Experiments and Simulations to Assess Exercise-Induced Pressure Drop Across Aortic Coarctations

Q: What is the clinical evidence from this study?

Population: Aortic coarctation (CoA) (n=5). Intervention: Fluid-structure interaction (FSI) simulations across rest and simulated exercise states vs. In vitro hybrid mock circulatory loop (HMCL) using 3D-printed compliant aortic phantoms. Primary outcome: Mean blood pressure gradient (ΔP) across the aortic coarctation between the ascending and descending aorta at rest and simulated exercise states (MD -1.6 mmHg (95% limits of agreement -3.7 to -0.5 mmHg); mean absolute error 1.6±1.1 mmHg).

Q: What does this research mean for the field?

Exercise-induced increases in cardiac output cause a nonlinear rise in blood pressure gradient across aortic coarctations that can be accurately modeled by fluid-structure interaction simulations with an error of 1.6±1.1 mmHg compared to hybrid mock circulatory loop experiments. Novelty: ClaimNovelty.METHODOLOGICAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

Priya J. Nair; Emanuele Perra; Doff B. McElhinney; Alison L. Marsden; Daniel B. Ennis; Seraina A. Dual

doi:10.1115/1.4068716

May 17, 2025Journal of Biomechanical EngineeringOpen Access

Experiments and Simulations to Assess Exercise-Induced Pressure Drop Across Aortic Coarctations

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Key result

Simulations track exercise-induced aortic coarctation pressure drops within ~1.6 mmHg of experimental mock loops.

MD -1.6 mmHg (95% limits of agreement -3.7 to -0.5 mmHg); mean absolute error 1.6±1.1 mmHg
n=5

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Why the study?

Invasive cardiac catheterization for measuring blood pressure gradient across an aortic coarctation requires anesthesia and does not capture the effects of daily activity or exercise, potentially underestimating functional disease burden.

Do fluid-structure interaction simulations and hybrid mock circulatory loop experiments accurately characterize patient-specific exercise-induced blood pressure drops across aortic coarctations?

Key Points

To evaluate exercise-induced blood pressure gradients across aortic coarctations using patient-specific physical mock loops and numerical fluid-structure interaction simulations.
Retrospective 4D-Flow MRI and cardiac catheterization data were collected from five patients with native or recurrent aortic coarctation (age 31 ± 16.8 yr, 4 males and 1 female).
Patient-specific compliant aorta phantoms were 3D-printed and coupled to a hybrid mock circulatory loop driven by a closed-loop lumped parameter network across flow rates from 0.75× to 2× resting cardiac output.
Matched three-dimensional fluid-structure interaction simulations were performed in SimVascular using dynamic inflow waveforms and three-element Windkessel boundary conditions.
Mean pressure drop across the aortic coarctation increased nonlinearly with rising cardiac output, displaying distinct progression patterns across individual patients.
Hybrid mock circulatory loop measurements and fluid-structure interaction simulations exhibited close agreement across cardiac output states, showing an error of 1.6±1.1 mmHg.

Structured PICO

Do fluid-structure interaction simulations and hybrid mock circulatory loop experiments accurately characterize patient-specific exercise-induced blood pressure drops across aortic coarctations?

P

Population

5 patients with native or recurrent aortic coarctation (mean age 31 years, 20% female) from a single US center with retrospective 4D-Flow MRI and invasive catheterization data used to create 3D-printed compliant aortic phantoms and fluid-structure interaction models.

I

Intervention

3D fluid-structure interaction (FSI) computational simulations in SimVascular (coupled momentum method, initialized with 0D models) and in vitro hybrid mock circulatory loop (HMCL) testing incorporating 3D-printed compliant aortic phantoms (Agilus30, Young's modulus 1.2 MPa) across simulated rest and exercise states (0.75x, 1.0x, 1.25x, 1.5x, and 2.0x cardiac output)

C

Comparator

Agreement comparison between 3D fluid-structure interaction (FSI) simulations and in vitro hybrid mock circulatory loop (HMCL) physical phantom measurements across rest and exercise hemodynamic states

O

Outcome

Mean trans-coarctation blood pressure drop (ΔP) between the ascending aorta (AAo) and descending aorta (DAo) over the cardiac cycle across rest and exercise cardiac output states, and agreement between HMCL and FSI measurementssurrogate

Main Result

Mean Difference: -1.6

Validated fluid-structure interaction simulations can noninvasively predict patient-specific, nonlinear exercise-induced pressure gradients across aortic coarctations with ~1.6 mmHg error compared to benchtop mock circulatory loops, overcoming the limitations of resting catheterization.

