Description

• Patent ductus arteriosus (PDA) is the persistence into postnatal life of the normal fetal vascular conduit between the central pulmonary and systemic arterial systems. Normally, the ductus arteriosus (DA) functionally closes within the first 1 to 3 days of life. Structural closure is usually completed by the 3rd week of life. If the DA remains patent beyond 3 months of life, it is considered abnormal and is unlikely to close spontaneously (spontaneous closure rate 0.6% per year).
• In the infant with a normal left aortic arch, the DA connects the main pulmonary artery (MPA) at the origin of the left pulmonary artery to the descending aorta, distal to the origin of the left subclavian artery.
• Many variations can occur, although they are less common. The main, proximal right, or proximal left pulmonary artery may be connected to virtually any location on the aortic arch or proximal portions of the brachiocephalic vessels.
• Five distinct clinical conditions are associated with PDA:
  • Isolated cardiovascular lesion in premature infants
  • Isolated cardiovascular lesion in otherwise healthy term infants and children
  • Incidental finding associated with more significant structural cardiovascular defects
  • Compensatory structure in cases of neonatal pulmonary hypertension without congenital heart disease (CHD)
  • Critical compensatory structure in some cyanotic or left-sided obstructive lesions

Epidemiology

• As an isolated defect, PDA is the 6th most common congenital cardiovascular lesion.
  • Represents 5% of all types of CHD
  • 1 per 2,000 live births
  • If “silent” PDA are included, the rate may be as high as 1:500 live births.
• Female-to-male ratio: 2:1

Risk Factors

• Prematurity
  • Increases with the degree of prematurity (50–80% in preterm infants <26 weeks’ gestation)
  • 60–70% of preterm infants of <28 weeks’ gestation receive medical or surgical therapy for a PDA.
• Incidence of PDA varies significantly depending on environmental factors (altitude), management style (e.g., amount of maintenance fluid prescribed, surfactant administration), and presence of coexisting diseases (e.g., respiratory distress syndrome, hypoxemia, fluid overload, necrotizing enterocolitis, sepsis, hypocalcemia).
• Higher rate of PDA in babies with
  • Trisomy 21
  • Wolf-Hirschhorn syndrome (4p deletion)
  • Char syndrome
  • Carpenter syndrome
  • Holt-Oram syndrome
  • Incontinentia pigmenti

Pathophysiology

• The PDA is derived from the distal portion of the left 6th embryonic arch, connecting the left pulmonary artery to the descending aorta.
  • The PDA is formed by the 8th week of fetal life.
  • It is necessary for fetal circulation throughout the remainder of gestation.
• Fetal blood flows from the MPA to the DA to the aorta, thus bypassing the pulmonary vascular bed and supplying systemic blood flow. With the first postnatal breaths, the pulmonary vascular resistance falls abruptly, the DA constricts, and pulmonary blood flow is directed into the lungs.
• With a PDA, excessive blood flow will continue from the aorta into the pulmonary artery, causing increased pulmonary blood flow and volume overloading of the left side of the heart.
• In premature infants and term infants with pulmonary hypertension, delayed closure represents an impaired developmental process, whereas in the healthy full-term infant, PDA probably reflects an anatomic abnormality of the ductal tissue.

Etiology

• Prematurity
• Rubella infection in the first trimester
• Genetic or familial factors
• High altitude
• Idiopathic

History

• Premature infants
  • Variable: ranging from asymptomatic to complete cardiovascular collapse
  • Increased ventilatory support, pulmonary hemorrhage, respiratory or metabolic acidosis from low cardiac output, and excessive pulmonary blood flow
  • Tachypnea, feeding intolerance, apnea, bradycardia, necrotizing enterocolitis, and decreased urine output
• Infants and older children
  • Small PDA: usually asymptomatic, with incidental heart murmur found on routine exam
  • Moderate PDA: possible congestive heart failure (CHF), poor feeding, and poor weight gain
  • Large PDA: symptoms as above and recurrent respiratory infections

Physical Exam

• Premature infants
  • Tachypnea, rales, tachycardia (±S3 gallop)
  • Hyperdynamic precordium and bounding pulses with wide pulse pressure (due to diastolic “runoff” from the aorta to the pulmonary artery)
  • The typical PDA murmur in a premature infant is a pansystolic murmur audible at the left upper or midsternal border.
  • With a large PDA and equalization of pressure between the MPA and the aorta, no murmur may be heard.
  • Hepatomegaly may exist with heart failure (late sign).
• Infants and older children: Findings vary with size of shunt.
  • Small PDA
    • Pansystolic murmur may be heard at the 2nd left intercostal space.
    • Murmur becomes continuous (i.e., extends into diastole), as the pulmonary vascular resistance decreases over the 1st months of life.
  • Moderate or large PDA
    • The murmur is louder, has a harsh quality, and acquires a machine-like quality often being heard posteriorly. In that case, a systolic thrill may be felt at the left upper sternal border.
    • Tachycardia, bounding pulses with a wide pulse pressure, and a mid-diastolic low-frequency rumbling murmur may be audible at the apex with a large PDA.
    • With severe left ventricular failure, the classic PDA signs may disappear, but there will be findings consistent with CHF (tachycardia, S3 gallop at the apex, hepatomegaly, tachypnea, rales).
    • In extreme cases, pulmonary hypertension may occur, with the murmur shortening, the diastolic component disappearing, and S2 becoming accentuated. At advanced stages of irreversible pulmonary vascular disease, cyanosis begins to appear, often more pronounced in the lower limbs, with reversal of shunting.

