Congenital heart disease (CHD) refers to congenital malformations caused by abnormal development of the heart and great vessels during the embryonic period. It is the most common type of heart disease in children. In China, the incidence rate among live newborns is 8.98‰, with severe cases accounting for 2.93‰. If untreated, infants with severe CHD may die within the first year of life due to severe complications such as profound hypoxia, heart failure, shock, or pneumonia. In recent years, the prognosis for congenital heart disease has significantly improved. Advances in cardiopulmonary bypass technology, deep hypothermic anesthesia for open-heart surgery, the use of valved conduits, and the widespread adoption of minimally invasive interventional procedures have greatly reduced surgical trauma and significantly increased the success rate of corrective surgeries.
Etiology
The development of congenital heart disease is associated with genetic, maternal, and environmental factors.
Genetic Factors
Genetic causes include single-gene mutations, such as the association of Holt-Oram syndrome with TBX5 gene mutations, Williams syndrome with Elastin gene defects, and Marfan syndrome with Fibrillin gene defects. Chromosomal abnormalities, such as Down syndrome (trisomy 21) and Edward syndrome (trisomy 18), also contribute to the development of CHD. However, most cases are linked to polygenic genetic defects.
Maternal Factors
Maternal infections, exposure to harmful substances, and maternal illnesses during the perinatal period are major contributors. Viral infections during early pregnancy, such as rubella, influenza, mumps, or coxsackievirus infections, significantly increase the risk. Metabolic disorders in the mother, such as diabetes, hypercalcemia, or phenylketonuria, are also associated with CHD. Other potential factors include maternal exposure to radiation, organic chemicals, certain medications (e.g., anticancer drugs, anticonvulsants), folic acid deficiency, and intrauterine hypoxia.
The majority of congenital heart disease cases have unidentified causes. It is currently believed that over 85% of cases likely result from the interplay between fetal genetic susceptibility and environmental factors. As such, improving maternal healthcare—especially in the early stages of pregnancy—through active prevention of viral infections such as rubella and influenza, avoiding exposure to known risk factors, maintaining a healthy lifestyle, and ensuring adequate supplementation of essential nutrients like folic acid can play a key role in reducing the incidence of congenital heart disease.
Classification
Congenital heart disease can be classified in various ways. One classification system is based on the presence or absence of a shunt between the left and right sides of the heart or the great vessels:
Left-to-Right Shunting (Acyanotic)
Conditions such as atrial septal defect (ASD), ventricular septal defect (VSD), and patent ductus arteriosus (PDA) belong to this group. In these cases, blood flows from the left side to the right side of the heart due to higher systemic pressure compared to pulmonary pressure, and cyanosis does not occur. However, under conditions such as vigorous crying, breath-holding, or any pathological situation that raises right-sided pressure above left-sided pressure, blood may shunt from right to left, temporarily causing cyanosis. As the disease progresses to obstructive pulmonary hypertension, Eisenmenger syndrome may develop. When this occurs, persistent cyanosis due to right-to-left shunting indicates a late-stage disease.
Right-to-Left Shunting (Cyanotic)
Conditions such as tetralogy of Fallot, transposition of the great arteries, and tricuspid atresia are included in this category. Due to forward blood flow obstruction on the right side or abnormal connections of the great vessels, a large amount of deoxygenated venous blood from the right heart enters systemic circulation, resulting in persistent cyanosis.
Non-Shunting (Acyanotic)
Conditions such as pulmonary stenosis, aortic valve stenosis, and coarctation of the aorta fall into this category. In these conditions, there are no abnormal pathways or shunts between the left and right sides of the heart or between the arterial and venous systems.
To be continued