PDA Iowa score Calculator

Important: The Iowa PDA Score Calculator was updated on April 19, 2026 based on the version published in: 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 Mar;46(3):364-369. doi: 10.1038/s41372-025-02437-4. Epub 2025 Sep 20. PMID: 40975717; PMCID: PMC12628839.

In the literature—particularly in the foundational cohorts described by Rios et al. (2021) and the clinical treatment protocols outlined by Giesinger et al. (2023)—the Iowa PDA Score is utilized as a standardized, quantitative tool to define the significance of the transductal left to right volume shunt and guide their approach to early, targeted intervention in extremely preterm infants. Rather than relying solely on ductal diameter, the 14-point discrete scale integrates ductal size with physiological markers of pulmonary overcirculation (e.g., LA:Ao ratio, mitral E velocity, pulmonary vein D-wave) and systemic hypoperfusion (e.g., reversed diastolic flow in the descending aorta). Clinically, a total score of 6 or more is established as the critical threshold indicating a high-volume, hemodynamically significant shunt (hsPDA); in the Iowa protocols, reaching this threshold typically triggers early medical pharmacotherapy within the first 18 to 24 hours of life to prevent downstream morbidities. Conversely, a score of < signifies a low-volume, restrictive shunt where conservative or expectant management is appropriate, while intermediate scores (4–5) identify a transitional or moderate state that requires close, serial echocardiographic surveillance to monitor for progression or spontaneous closure.

Of note - there is no data published on the usability of this score beyond the early first days of life of these infants. The timing of use has been reported in : Bischoff, A.R., Dias Maia, P. & McNamara, P.J. Beyond diameter: redefining echocardiography criteria in trials of early PDA therapy. J Perinatol 46, 332–336 (2026). https://doi.org/10.1038/s41372-025-02523-7. It seems that the current PIVOTAL trial will be using the Iowa PDA score although the closures are happening later than the first week of life (see: NCT05547165).

References

Pulmonary vein D wave

Mitral E wave

In a large left-to-right patent ductus arteriosus (PDA), increased pulmonary venous return and left atrial (LA) volume overload significantly impact mitral inflow dynamics, particularly the E-wave (early passive filling phase of the left ventricle). During ventricular systole, the mitral valve remains closed, while continuous pulmonary venous return leads to progressive LA filling. In the presence of a large PDA, excess pulmonary blood flow results in elevated LA pressure, reducing the LV-LA pressure gradient needed for mitral valve opening. When the mitral valve opens, the E-wave velocity increases, reflecting a rapid "gush" of blood into the LV due to high preload  (high LA pressure). This augmented early diastolic filling can mimic restrictive physiology in severe cases, characterized by shortened IVRT, increased E/A ratio, and shortened deceleration time due to elevated LA pressures.

Other considerations:

• E/A Ratio: Often increased due to the disproportionately higher E-wave compared to A-wave. 

• Deceleration Time (DT): May be shortened due to elevated left atrial pressures, resulting in rapid equilibration of LA-LV pressures. The pattern of shortened IVRT and increased E-wave velocity is a hallmark of significant left heart volume overload, commonly seen in large left to right PDAs with significant shunt volume.

Isovolumetric relaxation time

With a large left-to-right patent ductus arteriosus (PDA), the increased pulmonary venous return and left atrial (LA) volume overload have notable effects on isovolumic relaxation time (IVRT). The IVRT (Isovolumic Relaxation Time) shortens due to increased left atrial pressure and higher left ventricular (LV) preload. Elevated left atrial pressure reduces the pressure gradient required for the LV to relax to below LA pressure, thereby shortening IVRT. The rapid diastolic filling from the increased pulmonary venous return contributes to early LV filling.

