Congenital Heart Disease - Ductal Dependent

 Overview:

Congenital heart diseases (CHD) have been reported to be responsible for 30 to 50% of infant mortality caused by congenital disabilities. Ductal-dependent shunts refer to congenital heart defects in which the ductus arteriosus, a blood vessel connecting the pulmonary artery to the aorta, plays a crucial role in maintaining adequate blood flow. The ductus arteriosus is a fetal structure that normally closes shortly after birth. However, in certain congenital heart defects, the closure of the ductus arteriosus is necessary for survival, and the shunting of blood through this vessel is vital. 

1. Examples of ductal-dependent shunts include: 

a.Hypoplastic Left Heart Syndrome (HLHS): 

• Description: HLHS is a congenital heart defect characterized by the underdevelopment of the left side of the heart, including the left ventricle and aorta. 

• Ductal Dependency: In HLHS, the ductus arteriosus is crucial for maintaining blood flow to the body. It allows oxygenated blood from the right side of the heart to reach the systemic circulation. 

• Treatment: Surgical interventions, such as the Norwood procedure, are typically performed to address HLHS and reroute blood flow. 

  b. Interrupted Aortic Arch: 

• Description: This condition involves a gap or interruption in the aorta, the main artery that carries oxygenated blood from the heart to the body. 

• Ductal Dependency: In interrupted aortic arch, the ductus arteriosus serves as a bridge, allowing blood to reach the lower part of the body. 

• Treatment: Surgical repair is necessary to reconnect the interrupted segments of the aorta. 

  c.Coarctation of the Aorta: 

• Description: Coarctation of the aorta is a narrowing of the aorta, restricting blood flow to the lower part of the body. 

• Ductal Dependency: In severe cases, the ductus arteriosus provides an alternative route for blood flow, bypassing the narrowed segment. 

• Treatment: Surgical correction or catheter-based interventions are performed to alleviate the coarctation. 

  d. Pulmonary Atresia with Ventricular Septal Defect (VSD): 

• Description: Pulmonary atresia involves the absence or severe narrowing of the pulmonary valve, and a VSD is a hole in the septum between the heart's ventricles. 

• Ductal Dependency: The ductus arteriosus allows blood to flow from the right ventricle to the pulmonary artery, bypassing the atretic pulmonary valve. 

• Treatment: Surgical interventions are required to establish a connection between the right ventricle and the pulmonary artery. 

2. Importance of Keeping PDA Open: 

In certain congenital heart defects, particularly those characterized by ductal-dependent shunts, keeping the patent ductus arteriosus (PDA) open is crucial for maintaining adequate blood flow and ensuring oxygenation. The ductus arteriosus is a blood vessel connecting the pulmonary artery to the aorta, and it is a fetal structure that normally closes shortly after birth. However, in cases where the closure of the ductus arteriosus is necessary for survival, maintaining its patency becomes a priority. Here are a few conditions where keeping the PDA open is important and the methods used to achieve this: 

a. Hypoplastic Left Heart Syndrome (HLHS): 

• Importance: In HLHS, the left side of the heart, including the left ventricle and aorta, is underdeveloped. The PDA

  is essential for allowing oxygenated blood from the right side of the heart to reach the systemic circulation. 

• Intervention: Prostaglandin medication, such as alprostadil, is often administered to keep the ductus arteriosus

  open. This ensures a sufficient supply of oxygenated blood to the body until surgical interventions can be performed. 

  b. Pulmonary Atresia with Ventricular Septal Defect (VSD): 

• Importance: Pulmonary atresia involves the absence or severe narrowing of the pulmonary valve, and a VSD allows

  mixing of oxygenated and deoxygenated blood. The PDA serves as an alternate route for blood to reach the pulmonary

  artery. 

• Intervention: Prostaglandin therapy is used to maintain the patency of the ductus arteriosus, ensuring blood flow to the

  lungs. Surgical procedures are then performed to address the underlying defects. 

c.Transposition of the Great Arteries (TGA): 

• Importance: In TGA, the aorta and pulmonary artery are switched, leading to separate circulatory pathways. The PDA is essential for allowing some mixing of oxygenated and deoxygenated blood. 

• Intervention: Prostaglandin may be used to keep the ductus arteriosus open temporarily. Additionally, other procedures like balloon atrial septostomy might be performed to improve mixing. 

d. Interrupted Aortic Arch: 

• Importance: Interrupted aortic arch involves a gap in the aorta, and the PDA allows blood to bypass the interruption. 

• Intervention: Prostaglandin is administered to maintain the patency of the ductus arteriosus until surgical repair can be performed. 

The use of prostaglandin therapy is a common method to keep the PDA open temporarily. This medication prevents the physiological closure of the ductus arteriosus, allowing a critical shunt to persist until more definitive interventions, such as surgery, can be undertaken to address the underlying structural defects. It provides a bridge to maintain oxygenation and circulatory stability in neonates with these complex heart conditions. 

3. Oxygen Saturations:

Oxygen saturation will be set by your provider. In ductal dependent shunts, we must make sure we are adequately oxygenating the tissue, while also making sure we don’t over oxygenate, causing the PDA to close. Typically, saturations should be maintained at 75-85% SPO2 but variances may occur dependent on the situation. Make sure you follow your hospitals policy and consult your provider first! 

4. Why is ductal dependent shunting important to the RT?

For an RT, understanding ductal-dependent shunting is critical because it directly impacts respiratory care. Infants with these conditions may require prostaglandin E1 to keep the ductus arteriosus open or may need special ventilation strategies to manage oxygenation and carbon dioxide removal. Additionally, RTs may assist in the early identification of signs of inadequate blood flow (e.g., poor oxygenation, abnormal heart sounds) and work with the medical team to intervene appropriately. Recognizing these conditions ensures that the RT can help optimize respiratory support while preventing further complications, especially in the first few hours or days of life.