Tetralogy of Fallot is the most common (70-75% of cases) of cyanotic preconditioning and is a compound congenital malformation that includes four malformations: pulmonary stenosis, ventricular septal defect, aorta riding over the ventricular septum and right ventricular hypertrophy. The incidence is similar in males and females. Symptoms of tetralogy of Fallot Most of the cyanosis appears within 6 months after birth, and in severe cases it appears soon after birth. The latter can increase the resistance of the body circulation and reduce the right-to-left shunt and the amount of blood return to the heart, so that the symptoms are slightly relieved. In a few cases, epistaxis, hemoptysis, embolism and cerebral hemorrhage may occur. 1. X-ray examination: normal or slightly large heart shadow, obtuse upward curvature of the apical garden, clear lung field, sparse pulmonary vascular shadow, concave and hidden pulmonary artery segment. 2, ECG: right ventricular hypertrophy and strain, some people also have right atrial hypertrophy. The electrical axis is right deviated. 3.Echocardiography: continuous interruption of the anterior wall of the aorta and the septum, the septum is located between the anterior and posterior walls of the aorta, widening of the aorta, enlargement of the right ventricle, thickening of the anterior wall of the right ventricle and narrowing of the outflow tract. (4) Cardiac catheterization: The following features may be present: (1) The catheter may enter the aorta from the right ventricle via the septal defect. (2) There is a systolic pressure step difference between the right ventricle and the pulmonary artery. Analysis of the continuous pressure curve can determine the site, type, and degree of stenosis. (3) The oxygen content of the right ventricle is higher than that of the right atrium, indicating a left-to-right shunt at the ventricular level. (4) Decreased arterial oxygenation indicates a right-to-left shunt. (5) If the aortic, left ventricular and right ventricular systolic pressures are similar, this indicates a large septal defect and a significant aortic right span. (6) Red blood cell count and hemoglobin concentration are increased. (5) Cardiovascular imaging: right ventriculography shows the aorta and the left and right ventricles at the same time, and the aorta is widened. 6. Routine blood examination: red blood cell count, hemoglobin concentration and red blood cell ratio are significantly increased. Treatment 1. Internal treatment: timely control of respiratory tract infection to prevent infective endocarditis, and use of β-blockers in severe cases to reduce right ventricular outflow tract obstruction and prevent hypoxic attacks. 2, surgical treatment: direct vision radical surgery, including resection of the right ventricular outflow tract hypertrophic muscle bundle, separation of the narrowed pulmonary valve, repair of ventricular septal defect, this operation is more thorough. The age of surgery is within 1 year, and early surgery is required for severe cyanosis or hypoxic attacks. If the symptoms are serious, bypass surgery can also be used to make anastomosis between the subclavian artery, aorta or superior vena cava and pulmonary artery to establish body-pulmonary circulation traffic to improve hypoxia and prepare conditions for future radical surgery.