Overview
Definition:
Patent Ductus Arteriosus (PDA) is a persistent opening between the aorta and the pulmonary artery that normally closes shortly after birth
In preterm infants, especially those with very low birth weight, the ductus arteriosus often fails to close, leading to abnormal blood flow from the aorta to the pulmonary artery.
Epidemiology:
PDA is common in preterm infants, with incidence increasing as gestational age decreases
It occurs in up to 30% of infants <28 weeks gestation and up to 80% of extremely premature infants (<26 weeks gestation)
Risk factors include prematurity, respiratory distress syndrome, low birth weight, and maternal chorioamnionitis.
Clinical Significance:
An unclosed PDA in preterms can lead to increased pulmonary blood flow, pulmonary edema, respiratory failure, necrotizing enterocolitis, intraventricular hemorrhage, and increased mortality
Timely and appropriate management is crucial for improving outcomes in these vulnerable infants.
Clinical Presentation
Symptoms:
Shortness of breath
Tachypnea
Increased work of breathing
Intermittent apnea
Poor feeding tolerance
Lethargy
Palpable precordial impulse
Widened pulse pressure
Bounding pulses.
Signs:
Continuous machinery murmur heard best at the left upper sternal border or infraclavicular area
Differential cyanosis (lower extremities pinker than upper extremities) in severe cases
Signs of congestive heart failure (e.g., hepatomegaly, peripheral edema)..
Diagnostic Criteria:
Diagnosis is primarily made by echocardiography, which confirms the presence of a PDA, assesses its size, direction of flow (left-to-right shunt), and hemodynamic significance
Clinical signs and symptoms also contribute to the suspicion and urgency of diagnosis.
Diagnostic Approach
History Taking:
Gestational age at birth
Birth weight
Presence of respiratory distress syndrome
Need for mechanical ventilation
Any previous medical interventions for PDA
Clinical signs of heart failure
Feed intolerance..
Physical Examination:
Auscultation for murmurs (location, timing, character)
Assessment of respiratory status (rate, effort, retractions)
Evaluation of peripheral pulses (bounding, differential pressure)
Assessment for signs of systemic hypoperfusion.
Investigations:
Echocardiography: essential to visualize the PDA, measure its diameter, assess shunt volume, and evaluate for associated cardiac anomalies or pulmonary hypertension
Chest X-ray: may show cardiomegaly and pulmonary vascular plethora
ECG: may show signs of left ventricular volume overload.
Differential Diagnosis:
Other causes of respiratory distress in neonates, such as pneumonia, transient tachypnea of the newborn, respiratory distress syndrome
Other causes of murmurs, such as ventricular septal defect, aortic stenosis, or peripheral pulmonary stenosis
Sepsis.
Management
Initial Management:
Supportive care including mechanical ventilation or CPAP to support respiratory function
Fluid restriction to reduce preload
Adequate nutritional support
Monitoring vital signs, urine output, and fluid balance.
Medical Management:
Pharmacological closure is the first-line treatment for hemodynamically significant PDAs
Indomethacin: a cyclooxygenase inhibitor, traditionally used but can have renal and gastrointestinal side effects
Dosing typically 3 doses of 0.1-0.2 mg/kg intravenously
Ibuprofen: also a cyclooxygenase inhibitor, often preferred due to a potentially better safety profile, particularly regarding renal function
Dosing typically 3 doses of 10 mg/kg, then 5 mg/kg, then 5 mg/kg intravenously
Acetaminophen (Paracetamol): an alternative analgesic and antipyretic that also inhibits cyclooxygenase
Efficacy data is emerging, and it may be used in specific situations or as a rescue therapy
Dosing typically 15 mg/kg every 6 hours intravenously or orally
Contraindications to NSAIDs include significant renal impairment, coagulopathy, thrombocytopenia, and active bleeding.
Surgical Management:
Surgical ligation is considered if medical management fails or is contraindicated
It involves direct ligation of the PDA
This is a last resort due to increased risks associated with surgery in premature infants.
Watchful Waiting:
This approach is considered for PDAs that are not hemodynamically significant or are likely to close spontaneously
Criteria include absence of symptoms, minimal or no shunt on echocardiography, and stable respiratory status
This strategy aims to avoid unnecessary medical or surgical interventions and their associated risks
Close monitoring with serial echocardiograms is essential.
Complications
Early Complications:
Renal impairment (oligo-/anuria) with indomethacin
Gastrointestinal issues such as perforation or necrotizing enterocolitis with NSAIDs
Bleeding disorders (thrombocytopenia)
Bronchopulmonary dysplasia
Intraventricular hemorrhage
Pulmonary hypertension.
Late Complications:
Persistent pulmonary hypertension
Increased susceptibility to respiratory infections
Growth restriction
Neurodevelopmental delays.
Prevention Strategies:
Careful patient selection for medical therapy
Optimizing respiratory support
Avoiding excessive fluid administration
Early identification and management of side effects
Close monitoring of renal function and gastrointestinal status
Consideration of acetaminophen when NSAIDs are contraindicated or ineffective.
Prognosis
Factors Affecting Prognosis:
Gestational age and birth weight at presentation
Presence and severity of hemodynamic shunting
Presence of associated comorbidities (e.g., BPD, IVH)
Responsiveness to medical therapy
Need for surgical intervention.
Outcomes:
With timely and appropriate management, many preterm infants with PDA can achieve ductal closure and have favorable outcomes
However, significant PDAs, especially in extremely premature infants, are associated with higher morbidity and mortality.
Follow Up:
Infants who have received treatment for PDA require regular follow-up to assess for recurrence or potential long-term sequelae
This may include cardiology assessments, echocardiography, and monitoring for respiratory and neurodevelopmental issues.
Key Points
Exam Focus:
Understand the hemodynamics of PDA in preterms
Know the pharmacologic agents (ibuprofen, indomethacin, acetaminophen), their mechanisms, doses, and side effects
Recognize indications for watchful waiting and surgical intervention
Differentiate between significant and insignificant PDA.
Clinical Pearls:
Always correlate clinical findings with echocardiographic evidence of shunt significance
Consider acetaminophen as a viable alternative, especially in infants with renal concerns or contraindications to NSAIDs
Serial echocardiography is key to monitoring response to treatment and guiding further management.
Common Mistakes:
Treating small, asymptomatic PDAs with medication
Failing to consider contraindications for NSAIDs
Inadequate monitoring for drug-related complications
Delaying surgical intervention when medical management is clearly failing.