⚡ electrical engineering

Effects of Plaque Morphology and Vascular Curvature on Rupture Risk in Coronary Atherosclerosis: A Parametric Computational Fluid Dynamics Study

This parametric computational fluid dynamics study demonstrates that the interaction between plaque morphology (specifically eccentricity and skewness) and vascular curvature significantly influences wall shear stress and its gradient, thereby critically affecting coronary plaque rupture risk.

Original authors: Jian Huang, Claire Huang

Published 2026-10-23

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CC BY 4.0

Original authors: Jian Huang, Claire Huang

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

The human heart is a relentless pump, but the arteries that carry its lifeblood are not passive pipes. Over time, fatty deposits known as plaques can build up on the inner walls of these vessels, narrowing the channel and stiffening the tissue. This condition, called atherosclerosis, is the primary driver of heart attacks. When a plaque suddenly bursts, it triggers a clot that can block blood flow entirely, leading to a catastrophic event. For decades, doctors have understood that the physical forces exerted by flowing blood play a crucial role in this process. Specifically, the friction blood creates as it rubs against the vessel wall, and the way that friction changes from one spot to the next, can either stabilize a plaque or push it toward rupture. However, measuring these invisible forces inside a living person is incredibly difficult, leaving researchers to rely on computer models to visualize how blood moves through the complex, winding tunnels of the coronary system.

In a recent study, researchers Jian Huang and Claire Huang turned to a powerful simulation tool to untangle the specific geometric factors that make a plaque dangerous. They constructed a series of idealized computer models of coronary arteries, introducing artificial plaques with varying shapes and positions to see how the blood flow reacted. The team focused on four key variables: how much the plaque narrowed the artery, how off-center the plaque was, whether the plaque was shifted toward the start or the end of the narrowed section, and how sharply the artery itself curved. By running thousands of simulations with these different combinations, they mapped out exactly how these physical shapes altered the stress on the vessel walls.

The results revealed that the shape of the plaque and the curve of the artery do not act in isolation; they interact in ways that can either calm the flow or create a perfect storm of stress. When the plaque was centered within the artery, the relationship was straightforward: the sharper the curve of the vessel, the higher the stress on the wall. This stress increased in a steady, predictable line as the angle of the curve grew larger, regardless of whether the artery bent to the left or the right. However, the story changed completely when the plaque was off-center. In these cases, the artery's curvature did not simply add stress; it created a complex, uneven response where the direction of the bend mattered immensely.

The researchers found that the most dangerous combination occurred when an off-center plaque was also shifted toward the upstream side of the vessel, and the artery curved sharply in a specific direction. This particular arrangement generated the highest levels of stress and the steepest changes in that stress, conditions known to weaken the plaque's protective cap. Conversely, they discovered a surprising "safe zone" for off-center plaques. When the artery curved at a specific angle of negative fifteen degrees, the stress on the wall actually dropped to its lowest point, even though the plaque was still present. This suggests that the curve of the vessel can sometimes shield a vulnerable plaque by redirecting the flow away from the most sensitive areas, effectively canceling out some of the destabilizing forces.

These findings highlight that assessing the risk of a heart attack requires looking beyond just the size of the blockage. A plaque that looks moderately severe on a scan might be far more dangerous if it is positioned off-center in a sharply curving artery, while a similarly sized plaque in a different geometric configuration might be relatively stable. The study confirms that the three-dimensional dance between the shape of the plaque and the path of the vessel dictates the local forces that determine stability. While these results come from computer simulations rather than direct measurements in patients, they provide a clear framework for understanding why some plaques rupture and others do not. By accounting for these geometric details, future tools could help doctors better predict which patients are at risk, moving beyond simple measurements of blockage to a more nuanced understanding of the physical environment inside the heart's own plumbing.

