Pathological Intimal Thickening Research Articles

Immunohistochemical characterisation of dendritic cells in human atherosclerotic lesions: possible pitfalls

Previously we demonstrated decreased blood myeloid (m) and plasmacytoid (p) dendritic cell (DC) counts in atherosclerotic patients. Therefore, we examined whether DCs, in particular DC precursors, accumulate in human plaques. Blood DC antigen (BDCA)-1, CD11c (mDCs), BDCA-2, CD123 (pDCs), langerin, fascin, S-100 (immature/mature DCs), and CD1a and CD83 (mature DCs) were investigated by immunohistochemistry of carotid arteries obtained by endarterectomy (EAS, frozen n = 11, fixed n = 11) or autopsy (fixed, n = 87). Fascin and S-100 required formaldehyde fixation, other markers needed cryo-preservation. BDCA-1, BDCA-2, langerin, and S-100 appeared specific for intimal DCs, unlike CD123 and fascin (staining endothelial cells), CD11c and CD1a (staining monocytes, foam cells) or CD83 (staining lymphocytes). BDCA-1 and BDCA-2 cells were detected in EAS, preferentially near microvessels. S-100 cells increased successively from intimal thickening, via pathological intimal thickening, fibrous cap atheroma and finally complicated plaques. Fascin cells followed the same pattern, but were more abundant. However, in lesions containing microvessels (complicated plaques, plaque shoulders and most EAS) this was partly explained by fascin positive endothelial cells. Even complicated plaques contained relatively few mature CD83 DCs. Accumulation of BDCA-1 and BDCA-2 around neovessels showed that mDCs and pDCs are recruited to advanced plaques, which is in line with the previously described decline of circulating blood DCs in patients with coronary artery disease. Unexpectedly, several DC markers yielded false positive signals. Hence, some accounts on numbers, trafficking and activation of DCs in atherosclerotic plaques may require re-evaluation.

Detection of coronary atherosclerotic plaques with superficial proteoglycans and foam cells using real-time intrinsic fluorescence spectroscopy

ObjectivesThe protein components of low-density lipoprotein (LDL), oxidized LDL and proteoglycans such as versican contain tryptophan, an amino acid with characteristic fluorescence features at 308nm excitation wavelength. We hypothesize that intrinsic fluorescence spectroscopy at 308nm excitation wavelength IFS308, a method suitable for clinical use, can identify coronary artery lesions with superficial foam cells (SFCs) and/or proteoglycans. MethodsWe subjected 119 human coronary artery specimens to in vitro fluorescence and reflectance spectroscopy. We used 5 basis spectra to model IFS308, and extracted their contributions to each individual IFS308 spectrum. A diagnostic algorithm using the contributions of Total Tryptophan and fibrous cap to IFS308 was built to identify specimens with SFCs and/or proteoglycans in their top 50μm. ResultsWe detected SFCs and/or proteoglycans, such as versican or the glycosaminoglycan hyaluronan, in 24 fibrous cap atheromas or pathologic intimal thickening (PIT) lesions. An algorithm using the contributions of Total Tryptophan and fibrous cap to IFS308 was able to identify these segments with 92% sensitivity and 80% specificity. ConclusionWe were able to establish a set of characteristic LDL, oxidized LDL, versican and hyaluronan fluorescence spectra, ready to be used for real-time diagnosis. The IFS308 technique detects SFCs and/or proteoglycans in fibrous cap atheromas and PIT lesions. SFCs and proteoglycans are histological markers of vulnerable plaques, and this study is a step further in developing an invasive clinical tool to detect the vulnerable atherosclerotic plaque.

