Patent Ductus Arteriosus (PDA)

The ductus arteriosus (DA) is a fetal blood vessel connecting the left pulmonary artery to the aorta. The DA allows blood to bypass pulmonary circulation. After birth, the DA remains open for up to 72 hours and then constricts and involutes, becoming the ligamentum arteriosum. Failure of this process to occur results in patent ductus arteriosus (PDA), a condition that causes up to 10% of congenital heart defects. Patent ductus arteriosus is twice as common in girls (especially premature infants) and causes a continuous machinery-like murmur on clinical examination. Patent ductus arteriosus may be associated with other cardiac defects; an echocardiogram can confirm the diagnosis. Treatment aims at closure of the remnant structure either through pharmacological or surgical means.

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The ductus arteriosus (DA) is a fetal blood vessel connecting the left pulmonary artery to the aorta, bypassing the pulmonary circulation. Failure of the vessel to close and involute within 72 hours of birth results in a condition called patent ductus arteriosus (PDA).


  • Population statistics:
    • 5%–10% of all congenital heart defects (CHDs)
    • Incidence: 2 in 10,000 live term births 
    • Male:female ratio is 1:2
  • Risk factors:
    • Prematurity
    • Hypoxia:
      • History of perinatal asphyxia
      • Birth at high altitude
    • Maternal factors:
      • Rubella infection
      • Phenytoin use
    • Genetic predisposition:
      • Positive family history of PDA
      • DiGeorge syndrome
      • Cri-du-chat syndrome
      • Noonan syndrome
      • CHARGE syndrome
Ductus arteriosus

The DA:
The DA is a fetal blood vessel connecting the aorta (usually at the arch) to the left pulmonary artery. When this vessel persists after birth, it is termed PDA.

Image: “Blausen 0707 PatentDuctusArteriosus” by BruceBlaus. License: CC BY 3.0

Embryology and Pathophysiology


  • Fetal circulation:
    • In utero, lungs are fluid filled and their vasculature is vasoconstricted (oxygen comes from maternal circulation in the placenta).
    • DA shunts blood from the right (R) to left (L) in the heart, bypassing high-pressure pulmonary circulation.
  • After birth, DA closure is triggered by:
    • Increased systemic oxygen (O2) concentration → decreased pulmonary blood pressure
    • Reduced prostaglandin E2 (PGE2) levels due to separation from placenta 
  • Closure starts at the pulmonary end and finishes at the aortic end:
    • Functional closure by 15 hours of life
    • Anatomical closure by 3rd week of life
  • Histological changes turn ductus into ligamentum arteriosum.
  • Failure or disruption of transition from fetal to extrauterine life results in the persistent patency of the DA.


  • In PDA, the shunt reverses to L-R as pulmonary vascular resistance falls.
    • Increased end-diastolic volume in left atrium and left ventricle → volume overload → dilation → heart failure
    • Increased pressure in pulmonary artery → pulmonary hypertension → respiratory failure
  • Eisenmenger’s syndrome:
    • Pulmonary hypertension → right ventricle hypertrophy→  increasing right-sided pressure
    • Shunt reverses to R-L in the prenatal period.

Clinical Presentation

The severity of symptoms depends primarily on the degree of L-R shunt, which is dictated by size and length of the defect.

Table: Classification of PDA based on degree of shunt
Degree of shuntClinical presentationPhysical examination
Small shunt
  • May be asymptomatic
  • Incidental finding of murmur during routine check-up
  • Continuous machinery murmur (Gibson’s murmur)
  • Murmur peaks at S2.
  • Located in left infraclavicular region
Moderate shunt
  • Palpitations
  • Exercise intolerance
  • Wide pulse pressure
  • Bounding pulse
  • Continuous machinery murmur (Gibson’s murmur)
  • Displaced apex beat
Large shuntInfant:
  • Poor feeding
  • Labored breathing
  • Easy fatigability
  • Shortness of breath
  • Blue discoloration of lips
  • Increased abdominal girth
  • Failure to thrive
  • Continuous machinery murmur (Gibson’s murmur)
  • Respiratory distress:
    • Tachypnea
    • Apnea
  • Heart failure:
    • Tachycardia
    • Displaced apical impulse
    • S3 heart sound
  • Pulmonary hypertension:
    • Loud S2
    • Diastolic rumble
  • If Eisenmenger’s has occurred:
    • Absent murmur
    • Cyanosis in lower limbs
    • Clubbing
Cardiac murmurs after correction

Phonocardiograms of abnormal heart sounds caused by the following cardiac defects:
aortic regurgitation, mitral valve prolapse, mitral stenosis (MS), aortic stenosis (AS), tricuspid regurgitation, hypertrophic obstructive cardiomyopathy (HOCM), atrial septal defect (ASD), ventricular septal defect (VSD), and patent ductus arteriosus (PDA)

Image by Lecturio.


