What is patent ductus arteriosus (PDA)?

Patent Ductus Arteriosus (PDA) Definition

Patent ductus arteriosus (PDA) is a congenital cardiovascular finding in which the ductus arteriosus, a vascular connection between the aorta and pulmonary artery that is normally present during fetal life, remains open beyond the normal age of spontaneous closure after birth. 1

Anatomical Features

• The ductus arteriosus connects the proximal left pulmonary artery to the descending aorta just distal to the left subclavian artery 1
• In fetal circulation, this connection is essential for normal development
• Normally closes within 24-48 hours after birth in full-term infants 2
• Failure to close results in persistent communication between systemic and pulmonary circulation

Epidemiology

• Incidence: 0.3% to 0.8% of term infants 1
• More common in preterm infants, especially those with low birth weight 2, 3
• Female to male ratio is 2:1 2

Pathophysiology

The hemodynamic consequences of PDA depend on:

1. Size of the ductus:

   • Small: hemodynamically insignificant, often asymptomatic 1
   • Moderate to large: hemodynamically significant, can cause clinical symptoms 1

2. Direction of blood flow:

   • Left-to-right shunt: Most common, causes pulmonary overcirculation
   • Right-to-left shunt: Occurs with pulmonary hypertension, causes cyanosis

3. Pulmonary vascular resistance relative to systemic resistance:

   • Determines the magnitude and direction of shunting 1

Clinical Presentations

PDA can present with various clinical manifestations:

• Small PDA: Often asymptomatic with normal left ventricle and pulmonary artery pressure 1
• Moderate PDA with left ventricular volume overload: Enlarged left ventricle with normal or reduced function, may present with left heart failure 1
• Moderate PDA with pulmonary arterial hypertension: Pressure-overloaded right ventricle, may present with right heart failure 1
• Large PDA with Eisenmenger physiology: Differential hypoxemia and cyanosis (lower extremities and sometimes left arm show cyanosis) 1

Diagnostic Features

• Physical examination: Continuous "machinery" murmur (loudest in the left upper chest or infraclavicular area) 2
• Peripheral signs: Bounding pulses with wide pulse pressure in left-to-right shunts 1, 2
• Oxygen saturation: Should be measured in both hands and feet to detect differential cyanosis 1

Classification of Severity

• Small PDA: Likely to be hemodynamically insignificant 1
• Moderate to large PDA: Likely to be hemodynamically significant 1

Associated Conditions

PDA may be associated with:

• Chromosomal abnormalities (trisomy 21, trisomy 18) 2
• Genetic syndromes (Rubinstein-Taybi, CHARGE syndrome) 2
• Birth at high altitude 2
• Congenital rubella 2

Clinical Implications

Untreated moderate to large PDAs can lead to:

• Congestive heart failure 1, 2
• Pulmonary hypertension 1, 2
• Failure to thrive 2
• Recurrent respiratory infections 2
• Risk of endarteritis (though relatively low) 1

Management Considerations

Management depends on size, hemodynamic significance, and patient age:

• Closure is recommended when there is left atrial or left ventricular enlargement attributable to PDA with net left-to-right shunt and pulmonary artery systolic pressure less than 50% systemic 1
• Closure may be considered with net left-to-right shunt if pulmonary artery systolic pressure is ≥50% systemic 1
• Closure should not be performed in adults with net right-to-left shunt and pulmonary artery systolic pressure greater than two-thirds systemic 1

Closure Methods

• Transcatheter closure: Preferred method in adults when technically suitable 1
• Surgical closure: Alternative when percutaneous approach is not feasible 1

Understanding PDA is essential for appropriate management decisions to prevent complications and improve long-term outcomes in affected individuals.