Technical Summary: Effects of Plaque Morphology and Vascular Curvature on Rupture Risk in Coronary Atherosclerosis

Problem Statement
Plaque rupture is the primary mechanism underlying acute myocardial infarction, accounting for approximately 60–75% of such events. While hemodynamic factors, specifically wall shear stress (WSS) and wall shear stress gradient (WSSG), are known to influence plaque progression and instability, isolating the specific contributions of geometric variables remains challenging. Previous studies have utilized patient-specific imaging, which complicates the derivation of generalized relationships due to the confounding effects of individual anatomical variations. Furthermore, existing parametric studies have often overlooked the combined effects of vascular curvature and percent area stenosis (PAS) alongside plaque morphology. This study addresses the need to systematically quantify how vascular curvature interacts with specific plaque morphological features (eccentricity and longitudinal skewness) to alter local hemodynamics and rupture risk.

Methodology
The authors employed a parametric Computational Fluid Dynamics (CFD) approach using OpenFOAM to simulate hemodynamics in idealized, non-bifurcated coronary artery geometries.

Geometry Generation: A generic vessel model (3 mm diameter, 35 mm length) was constructed containing atherosclerotic plaques. The geometry was defined by four key parameters: percent area stenosis (PAS), plaque eccentricity, plaque longitudinal skewness, and vascular curvature angle ( $\theta$ ).
Governing Equations: The incompressible Navier-Stokes equations were solved using a non-Newtonian blood viscosity model (Bird-Carreau model) to account for shear-thinning behavior.
Boundary Conditions: A pulsatile inflow velocity profile (based on the left anterior descending artery) was applied at the inlet. A three-element Windkessel (RCR) model was used at the outlet to simulate downstream vascular resistance and compliance.
Simulation Protocol: Three consecutive cardiac cycles were simulated to ensure flow field periodicity, with data from the third cycle used for analysis.
Parametric Scope: The study systematically varied PAS (up to 80%), eccentricity (0 to 0.2), longitudinal skewness ( $x$ from -0.2 to 0.2), and vascular curvature ( $\theta$ from -45° to +45°).

Key Results
The study yielded distinct findings regarding the individual and interactive effects of the geometric parameters on WSS and WSSG:

Percent Area Stenosis (PAS): Both WSS and WSSG exhibited a nonlinear increase with increasing PAS. However, the relationship between maximum WSS and maximum WSSG remained approximately linear across the tested range.
Plaque Eccentricity: WSS and WSSG increased moderately and approximately linearly with increasing eccentricity.
Longitudinal Skewness: This parameter demonstrated a pronounced effect. Proximally skewed plaques ( $x < 0$ ) generated significantly higher WSS and WSSG compared to distally skewed plaques. The effect of skewness plateaued for values beyond $|x| > 0.2$ .
Vascular Curvature (Concentric Plaques): For concentric plaques, WSS and WSSG increased approximately linearly with the magnitude of the curvature angle. Positive and negative curvature angles of equal magnitude produced symmetric responses.
Vascular Curvature (Eccentric Plaques): In the presence of eccentricity, the response to curvature became asymmetric and non-monotonic.
- For an eccentricity of 0.2, the lowest peak WSS and WSSG occurred at a curvature angle of -15°, rather than at 0°.
- Positive curvature angles produced substantially higher WSS and WSSG than negative angles of the same magnitude.
- The combination of proximally skewed eccentric plaques with large positive curvature angles resulted in the highest hemodynamic stress values.

Significance and Claims
The paper claims that plaque morphology and vascular geometry interact strongly to influence local coronary hemodynamics. The study demonstrates that assessing rupture risk based solely on stenosis severity or isolated geometric factors is insufficient. Specifically, the interaction between plaque eccentricity/skewness and vascular curvature can lead to markedly different hemodynamic environments, with certain combinations (e.g., proximally skewed eccentric plaques with positive curvature) creating conditions highly conducive to rupture.

The authors posit that their systematic parametric framework provides a foundation for developing comprehensive CFD databases. They suggest that such data could eventually support the creation of machine-learning models for the rapid, cost-effective estimation of plaque-related hemodynamic risk in patient-specific applications, thereby offering a potential additional tool for clinical assessment and treatment planning. The study emphasizes the necessity of accounting for both plaque morphology and vascular geometry when evaluating conditions associated with plaque vulnerability.

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