Pulmonary blood flow is a symptom of tricuspid atresia, and the length of patient survival is closely related to pulmonary blood flow. Those with near-normal pulmonary blood flow can survive up to 8 years or more; those with a lot of pulmonary blood flow generally survive only 3 months after birth. Tricuspid atresia is a type of cyanotic congenital heart disease, the incidence of which accounts for about 1-5% of congenital heart disease. It is the third most common form of cyanotic congenital heart disease after tetralogy of Fallot and aortic dislocation. The main pathological changes are tricuspid atresia or absence of tricuspid orifice, foramen ovale unclosed or atrial septal defect, mitral valve and left ventricular hypertrophy, and right ventricular dysplasia. There are many tests needed for pulmonary blood flow: (1) Electrocardiogram (ECG) In 90% of cases, the electrical axis is left deviated and the large arteries are misaligned. The electrical axis is normal or right deviated in those with pulmonary artery thickening. The precordial leads all show left ventricular hypertrophy and T-wave inversion changes. 80% of cases show high or widened P-wave with tangent. (2) X-ray examination The chest X-ray shows quite a lot of variability. The heart image is normal or mildly enlarged in cases with reduced pulmonary blood flow, and significantly enlarged in cases with increased pulmonary blood flow. The typical chest X-ray signs are a flat right edge of the heart, a rounded left edge, an elevated heart tip, and a depressed heart waist, sometimes the heart shadow is similar to that of tetralogy of Fallot. The heart shadow may be egg-shaped in cases of large artery misalignment. In cases with low pulmonary blood flow, the lung lines are significantly reduced, and in cases with pulmonary congestion, the lung lines are increased. (3) Cardiac catheterization and cardiovascular angiography The right cardiac catheter can enter the left atrium through the atrial defect, and the pressure in the right atrium is higher than that in the left atrium. The size of the pressure difference is inversely proportional to the diameter of the atrial defect, with a small defect and a large pressure difference. The arterial oxygen content is reduced, and the oxygen content in the left atrium, left ventricle, pulmonary artery and aorta is the same. (4) Selective right atrial angiography shows the contrast entering the left atrium and left ventricle from the right atrium and then into the pulmonary artery and aorta. An undeveloped triangle, the right ventricular window, is seen below the cardiac shadow, between the right atrium, left ventricle, and diaphragm. Sometimes the angiogram may show a ventricular septal defect, the right ventricular cavity and outflow tract, and the pulmonary artery. The left ventriculogram can determine the presence or absence of mitral valve insufficiency. (5) M-mode echocardiography shows the disappearance of the bimodal curve of the tricuspid valve, failure to see the tricuspid echogenic reflection in the four-chamber view, interruption of the septal echo, and interruption of the upper ventricular septal echo. The echocardiogram and Doppler examination also showed blood flow from the right atrium to the left atrium and then into the left ventricle. The mitral valve activity is increased, the right atrial, left atrial, and left ventricular chambers are enlarged, and the right ventricle is small or absent.