What conditions in children (patients) with precardiac disease predispose to pulmonary hypertension? All left-to-right shunt precardiac disease may lead to pulmonary hypertension. A left-to-right shunt is a pathophysiological process in which blood from the body circulation is shunted to the pulmonary circulation through a congenitally abnormal channel; its counterpart is right-to-left shunt precardiac disease. Left-to-right shunt preconditioning includes many of the most common types of preconditioning, such as ventricular septal defect, atrial septal defect, patent ductus arteriosus, and to a lesser extent, patent ductus arteriosus, main pulmonary window, and certain types of aortic dislocation. Why does left-to-right shunt preconditioning cause pulmonary hypertension? The main pathophysiological feature of left-to-right shunt preconditioning is the transfer of blood from the body circulation to the pulmonary circulation, which leads to a significant increase in the volume of blood in the pulmonary circulation and a constant state of congestion in the pulmonary vascular bed, thus causing an increase in pulmonary artery pressure. We refer to this pulmonary hypertension due to congestion as powered pulmonary hypertension. At this stage, as long as the heart malformation is corrected in time and the left-to-right shunt is eliminated, the blood volume of the pulmonary circulation will return to normal and the pulmonary hypertension will be reduced. However, if the precordial disease is not effectively corrected in time, the pulmonary vessels will gradually increase, thicken and harden under the influence of long-term congestion, and lose their normal elasticity; the pulmonary circulation pressure will also increase progressively, thus evolving from dynamic to organic pulmonary hypertension, and when it develops to a certain degree, pulmonary hypertension will be irreversible; even if the heart malformation is corrected at this time, the pulmonary artery pressure will not be able to be reduced. At this point, the Eisenmenger syndrome stage is reached, which means that the opportunity for surgery is lost.