LA:Ao ratio

See more nuances approaches to LA:Ao in the Parasternal Short Axis (PSAX) section and in the Parasternal Long Axis (PLAX) section 

LV output - Calculator

For VTI/output, the Doppler is obtained usually just proximal to / just beneath the semilunar valve, so that the Doppler site matches the diameter used for the area calculation. For the RVOT/pulmonary VTI, the RVOT VTI is obtained by placing a 1–2 mm PW Doppler sample volume within the distal RVOT just beneath the pulmonary valve from the parasternal short-axis view. For the LVOT/aortic VTI, the PW sample volume should be positioned just proximal to the aortic valve so that the location of the velocity recording matches the LVOT diameter measurement. some neonatal references say “at the level of the annulus,” that is often shorthand for this same annular/subvalvar sampling region rather than meaning well into the great artery or directly through the leaflets. The key is that the diameter and VTI must come from the same anatomic level; otherwise stroke volume will be off. The neonatal ASE TNE update describes aortic VTI with the sample at the level of the aortic valve annulus, while pediatric quantification guidance emphasizes annular measurement and consistent outflow tract sampling for stroke volume calculations.

With a large left-to-right patent ductus arteriosus (PDA), left ventricular output (LVO) is typically increased due to the significant volume overload on the left heart. Here’s why:

1. Increased Pulmonary Blood Flow → Increased Pulmonary Venous Return

   • The left-to-right shunt directs a portion of the systemic output back into the pulmonary circulation, leading to excessive pulmonary venous return to the left atrium (LA).

   • This results in elevated left atrial pressures and increased preload for the left ventricle (LV).

   • When a large PDA is present, the blood splits after leaving the heart, creating a "steal" effect: 

     1. The LV pumps a massive amount (LVO): This blood enters the aorta.

     2. The Split: At the ductus, the blood splits. Some goes to the body (Qs), and a large portion "leaks" through the PDA into the lungs. The lungs now contain the blood from the RV PLUS the leak from the PDA. All of this combined volume (Qp) travels through the lungs and heads straight back to the LV.

2. Increased LV Stroke Volume and Cardiac Output

   • Due to the increased preload, the LV must accommodate a higher volume of blood, leading to increased stroke volume and, consequently, an elevated left ventricular output (LVO).

   • The Frank-Starling mechanism contributes to increased contractility, maintaining a high cardiac output.

3. In the context of large left to right PDA: LVO = Qp (and RVO = Qs). This is based on where the blood returns from. In a steady state, the amount of blood a ventricle pumps out must equal the amount of blood it receives. Pulmonary Flow (Qp): This is the total volume of blood that passes through the lungs. Every drop of blood that passes through the lungs eventually drains into the pulmonary veins, enters the left atrium, and fills the left ventricle. Therefore, the Left Ventricular Output (LVO) is exactly equal to flow going through the mitral valve (unless there is a significant left to right inter-atrial shunt) and must be equal to the total pulmonary blood flow (Qp). Systemic Flow (Qs): This is the total volume of blood that reaches the body's tissues. Every drop of blood that services the body (brain, gut, kidneys) eventually returns via the Vena Cava (and the coronary sinus) into the right atrium and fills the right ventricle. Therefore, the Right Ventricular Output (RVO) is exactly equal to the flow crossing the tricuspid valve, which is equal to the systemic blood flow (Qs). Qs is the blood flow feeding the coronary arteries and the systemic vessels.

Key Echocardiographic Findings:

• Increased LVO (measured via LVOT VTI and diameter)

• Elevated E-wave velocity due to high preload

• Shortened IVRT and deceleration time

• Increased left atrial and LV dimensions (LA dilation, LVEDD increase)

RV output

Doppler flow reversal

Diameter of the PDA

For B-mode assessment of PDA size, the duct should be imaged in the view that best elongates its course—most commonly a high left parasternal “ductal” view and, when helpful, a sagittal suprasternal view—and the diameter should be measured on 2D grayscale, not by color alone, at the site of maximal constriction, which is usually the narrowest pulmonary end just before entry into the main/left pulmonary artery (may depend based on the PDA conformation); color Doppler can help localize the duct but may overestimate caliber if used for the actual measurement. Because the duct is dynamic over the cardiac cycle, it is good practice to review the cineloop frame by frame and use the ECG to standardize timing, aiming to measure the smallest true internal diameter consistently from study to study; in practical neonatal scanning, this is often taken at end-diastole or just before the QRS, since the duct may appear more stretched during systolic ejection, but the most important principle is reproducibility and documenting the narrowest 2D luminal diameter rather than a larger systolic frame.