Do the extent and direction of arterial remodelling predict subsequent progression of coronary atherosclerosis? A serial intravascular ultrasound study

Relationship between arterial remodelling and serial changes in coronary atherosclerosis by intravascular ultrasound: an analysis of the IBIS-4 study

AIMS

Arterial remodelling is an important determinant of coronary atherosclerosis. Assessment of the remodelling index, comparing a lesion to a local reference site, is a suboptimal correlate of serial vascular changes. We assessed a novel approach which, unlike the local-reference approach, uses the entire artery's global remodelling as reference.

METHODS AND RESULTS

Serial (baseline and 13 months) intravascular ultrasound was performed in 146 non-infarct-related arteries of 82 patients treated with high-intensity statin. Arteries were divided into 3-mm segments (n = 1479), and focal remodelling was characterized in individual segments at both timepoints applying the global arterial reference approach. First, we compared preceding vascular changes in relation to follow-up remodelling. Second, we examined whether baseline remodelling predicts subsequent plaque progression/regression. At follow-up, segments with constrictive vs. compensatory or expansive remodelling had greater preceding reduction of vessel area (-0.67 vs. -0.38 vs. -0.002 mm2; P < 0.001) and lumen area (-0.82 vs. -0.09 vs. 0.40 mm2; P < 0.001). Overall, we found significant regression in percent atheroma volume (PAV) [-0.80% (-1.41 to -0.19)]. Segments with constrictive remodelling at baseline had greater subsequent PAV regression vs. modest regression in the compensatory, and PAV progression in the expansive remodelling group (-6.14% vs. -0.71% vs. 2.26%; P < 0.001). Lesion-level analyses (n = 118) showed no differences when remodelling was defined by the local reference approach at baseline or follow-up.

CONCLUSION

Remodelling assessment using a global arterial reference approach, but not the commonly used, local reference site approach, correlated reasonably well with serial changes in arterial dimensions and identified arterial segments with subsequent PAV progression despite intensive statin treatment and overall atheroma regression.

Atherosclerosis and atheroma plaque rupture: imaging modalities in the visualization of vasa vasorum and atherosclerotic plaques

Invasive angiography has been widely accepted as the gold standard to diagnose cardiovascular pathologies. Despite its superior resolution of demonstrating atherosclerotic plaque in terms of degree of lumen stenosis, the morphological assessment for the plaque is insufficient for the analysis of plaque components, and therefore, unable to predict the risk status or vulnerability of atherosclerotic plaque. There is an increased body of evidence to show that the vasa vasorum play an important role in the initiation, progression, and complications of atherosclerotic plaque leading to major adverse cardiac events. This paper provides an overview of the evidence-based reviews of various imaging modalities with regard to their potential value for comprehensive characterization of the composition, burden, and neovascularization of atherosclerotic plaque.

Estimation of the viscoelastic properties of vessel walls using a computational model and Doppler ultrasound

Human arteries affected by atherosclerosis are characterized by altered wall viscoelastic properties. The possibility of noninvasively assessing arterial viscoelasticity in vivo would significantly contribute to the early diagnosis and prevention of this disease. This paper presents a noniterative technique to estimate the viscoelastic parameters of a vascular wall Zener model. The approach requires the simultaneous measurement of flow variations and wall displacements, which can be provided by suitable ultrasound Doppler instruments. Viscoelastic parameters are estimated by fitting the theoretical constitutive equations to the experimental measurements using an ARMA parameter approach. The accuracy and sensitivity of the proposed method are tested using reference data generated by numerical simulations of arterial pulsation in which the physiological conditions and the viscoelastic parameters of the model can be suitably varied. The estimated values quantitatively agree with the reference values, showing that the only parameter affected by changing the physiological conditions is viscosity, whose relative error was about 27% even when a poor signal-to-noise ratio is simulated. Finally, the feasibility of the method is illustrated through three measurements made at different flow regimes on a cylindrical vessel phantom, yielding a parameter mean estimation error of 25%.

