonary venous trunk and associated cardiovascular anomalies. Doppler examination can demonstrate abnormal flow connections and right-to-left atrial shunting.
The efficacy of total anomalous pulmonary venous connection (TAPVC) repair depends on factors such as age, the site of anomalous connection, the presence of pulmonary venous obstruction, and the size of the atrial septal defect. In infants and young children with pulmonary venous obstruction and a small atrial septal defect, early-onset heart failure is associated with an extremely high mortality rate. The Texas Heart Institute reported a mortality rate of 52% in surgical patients under 1 year of age, 20% in those aged 1–2 years, and 15% in those over 2 years. No surgical deaths occurred in children over 10 years of age. Radical surgery is recommended when pulmonary blood flow is more than twice systemic blood flow and pulmonary vascular resistance is below 6 Wood units/m2 of body surface area. For infants under 1 year of age, aggressive medical treatment should be pursued first to improve symptoms. If the atrial septal defect is small, a balloon catheter can be used to enlarge it, improving hemodynamics and clinical symptoms to delay surgery.
**Surgical Technique:** Under cardiopulmonary bypass, the anomalously connected pulmonary veins are redirected to the left atrium, the atrial septal defect is closed, and the vertical vein is ligated. Specific methods include: 1. **Supracardiac Type:** A longitudinal incision is made in the right atrium to expose the atrial cavity. The atrial septal defect is enlarged by incising its right margin. A transverse incision is made on the posterior wall of the left atrium opposite the common pulmonary venous trunk, extending to the interatrial groove to create an elliptical opening approximately 2.5–3 cm long. A corresponding incision is made in the common pulmonary vein. Anastomosis begins at the left apex with continuous suturing between the left atrium and the common pulmonary vein. The atrial septal defect is closed with a Dacron or autologous pericardial patch to enlarge the left atrial cavity. The right atrial incision is closed, and the vertical vein is ligated (Figure 1⑴). 2. **Intracardiac Type:** The right atrium is incised, and the tissue between the patent foramen ovale or atrial septal defect and the enlarged coronary sinus ostium is excised to create a large opening. If necessary, the pulmonary venous drainage is further enlarged by extending the incision along the coronary sinus. A large Dacron patch is then used to cover the defect and coronary sinus ostium. For cases where all pulmonary veins drain directly into the right atrium, the atrial septal defect is enlarged, and a Dacron patch is used to redirect the anomalous pulmonary venous orifices along with the enlarged defect to the left atrium (Figure 1⑶). 3. **Infracardiac Type:** Two approaches are possible. The first is similar to the supracardiac method, involving anastomosis of the left atrium and common pulmonary vein, followed by closure of the atrial septal defect and ligation of the anomalous descending vein. The second method (Clarke’s technique) involves tilting the cardiac apex to access the posterior aspect of the heart. The common pulmonary vein is transected and ligated. A longitudinal incision is made in the proximal end to extend the common pulmonary vein. After excising the left atrial appendage, an oblique incision is made on the posterior left atrial wall, and the edges of the left atrial and pulmonary venous incisions are sutured to form an anastomosis. After repositioning the heart, the left atrium is incised to close the atrial septal defect. The anastomosis should match the size of the mitral orifice to ensure unobstructed pulmonary venous return. The left atrial cavity must be enlarged to accommodate pulmonary venous return, preventing postoperative pulmonary
edema. A well-executed procedure can relieve symptoms and significantly improve cardiac function (Figure 1⑷). 
(1) Supracardiac TAPVC: Anastomosis of the left atrium and common pulmonary vein
(2) Supracardiac TAPVC: Completion of anastomosis and enlargement of the left atrial cavity
(3) Intracardiac TAPVD: Excision of the coronary sinus septum and fossa ovalis septum, with pericardial patch closure of the fossa ovalis and coronary sinus ostium
(4) Supracardiac TAPVD incision of the vertical vein and left atrial wall
(5) Infradiaphragmatic TAPVD anastomosis between left atrium and vertical vein
Figure 1 Schematic diagram of surgical procedures for various types of total anomalous pulmonary venous drainage
In cases of total anomalous pulmonary venous return, 90% of patients die within the first year after birth. For cases with pulmonary venous obstruction, surgical treatment must be performed immediately upon definitive diagnosis. For patients without pulmonary venous obstruction, if congestive heart failure can be controlled through medical treatment and balloon catheter dilation of the atrial septal defect, radical surgery may be temporarily postponed for a short period.
