PDA: Echo Assessment

Name: Echo: PDA Assessment · HeartCalc
Creator: Piyawat Arichai, MD, FAAP

Preterm infants: a suggested definition, shunt-size markers and scores, and what to measure

Suggested hsPDA definition

Needs	Criteria	Source
Echo: ≥1 of 4	Minimum diameter >1.5 mm · unrestrictive left-to-right flow, Vmax <2 m/s · left volume overload (≥moderate LA or LV enlargement) · decreased, absent or reversed end-diastolic flow in the abdominal descending aorta	AAP 2025, Table 1
and clinical: ≥2 of 4	High CPAP/NIMV with high FiO₂, or moderate–high ventilator settings · hypotension needing a vasopressor · persistent oliguria or renal dysfunction · abdominal distension, feeding intolerance, poor growth despite optimized nutrition, or prior NEC	AAP 2025, Table 1

Markers by shunt size

Preterm infants, mostly the first days of life. Consensus compiled from cited studies, not validated (NPE 2018, Table 2).
Marker	Small	Moderate	Large
Diameter (mm)	<1.5	1.5–2.0	>2.0
Diameter : LPAFirst 96 h	<0.5	0.5–1	>1
Diameter / weight			≥1.4 mm/kg
Peak velocity, Vmax (m/s)First 72 h	>2	1.5–2.0	<1.5
Systolic : diastolic velocityMisleading with chronic high-volume shunts	<2	2–4	>4
LA:AoAn atrial shunt can lower it	<1.5	1.5–2.0	>2.0
LV output (mL/kg/min)Limited use during transition	<200	200–300	>300
LPA end-diastolic velocity (m/s)	<0.2	0.2–0.5	>0.5
Pulmonary vein D wave (m/s)	<0.3	0.3–0.5	>0.5
IVRT (ms)	>40	30–40	<30
Mitral E/A	<1	1	>1
Descending aorta, diastolic flow	Forward	Absent	Reversed
Celiac, diastolic flow	Forward	Absent	Reversed
MCA, diastolic flow	Forward	Forward	Absent or reversed

How to measure

Diameter: narrowest internal diameter, usually at the pulmonary end, high left parasternal (ductal) view. 2D (El-Khuffash 2015, de Freitas Martins 2018) and colour Doppler (Groves 2008) may not agree: do not carry cut-offs across methods. Interobserver concordance 0.85 (LPA diameter 0.62, which weakens the diameter:LPA ratio). Boundaries differ: AAP uses >1.5 mm, Kluckow ≥1.5 mm, and NPE counts 1.5 mm as moderate.
Direction and Vmax: colour, then pulsed Doppler at the pulmonary end; continuous wave if it aliases. A right-to-left jet is blue and easy to mistake for pulmonary artery or arch flow.
LA:Ao: parasternal long-axis M-mode at the aortic valve. ASE times it at end-diastole, the Iowa group at end-systole. The least reproducible marker (concordance 0.65; de Freitas Martins 2018, Table II).
LV output: πr² × VTI × heart rate ÷ weight; aortic annulus hinge to hinge (parasternal long axis), VTI from the apical 5-chamber view, no angle correction. The most reproducible marker (0.97). ASE gives a normal of 150–300 mL/kg/min with no age or gestation, which overlaps the NPE moderate band.
Post-ductal diastolic flow: pulsed Doppler in the descending aorta at the diaphragm from the suprasternal view. "Normal" is disputed: ASE calls absent diastolic flow normal; NPE 2018 grades it moderate.
LPA: pulsed Doppler in the proximal LPA. ASE calls a diastolic velocity <0.3 m/s normal; NPE counts 0.2–0.5 m/s as moderate, and El Hajjar found ≥0.20 m/s end-diastolic in large shunts.