The Dynamic Nature of Coronary Artery Lesion Morphology Assessed by Serial Virtual Histology Intravascular Ultrasound Tissue Characterization

We used virtual histology intravascular ultrasound (VH-IVUS) to investigate the natural history of coronary artery lesion morphology. Plaque stability is related to its histological composition. We performed serial (baseline and 12-month follow-up) VH-IVUS studies and examined 216 nonculprit lesions (plaque burden >or=40%) in 99 patients. Lesions were classified into pathological intimal thickening (PIT), VH-IVUS-derived thin-capped fibroatheroma (VH-TCFA), thick-capped fibroatheroma (ThCFA), fibrotic plaque, and fibrocalcific plaque. At baseline, 20 lesions were VH-TCFAs; during follow-up, 15 (75%) VH-TCFAs "healed," 13 became ThCFAs, 2 became fibrotic plaque, and 5 (25%) VH-TCFAs remained unchanged. Compared with VH-TCFAs that healed, VH-TCFAs that remained VH-TCFAs located more proximally (values are median [interquartile range]) (16 mm [15 to 18 mm] vs. 31 mm [22 to 47 mm], p = 0.013) and had larger lumen (9.1 mm(2) [8.2 to 10.7 mm(2)] vs. 6.9 mm(2) [6.0 to 8.2 mm(2)], p = 0.021), vessel (18.7 mm(2) [17.3 to 28.6 mm(2)] vs. 15.5 mm(2) [13.3 to 16.6 mm(2)]; p = 0.010), and plaque (9.7 mm(2) [9.6 to 15.7 mm(2)] vs. 8.4 mm(2) [7 to 9.7 mm(2)], p = 0.027) areas; however, baseline VH-IVUS plaque composition did not differ between VH-TCFAs that healed and VH-TCFAs that remained VH-TCFAs. Conversely, 12 new VH-TCFAs developed; 6 late-developing VH-TCFAs were PITs, and 6 were ThCFAs at baseline. In addition, plaque area at minimum lumen sites increased significantly in PITs (7.8 mm(2) [6.2 to 10.0 mm(2)] to 9.0 mm(2) [6.5 to 12.0 mm(2)], p < 0.001), VH-TCFAs (8.6 mm(2) [7.3 to 9.9 mm(2)] to 9.5 mm(2) [7.8 to 10.8 mm(2)], p = 0.024), and ThCFAs (8.6 mm(2) [6.8 to 10.2 mm(2)] to 8.8 mm(2) [7.1 to 11.4 mm(2)], p < 0.001) with a corresponding decrease lumen areas, but not in fibrous or fibrocalcific plaque. Most VH-TCFAs healed during 12-month follow-up, whereas new VH-TCFAs also developed. PITs, VH-TCFAs, and ThCFAs showed significant plaque progression compared with fibrous and fibrocalcific plaque.

Immunolocalisation of fibrin in coronary atherosclerosis: implications for necrotic core development

Intraplaque haemorrhage has been shown to be important in necrotic core enlargement. Immunolocalisation of fibrin within progressive stages of plaque progression has not been extensively studied. Histological sections (n = 74) of human coronary arteries were stained immunohistochemically for fibrin II, red blood cell antigen (glycophorin A), and CD31. Plaques were chosen to represent a range of lesions [6 adaptive intimal thickening, AIT (AHA grade I); 4 intimal xanthomas (AHA grade II), 19 pathologic intimal thickening, PIT (AHA grade III, or pre-atheroma); 34 fibroatheromas, FA (AHA grade IV and V); and 11 thin cap fibroatheromas (TCFA, AHA grade IV)]. Fibrin was generally absent in the intima of AIT and PIT, with moderate staining in cores of early FA (2.6 +/- 0.3). All late FA and TCFA demonstrated intracore fibrin, with mean scores of 2.9 +/- 0.3 and 3.0 +/- 0.3, respectively. Intimal vasa vasorum counts increased with intimal fibrin score (p < 0.0001); in 68% of cores with fibrin staining, there was minimal or no evidence of red cell breakdown. Fibrin in necrotic cores is present proportional to intraplaque vasa vasorum and before red cells, suggesting leakage of vessels before frank intraplaque haemorrhage. Fibrin may play a role in the bridge between pre-atheroma and atheroma.