Limitations

Small sample size (N=5) limited to patients with both 4D-Flow MRI and invasive catheterization data
All 3D-printed aortic phantoms used the same material with a uniform Young's modulus (1.2 MPa), which may not match individual native vessel wall properties
Hardware limitations prevented achieving instantaneous flow rates >430 mL/s in the HMCL, requiring reporting of mean ΔP rather than peak systolic ΔP
One patient phantom (P-5) burst beyond 1.5x cardiac output, and high resting cardiac output in another (P-1) prevented achieving 1.5x and 2x cardiac output states
Small sample size (N=5) restricted to patients with both 4D-Flow MRI and invasive catheterization data
Uniform Young's modulus (1.2 MPa) across all 3D-printed phantoms rather than patient-specific native vessel wall stiffness
Hardware restrictions in the HMCL limited instantaneous peak flow rates to ≤430 mL/s, preventing peak systolic ΔP matching and requiring use of mean ΔP
Inability to complete all high-exercise states in all phantoms (P-5 phantom burst above 1.5x CO; P-1 had LPN instabilities at 1.5x and 2x CO due to high baseline CO)

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Implication

Enables noninvasive exercise gradient modeling in coarctation; leaves open prospective human validation before clinical adoption.

Abstract

Blood pressure gradient (ΔP) across an aortic coarctation (CoA) is an important measurement to diagnose CoA severity and guide treatment. While invasive cardiac catheterization is the clinical gold-standard for measuring ΔP, it requires anesthesia and does not capture the effects of daily activity or exercise, potentially underestimating the disease's functional burden. This study aimed to identify patients with functionally significant CoA by evaluating exercise-induced ΔP using a hybrid mock circulatory loop (HMCL). Patient-specific aorta geometries (N = 5) of patients with CoA were generated from 4D-Flow magnetic resonance imaging (MRI) scans, then three dimensional (3D)-printed to create compliant aortic phantoms. The phantoms were incorporated into an HMCL with flow and pressure waveforms tuned to patient-specific rest and exercise states. Matched fluid-structure interaction (FSI) simulations were performed using simvascular for comparison. Results showed that mean ΔP increased nonlinearly with cardiac output (CO), with trends differing between patients. HMCL and FSI simulations exhibited excellent agreement in trends of ΔP change with CO, with minimal error of 1.6±1.1 mmHg. This study emphasizes the need for assessing exercise CoA hemodynamics beyond resting ΔP measurements. Overall, HMCLs and FSI simulations enable assessment of patient-specific hemodynamic response to exercise unattainable in clinical practice, thereby facilitating a comprehensive noninvasive assessment of CoA severity. Further, the excellent agreement between HMCL and FSI results indicates that our validated FSI approach can be used independently to assess exercise CoA hemodynamics hereafter, eliminating the need for repeated complex HMCL experiments.

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Cite This Study

Nair et al. (2025) studied Aortic coarctation (CoA) (n=5). Fluid-structure interaction (FSI) simulations across rest and simulated exercise states vs. In vitro hybrid mock circulatory loop (HMCL) using 3D-printed compliant aortic phantoms was evaluated on Mean blood pressure gradient (ΔP) across the aortic coarctation between the ascending and descending aorta at rest and simulated exercise states (MD -1.6 mmHg (95% limits of agreement -3.7 to -0.5 mmHg); mean absolute error 1.6±1.1 mmHg). Fluid-structure interaction simulations and hybrid mock circulatory loop experiments showed nonlinear exercise-induced increases in aortic coarctation pressure drop with a mean error of 1.6±1.1 mmHg.

synapsesocial.com/papers/6a917e8c80800acc72340d52 https://doi.org/10.1115/1.4068716

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Experiments and Simulations to Assess Exercise-Induced Pressure Drop Across Aortic Coarctations

Figures

Key Points

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Experiments and Simulations to Assess Exercise-Induced Pressure Drop Across Aortic Coarctations

Figures

Key Points

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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