Partial pulmonary vein anomaly in children

　　The Etiology of the Disease

　　The key period of cardiac embryonic development is during the 2nd to 8th week of pregnancy, and congenital cardiovascular malformations also mainly occur during this stage. The occurrence of congenital heart disease has many reasons, which are roughly divided into two categories: intrinsic and extrinsic, of which the latter is more common. Intrinsic factors are mainly related to genetics, especially chromosomal translocation and mutation, such as trisomy 21, trisomy 13, trisomy 14, trisomy 15, and trisomy 18, which often accompany congenital cardiovascular malformations; in addition, the incidence of cardiovascular malformations in the offspring of patients with congenital heart disease is significantly higher than the expected incidence. Important extrinsic factors include intrauterine infection, especially viral infection, such as rubella, mumps, influenza, and coxsackievirus; other factors such as exposure to high doses of radiation during pregnancy, use of certain drugs, metabolic diseases or chronic diseases, hypoxia, and advanced maternal age (close to menopause) all have the risk of causing congenital heart disease.

　　Second, pathogenesis

　　1. Pathological anatomy

　　Partial pulmonary vein connection abnormalities can exist alone or be combined with other cardiac malformations. The most common is sinus venosus atrial septal defect, less common are mitral stenosis, double outlet right ventricle, ventricular septal defect, tetralogy of Fallot, pulmonary stenosis, aortic stenosis, patent ductus arteriosus, dextrocardia, etc. There are many types of this disease, such as direct drainage of the right upper pulmonary vein into the right superior vena cava, connection of the right pulmonary vein with the right atrium, connection of the right pulmonary vein with the inferior vena cava, connection of the left pulmonary vein with the left innominate vein, and the connection of the right pulmonary vein with the right superior vena cava is the most common. Abnormalities of the right pulmonary vein are more common than those of the left pulmonary vein, and the convergence of ipsilateral pulmonary veins into the same atrium can be seen in hepsipetal syndrome and common atrium.

　　(1) Right pulmonary vein connected to the superior vena cava or right atrium: The most common, accounting for about 3/4, the pulmonary veins of the upper and middle lobes of the right lung are connected to the superior vena cava between the entry of the azygos vein and the right atrium, and the superior vena cava connection, while the pulmonary veins of the lower right lung lobe normally return to the left atrium. It is often accompanied by sinus venosus atrial septal defect, and occasionally the superior vena cava straddles the defect.

　　(2) Right pulmonary vein connected to the inferior vena cava: All right pulmonary veins (occasionally, the pulmonary veins of the right middle and lower lobes) form a common trunk that drains into the inferior vena cava. This type is not common, and the connection of the common trunk to the inferior vena cava is characterized by a crescent-shaped shadow in the right lower lung field on the chest film, hence it is also called 'scimitar syndrome' (scimitarsyndrome). It is also accompanied by cardiac ectopia, underdevelopment of the right lung, abnormal vascular supply of the right lung by the aorta, and other malformations.

　　2. Pathophysiology

　　1. At present, pulmonary vein obstruction has not been found in this disease, so the hemodynamic characteristics are only partial connection abnormalities of pulmonary vein left-to-right shunting, and the blood flow of a single pulmonary vein abnormal connection accounts for only 20% of all pulmonary venous blood flow, so there are no obvious clinical manifestations.

　　2. In the presence of atrial septal defect, hemodynamic changes include left-to-right shunting at the atrial level and pulmonary venous level, pulmonary hypertension is less common, but in children with scimitar syndrome, if accompanied by pulmonary consolidation, thickening of the pulmonary artery muscular layer, and increased pulmonary vascular resistance, pulmonary hypertension may occur.

　　Patients with unilateral pulmonary venous ectopic connection have no clinical symptoms; patients with unilateral pulmonary venous drainage have symptoms similar to those with non-obstructive complete pulmonary venous ectopic connection, with cyanosis being uncommon and heart failure rare.

　　Patients with unilateral pulmonary venous ectopic connection have no clinical symptoms; patients with unilateral pulmonary venous drainage have symptoms similar to those with non-obstructive complete pulmonary venous ectopic connection, with cyanosis being uncommon and heart failure rare. In severe cases, recurrent pulmonary infections may occur, and obstructive pulmonary hypertension may appear in the late stage.

　　1. Abandon bad habits, including the pregnant woman herself and her spouse, such as smoking and drinking.

　　2. Before pregnancy, actively treat diseases that affect fetal development, such as diabetes, lupus erythematosus, anemia, etc.