The natural history of aortic atherosclerosis: A systematic histopathological evaluation of the peri-renal region

BackgroundRisk factor profiles for the different vascular beds (i.e. coronary, carotid, peripheral and aortic) are remarkably different, suggesting that atherosclerosis is a heterogeneous disorder. Little is known about the morphologic progression of atherosclerosis in the peri-renal aorta, one of the primary predilection sites of atherosclerosis. MethodsA systematic analysis was performed in 260 consecutive peri-renal aortic patches (stained with Movat Pentachrome and H&E) collected during organ transplantation (mean donor age 46.5 (range 5–76) years; 54% ♂; mean BMI 24.9; 40% smokers; 20% hypertensive). Plaque morphology was classified according to the modified AHA classification scheme proposed by Virmani et al. [4]. Immunostaining against CD68 was used to identify the distribution of intimal macrophages and monocytes in several predefined locations among various plaque types and fibrous cap thickness. ResultsThere was significant intimal thickening (p<0.013) and medial thinning (p<0.032) with advancing age. The incidence of atherosclerotic plaques in the abdominal aorta correlated with age (r=0.640, p=0.01). During the first three decades of life adaptive intimal thickening and intimal xanthomas were the predominant lesions. In contrast, the fourth, fifth and sixth decades hallmarked more complicated plaques of pathological intimal thickening, early and late fibroatheromas (EFAs and LFAs), thin-cap FAs (TCFAs; cap thickness <155μm), ruptured plaques (PRs), healed rupture and fibrotic calcified plaques. The mean percentage of lesional macrophages increased significantly from LFAs to TCFAs (5–17%; p<0.001). Macrophage infiltration of the fibrous cap was negatively correlated with fibrous cap thickness (p<0.0004); TCFAs and PRs (caps<100μm) contained significantly more macrophages (19%) compared with caps 101–300μm (6%) and >300μm (2%). Macrophages in shoulder regions were highest in early and late FAs (∼45%) followed by TCFAs (27%) and PR (20%). Further, intimal vasa vasorum were mostly seen adjacent to the necrotic core of advanced atherosclerotic plaques and remained confined to the intimo-medial border despite marked thickening of the intima. ConclusionThis study shows that peri-renal aortic atherosclerosis starts early in life. Gross plaque morphologies of the peri-renal abdominal aorta are similar to coronary atherosclerosis yet indications were found for site specific differences in macrophage content and neovascularization.

Virtual Histology Intravascular Ultrasound Analysis of Non-Culprit Attenuated Plaques Detected by Grayscale Intravascular Ultrasound in Patients With Acute Coronary Syndromes

Noncalcific attenuated plaques identified by grayscale intravascular ultrasound (IVUS) are often seen in patients with acute coronary syndromes and have been associated with no reflow and creatine kinase-MB elevation after percutaneous coronary intervention. Histopathology has shown cholesterol clefts, microcalcification, or organized thrombus. One hundred twenty-four vessels in 64 patients with acute coronary syndromes from the PROSPECT trial were identified for inclusion in the present analysis. After excluding 4 vessels with severe calcification, 9 vessels with <40% plaque burden, and 3 vessels with too few (<3) virtual histology (VH)-IVUS frames for analysis, complete grayscale IVUS and VH-IVUS was available for 108 vessels in 64 patients that contained 39 VH-IVUS thin-capped fibroatheromas (VH-TCFA), 40 thick-capped fibroatheromas (VH-ThFA), and 33 pathologic intimal thickening but no fibrotic or fibrocalcific plaques. Overall, there were 47 grayscale IVUS attenuated plaques in 43 vessels. Compared to the minimum luminal sites of the remaining 65 vessels (controls), attenuated plaques contained larger necrotic core areas (1.5 +/- 0.9 vs 0.9 +/- 0.8 mm(2) in controls, p = 0.001). Fibroatheromas (VH-TCFA or VH-ThFA) were more common at the sites of attenuated plaques than at control sites (VH-TCFA 42.5% vs 29.2%, VH-ThFA 53.2% vs 23.1%, pathologic intimal thickening 4.3% vs 47.7%, p <0.0001). In conclusion, grayscale IVUS attenuated plaques are associated with a large amount of VH-IVUS necrotic core and are markers of the presence of fibroatheromas (VH-TCFA or VH-ThFA). This may explain the biologic instability of these lesions.

Plaque type and composition as evaluated non-invasively by MSCT angiography and invasively by VH IVUS in relation to the degree of stenosis

Background:Imaging of coronary plaques has traditionally focused on evaluating degree of stenosis, as the risk for adverse cardiac events increases with stenosis severity. However, the relation between plaque composition and...