Differential Diagnosis

• Aortopulmonary window
• Systemic or pulmonary arteriovenous communications
• Ruptured sinus of Valsalva
• Coronary artery fistula
• Truncus arteriosus
• Aortic insufficiency
• Innocent venous hum in older children
• Pulmonary atresia with collaterals
• Ventricular septal defect with aortic regurgitation
• Ventricular septal defect in infancy

Diagnostic Tests and Interpretation

• ECG
  • Usually normal with a small PDA
  • Left atrial enlargement and left ventricular hypertrophy with moderate and large PDA
  • Biventricular hypertrophy in later stages
• Chest radiograph
  • Usually normal with a small PDA, although prominence of main and peripheral pulmonary arteries may be seen
  • In moderate and large PDAs, these findings become more pronounced, along with an enlarged heart. Increased pulmonary vascular markings are proportionate to the left-to-right shunt. Pulmonary edema can be seen if CHF develops. In premature infants with respiratory distress syndrome, there is evidence of deteriorating lung disease with unclear cardiac borders.
• Echocardiogram
  • Delineates the PDA and assesses the size of the left atrium and the left ventricle
  • Doppler techniques assess the ductal flow pattern and may be useful for estimating the pulmonary artery pressure.
• Cardiac catheterization
  • Most often not essential for diagnosis
  • Indicated for suspected concomitant pulmonary hypertension
  • Can be performed for treatment via transcatheter closure techniques

General Measures

• Premature infant
  • Supportive treatment (careful use of oxygen, respiratory assistance, correction of metabolic acidosis)
  • Management of CHF with fluid restriction and diuretics
  • If PDA persists or patient is symptomatic, closure of PDA is indicated.
  • Medical closure: Indomethacin is most often used; ibuprofen is as effective. Meta-analysis of controlled and uncontrolled studies has demonstrated an efficacy of paracetamol (acetaminophen) comparable with that reported for ibuprofen.
    • Contraindications to medical management with nonsteroidal medications include renal failure (creatinine >1.8 mg/dL), thrombocytopenia (platelets <100,000), and associated conditions (necrotizing enterocolitis, intraventricular hemorrhage). Paracetamol appears to be a suitable alternative.
  • Surgical closure is indicated if medical treatment fails or use of indomethacin is contraindicated.
• Infants and older children
  • Medical management of CHF with diuretics and afterload reduction
  • PDA is no longer a stated indication for subacute bacterial endocarditis (SBE) prophylaxis, but clinical practice may vary.
  • Spontaneous closure rate is low, and closure with indomethacin is not usually effective in this group of patients.
  • Closure is indicated whenever a symptomatic or hemodynamically significant PDA exists.
  • For asymptomatic audible PDA, closure can be performed electively and is primarily performed to reduce the risk of endocarditis. Recommendations for closure of an asymptomatic, incidentally found (“silent” ductus) PDA are not standard.
  • Most infants and children can have a PDA safely and effectively closed during cardiac catheterization, obviating the need for a surgical procedure.

Diagnostic Procedures/Other

Surgical closure of PDA can be achieved by one of three techniques:

• Open surgical ligation and division: mostly in premature infants
• Video-assisted thoracoscopic ligation: depends on the institution
• Transcatheter occlusion with coils or other devices

Prognosis

• Outcome in treated premature infants is generally good but depends mostly on the degree of prematurity and the presence of associated conditions.
• Outcome in term infants and older children is excellent if no complications have occurred.
• PDA among adults may be associated with significant mortality with or without surgery.
• After closure of PDA, no endocarditis prophylaxis is needed if complete obliteration of flow is achieved. Most cardiologists continue prophylaxis for 6 months after the procedure that closed the PDA if closed by a coil or device.

Complications

• Pulmonary edema and CHF
• Pulmonary hemorrhage
• Pulmonary vascular obstructive disease
• Increased chronic lung disease
• Failure to thrive
• Recurrent respiratory infections
• Lobar emphysema or collapse
• Infective endarteritis
• Thromboembolism of cerebral arteries
• Aneurysm of the ductus
• Intracranial hemorrhage
• Necrotizing enterocolitis
• Renal dysfunction

ICD-9

747.0 Patent ductus arteriosus

ICD-10

Q25.0 Patent ductus arteriosus

SNOMED

• 83330001 Patent ductus arteriosus (disorder)
• 253686000 Patent ductus arteriosus - persisting type (disorder)
• 125963005 Patent ductus arteriosus with left-to-right shunt
• 125964004 Patent ductus arteriosus with right-to-left shunt (disorder)