Patent Ductus Arteriosus (PDA)

smart doctor on

 

Patent Ductus Arteriosus (PDA)

Description

Patent ductus arteriosus is defined as the failure of the ductus arteriosus to close after birth, resulting in persistent communication between the descending thoracic aorta and the pulmonary artery. This maintains abnormal shunting of blood, typically left-to-right after birth, and can lead to progressive hemodynamic compromise depending on ductal size and pulmonary vascular resistance.

Epidemiology

  • Represents 5–10% of congenital heart disease in full-term infants.

  • Much more frequent in preterm neonates: incidence of 20–60%, particularly in extremely low birth weight infants.

  • Female predominance with a female-to-male ratio of approximately 2:1.

  • Common in association with genetic syndromes and other congenital malformations.

Etiology

Factors that interfere with normal ductal closure or increase ductal patency:

  • Prematurity (immature ductal smooth muscle, reduced oxygen sensitivity).

  • Maternal factors and exposures:

    • Rubella infection during the first trimester.

    • Alcohol consumption in pregnancy.

    • Phenytoin exposure (fetal hydantoin syndrome).

    • Chronic prostaglandin administration.

  • Neonatal conditions:

    • Respiratory distress syndrome, hypoxemia.

  • Chromosomal abnormalities:

    • Trisomy 21 (Down syndrome).

    • Other trisomies (e.g., Edwards, Patau).

Pathophysiology

  • In utero: the ductus arteriosus allows right-to-left shunting of blood from the pulmonary artery to the aorta, bypassing the nonfunctional fetal lungs. This patency is maintained by low oxygen tension and high circulating prostaglandins (mainly PGE₂).

  • Postnatally: with the first breaths, pulmonary vascular resistance (PVR) falls and systemic oxygen tension rises, normally leading to functional closure within hours and anatomical closure within weeks.

  • In PDA: failure of closure results in persistent left-to-right shunting (aorta → pulmonary artery), producing:

    • Pulmonary overcirculation → pulmonary vascular congestion.

    • RV and/or LV volume overload depending on shunt size.

    • Progressive cardiac dilation and failure if untreated.

  • Eisenmenger physiology may develop: chronic pulmonary hypertension reverses the shunt (right-to-left) and produces differential cyanosis (cyanotic lower extremities, pink upper extremities).

Clinical Features

General manifestations

  • Small PDA: often asymptomatic; physical examination may be normal.

  • Large PDA:

    • Infancy: failure to thrive, recurrent respiratory infections, feeding difficulties, tachypnea, diaphoresis.

    • Signs of heart failure (tachycardia, hepatomegaly, pulmonary edema).

    • Bounding pulses and wide pulse pressure due to diastolic runoff.

    • Heaving and displaced apical impulse (LV enlargement).

Auscultation

  • Small PDA: incidental murmur, or no murmur.

  • Classic finding in large PDA:

    • “Machinery murmur” — continuous, harsh murmur best heard in the left infraclavicular region; peaks around S2.

    • Thrill may be palpable in significant shunts.

    • Accentuated second heart sound if pulmonary hypertension develops.

Diagnostics

Echocardiography (first-line, confirmatory)

  • Color Doppler shows abnormal continuous flow from descending aorta to main pulmonary artery.

  • Allows assessment of shunt size, left atrial/ventricular dilation, and pulmonary artery pressures.

Electrocardiography (ECG)

  •  Small PDA: usually normal.

  • Large PDA:

    • Left atrial enlargement.

    • Left ventricular hypertrophy with left axis deviation.

Chest X-ray

  • Enlarged pulmonary artery and prominent aortic knob.

  • Pulmonary overcirculation with increased vascular markings.

  • Cardiomegaly in hemodynamically significant shunts.

Management

Pharmacological closure in premature infants

  • Indications:

    • Infants < 1 kg requiring mechanical ventilation.

    • Symptomatic PDA in infants > 1 kg (respiratory distress, CHF signs).

  • Contraindications:

    • Ductal-dependent congenital heart disease (e.g., hypoplastic left heart, transposition).

    • Persistent pulmonary hypertension of the newborn.

  • Agents: indomethacin or ibuprofen (inhibit prostaglandin synthesis and promote closure).

When ductal patency is needed

  • In ductal-dependent lesions, PGE₁ infusion is administered to keep the ductus open until definitive surgery or intervention.

Definitive closure in older infants and children

  • Indications:

    • Echocardiographic evidence of left atrial and/or LV enlargement.

    • Pulmonary artery systolic pressure < 50% systemic.

    • Pulmonary vascular resistance (PVR) < ⅓ systemic.

  • Methods:

    • Transcatheter device occlusion (preferred in many centers).

    • Surgical ligation (for unsuitable anatomy or failed catheter closure).

  • Contraindications:

    • Ductal-dependent lesions.

    • Severe pulmonary hypertension with right-to-left shunting (irreversible).

Complications

  • Congestive heart failure in infancy if untreated.

  • Infective endocarditis, especially in older children and adults with uncorrected PDA.

  • Progressive pulmonary hypertension leading to Eisenmenger syndrome.

  • Differential cyanosis (lower limbs cyanotic, upper limbs pink) once shunt reverses.

Comments

Post a Comment