Diabetes mellitus is associated with plaque classified as thin cap fibroatheroma: an intravascular ultrasound study

We compared measures of ID coronary atherosclerosis between diabetic and non-diabetic patients enrolled in a prospective multinational IVUS registry. The region of interest was the most diseased 10 mm segment of a single coronary artery. Coronary plaque was quantified using greyscale IVUS and further classified by phenotype (ID-adaptive intimal thickening, ID-pathological intimal thickening, ID-TCFA, ID-fibroatheroma, or ID-fibrocalcific) using VH-IVUS. There was a non-significant trend for greater total plaque volume in diabetic (n=191) compared with non-diabetic (n=584) patients (94.8 vs. 88.1 mm(3), p=0.36, adjusted for multiple comparisons). There was a greater proportion of ID-TCFA among diabetic patients (21.6 vs. 13.6%, p=0.01 after adjustment for multiple comparisons; p=0.08 following multivariable adjustment for age and clinical demographics), while differences in pathological intimal thickening, fibroatheroma and fibrocalcific plaque were not significant between groups. ID-TCFA was more common in the most diseased 10 mm segment of diabetic than in non-diabetic coronary arteries. Multivariable adjustment demonstrated age and possibly the presence of diabetes to be independent predictors of ID-TCFA.

Diabetes Duration Is Associated With Increased Thin-Cap Fibroatheroma Detected by Intravascular Ultrasound With Virtual Histology

Coronary plaque classified as thin-cap fibroatheroma (TCFA) is believed to be associated with plaque rupture and coronary heart disease-related events. Although an association between duration of diabetes and increased coronary heart disease risk has been demonstrated, the relationship between TCFA and diabetes duration is unknown. Prospective registry of diabetic patients undergoing diagnostic coronary angiography and intravascular ultrasound (IVUS) enrolled in a diabetic gene and biomarker banking registry. Plaque composition in the most diseased 10-mm segment of a single coronary artery was assessed using IVUS virtual histology and was classified by phenotype as IVUS-defined adaptive intimal thickening, pathological intimal thickening, TCFA, fibroatheroma, or fibrocalcific. Patients (n=54) were stratified by duration of diabetes (<10 or > or = 10 years). Patients with diabetes > or = 10 years were older, less likely to have a history of tobacco use, had higher total cholesterol levels, and were more likely to be treated with insulin compared with patients with diabetes <10 years. Longer duration of diabetes was associated with greater plaque burden in the most diseased 10-mm segment (60.4% [53.4% to 66.8%] versus 50.2% [47.7% to 58.4%], P=0.008). The proportion of IVUS-defined TCFA in the > or = 10-year group was greater than the <10-year group (54.4% [11.6% to 77.5%] versus 10.8% [0.0% to 26.1%], P=0.009). This association persisted after adjustment for multiple comparisons, clinical characteristics, and diabetes treatment. In this cohort, longer duration of diabetes was associated with IVUS-defined TCFA, a plaque phenotype associated with risk of rupture and coronary heart disease events. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00428961.

Correlation Between Carotid Intimal/Medial Thickness and Atherosclerosis

A widely adopted surrogate for predicting rates of cardiovascular events involves measure of carotid intimal-medial thickness (CIMT) by B mode ultrasound, a technique available since the mid 1980s. The value of this modality remains in its ability to noninvasively assess cardiovascular risk beyond traditional factors identified by the Framingham risk score, and it is among the few available techniques for monitoring the effectiveness of pharmacotherapy on plaques. There are, however, existing limitations to this methodology. Perhaps the most important distinction is that IM thickness measurements are generally acquired in the common carotid artery, whereas advanced atherosclerotic disease occurs predominantly downstream in the internal carotid. Moreover, primary contributors to IM thickening are age and hypertension, which do not necessarily reflect the atherosclerotic process. Initiation of disease-related plaques begins as what is referred to as pathological intimal thickening; lesions characterized by the formation of lipid pools in the absence of a necrotic core. The eventual development of a necrotic core, however, is considered a key indicator of significant plaque advancement and recognized feature of lesion vulnerability. Necrotic cores are thought to arise from macrophage infiltration of lipid pools followed by secondary necrosis where defective clearance of debris, tissue disruption proteases, and intraplaque hemorrhage, likely contribute to its enlargement. Therefore, one of the primary limitations to CIMT is its inability to distinguish lesions with a necrotic core. Moreover, in most cases measures of plaque area or volume are generally considered better predictors of an inflammatory process consistent with atherosclerotic disease rather than intimal medial thickness.