　　3. Actively do a good job of prenatal examination, prevent colds, and try to avoid using drugs that have been proven to have teratogenic effects, and avoid contact with toxic and harmful substances.

　　For elderly pregnant women, those with a family history of congenital heart disease, or with serious diseases or defects in one of the couple, it is necessary to focus on monitoring.

　　1. Chest X-ray

　　With moderate left-to-right shunt, the X-ray findings are similar to those of moderate atrial septal defect, that is, abundant pulmonary blood, enlargement of the right ventricle, and sometimes ectopic veins can be seen. When the pulmonary veins are ectopically connected to the left brachiocephalic vein, the 'snowman sign' may appear.

　　2. Electrocardiogram

　　Similar to atrial septal defect, it is manifested as rsr' or rsR' in lead V1, but the electrocardiogram is often normal for patients with intact atrial septum and only small left-to-right shunts at the pulmonary vein ostia.

　　3. Echocardiography

　　Echocardiography is difficult to diagnose the four pulmonary vein ostia of this disease, and sometimes even when the pulmonary veins are completely normal, they are not clear. When there is no atrial septal defect but an increase in the volume load of the right ventricle, it is necessary to consider partial pulmonary venous ectopic connection. When there is a sinus venosus type atrial septal defect, the ectopic opening of the right pulmonary vein into the right atrium can be seen at the level of the xiphoid process. In a later section, the ectopic opening of the pulmonary veins within the coronary sinus can be displayed; for children suspected of having katayama syndrome, the inferior vena cava and the junction of the inferior vena cava with the right atrium can be seen from the long-axis and short-axis sections below the xiphoid process, thereby displaying the ectopic pulmonary veins. The vertical vein can be displayed from the short-axis section above the sternum. Sometimes echocardiography can correctly diagnose this disease, but even if the ectopic opening of the pulmonary veins is not captured, this disease cannot be excluded.

　　4. Cardiac catheter

　　Most cases of this disease do not require catheterization, which is only used for diagnosing cases with unknown etiology and to understand the pulmonary artery course, lung consolidation status, selective pulmonary angiography, and observe the pulmonary venous return situation to show the ectopic connection of pulmonary veins; if the catheter can be inserted into the pulmonary vein, selective pulmonary venography can clearly show the anatomical position of the pulmonary veins; in the case of katayama syndrome, selective aortic angiography is also very necessary.

　　5. Other non-invasive imaging

　　CT and MRI can both be used for the diagnosis of this disease. In non-invasive examinations, this may be the most accurate, and it can also simultaneously detect concomitant malformations such as pulmonary consolidation.

　　Children should eat light, nutritious, and fluid foods such as congee, lotus root starch, and avoid eating fried and greasy foods. Pregnant women should quit bad habits, including themselves and their partners, such as smoking and excessive drinking. Before pregnancy, actively treat diseases that affect fetal development, such as diabetes, lupus erythematosus, anemia, etc. Actively do a good job of prenatal examinations, prevent colds, and try to avoid using drugs that have been proven to have teratogenic effects, and avoid contact with toxic and harmful substances. For elderly mothers, those with a family history of congenital heart disease, or couples with serious diseases or defects, special monitoring should be emphasized.

　　I. Treatment

　　In cases without signs of congestion, there is no need for medication. If the pulmonary circulation to systemic circulation ratio is greater than 2:1, surgery is required to correct it. For those with right pulmonary vein anomalies, a human-made tunnel can be used to directly connect the pulmonary vein to the left atrium in the inferior vena cava or right atrium, or the right pulmonary vein can be directly anastomosed to the left atrium. For patients with cor triatriatum with large main pulmonary artery connections, heart failure and pulmonary hypertension may occur, and a cardiac catheterization should be performed before surgery to fill the main pulmonary artery connection with a coil to improve heart failure symptoms and reduce pulmonary artery pressure. In a very few cases, it may be necessary to resect part of the lung.

　　II. Prognosis

　　The prognosis of most children is similar to that of left-to-right atrial septal defects, and there are few cases of pulmonary vascular disease. Long-term follow-up after surgery has confirmed that there is no pulmonary vein obstruction and pulmonary hypertension, but children still need regular monitoring. For children with anomalous pulmonary venous drainage associated with sinus venosus atrial septal defects, 30% to 40% may develop sick sinus syndrome after surgery. In other types of children, arrhythmias are less common.