Abstract
Introduction: Cyclic plaque structural stress has been hypothesized as a mechanism for plaque fatigue and eventually plaque rupture. A novel approach to derive cyclic plaque stress in vivo from optical coherence tomography (OCT) is hereby developed.Materials and Methods: All intermediate lesions from a previous OCT study were enrolled. OCT cross-sections at representative positions within each lesion were selected for plaque stress analysis. Detailed plaque morphology, including plaque composition, lumen and internal elastic lamina contours, were automatically delineated. OCT-derived vessel and plaque morphology were included in a 2-dimensional finite element analysis, loaded with patient-specific intracoronary pressure tracing data, to calculate the changes in plaque structural stress (ΔPSS) on vessel wall over the cardiac cycle.Results: A total of 50 lesions from 41 vessels were analyzed. A significant ΔPSS gradient was observed across the plaque, being maximal at the proximal shoulder (45.7 [32.3, 78.6] kPa), intermediate at minimal lumen area (MLA) (39.0 [30.8, 69.1] kPa) and minimal at the distal shoulder (35.1 [28.2, 72.3] kPa; p = 0.046). The presence of lipidic plaques were observed in 82% of the diseased segments. Larger relative lumen deformation and ΔPSS were observed in diseased segments, compared with normal segments (percent diameter change: 8.2 ± 4.2% vs. 6.3 ± 2.3%, p = 0.04; ΔPSS: 59.3 ± 48.2 kPa vs. 27.5 ± 8.2 kPa, p < 0.001). ΔPSS was positively correlated with plaque burden (r = 0.37, p < 0.001) and negatively correlated with fibrous cap thickness (r = −0.25, p = 0.004).Conclusions: ΔPSS provides a feasible method for assessing plaque biomechanics in vivo from OCT images, consistent with previous biomechanical and clinical studies based on different methodologies. Larger ΔPSS at proximal shoulder and MLA indicates the critical sites for future biomechanical assessment.
Highlights
Cyclic plaque structural stress has been hypothesized as a mechanism for plaque fatigue and eventually plaque rupture
We present for the first time a new methodology to calculate the changes in plaque structural stress within the cardiac cycle in vivo using Optical coherence tomography (OCT) images and finite element analysis (FEA) simulation
The key findings of this study can be summarized as follows: 1) PSS provides a feasible and reasonable approach for OCT-based biomechanical assessment; 2) diseased segments, especially the proximal shoulder and minimal lumen area of the lesion, bear the highest PSS, highlighting the critical importance of these sites for future biomechanical studies of plaque vulnerability and prediction of event risk; 3) correlation between PSS and plaque morphology is consistent with previous clinical and imaging studies, reassuring the rationale of our method. This novel method is original in many aspects, including the automatic plaque characterization from OCT images using artificial intelligence, the incorporation of the threelayered structure of the vessel wall into 2D FEA model, the accurate position-specific load derived from intracoronary pressure tracing data
Summary
Cyclic plaque structural stress has been hypothesized as a mechanism for plaque fatigue and eventually plaque rupture. A novel approach to derive cyclic plaque stress in vivo from optical coherence tomography (OCT) is hereby developed. The evaluation of cyclic plaque structural stress might add prognostic value for future cardiac events and subsequently for ACS prevention. Direct in vivo measurement of plaque structural stress is not currently feasible, finite element analysis (FEA) might provide a reliable estimation [15]. Optical coherence tomography (OCT) provides optimal image resolution, enabling detailed visualization and precise characterization of plaque composition [16]. Intracoronary pressure tracing from pressure wire could serve as an accurate load for cyclic plaque stress evaluation using FEA. The aim of this study was to propose a novel method to derive the changes in plaque structural stress during the cardiac cycle in vivo using a combination of OCT images and intracoronary pressure recordings
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