What Is the Function of the Ductus Arteriosus?

The ductus arteriosus (DA) is a vascular connection between the aorta and the pulmonary arterial circulation. During fetal life, prior to lung expansion, high pulmonary venous resistance (PVR) forces blood to bypass the lungs via the ductus arteriosus. It is usually located proximal to the take-off of the left subclavian artery; however, this location may vary in a small percentage of the population.

How Is a PDA Diagnosed?

The history of prematurity, feeding intolerance, and wide pulse pressure all point in the direction of a patent ductus arteriosus (PDA). PDAs may be identified as a murmur in an asymptomatic patient or may present as heart failure. Most commonly, echocardiography is performed to visualize the PDA and exclude other structural heart disease lesions.

What Are the Important Diagnoses to Consider?

Other forms of structural heart disease that should be excluded include atrial septal defect (ASD), aortopulmonary window, and aortic insufficiency.

What Are the Signs/Symptoms of a PDA?

Patients often present with a murmur that can be heard across the entire precordium although best auscultated in the upper left sternal border and infra-clavicular regions. As pulmonary pressures fall in the first few days to weeks of life, aortic pressure exceeds pulmonary pressures in both systole and diastole, producing a continuous flow murmur, often referred to as a “machine-like” murmur.

Patients may also have widened pulse pressure due to diastolic run-off, bounding pulses, tachypnea, pulmonary edema, and/or a history of poor feeding.

Findings associated with other diseases of prematurity, i.e., necrotizing enterocolitis (NEC), intraventricular haemorrhage (IVH), bronchopulmonary dysplasia (BPD), should be considered.

What Is the Incidence of PDA?

The incidence of an isolated PDA is approximately 1 in 2,500–5,000 cases and is more common in females than males. The incidence of PDA is highest in premature infants.

What Is the Most Likely Age for Presentation?

The age at presentation is variable. Symptoms usually appear as the PVR decreases in the first weeks of life.

Describe the Anatomic Location of the Ductus Arteriosus

The DA most often originates from the aorta, immediately distal to the left subclavian artery take-off, and attaches to the left pulmonary artery. The location of the ductus arteriosus may vary, complicating surgical identification at times.

What Is the Pathophysiology of a PDA?

Most often, a PDA results in a left-to-right cardiac shunt. As the PVR decreases in the first few days to months of life, the volume shunted from left to right may increase significantly. The volume of blood shunted is generally proportional to the length and diameter of the PDA as well as the balance of systemic vascular resistance (SVR) and PVR.

What Are the Major Hemodynamic Consequences of a PDA?

Large PDAs result in large left-to-right cardiac shunts and pulmonary overcirculation. These children can have dyspnea with feedings, poor weight gain, and pulmonary vascular enlargement from increased flow. Additionally, diastolic run-off (L➔R flow through the PDA in diastole) reduces the coronary perfusion pressure which can result in myocardial ischemia, especially in the presence of anemia or reduced SVR. Reduced systemic blood flow as a result of pulmonary overcirculation may result in decreased renal and splanchnic perfusion with resulting necrotizing enterocolitis.