Endothelial Shear Stress and Coronary Plaque Characteristics in Humans

Abstract

Background-Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factors, atherosclerotic plaques preferentially develop at sites with disturbed flow. This study aimed at exploring in vivo the relationship between local endothelial shear stress (ESS) and coronary plaque characteristics in humans using computational fluid dynamics and frequency-domain optical coherence tomography. Methods and Results-Three-dimensional coronary artery reconstruction was performed in 21 patients (24 arteries) presenting with acute coronary syndrome using frequency-domain optical coherence tomography and coronary angiography. Each coronary artery was divided into sequential 3-mm segments and analyzed for the assessment of local ESS and plaque characteristics. in arterial segments that are straight and have no obstruction, is typically vasculoprotective, whereas high ESS (>≈2.5 Pa), occurring at the throat of an obstruction or at the outer curvature of an artery, may be associated with local erosion and enhanced platelet aggregation. [4][5][6] Recently, the Prediction of Progression of Coronary Artery Disease and Clinical Outcome Using Vascular Profiling of Shear Stress and Wall Morphology (PREDICTION) study showed in vivo the effect of low ESS on plaque progression by means of a systematic vascular profiling, which combined ESS computation with intravascular ultrasound (IVUS)-derived morphometric data.1 Interestingly, virtual histology-IVUS studies suggested an association between low ESS and plaque necrotic core and calcium areas.7 However, because of the lack of imaging modalities with adequate resolution, the in vivo relationship between local ESS and microscopic coronary plaque characteristics has never been investigated in humans.Optical coherence tomography (OCT) is a high-resolution intracoronary imaging modality enabling an accurate in vivo characterization of atherosclerotic plaques.8 OCT is able to detect microstructural features, such as fibrous cap thickness, neovascularization, and macrophage density, and represents the modality of choice for the identification of thin-cap fibroatheroma (TCFA), considered the prototype of the ruptured-prone plaque. The aim of this study was to investigate in vivo the relationship between local ESS and coronary plaque features, using systematic vascular profiling, which combines computational fluid dynamics and frequency-domain (FD)-OCT analysis in humans. Methods Study PopulationPatients with acute coronary syndrome (ACS) who underwent FD-OCT imaging before percutaneous coronary intervention were identified from the Massachusetts General Hospital OCT Registry database. Inclusion criteria were (1) FD-OCT pullback length ≥25 mm between corresponding proximal and distal anatomic landmarks (ie, major branches) to be used for three-dimensional (3D) reconstruction; (2) X-ray coronary angiograms with ≥2 projections with a difference in angle >35°; and (3) no history of previous stent implantation in the artery to be studied. From a total of 117 patients wit...

Quantifying the effect of side branches in endothelial shear stress estimates

“…For display, the y-extent of the maps was further shaped by the vessel radius at each longitudinal location, and side branches were depicted as voids (Figure 1C). In keeping with ESS profiling clinical study designs [7, 33], each artery was divided into 3 mm-long sections wherein ESS was averaged. Based on the findings of studies using this design [6, 7, 34], we categorized ESS in each 3-mm section of the reference model as low if it was < 1Pa, and as high if it was > 3 Pa. A binary outcome variable was then assigned to each 3 mm-long section depending on whether it was categorized as low ESS, and a second binary outcome variable was assigned based on whether it was categorized as high ESS (Figure 1C).…”

Prevalence and Predictors of Multiple Coronary Plaque Ruptures

“…Overall, patients with multiple plaque rupture had thinner FCT It may be possible that the relatively low prevalence of TCFA was related to the definition itself (ie, lipid-rich plaque with a fibrous cap thinner than 65 µm), although our definition of TCFA was the same proposed by the Consensus OCT documents 23,24 and widely used in previous OCT studies. 25,26 Independent clinical predictors of multiple plaque ruptures were presentation with AMI and chronic kidney disease ( Figure 6). Enhanced inflammatory activity, surges in sympathetic activity, and local mechanical and hemodynamic stress may be potential mechanisms linking AMI with the presence of multiple plaque ruptures.…”

Influence of shear stress magnitude and direction on atherosclerotic plaque composition

“…Studies in patients have identified that plaque progression occurs within regions experiencing changes in the magnitude and/or direction of WSS [2,3], but there is debate as to which flow disturbance is most responsible for the development of advanced plaques [4–6]. …”

“…Despite the wide use and importance of this animal model for studying experimental advanced plaques, no study has systematically characterized the flow profiles that result from cuff placement in vivo , which may aid in understanding the discrepant results between studies as to which flow profile promotes each advanced plaque type [4,5]. We hypothesize that vulnerable plaques are promoted by low WSS magnitude, whereas stable plaques are promoted by altered WSS direction.…”