Symptoms and manifestations (a) Symptoms are mainly progressive cyanosis and dyspnea since childhood, more so when crying, accompanied by pestle-like fingers (toes) and erythrocytosis. The child is prone to weakness, and the dyspnea and weakness after exertion often cause the child to rest in a squatting position. Other complications include heart failure, cerebrovascular accident, infective endocarditis, lung infection, etc. If left untreated, physical activity is greatly restricted and does not grow easily. (B) Physical signs may be poorly developed, with possible bulging of the anterior chest, cyanosis and pestle-like fingers (toes). There is a systolic blowing wind-like jet murmur between the second and third ribs at the left edge of the sternum, which may be accompanied by tremor. This murmur is due to pulmonary artery stenosis, and its loudness is inversely proportional to the degree of stenosis, because the more severe the stenosis, the more blood from the right ventricle enters the riding aorta, and the less enters the pulmonary artery. The other differences between the murmur and simple pulmonary stenosis include shorter duration, earlier peak, reduction rather than enhancement after isoamyl nitrite inhalation, and less chance of tremor. In severe pulmonary stenosis, the murmur may disappear and a continuous murmur may appear, caused by collateral circulation between the bronchial vessels and the pulmonary vessels or by a combined unclosed ductus arteriosus. In atypical tetralogy of Fallot and less severe pulmonary stenosis with a left-to-right shunt at the ventricular level, a systolic murmur caused by a ventricular septal defect may be heard between the third and fourth ribs at the left sternal border. The second heart sound in the pulmonary valve area is diminished and split, but may also be single and loud (transmitted from the second heart sound in the aortic valve area). Systolic jet sounds can be heard in the aortic valve area and are conducted along the left sternal border toward the apex of the heart. The turbinate may be unenlarged or slightly enlarged. There may be elevated pulsations in the precordial and mid-epicardial regions. Examination and diagnosis (a) The pulmonary field is abnormally clear, the arc of the common pulmonary artery trunk is inconspicuous or concave, the right ventricle is enlarged, the apex is upwardly elevated, and the heart is shadowed in a wooden shoe shape (with a transverse rectangle) on the posterior anterior view. The right aortic arch is visible in nearly ¼ of patients. (B) Electrocardiographic examination shows right ventricular hypertrophy and strain, with markedly elevated R waves and inverted T waves in all leads of the right precordial region. In some patients, high and sharp P waves in the standard leads and right precordial leads indicate right atrial hypertrophy. The electrocardiographic axis is right deviated. (C) Echocardiography shows enlargement of the aortic root, which moves forward and rides over the ventricular septum. The continuity between the anterior wall of the aorta and the ventricular septum is interrupted, and the septal echogenicity is lost there, while the posterior wall of the aorta and the mitral valve remain continuous. The right ventricle is hypertrophied, and its outflow tract, pulmonary valve, or pulmonary artery inner diameter is narrowed. Echocardiography may also show a right-to-left shunt from the right ventricle to the aorta. (iv) Selective cardiovascular angiography or 64-row CT angiography, in which contrast is injected into the right ventricle through the right heart catheter, may show both the aorta and the pulmonary artery, and may reveal that the pulmonary orifice stenosis is valvular, leaky, or pulmonary, in addition to the possibility of seeing contrast entering the left ventricle through the ventricular septal defect. (e) Routine blood tests have a significantly higher red blood cell count, hemoglobin content and red blood cell pressure. (vi) Magnetic resonance computed tomography shows an enlarged ascending aorta riding over the ventricular septum, which is defective, a small common pulmonary artery trunk, stenosis of the funnel portion of the right ventricle, and stenosis of the pulmonary valve annulus may also be seen. (vii) Cardiac catheterization Right heart catheterization may reveal the following findings: 1. The systolic pressure step difference between the right ventricle and the pulmonary artery caused by stenosis of the pulmonary orifice, and analysis of the shape of the pressure curve may help determine the type of stenosis. 2. The cardiac catheter may enter the aorta directly from the right ventricle, thus confirming the presence of a riding aortic and ventricular septal defect. 3, A decrease in arterial oxygen saturation to less than 89% indicates a right-to-left shunt. If there is also a left-to-right shunt through the ventricular septal defect, the oxygen content of the right ventricle is higher than that of the right atrium. 4. In patients with a large ventricular septal defect and a more pronounced right aortic position, the systolic pressure of the aorta, left ventricle and right ventricle are equal. (H) Selective indicator dilution curve determination was performed by injecting indicator (dye or vitamin C, etc.) into the right atrium, right ventricle and pulmonary artery through the right heart catheter, and recording the indicator dilution curve in the peripheral artery (with an otocardiometer or platinum electrode system, etc.), which was seen in the right ventricle and its upstream chambers when the indicator was injected, and the right-to-left shunt curve with a short emergence time and a bimodal descending branch of the curve was recorded in the common pulmonary artery The site of right-to-left shunt was determined by recording a normal curve when the indicator was injected into the right ventricle and its upstream chambers, while a normal curve was recorded in the common pulmonary artery and its downstream chambers. Treatment 1. Indication and timing of surgery Most cases of tetralogy of Fallot are born with satisfactory oxygen saturation of the body circulation without treatment, but hypoxia progresses gradually and surgical