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Patent Ductus Arteriosus (PDA)
Patent ductus arteriosus (PDA) is a persistence of the fetal connection (ductus arteriosus) between the aorta and pulmonary artery after birth, resulting in a left-to-right shunt. Symptoms may include failure to thrive, poor feeding, tachycardia, and tachypnea. A continuous murmur at the upper left sternal border is common. Diagnosis is by echocardiography. Administration of indomethacin with or without fluid restriction may be tried in premature infants with a significant shunt, but this therapy is not effective in term infants or older children with PDA. If the connection persists, surgical or catheter-based correction is indicated.
PDA accounts for 5 to 10% of congenital heart anomalies; the male:female ratio is 1:3. PDA is very common among premature infants (present in about 45% with birth weight < 1750 g and in about 80% with birth weight < 1200 g). A significant PDA causes heart failure (HF) in 15% of premature infants with birth weight < 1750 g and in 40 to 50% of infants with birth weight < 1500 g.
The ductus arteriosus is a normal connection between the pulmonary artery and aorta; it is necessary for proper fetal circulation. At birth, the rise in Pao2 and decline in prostaglandin concentration cause closure of the ductus arteriosus, typically beginning within the first 10 to 15 h of life. If this normal process does not occur, PDA results (see Figure: Patent ductus arteriosus.).
Physiologic consequences depend on ductal size. A small ductus rarely causes symptoms. A large ductus causes a large left-to-right shunt. Over time, a large shunt results in left heart enlargement, pulmonary artery hypertension, and elevated pulmonary vascular resistance, ultimately leading to Eisenmenger syndrome (see Eisenmenger Syndrome).
Clinical presentation depends on PDA size and gestational age at delivery. Infants and children with a small PDA are generally asymptomatic; infants with a large PDA present with signs of HF (eg, failure to thrive, poor feeding, tachypnea, dyspnea with feeding, tachycardia). Premature infants may present with respiratory distress, apnea, worsening mechanical ventilation requirements, or other serious complications (eg, necrotizing enterocolitis). Signs of HF occur earlier in premature infants than in full-term infants and may be more severe. A large ductal shunt in a premature infant often is a major contributor to the severity of the lung disease of prematurity.
Most children with a small PDA have normal heart sounds and peripheral pulses. A grade 1 to 3/6 continuous murmur is heard best in the upper left sternal border. The murmur extends from systole to beyond the 2nd heart sound (S2) into diastole and typically has a different pitch in systole and diastole.
Full-term infants with a significant PDA shunt have full or bounding peripheral pulses with a wide pulse pressure. A grade 1 to 4/6 continuous murmur is characteristic. If the murmur is loud, it has a “machinery-sounding” quality. An apical diastolic rumble (due to high flow across the mitral valve) or gallop rhythm may be audible if there is a large left-to-right shunt or HF develops.
Premature infants with a significant shunt have bounding pulses and a hyperdynamic precordium. A heart murmur occurs in the pulmonary area; the murmur may be continuous, systolic with a short diastolic component, or only systolic, depending on the pulmonary artery pressure. Some infants have no audible heart murmur.
Diagnosis is suggested by clinical examination, supported by chest x-ray and ECG, and established by 2-dimensional echocardiography with color flow and Doppler studies.
Chest x-ray and ECG are typically normal if the PDA is small. If the shunt is significant, chest x-ray shows prominence of the left atrium, left ventricle, and ascending aorta and increased pulmonary vascular markings; ECG may show left ventricular hypertrophy. Cardiac catheterization is not necessary unless used for therapy.
In premature infants with compromised respiratory status, the PDA can sometimes be closed by using a prostaglandin synthesis inhibitor (eg, indomethacin [see Table: Indomethacin Dosing Guidelines (mg/kg)* for doses]). Three doses of indomethacin are given IV q 12 to 24 h based on urine output; doses are withheld if urine output is < 0.6 mL/kg/h. An alternative is ibuprofen 10 mg/kg po followed by 2 doses of 5 mg/kg at 24-h intervals). Fluid restriction may facilitate ductal closure. In the past, if this treatment was unsuccessful, the PDA was ligated surgically. However, current data do not show improved long-term outcome after surgical intervention, but experts are evaluating whether there are subgroups of patients in whom surgery might be beneficial. In premature infants without respiratory compromise, a PDA is generally not treated.
In full-term infants, indomethacin is usually ineffective. Transcatheter closure has become the treatment of choice in children > 1 yr; a variety of catheter-delivered occlusion devices are available (eg, coils, Amplatzer® duct occluder). In infants < 1 yr or who have certain anatomic varieties of the ductus, surgical division and ligation may be preferred over the transcatheter approach. For a PDA with a shunt large enough to cause symptoms of HF or pulmonary hypertension, closure should be done after medical stabilization. For a persistent PDA without HF or pulmonary hypertension, closure can be done electively any time after 1 yr. Outcomes after PDA closure are excellent.
Endocarditis prophylaxis is not needed preoperatively and is required only for the first 6 mo after closure or if there is a residual defect adjacent to a transcatheter-placed device or surgical material.
Patent ductus arteriosus (PDA) is a persistence after birth of the normal fetal connection (ductus arteriosus) between the aorta and pulmonary artery, resulting in a left-to-right shunt.
Manifestations depend on the size of the PDA and the degree of prematurity, but a continuous murmur is characteristic and, if loud, has a “machinery-sounding” quality.
Premature infants may have respiratory distress or other serious complications (eg, necrotizing enterocolitis).
Over time, a large shunt causes left heart enlargement, pulmonary artery hypertension, and elevated pulmonary vascular resistance, ultimately leading to Eisenmenger syndrome.
Give premature infants a prostaglandin inhibitor (eg, indomethacin) to close the PDA; surgical closure has not been shown to improve outcomes.
Prostaglandin inhibitors are usually ineffective in full-term infants, but catheter-delivered occlusion devices or surgery is typically beneficial.
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