Sex differences in mortality associated with computed tomographic angiographic measurements of obstructive and nonobstructive coronary artery disease: an exploratory analysis

BACKGROUND

Sex differences exist in the prevalence and severity of obstructive coronary artery disease (CAD). Limited data are available to explore sex differences in prognosis with coronary computed tomographic angiographic (CCTA) measurements of CAD including novel nonobstructive plaque extent.

METHODS AND RESULTS

A total of 1127 consecutive patients were clinically referred to 16-slice CCTA and followed for the occurrence of all-cause death. Time to death was calculated by univariable and multivariable Cox proportional hazard models. Four-year survival (92.1%) was similar by sex (P=0.52). Women more often had no coronary stenosis (54%) as compared with men (28%) (P<0.0001). Mortality worsened for both women (P<0.0001) and men (P=0.002) by the number of vessels with > or =50% stenosis. For women, overall mortality ranged from 3.5% for no CAD to 25.0% for women with 3-vessel plus left main obstructive CAD (P<0.0001). For men, overall mortality ranged from 2.7% for no CAD to 17.4% for males with 3-vessel plus left main obstructive CAD (P=0.002). Nonobstructive disease was prevalent in women (range, 24% to 66%) and men (range, 45% to 74%) ages 45 to > or =80 years. Nonobstructive CAD extent was a significant estimator of all-cause mortality when added to a model containing pretest CAD likelihood and obstructive CAD extent (P=0.039). For men, in a risk-adjusted model including pretest CAD likelihood and obstructive CAD, the number of nonobstructive lesions was not a significant estimator of mortality (P=0.9). For women, the relative hazard for mortality, in a multivariable model, was 1.3 per nonobstructive lesion (P=0.003), including pretest CAD likelihood and obstructive CAD as covariates. For women, risk-adjusted median mortality ranged from 2.9% to 10.9% for none to > or =4 nonobstructive lesions (P<0.0001).

CONCLUSIONS

Based on our preliminary analyses, CCTA obstructive and nonobstructive CAD adds incremental value to clinical assessment for risk stratification. Moreover, the extent of nonobstructive CAD by CCTA predicts mortality in women but not in men and may be helpful to optimize therapeutic strategies for women.

Natural history of experimental coronary atherosclerosis and vascular remodeling in relation to endothelial shear stress: a serial, in vivo intravascular ultrasound study

BACKGROUND

The natural history of heterogeneous atherosclerotic plaques and the role of local hemodynamic factors throughout their development are unknown. We performed a serial study to assess the role of endothelial shear stress (ESS) and vascular remodeling in the natural history of coronary atherosclerosis.

METHODS AND RESULTS

Intravascular ultrasound-based 3-dimensional reconstruction of all major coronary arteries (n=15) was performed serially in vivo in 5 swine 4, 11, 16, 23, and 36 weeks after induction of diabetes mellitus and hyperlipidemia. The reconstructed arteries were divided into 3-mm-long segments (n=304). ESS was calculated in all segments at all time points through the use of computational fluid dynamics. Vascular remodeling was assessed at each time point in all segments containing significant plaque, defined as maximal intima-media thickness >/=0.5 mm, at week 36 (n=220). Plaque started to develop at week 11 and progressively advanced toward heterogeneous, multifocal lesions at all subsequent time points. Low ESS promoted the initiation and subsequent progression of plaques. The local remodeling response changed substantially over time and determined future plaque evolution. Excessive expansive remodeling developed in regions of very low ESS, further exacerbated the low ESS, and was associated with the most marked plaque progression. The combined assessment of ESS, remodeling, and plaque severity enabled the early identification of plaques that evolved to high-risk lesions at week 36.

CONCLUSIONS

The synergistic effect of local ESS and the remodeling response to plaque formation determine the natural history of individual lesions. Combined in vivo assessment of ESS and remodeling may predict the focal formation of high-risk coronary plaque.