intervention is necessary when the oxygen saturation of the body circulation falls to 75-80%. The onset of hypoxic episodes is usually considered an indication for surgery. Stage I radical surgery is preferred for tetralogy of Fallot, and generally most centers recommend stage I radical treatment for typical tetralogy of Fallot patients, even if the disease is severe, regardless of age. In recent years, there has been a trend toward younger age groups, partly due to advances in surgical techniques and, more importantly, to a better understanding of the pathophysiology of tetralogy of Fallot. Early surgery is beneficial to protect the function of the right and left ventricles, promote the development and growth of the pulmonary arteries, especially the peripheral pulmonary arteries, reduce the damage of chronic hypoxia to the heart, nervous system and other organs, and promote the normal growth and development of organs, in addition to avoiding and reducing preoperative episodes of hypoxia and sudden death due to ventricular arrhythmias in the late postoperative period. Based on the above understanding, surgery can be performed on small symptomatic infants or newborns, and for cases when no specific surgical indications are available, elective surgery can be done at 1-2 years of age, or at 3-6 months. Classical radical surgery for tetralogy of Fallot requires pulmonary artery and left ventricular development of more than 60% of normal, McGoon ratio ≥ 1.2 (normal ≥ 2), pulmonary artery index (Nakataindex) ≥ 150 mm2/m2 (normal ≥ 330 mm2/m2), and left ventricular end-diastolic volume index of 30 ml/m2 (normal 55 ml/m2), and some studies Hennein et al. 1995 reported 30 cases of neonates with tetralogy of Fallot in which radical surgery was performed without regard to left ventricular development and pulmonary artery development, and satisfactory results were obtained. However, the extent to which the indications for surgery are relaxed depends on the technical capabilities and equipment of each cardiac center and the experience of the physicians. For those who have severe right ventricular outflow tract stenosis and severe distal pulmonary artery dysplasia, or missing pulmonary artery with large body-pulmonary side branches, as well as infant coronary artery malformation, it is difficult to perform right ventricular outflow tract patch enlargement, and it is also inappropriate to perform extracardiac pipeline or one with ventricular correction should do palliative surgery first, the purpose of which is to establish body-pulmonary artery shunt and increase pulmonary artery blood flow, and then do second-stage radical surgery after the pulmonary artery development is improved. 2.Surgical methods 2.1 Palliative surgery: Its purpose is to increase pulmonary blood flow, eliminate and improve cyanosis and other symptoms, expand the pulmonary vascular bed, promote pulmonary vascular development, and prepare for radical surgery. Due to the relaxation of indications for stage I radical surgery, palliative surgery is currently used only in patients with very poor pulmonary artery development and with other severe intracardiac malformations that are not suitable for stage I radical surgery. The classic or modified Blalock-Taussig (B-T) shunt is the most common, whereas the Waterson anastomosis (ascending aorta-right pulmonary artery) and Potts anastomosis (descending aorta-left pulmonary artery) are now largely abolished due to the disadvantages of more difficult flow control, difficult removal and pulmonary artery tortuosity. the B-T shunt can be performed at any age and on any size pulmonary artery, but Due to the small size of the subclavian artery in neonates, most physicians prefer to apply a modified B-T shunt in the neonatal period, which has excellent results due to a low rate of shunt failure and excellent reduction performance. Treatment outcomes: The mortality rate for correction of tetralogy of Fallot continues to decline. The results of direct visualization orthoprosthesis have been satisfactory. Most reports show an early mortality rate of 1-5% for correction of tetralogy of Fallot. Many series suggest that radical surgery for tetralogy of Fallot up to 1 year of age does not affect early outcomes due to improved surgical techniques, especially avoidance of excision of excessive right ventricular outflow tract muscle bundles, improved cardiopulmonary diversion techniques and postoperative monitoring. The main causes of early death: left ventricular hypoplasia, bilateral pulmonary artery or peripheral pulmonary artery hypoplasia, one pulmonary artery agenesis, pulmonary atresia, pulmonary artery agenesis, and combined complete endocardial cushion defects. Long-term results are good [38], with survival rates of 93%, 92%, 92%, and 87% at 1 month, 1 year, 5 years, and 20 years in a group of 814 completely radical cases by Kirklin et al. Risk factors for later mortality: older age at radicalization, severe preoperative left ventricular degeneration; prolonged right ventricular hypertension above 60 mmHg, and distant high incidence of arrhythmias, especially ventricular arrhythmias. The most common indications for reoperation are long-term complications related to the right ventricular outflow tract, such as severe pulmonary regurgitation, residual outflow tract obstruction, and ductal failure [39]. Due to poor tolerance of postoperative residual shunts in tetralogy of Fallot, reclosure of residual ventricular septal defects is recommended when the pulmonary circulation-to-body circulation flow ratio is greater than 1.5. In conclusion, the timing of surgery for simple correction of tetralogy of Fallot has matured, i.e., radical surgery should be performed in neonates and small infants for symptomatic ones, and early surgery for asymptomatic ones, which can be elective at 1-2 years of age. Surgery in infants and young children is performed via a right atrial transection instead of a right ventricular transection. Minimize damage to the right ventricle during surgery to avoid pulmonary regurgitation and to reduce persistent postoperative right ventricular hypertension. How to improve the outcome of complex tetralogy of Fallot is the direction of future efforts.