Relationship among coronary plaque compliance, coronary risk factors and tissue characteristics evaluated by integrated backscatter intravascular ultrasound

Relationship between tissue characteristics and mechanical properties of coronary plaques: a comparison between integrated backscatter intravascular ultrasound (IVUS) and speckle-tracking IVUS

High-risk coronary plaques have certain morphological characteristics. Thus, comprehensive assessment is needed for the risk stratification of plaques in patients with coronary artery disease. Integrated backscatter intravascular ultrasound (IB-IVUS) has been used successfully used to evaluate the tissue characteristics of coronary plaques; however, the mechanical properties of plaques have been rarely assessed. Therefore, we developed Speckle-tracking IVUS (ST-IVUS) to evaluate the mechanical properties of coronary plaque. This study aimed to evaluate the relation between the tissue characteristics of coronary plaques using IB-IVUS and their mechanical properties using ST-IVUS. We evaluated 95 non-targeted plaques in 95 patients undergoing elective percutaneous coronary intervention to the left anterior descending artery. We set regions of interest (ROIs) in the cross-sectional images of coronary plaques where we divided 120 degree plaques into four quadrants (every 30 degrees), with the center at the area of maximum atheroma thickness. We measured relative calcification area (%CA, relative fibrous area (%FI) and relative lipid pool area (%LP) in a total of 380 ROIs. In ST-IVUS analysis, we measured strain in the circumferential direction of the lumen area (LA strain: %), the external elastic membrane area strain (EEM strain: %), and strain in the radial direction (radial strain: %). On global cross-sectional area IB-IVUS analysis, the %CA was 1.2 ± 1.2%; the %FI was 49.0 ± 15.9%, and the %LP was 49.7 ± 16.5%. In ST-IVUS analysis, the LA strain was 0.67 ± 0.43%; the EEM strain was 0.49 ± 0.33%, and the radial strain was 2.02 ± 1.66%. On regional analysis, the %LP was not associated with the LA strain (r = - 0.002 p = 0.97), the EEM strain (r = - 0.05 p = 0.35), or with the radial strain (r = - 0.04 p = 0.45). These trends were seen between the %FI and the LA strain (r = 0.02 p = 0.74), the %FI and the EEM strain (r = 0.05 p = 0.35), and the %FI and the radial strain (r = 0.04 p = 0.50). A significant correlation was only observed between the %CA and the LA strain (r = - 0.15 p = 0.0038). Our findings indicate that the associations between mechanical properties and tissue characteristics lacked statistical significance, more often than not, and that it is necessary to evaluate the mechanical properties as well as plaque characteristics for risk stratification of coronary plaques.

The Interplay between Features of Plaque Vulnerability and Hemodynamic Relevance of Coronary Artery Stenoses

Fractional flow reserve (FFR) may not be immune from hemodynamic perturbations caused by both vessel and lesion related factors. The aim of this study was to investigate the impact of plaque- and vessel wall-related features of vulnerability on the hemodynamic effect of intermediate coronary stenoses. Methods and Results: In this cross-sectional study, patients referred to catheterization laboratory for clinically indicated coronary angiography were prospectively screened for angiographically intermediate stenosis (50-80%). Seventy lesions from 60 patients were evaluated. Mean angiographic stenosis was 62.1 ± 16.3%. After having performed FFR assessment, intravascular ultrasound (IVUS) was performed over the FFR wire. Virtual histology IVUS was used to identify the plaque components and thin cap fibroatheroma (TCFA). TCFA was significantly more frequent (65 vs. 38%, p = 0.026), and necrotic core volume (26.15 ± 14.22 vs. 16.21 ± 8.93 mm3, p = 0.04) was significantly larger in the positively remodeled than non-remodeled vessels. Remodeling index correlated with necrotic core volume (r = 0.396, p = 0.001) and with FFR (r = -0. 419, p = 0.001). With respect to plaque components, only necrotic core area (r = -0.262, p = 0.038) and necrotic core volume (r = -0.272, p = 0.024) were independently associated with FFR. In the multivariable model, presence of TCFA was independently associated with significantly lower mean FFR value as compared to absence of TCFA (adjusted, 0.71 vs. 0.78, p = 0.034). Conclusion: The current study demonstrated that for a given stenosis geometry, features of plaque vulnerability such as necrotic core volume, TCFA, and positive remodeling may influence the hemodynamic relevance of intermediate coronary stenoses.