Validation of in vivo plaque characterisation by virtual histology in a rabbit model of atherosclerosis

Most acute coronary syndromes are caused by plaque rupture. The risk of plaque rupture is related to plaque composition. The purpose of this study was to validate VH-IVUS for in vivo plaque characterisation. Six rabbits were fed a cholesterol-supplemented diet for 12 to 18 months. Thereafter, VH-IVUS imaging of the aorta was performed. After sacrifice, the VH-IVUS images were matched to the corresponding histological cross sections. A total of 260 atherosclerotic plaques were analysed. VH-IVUS had a high sensitivity, specificity and positive predictive value for the detection of non-calcified thin cap fibroatheroma (88%, 96%, 87%, respectively) and calcified thin cap fibroatheroma (95%, 99%, 93%, respectively). These values were respectively 82%, 94%, 85% for non-calcified fibroatheroma and 78%, 98%, 84% for calcified fibroatheroma. The lowest values were obtained for pathological intimal thickening (74%, 92%, 70%, respectively). For all plaque types, VH-IVUS had a kappa-value of 0.79. Linear regression analysis and Bland-Altman plots showed a strong correlation between VH-IVUS and histology for fibrous tissue, fibrofatty tissue, necrotic calcified tissue and confluent necrotic core. VH-IVUS showed a good accuracy for in vivo plaque characterisation and is a promising technique for the detection of the vulnerable plaque.

Abstract 512: Infiltrating CD4 Positive T cells may Support an Angiogenic Switch in Human Coronary Atheroma

Background: Pathologic angiogenesis has been implicated in the development of high-risk plaques where nascent immature leaky vessels become the primary source of intraplaque hemorrhage contributing to necrotic core expansion. The stage of lesion progression, however, favoring an angiogenic response has not been identified. Methods and Results: Multiple coronary lesions collected from 73 sudden coronary death victims at autopsy were examined. Plaque morphologies included pathologic intimal thickening (PIT), fibroatheromas whose cores were in an early stage (eFA) or late stage (lFA) of necrosis, thin-cap fibroatheromas (TCFA) and ruptures (pR). Lesions were characterized by immunostaining using specific markers directed against endothelial cells (CD31/CD34), smooth muscle cells (α-actin), macrophages (CD68), and T-lymphocytes (CD45RO, CD4). Mean intraplaque vessel densities per mm 2 between lesions with PIT and eFA increased significantly (PIT= 15.84±16.73 vs. eFA= 42.07±40.70, p=0.0054) where maximal numbers of vessels were found in pR (66.57±33.42). Overall, intraplaque vessels associated with actin 3 SMCs, were generally &lt;10%, suggesting a more immature phenotype. Increased vessel densities coincided with greater numbers of inflammatory macrophages and T-cells. Notably, T-cell numbers in areas with high intraplaque vessel densities increased approximate 3-fold between lesions with PIT and eFA (PIT= 62.62±76.50 vs. eFA= 182.33±171.54, p=0.0043) with maximal numbers displayed in TCFAs and pRs, in particular at the intimal/medial border. Populations infiltrating T cells were predominantly CD4 3 and most of these appeared to be activated (human leukocyte antigen DR positive). Conclusion: Atherosclerotic coronary arteries express a latent proangiogenic phenotype coinciding with a localized increased in activated CD4 3 T-cells and early plaque necrosis.

