Association of coronary wall shear stress with atherosclerotic plaque burden, composition, and distribution in patients with coronary artery disease

Abstract

Background: Extremes of wall shear stress (WSS) have been associated with plaque progression and transformation, which has raised interest in the clinical assessment of WSS. We hypothesized that calculated coronary WSS is predicted only partially by luminal geometry and that WSS is related to plaque composition.

Methods and results: Twenty-seven patients with coronary artery disease underwent virtual histology intravascular ultrasound and Doppler velocity measurement for computational fluid dynamics modeling for WSS calculation in each virtual histology intravascular ultrasound segment (N=3581 segments). We assessed the association of WSS with plaque burden and distribution and with plaque composition. WSS remained relatively constant across the lower 3 quartiles of plaque burden (P=0.08) but increased in the highest quartile of plaque burden (P<0.001). Segments distal to lesions or within bifurcations were more likely to have low WSS (P<0.001). However, the majority of segments distal to lesions (80%) and within bifurcations (89%) did not exhibit low WSS. After adjustment for plaque burden, there was a negative association between WSS and percent necrotic core and calcium. For every 10 dynes/cm(2) increase in WSS, percent necrotic core decreased by 17% (P=0.01), and percent dense calcium decreased by 17% (P<0.001). There was no significant association between WSS and percent of fibrous or fibrofatty plaque components (P=NS).

Conclusions: IN PATIENTS WITH CORONARY ARTERY DISEASE: (1) Luminal geometry predicts calculated WSS only partially, which suggests that detailed computational techniques must be used to calculate WSS. (2) Low WSS is associated with plaque necrotic core and calcium, independent of plaque burden, which suggests a link between WSS and coronary plaque phenotype. (J Am Heart Assoc. 2012;1:e002543 doi: 10.1161/JAHA.112.002543.).

Keywords: atherosclerosis; computational fluid dynamics; coronary arteries; histology, virtual; ultrasonography, intravascular; wall shear stress.

Figures

Figure 1.

An example of WSS profile of the left anterior descending coronary artery from a study patient, showing areas of variable WSS. Time‐averaged WSS values were circumferentially averaged for each IVUS segment to provide quantitative hemodynamic data to correlate with plaque data. The colors represent different values of WSS as depicted in the scale on the right side. The outer mesh represents the EEM, and the area between EEM and lumen (colored) is considered to be plaque. Each cross‐sectional line in the mesh represents 1 VH‐IVUS frame.

Figure 2.

An example of WSS profile of another patient demonstrating heterogeneity of distribution of WSS, which would be difficult to ascertain from geometry alone. The colors represent different values of WSS as depicted in the scale on the right side. Black dots are superimposed VH‐IVUS–derived necrotic core and dense calcium data. A cross‐sectional view of study segment representing 1 VH‐IVUS segment with 0.5‐mm thickness is also shown.

Figure 3.

Association between WSS and quartiles of plaque burden. The range of plaque burden in each quartile is shown in brackets. Error bars are 1 standard error.

Figure 4.

A, Percentage of segments with low WSS (2) within the lesions and proximal to and distal to lesions. B, Percentage of segments with high WSS (≥25 dynes/cm2) within the lesions and proximal to and distal to lesions. *P value: The GLIMMIX procedure in SAS did not converge when fitting the statistical model for Figure 4B. Convergence was achieved when lesion and distal were consolidated into 1 category.

Figure 5.

Percentage of segments with low WSS (2) within the bifurcations, and 0 to 5 mm, 5 to 10 mm, and 10 to 15 mm distal to bifurcations.