Single-marker studies

Marker	Finding	Source
Diameter, early	≥1.5 mm at mean 19 h predicted later symptomatic PDA: sensitivity 81%, specificity 85% (116 ventilated infants <1500 g)	Kluckow 1995 abstract
LA:Ao	≥1.5 for a wide-open duct: sensitivity 79%, specificity 95% (56 infants <1500 g). Unreliable on day 1.	Iyer 1994 abstract
Several	Against LV output / SVC flow ≥4: diameter ≥1.4 mm/kg, LA:Ao ≥1.4, LPA mean velocity ≥0.42 m/s or end-diastolic ≥0.20 m/s, each >90% sensitive and specific (n = 23, 24–30 weeks, <48 h)	El Hajjar 2005 abstract
Flow pattern	Pulsatile pattern in the first 4 days: sensitivity 93.5%, specificity 100% for later clinically significant PDA (growing pattern 64.5% / 81.1%; 68 ventilated infants <1500 g)	Su 1997 abstract
Aortic diastolic reversal	In 34–48% of above-median ducts, first 48 h (<31 weeks). With vs without reversal at 24 h, medians: LV output 398 vs 312 mL/kg/min, descending aorta flow 107 vs 165 mL/kg/min; SVC flow unchanged	Groves 2008, text and Table 2
LA volume index	<30 weeks, biplane, mL/kg, mean (SD): day 3 no PDA (or <1.0 mm) 0.88 (0.23) vs PDA >1.5 mm at both scans 1.25 (0.37); week 4 1.13 (0.21) vs 1.75 (0.51). Group means, 16 per group, one centre; no cut-off proposed.	de Waal 2018, Table 3

Scores and staging

Score	What it is	Source
El-Khuffash	<29 weeks, day-2 scan (median 43 h). GA (wk) × −1.304 + diameter (mm) × 0.781 + LV output (mL/kg/min) × 0.008 + Vmax (m/s) × −1.065 + LV a′ (cm/s) × −0.470 + 41. ≥5: high risk of chronic lung disease (oxygen at 36 weeks) or death before discharge; AUC 0.92 (n = 141). Not validated in another cohort. Calculator Experimental	El-Khuffash 2015
Iowa	Current version: 7 items, 0–2 points each (diastolic reversal scores 0 or 2): mitral E, IVRT, pulmonary vein D, LA:Ao, LV:RV output, diastolic reversal (aorta, celiac or MCA), diameter/weight. <6: low-volume shunt. The original Rios version uses LV output bands and adds diameter/weight unbanded (≥6 presumed significant). A volume surrogate; not validated against outcomes. Calculator Experimental	Brandt 2026, Table 1; Rios 2021
McNamara staging	Clinical C1–C4 plus echo E1–E4. E4 (large): diameter >3.0 mm, LA:Ao >2:1, reversed end-diastolic flow in SMA, MCA or renal artery. Proposed, not validated.	McNamara 2007, Table 1

Term infants and older children

Group	What is known	Source
Term	Functionally closed in 90% by 48 h, nearly all by 96 h	AAP 2025
Preterm after discharge	Of those discharged with a PDA, 50% close by 9 months, 80% by 2 years	AAP 2025
Child	No echo grading in these sources; do not apply preterm cut-offs	—

Key points

No validated definition of a hemodynamically significant PDA. AAP 2025 suggests ≥2 of 4 clinical criteria and ≥1 of 4 echo criteria; it endorses no score.
Look past the diameter: the shunt (size, direction, flow pattern), pulmonary overcirculation (LA:Ao, LV output, branch PA diastolic flow) and systemic hypoperfusion (post-ductal diastolic flow).
First study: exclude structural and duct-dependent heart disease before anyone treats the duct.
Right-to-left, or bidirectional with right-to-left >30% of the cycle: think pulmonary hypertension or a duct-dependent circulation.
Preterm data only. These sources give no echo grading for older infants or children.

Why

AAP 2025: a precise definition of hsPDA "remains elusive"; echo is critical for diagnosis and for judging response to treatment, read alongside gestational and postnatal age.
ASE 2024 TNE: every neonate with a suspected PDA, or born <28 weeks, should have a first study complete enough to exclude major CHD; screening within 72 h may be considered <28 weeks; no consensus on whether or when to treat; judge significance on several parameters.
In established shunts (day 7–30), diameter explained at most 24% of the variance in any shunt marker (de Freitas Martins 2018), and alone predicted chronic lung disease or death with AUC 0.59 (El-Khuffash 2015).
Right-to-left flow for >30% of the cycle may be pathological: look for a duct-dependent lesion or raised pulmonary pressure, both contraindications to medical closure (NPE 2018).

