Cardiac catheterization will be a specially designed, X-ray impervious catheter with a certain degree of toughness, delivered to the designated parts of the heart and large blood vessels via the peripheral vessels, and according to the route of the cardiac catheter, the pressure and blood oxygen content of the heart and cardiovascular parts will be measured to calculate the cardiac blood displacement, fractional flow and blood flow resistance, and the waveform and value of the pressure curve will be analyzed for diagnosis and differential diagnosis, and for congenital heart disease, the contrast agent can be For congenital heart disease, contrast can be injected into the heart chambers to show the abnormalities of cardiac vascular structures and provide important data for the treatment of the disease. Although current cardiac Doppler echocardiography technology can provide more accurate real-time structural and hemodynamic information of the heart, and some children with congenital heart disease can undergo direct cardiac surgery without cardiac catheterization, cardiac catheterization is still required for complex congenital heart disease. In our clinical practice, we found that cardiac catheterization has an irreplaceable role for the examination of congenital heart disease because of its accurate display and comprehensive data, which can provide a comprehensive and accurate evaluation of congenital heart disease, thus providing comprehensive data support for clinical treatment, resulting in a better prognosis for the child and avoiding unnecessary losses. I. Detection of occult diseases: congenital heart diseases are often multiple, predominantly one kind, and also accompanied by other malformations. If treatment is carried out without clear diagnosis, the lighter the disease, the more life-threatening it is to miss the diagnosis and treatment. For example, arteriovenous catheter failure is often accompanied by narrowing or dissection of the aortic arch. If the arteriovenous catheter is ligated, blood flow cannot enter the descending aorta, which can lead to lower body defects and death from acute renal failure. During a contrast examination of ventricular septal defect, the child was found to have a mild prolapse of the aortic valve. If the ventricular septal defect is simply blocked and the aortic valve prolapse is not treated, it will become more and more serious, so we recommend the child to be treated with open-heart surgery at the same time. Second, unnecessary surgery is avoided: some children with mild precordial symptoms and the defect is found to be treated by ultrasonography, but the defect is found to have a small opening and minimal fractional flow by contrast, so there is no need for surgical treatment and losses are avoided. Such problems are often found in our interventional blocking treatment, and the reason for this is because of the presence of colored spillover of blood flow measured by Doppler ultrasound, which results in inaccurate results due to large measurement data. Third, differential diagnosis: some diseases have similar clinical manifestations, and the diagnosis cannot be confirmed by ultrasound, so it is necessary to perform imaging examination. For example, a patient with a coronary artery fistula diagnosed by ultrasound was found to have a coronary artery originated from the pulmonary artery by angiography. In a patient with an atrial septal defect, a left pulmonary artery sling malformation was also present on imaging.