Cardiology · Congenital Heart Disease
The facts most likely to be tested
Patent ductus arteriosus results from the failure of the ductus arteriosus to close after birth, leading to a left-to-right shunt between the aorta and the pulmonary artery.
The classic physical exam finding is a continuous machine-like murmur best heard at the left infraclavicular area or second left intercostal space.
Patients often present with a wide pulse pressure and bounding peripheral pulses due to the continuous runoff of blood from the systemic circulation into the pulmonary circulation.
Premature infants are at the highest risk for symptomatic patent ductus arteriosus due to prolonged prostaglandin E2 exposure and immature ductal tissue.
Indomethacin or ibuprofen (cyclooxygenase inhibitors) are the first-line pharmacologic treatments to promote ductal closure in premature neonates.
Surgical ligation or transcatheter closure is indicated for symptomatic infants who fail medical management or for older children to prevent Eisenmenger syndrome.
Congenital rubella infection is a classic maternal history association that increases the risk of developing a patent ductus arteriosus.
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A 3-week-old premature infant born at 30 weeks gestation is being evaluated in the NICU. On physical examination, the infant is noted to have bounding peripheral pulses and a wide pulse pressure. Auscultation reveals a continuous machine-like murmur heard best at the left upper sternal border. The infant has no cyanosis and oxygen saturation is 98% on room air.
What is the most appropriate initial pharmacologic management for this patient?
Indomethacin
The patient presents with classic signs of a patent ductus arteriosus (PDA), and in premature infants, the first-line treatment to induce closure is a cyclooxygenase inhibitor like indomethacin.
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High yield triage
Etiology / Epidemiology
Failure of the ductus arteriosus to close after birth; highly associated with prematurity and rubella infection.
Clinical Manifestations
Presents with a machinery-like continuous murmur at the left upper sternal border and bounding pulses.
Diagnosis
Confirmed via echocardiogram showing retrograde flow in the ductus.
Treatment
First-line is indomethacin or ibuprofen; contraindicated in renal failure.
Prognosis
Untreated leads to Eisenmenger syndrome and irreversible pulmonary hypertension.
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Epidemiology & Etiology
Common in preterm infants due to decreased sensitivity to oxygen-induced closure. Maternal rubella infection during the first trimester is a classic high-yield association. Female-to-male ratio is approximately 2:1.
Pertinent Anatomy
The ductus arteriosus connects the pulmonary artery to the descending aorta. It is essential for fetal circulation, bypassing the non-functional fetal lungs.
Pathophysiology
Post-birth, the drop in pulmonary vascular resistance and rise in systemic pressure normally triggers closure. Failure to close results in a left-to-right shunt from the aorta to the pulmonary artery. Chronic volume overload leads to left atrial and ventricular dilation, eventually causing pulmonary hypertension.
Clinical Manifestations
Classic machinery-like continuous murmur heard best at the left infraclavicular area. Patients exhibit wide pulse pressure and bounding peripheral pulses. Signs of heart failure include poor feeding, tachypnea, and failure to thrive.
Diagnosis
The echocardiogram is the gold standard for visualization and flow assessment. Chest X-ray may show cardiomegaly and increased pulmonary vascular markings. ECG often reveals left ventricular hypertrophy.
Treatment
Pharmacologic closure is attempted with indomethacin or ibuprofen (COX inhibitors). Contraindicated in renal failure or active bleeding. If medical therapy fails or the patient is symptomatic, surgical ligation is the definitive treatment.
Prognosis
Small defects may be asymptomatic. Large, untreated shunts lead to Eisenmenger syndrome, characterized by cyanosis and reversal of the shunt. Long-term monitoring for infective endocarditis is required.
Differential Diagnosis
Ventricular Septal Defect: Holosystolic murmur, not continuous
Aortic Regurgitation: Diastolic decrescendo murmur
Coarctation of the Aorta: Brachial-femoral pulse delay
Atrial Septal Defect: Fixed split S2
Truncus Arteriosus: Cyanotic heart disease