Screening for pda in neonates

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"patent ductus arteriosus" AND screening AND neonates

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PMID: 37899032

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PMID: 41749152

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PMID: 40870487

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PDA screening neonates pulse oximetry echocardiography criteria 2024 2025 guidelines

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https://publications.aap.org/pediatrics/article/155/5/e20250…

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Screening for PDA in Neonates

Background

Patent ductus arteriosus (PDA) is a failure of postnatal closure of the ductus arteriosus - the fetal vessel connecting the pulmonary artery to the descending aorta. At birth, rising oxygen tension triggers smooth muscle contraction and functional closure within 10-15 hours, followed by anatomic fibrosis (ligamentum arteriosum) over days to weeks.

Incidence: ~1 in 2,000 term births; rises dramatically with prematurity
40-60% of VLBW infants have a PDA; reaches 60-75% in neonates <28-30 weeks gestation
Female predominance (2:1 ratio)
Untreated isolated PDA carries ~30% mortality, primarily from CHF

- Harriet Lane Handbook, 23rd ed., p. 243; Schwartz's Principles of Surgery, 11th ed., p. 787

Why Screening Matters

A clinically silent or small PDA may still carry risks (infectious endarteritis ~0.45%/year after the second decade). A hemodynamically significant PDA (hs-PDA) in preterm infants causes:

Left-to-right shunting → left ventricular volume overload
Pulmonary over-circulation → respiratory distress, BPD risk
Diastolic "steal" → mesenteric/renal underperfusion, NEC risk
Intraventricular hemorrhage risk in extreme preterms

Screening Methods

1. Clinical Assessment

Signs suggestive of PDA:

Feature	Finding
Murmur	Continuous "machinery" murmur, grade 1-4/6, loudest at LUSB (left upper sternal border) / left infraclavicular area
Pulse	Wide pulse pressure; bounding/waterhammer pulses
Precordium	Hyperactive; left ventricular heave
Tachycardia/tachypnea	From increased sympathetic discharge
Cyanosis	Absent in uncomplicated left-to-right PDA; differential cyanosis (lower limbs more cyanosed than upper) if Eisenmenger reversal occurs

In neonates, the murmur is often only systolic on the first day of life (audible at upper left sternal border / left infraclavicular area) and becomes continuous as pulmonary vascular resistance falls. In very premature infants, the classic murmur may be absent even with large shunts - clinical signs alone are unreliable.

- Goldman-Cecil Medicine, p. 1064; Schwartz's, p. 788

2. Pulse Oximetry (CCHD Screening)

The AAP 2025 updated algorithm uses pre- and post-ductal SpO₂ to screen for critical congenital heart disease (CCHD):

Timing: At 24-48 hours of age (or just before discharge if <24 hours)

Sites:

Pre-ductal: Right hand (reflects aortic arch blood, before ductus joins)
Post-ductal: Either foot

Interpretation:

Result	Criteria
Pass	SpO₂ ≥95% in both sites AND difference ≤3%
Rescreen in 1 hr	SpO₂ 90-94% in either site, OR >3% difference
Fail (immediate echo)	SpO₂ <90% in either site, OR fails 3 consecutive screens

A passing pulse oximetry screen does NOT exclude PDA. Isolated left-to-right PDA (without right-to-left shunt) typically passes oximetry. The test is most useful for detecting ductal-dependent cyanotic lesions.

- AAP 2025 CCHD Screening Protocol; CDC CCHD screening page

3. Echocardiography - The Gold Standard

Echocardiography (2D + colour Doppler) is the definitive tool for PDA diagnosis and characterisation.

Echocardiogram showing PDA: parasternal short-axis view with colour Doppler jet in the PA from the descending aorta, and CW Doppler showing continuous diastole-to-systole flow

Fig. Parasternal short-axis view (left): colour Doppler jet (arrow) in the PA arising from the descending aorta (DA) in diastole. CW Doppler (right): characteristic continuous high-velocity flow from diastole through systole. (Textbook of Clinical Echocardiography)

Key echocardiographic criteria for hs-PDA:

Ductal diameter >1.5 mm (or >1.4-1.5 mm/kg in VLBW)
Left atrium:aortic root (LA:Ao) ratio >1.4-1.5 (indicates volume overload)
Antegrade diastolic flow reversal in descending aorta
Left-to-right or bidirectional ductal flow on colour Doppler
Diastolic ductal flow in the PA has sensitivity 96%, specificity 100% for PDA diagnosis
LV dilatation / reduced LV function

- Textbook of Clinical Echocardiography, p. 548

Targeted Neonatal Echocardiography (TnECHO)

A 2025 systematic review (PMID 40870487) of 11 studies (PRISMA, Feb 2025) found:

TnECHO implementation associated with a 49% reduction in PDA ligation rates
Improved diagnostic precision for shunt significance and myocardial function
Enables physiology-guided decisions, reducing unnecessary interventions
The 2024 ASE guidelines from the American Society of Echocardiography updated indications and training requirements for TnECHO/cPOCUS in the NICU

4. Biomarkers

BNP / NT-proBNP (serum or urinary):

Elevated in hs-PDA due to ventricular volume/pressure overload
A 2024 systematic review (PMID 37899032) found urinary NT-proBNP has modest sensitivity and specificity for hs-PDA; requires local validation before routine use
NT-proBNP levels >1800 pg/mL in preterm infants are often used as a threshold, though cutoffs vary by gestational age and postnatal age

5. Near-Infrared Spectroscopy (NIRS) - Emerging

A 2026 meta-analysis (PMID 41749152) of 9 studies found:

Cerebral rSO₂ (regional oxygen saturation) is significantly lower in PDA infants vs. controls (SMD -0.42, 95% CI -0.74 to -0.10)
Renal rSO₂ and peripheral SpO₂ did not show significant differences
Suggests cerebral NIRS may serve as a non-invasive bedside indicator for PDA, but AUC studies are still needed

6. Other Investigations

Test	Finding in PDA
Chest X-ray	Cardiomegaly, increased pulmonary vascular markings, pulmonary oedema in large shunts
ECG	Small-moderate PDA: normal or LVH; large PDA: BVH
Cardiac catheterization	Reserved only when pulmonary hypertension is suspected

Screening Strategy by Population

Term Neonates

Routine newborn examination (auscultation at 6-24 hours and again at discharge)
Pulse oximetry CCHD screen at 24-48 hours
Echo only if murmur persists, abnormal oximetry, or clinical concern

Preterm Neonates (<32 weeks or VLBW)

Routine clinical reassessment daily in NICU (murmur, bounding pulses, hyperdynamic precordium)
Echocardiography is the standard - many units perform a screening echo at 3-7 days of life in all infants <28 weeks gestation
Repeat echo if clinical deterioration, increasing FiO₂ requirement, or feeding intolerance
Consider urinary NT-proBNP or cerebral NIRS as adjuncts where echo is unavailable

Key Points Summary

Clinical signs are insensitive in very preterm infants - a large PDA can be silent on auscultation.
Pulse oximetry screens for CCHD broadly, not PDA specifically; a left-to-right PDA will usually pass.
Echocardiography with colour Doppler is the gold standard; diastolic PA jet has 96% sensitivity, 100% specificity.
TnECHO by trained neonatologists is now supported by ASE 2024 guidelines and reduces overtreatment.
Biomarkers (NT-proBNP) and cerebral NIRS are adjuncts, not replacements for echo.
Management after diagnosis: watchful waiting in asymptomatic, COX inhibitors (indomethacin/ibuprofen/acetaminophen) for hs-PDA in preterms, catheter-based or surgical closure in term infants or those refractory to medical therapy.

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