  • Clinical findings are confirmed by echocardiogram.
  • Echocardiography:
    •  Evaluates:
      • Presence of defect
      • Hemodynamics of left atrium and ventricle
      • Doppler → degree of shunt and pulmonary arterial pressure
    • All preterm infants should be screened.
  • Chest X-ray:
    • Normal in small shunts
    • Large shunts may show:
      • Increased pulmonary vascularization
      • Cardiomegaly
  • Electrocardiogram (ECG):
    • Biventricular or right ventricular hypertrophy in advanced cases
Patent ductus arteriosus in Kawasaki disease

Echocardiogram showing PDA:
An echocardiogram depicting PDA with a small shunt (white arrow) found incidentally in a patient with Kawasaki disease

Image: “Spontaneous closure of patent ductus arteriosus after an episode of Kawasaki disease: a case report” by Lin MC, Fu YC, Jan SL. License: CC BY 2.0, edited by Lecturio.

Management, Complications, and Prognosis


  • Observation indicated in smaller defects with no physiological changes:
    • Requires close follow-up
  • Closure indicated in:
    • Moderate and large PDA
    • Small PDA with audible murmur
    • Presence of pulmonary hypertension
    • Heart failure
    • Respiratory compromise
    • History of infective endocarditis
  • Medical therapy (pharmacological closure):
    • Decrease prostaglandin synthesis:
      • Indomethacin
      • Ibuprofen
    • Follow-up after 48 hours with echocardiography to ensure closure
    • Contraindicated in:
      • Cardiac defects where DA required to maintain perfusion for systemic circulation
      • Active bleeding
      • Suspicious or diagnosed necrotizing enterocolitis
      • Impaired renal function
  • Surgical therapy:
    • Indicated when medical therapy fails and/or infant > 6 kg
    • Includes percutaneous closure or surgical ligation


  • Pulmonary hypertension
  • Bronchopulmonary dysplasia
  • Congestive heart failure
  • Infective endocarditis
  • Post-surgery → paralysis of recurrent laryngeal nerve and stridor


  • Spontaneous closure in up to 75% of infants if < 3 months of age
  • Isolated PDA has an excellent prognosis (especially small defects).

Differential Diagnosis

Continuous murmur of PDA should be differentiated from:

  • Venous hum: benign, common murmur secondary to forces hitting venous walls; heard in children. A continuous murmur best heard on the right side and changes with position (unlike PDA). An echocardiogram is done to confirm no pathology.
  • Coronary artery fistula: congenital vascular abnormality whereby the coronary artery drains directly into chambers of heart without a capillary bed. Presentation includes a continuous murmur in the lower pericardium. An echocardiogram with Doppler will show direct drainage into the chambers.
  • Aortic regurgitation: a defect of the aortic valve wherein the leaflets do not oppose perfectly, allowing blood to backflow during diastole. Patients may present with a continuous murmur and bounding pulses. Aortic regurgitation is usually seen in older patients. An echocardiogram can diagnose and quantify the severity of valvular defect.


  1. Thomas D. and Anne K. (2020). Clinical manifestations and diagnosis of patent ductus arteriosus in term infants, children, and adults. UpToDate. Retrieved January 09, 2021, from
  2. Bernstein, D. (2020). General principles of treatment of congenital heart disease. In R. M. Kliegman MD, J. W. St Geme MD, N. J. Blum MD, Shah, Samir S., MD, MSCE, Tasker, Robert C., MBBS, MD & Wilson, Karen M., MD, MPH (Eds.), Nelson textbook of pediatrics (pp. 242–2436.e1) doi: Retrieved January 31, 2021, from!/content/3-s2.0-B9780323529501004612
  3. Benitz, W. E., & Bhombal, S. (2020). Patent ductus arteriosus. In Martin, Richard J., MBBS, FRACP, Fanaroff, Avroy A., MD, FRCPE, FRCPCH & Walsh, Michele C., MD, MSE (Eds.), Fanaroff and martin’s neonatal-perinatal medicine (pp. 1334–1341) doi: Retrieved January 31, 2021, from!/content/3-s2.0-B9780323567114000742
  4. Gillam-Krakauer, M., & Reese, J. (2018). Diagnosis and Management of Patent Ductus Arteriosus. NeoReviews, 19(7), e394–e402. DOI:10.1542/neo.19-7-e394. Retrieved January 31, 2021, from

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