Evaluation of coronary features of HIV patients presenting with ACS: The CUORE, a multicenter study

BACKGROUND AND AIMS

The risk of recurrence of myocardial infarction (MI) in HIV patients presenting with acute coronary syndrome (ACS) is well known, but there is limited evidence about potential differences in coronary plaques compared to non-HIV patients.

METHODS

In this multicenter case-control study, HIV patients presenting with ACS, with intravascular-ultrasound (IVUS) data, enrolled between February 2015 and June 2017, and undergoing highly active antiretroviral therapy (HAART), were retrospectively compared to non-HIV patients presenting with ACS, before and after propensity score with matching, randomly selected from included centers. Primary end-point was the prevalence of multivessel disease. Secondary end-points were the prevalence of abnormal features at IVUS, the incidence of major-acute-cardiovascular-events (MACE), a composite end point of cardiovascular death, MI, target lesion revascularization (TLR), stent thrombosis (ST), non-cardiac death and target vessel revascularization (TVR). For each end-point, a subgroup analysis was conducted in HIV patients with CD4 cell count <200/mm³.

RESULTS

Before propensity score, 66 HIV patients and 120 non-HIV patients were selected, resulting in 20 and 40 after propensity score. Patients with multivessel disease were 11 and 17, respectively (p = 0.56). IVUS showed a lower plaque burden (71% vs. 75%, p < 0.001) and a higher prevalence of hyperechoic non-calcified plaques (100% vs. 35%, p < 0.05) in HIV patients; a higher prevalence of hypoechoic plaques (7% vs. 0%, p < 0.05), a higher incidence of MACE (17.4% vs. 9.1% vs. l'8.0%, p < 0.05), MI recurrence (17.2% vs. 0.0% vs. 2.3%, p < 0.05), and ST (6.7% vs. 0.3% vs. 03%, p < 0.05) in HIV patients with CD4 < 200/mm³.

CONCLUSIONS

Our study may provide a part of the pathophysiological basis of the differences in coronary arteries between HIV-positive and HIV-negative patients, suggesting that the former present with peculiar morphological features at IVUS, even after adjustment for clinical variables. Furthermore, we confirmed that an advanced HIV infection is associated with a high risk of non-calcific plaques and with a worse prognosis, including cardiovascular events and ACS recurrence.

Ghrelin attenuates vascular calcification in diabetic patients with amputation

Vascular calcification is established to be a critical factor in diabetes mellitus, which causes cardiovascular and amputation complication of diabetic patients. OPG/RANKL/RANK axis serves as a regulatory role in vascular calcification. Ghrelin, an endogenous ligand of growth hormone secretagogue receptor (GHSR), has been reported to exhibit potent cardiovascular protective effects. However, the role of ghrelin in the regulation of diabetic vascular calcification is still elusive. Here, we reported the role of ghrelin and its relationship with OPG/RANKL/RANK system in patients with diabetic foot amputation. In vivo and in vitro investigations were performed. Sixty type 2 diabetic patients with foot amputation were enrolled in vivo investigation, and they were divided into three groups through Doppler ultrasound: mild stenosis group (n=20), moderate stenosis group (n=20), and severe stenosis/occlusion group (n=20). Morphological analysis results showed diffused calcium depositions in the anterior tibial artery of diabetic amputees. Compared with the mild and moderate stenosis group, the severe stenosis/occlusion group had more spotty calcium depositions in atherosclerotic plaques. Western blot analysis indicated the expressions of osteoprotegerin (OPG) and ghrelin were downregulated, while the expression of receptor activator of nuclear factor kappa B ligand (RANKL) was upregulated with the vascular stenosis aggravation. Pearson correlation analysis revealed a negative correlation between calcium content and ghrelin levels (r=-0.58, P<0.001), as well as the ghrelin levels and sRANKL levels (r=-0.57, P<0.001). Meanwhile, OPG levels were positively correlated with ghrelin levels (r=0.63, P<0.001). From in vitro investigation, we found that the high-glucose (HG), high-lipid (HL), and β-glycerophosphate (β-GP) considerably increased the total calcium content, ALP activity, and expression of osteogenic markers in vascular smooth muscle cells (VSMCs). Ghrelin blunted calcification in a dose-dependent manner. In addition, ghrelin upregulated OPG expression and downregulated RANKL expression in VSMC calcification when anti-OPG antibody and RANKL were performed. Collectively, we therefore conclude serum ghrelin level may be a predictor of diabetic vascular calcification. The possible mechanism may be related with OPG/RANKL signal.

