A Eisenmenger syndrome A large defect leads to a significant increase in pulmonary vascular resistance and a reversal of the direction of the body-pulmonary shunt or a bidirectional shunt. Clinical manifestations include cyanosis, erythrocytosis and multi-organ involvement. B. Body-pulmonary shunt-associated PAH Medium-large defect leads to a mild to moderate increase in pulmonary vascular resistance, with a predominantly left-to-right shunt and no cyanosis at rest. C PAH combined with small defects The presence of small defects (WHO and foreign documents such as the European Society of Cardiology guidelines recommend echocardiographic evaluation of ventricular defects <1 cm and atrial defects <2 cm as small defects; some experts in China recommend ventricular defects <5 mm and atrial defects <10 mm as small defects) has clinical features similar to those of IPAH. D PAH after cardiac repair PAH persists after cardiac malformation repair. It improves significantly after surgery but worsens significantly again after several months or even years, and there is no significant postoperative residual fistula.