Sources and how this page was checked

Guidance (full text read)

Ambalavanan N, Aucott SW, Salavitabar A, Levy VY; American Academy of Pediatrics Committee on Fetus and Newborn and Section on Cardiology and Cardiac Surgery. Patent ductus arteriosus in preterm infants. Pediatrics 2025;155(5):e2025071425. doi:10.1542/peds.2025-071425. Clinical report; Table 1 is a suggested definition.
McNamara PJ, Jain A, El-Khuffash A, et al. Guidelines and recommendations for targeted neonatal echocardiography and cardiac point-of-care ultrasound in the NICU: an update from the ASE. J Am Soc Echocardiogr 2024;37:171-215. doi:10.1016/j.echo.2023.11.016 (corrected version).
van Laere D, van Overmeire B, Gupta S, et al. Application of NPE in the assessment of a patent ductus arteriosus. Pediatr Res 2018;84(Suppl 1):46-56. doi:10.1038/s41390-018-0077-x.
McNamara PJ, Sehgal A. Towards rational management of the patent ductus arteriosus: the need for disease staging. Arch Dis Child Fetal Neonatal Ed 2007;92:F424-F427. doi:10.1136/adc.2007.118117.

Studies

El-Khuffash A, James AT, Corcoran JD, et al. A patent ductus arteriosus severity score predicts chronic lung disease or death before discharge. J Pediatr 2015;167:1354-1361.e2. doi:10.1016/j.jpeds.2015.09.028 (full text; formula and Table III).
Brandt C, Mat HD, Bischoff AR, McNamara PJ, Rios DR. Association of low shunt burden from PDA and adverse outcomes in premature infants. J Perinatol 2026;46:364-369. doi:10.1038/s41372-025-02437-4 (full text; current Iowa score, Table 1).
Rios DR, Martins FF, El-Khuffash A, et al. Early role of the atrial-level communication in premature infants with patent ductus arteriosus. J Am Soc Echocardiogr 2021;34:423-432.e1. doi:10.1016/j.echo.2020.11.008 (full text; original Iowa score).
de Freitas Martins F, Ibarra Rios D, Resende MHF, et al. Relationship of patent ductus arteriosus size to echocardiographic markers of shunt volume. J Pediatr 2018;202:50-55.e3. doi:10.1016/j.jpeds.2018.06.045 (full text).
Groves AM, Kuschel CA, Knight DB, Skinner JR. Does retrograde diastolic flow in the descending aorta signify impaired systemic perfusion in preterm infants? Pediatr Res 2008;63:89-94. doi:10.1203/PDR.0b013e31815b4830 (full text).
de Waal K, Phad N, Boyle A. Left atrium function and deformation in very preterm infants with and without volume load. Echocardiography 2018;35:1818-1826. doi:10.1111/echo.14140 (full text).
Kluckow M, Evans N. Early echocardiographic prediction of symptomatic patent ductus arteriosus in preterm infants undergoing mechanical ventilation. J Pediatr 1995;127:774-779. doi:10.1016/S0022-3476(95)70172-9 (abstract).
Iyer P, Evans N. Re-evaluation of the left atrial to aortic root ratio as a marker of patent ductus arteriosus. Arch Dis Child Fetal Neonatal Ed 1994;70:F112-F117. doi:10.1136/fn.70.2.f112 (abstract).
El Hajjar M, Vaksmann G, Rakza T, Kongolo G, Storme L. Severity of the ductal shunt: a comparison of different markers. Arch Dis Child Fetal Neonatal Ed 2005;90:F419-F422. doi:10.1136/adc.2003.027698 (abstract).
Su BH, Watanabe T, Shimizu M, Yanagisawa M. Echocardiographic assessment of patent ductus arteriosus shunt flow pattern in premature infants. Arch Dis Child Fetal Neonatal Ed 1997;77:F36-F40. doi:10.1136/fn.77.1.f36 (abstract).

How it was checked

Sources marked full text were read in full (October 2026; the ASE guideline in its PDA sections). Studies marked abstract are quoted from the authors' abstracts.
Wording is condensed; numbers are as printed in the table named in each row.
Where sources disagree, the page says so: the NPE 2018 velocity unit; "normal" post-ductal diastolic flow; LA:Ao timing; the El-Khuffash accuracy figures; and the McNamara staging IVRT bands, which run opposite to later sources and are left out.
Not reproduced: the velocity criteria of the Su 1997 flow patterns (full text not read) and any external validation of the El-Khuffash or Iowa scores (none found).