The formation of mixed blood in the atria is known as monoventricular. Monoventricular is a rare congenital heart disease, which is caused by the lack of development of both septum 1 and septum 2 of the atrial septum during embryonic development. Traces of the interatrial septum are also absent, and the interventricular septum is intact, so it is also called a two-chambered, three-chambered heart or a single-ventricle, three-chambered heart. A single atrium may exist alone, but is often combined with a left superior vena cava and a right heart, a left heart or abdominal visceral transposition malformations, and it is particularly common to have a cleft anterior mitral leaflet, or even an atrioventricular canal deformity. What are the symptoms that are easily confused with it? 1.Ventricular septal defect is a condition in which the interventricular septum is underdeveloped during embryonic life, forming abnormal traffic and producing a left-to-right shunt at the level of the ventricles, which can exist alone or be part of a complex cardiac malformation. Ventricular septal defects are the most common form of congenital heart disease. Ventricular septal defects account for approximately 20% of all congenital heart disease and may exist alone or in association with other malformations. The defects range from 0.1-3 cm and are larger when located in the membranous region and smaller when located in the muscular region, which is also known as Roger’s disease. If the defect is <0.5 cm, the shunt volume is small and there are no clinical symptoms. If the defect is small, the right ventricle will be enlarged, and if the defect is large, the left ventricle will be enlarged more than the right ventricle. Complete aortic malposition The meaning of complete aortic malposition is that the position of the two large arteries is wrongly exchanged, the aorta receives venous blood from the right ventricle, and the pulmonary artery receives oxygenated blood from the left ventricle's pulmonary vein, thus forming two isolated circulatory systems, i.e., right atrium → right ventricle → aorta → systemic → body venous → right atrium for a cycle; left atrium → left ventricle → pulmonary artery → pulmonary → left atrium for a cycle; left atrium → left ventricle → pulmonary artery → lung → pulmonary vein → left atrium for a cycle. The left atrium→left ventricle→pulmonary artery→pulmonary→left vein→left atrium is another circulatory system. If the ventricle is in a normal position and the opening of the aorta is located on the right side of the pulmonary artery, it is called right-loop malposition of the great arteries (D-TGA). D-TGA is a common type in clinical practice, and it is often accompanied by ventricular septal defect, ventricular septal defect, arterial ductus arteriosus, pulmonary artery stenosis, and atrioventricular canal anomalies. Tricuspid atresia Tricuspid atresia is a kind of cyanosis congenital heart disease, the incidence rate accounts for 1% to 5% of congenital heart disease. The incidence of tricuspid atresia is a kind of cyanotic congenital heart disease, which accounts for 1%~5% of congenital heart disease. It ranks third in cyanotic congenital heart disease after tetralogy of Fallot and transposition of the great arteries. The main pathologic changes are tricuspid atresia or absence of tricuspid valve orifice, patent foramen ovale or atrial septal defect, left ventricular enlargement, and right ventricular hypoplasia. The fusion of the endocardial cushions under normal development of the embryo divides the atrioventricular canal equally into right and left orifices and participates in the formation of the membranous ventricular septum and closure of foramen 1 of the atrial septum. It is generally believed that the fusion of endocardial cushions before and after the embryonic period is biased toward the right side, the ventricular septum is shifted to the right causing the atrioventricular orifices to be separated unequally, and the right atrioventricular orifices to be occluded to form tricuspid atresia in the future. 4, atrioventricular canal malformation, also known as endocardial cushion defect and atrial septal defect, is a cardiac malformation caused by incomplete development or arrest of endocardial cushion in the process of embryonic development, the lesion includes the upper atrioventricular valve, lower atrioventricular septal defect and atrioventricular valve anomalies, the formation of a simple primary hole-type atrial septal defect to the simultaneous combination of a large ventricular septal defect and a composite malformation of the serious abnormalities of the bicuspid and tricuspid valves. Atrioventricular canal malformation is rare clinically, the incidence of men and women is basically equal, because of the seriousness of the cardiac malformation, often in infancy and early childhood serious heart failure and pulmonary hypertension. 5.Atrial septal defect, abbreviated as atrial septal defect, is one of the most common types of congenital heart disease, second only to ventricular septal defect, is the embryonic development of the atrial septum on the residual unclosed defect and the formation of the atrial septum. The vast majority of atrial septal defects are uniportal, a few are multiportal, and a very few are sieve-shaped. Atrial septal defects account for about 15-20% of congenital heart disease, with a male-to-female ratio of 1.7:1, and are not recognized until adulthood in a large proportion of patients because of the mild symptoms and lack of obvious signs in childhood.