Activation of AKT by O-linked N-acetylglucosamine induces vascular calcification in diabetes mellitus

RATIONALE

Vascular calcification is a serious cardiovascular complication that contributes to the increased morbidity and mortality of patients with diabetes mellitus. Hyperglycemia, a hallmark of diabetes mellitus, is associated with increased vascular calcification and increased modification of proteins by O-linked N-acetylglucosamine (O-GlcNAcylation).

OBJECTIVE

We sought to determine the role of protein O-GlcNAcylation in regulating vascular calcification and the underlying mechanisms.

METHODS AND RESULTS

Low-dose streptozotocin-induced diabetic mice exhibited increased aortic O-GlcNAcylation and vascular calcification, which was also associated with impaired aortic compliance in mice. Elevation of O-GlcNAcylation by administration of Thiamet-G, a potent inhibitor for O-GlcNAcase that removes O-GlcNAcylation, further accelerated vascular calcification and worsened aortic compliance of diabetic mice in vivo. Increased O-GlcNAcylation, either by Thiamet-G or O-GlcNAcase knockdown, promoted calcification of primary mouse vascular smooth muscle cells. Increased O-GlcNAcylation in diabetic arteries or in the O-GlcNAcase knockdown vascular smooth muscle cell upregulated expression of the osteogenic transcription factor Runx2 and enhanced activation of AKT. O-GlcNAcylation of AKT at two new sites, T430 and T479, promoted AKT phosphorylation, which in turn enhanced vascular smooth muscle cell calcification. Site-directed mutation of AKT at T430 and T479 decreased O-GlcNAcylation, inhibited phosphorylation of AKT at S473 and binding of mammalian target of rapamycin complex 2 to AKT, and subsequently blocked Runx2 transactivity and vascular smooth muscle cell calcification.

CONCLUSIONS

O-GlcNAcylation of AKT at 2 new sites enhanced AKT phosphorylation and activation, thus promoting vascular calcification. Our studies have identified a novel causative effect of O-GlcNAcylation in regulating vascular calcification in diabetes mellitus and uncovered a key molecular mechanism underlying O-GlcNAcylation-mediated activation of AKT.

Impact of tissue characteristics on luminal narrowing of mild angiographic coronary stenosis: assessment of integrated backscatter intravascular ultrasound

Integrated backscatter intravascular ultrasound (IB-IVUS) is a useful method for analyzing coronary plaque tissue. We evaluated whether tissue composition determined using IB-IVUS is associated with the progression of stenosis in coronary angiography. Sixty-three nontarget coronary lesions in 63 patients with stable angina were evaluated using conventional IVUS and IB-IVUS. IB-IVUS images were analyzed at 1-mm intervals for a length of 10 mm. After calculating the relative areas of the tissue components using the IB-IVUS system, fibrous volume (FV) and lipid volume (LV) were calculated through integration of the slices, after which percentages of per-plaque volume (%FV/PV, %LV/PV) and per-vessel volume (%FV/VV, %LV/VV) were calculated. Progression of coronary stenosis was interpreted from the increase in percent diameter stenosis (%DS) from baseline to the follow-up period (6-9 months) using quantitative coronary angiography. %DS was 24.1 ± 12.8 % at baseline and 23.2 ± 13.7 % at follow-up. Using IB-IVUS, LV was 31.7 ± 10.5 mm(3), and %LV/PV and %LV/VV were 45.6 ± 10.3 % and 20.2 ± 6.0 %, respectively. FV, %FV/PV, and %FV/VV were 35.5 ± 12.1 mm(3), 52.1 ± 9.5 %, and 23.4 ± 7.1 %, respectively. The change in %DS was -0.88 ± 7.25 % and correlated closely with %LV/VV (r = 0.27, P = 0.03) on simple regression. Multivariate regression after adjustment for potentially confounding risk factors showed %LV/VV to be correlated independently with changes in %DS (r = 0.42, P = 0.02). Logistic regression analysis after adjusting for confounding coronary risk factors showed LV (odds ratio 1.08; 95 % confidence interval 1.01-1.16; P = 0.03) and %LV/VV (odds ratio 1.13; 95 % confidence interval 1.01-1.28; P = 0.03) to be independent predictors of the progression of angiographic coronary stenosis. Our findings suggest that angiographic luminal narrowing of the coronary artery is likely associated with tissue characteristics. IB-IVUS may provide information about the natural progression of luminal narrowing in coronary stenosis.