Abstract 906: Healing of Thin-Capped Fibroatheroma Assessed by Serial VH-IVUS Tissue Characterization

Thin-cap fibroatheromas (TCFA) are prone to plaque rupture and thrombosis. Intravascular ultrasound (IVUS) virtual histology (VH) assesses plaque composition and lesion morphology in vivo. Methods &amp; Results: We used serial (baseline and follow-up @11 mos) VH-IVUS to study non-culprit plaque morphology in 221 lesions (plaque burden &gt;40%) in 106 pts. Lesions were classified into 4 types based on plaque composition; pathological intimal thickening (PIT), thin-capped fibroatheroma (TCFA), thick-capped fibroatheroma (ThCFA), fibrotic/fibrocalcific. At baseline, 21 lesions were TCFAs (confluent necrotic core contacting to the lumen). Overall during follow-up (Figure ), 16/21 (76%) TCFAs healed: 13 became ThCFAs, 2 TCFAs became PIT, 1 TCFA became fibrotic, and 5 TCFAs (24%) remains unchanged although the location of the necrotic core in contact with the lumen shifted axially. Compared to TCFAs that healed, TCFAs that remained TCFAs were more often proximal in location (distance from coronary ostium to the lesion of 19±6 vs. 41±22mm, respectively, p=0.037) and had larger lumen area (9.9±3.1 vs. 6.9±1.8 mm2, p=0.013), vessel area (22.8±6.4 vs. 15.3±2.6 mm2, p=0.001), plaque area (12.9±4.9 vs. 8.4±1.7 mm2, p=0.005), calcium area (1.3±0.6 vs. 0.6±0.3 mm2, p=0.014), and necrotic core area (2.6±1.0 vs. 1.6±0.7 mm2, p=0.015). In addition, 6 new TCFAs developed; these 6 late-developing TCFAs had the appearance of PIT at baseline (Figure ). Conclusion: Although most TCFAs seem to stabilize or heal during 12 mos follow-up, proximal TCFAs in larger vessels with more plaque and calcium and a larger necrotic core appear to heal less often and new TCFAs can develop.

Apolipoprotein E (APOE) and lipoprotein lipase (LPL) gene variants and carotid atherosclerotic lesions in the oldest old: A population-based autopsy study

We investigated the association between histologically defined atherosclerotic lesions in the carotid arteries and the genetic variants of APOE and LPL in a population-based sample of Finns aged 85 or over. Post-mortem analysis of carotid arteries was performed in 240 subjects. Atherosclerotic lesions were categorized according to the modified American Heart Association criteria, and classified into four different categories: pathological intimal thickening (PIT), fibrous cap atheromas (FCA), calcified lesions (CL), and atherosclerotic burden (AB) (a combination of the other three categories). APOE ɛ4 genetic variant was associated with PIT ( p = 0.018) and AB ( p = 0.006) in the carotid arteries, and its effect was independent of the serum lipid levels. The genetic variant LPL Ser447Ter was protective against FCA ( p = 0.031) and AB ( p = 0.012), while APOE ɛ2 was protective against FCA ( p = 0.035). Our results suggest that the APOE ɛ4, ɛ2 and LPL Ser447Ter variants may have different roles in the atherosclerotic process and their effects are seen even in the oldest old population.

Low Adiponectin Levels Are Associated With Atherogenic Dyslipidemia and Lipid-Rich Plaque in Nondiabetic Coronary Arteries

The purpose of this study was to determine whether an association exists between adiponectin and plaque composition in human coronary arteries. Adiponectin is an adipocyte-derived protein with antiatherogenic and insulin-sensitizing properties. To date, the relationship between adiponectin and plaque composition is unknown. Fasting blood samples were collected from 185 patients undergoing coronary angiography and intravascular ultrasound (IVUS). Plaque composition was categorized as fibrous, fibrofatty, necrotic core, or dense calcium and further classified as IVUS-derived adaptive or pathological intimal thickening, fibroatheroma, fibrocalcific, or thin cap fibroatheroma. Adiponectin correlated with normalized plaque volume (r = -0.16, P = 0.025) and atheroma lipid content as measured by normalized fibrofatty volume (r = -0.19, P = 0.009). Low adiponectin levels were associated with IVUS-derived pathological intimal thickening (r = -0.18, P = 0.01). With increasing quartiles (Q) of adiponectin, the normalized volume of fibrofatty plaque decreased (P = 0.03), which was driven by reductions in the nondiabetic cohort (Q1 44.2 mm(3); Q2 28.2 mm(3); Q3 24.7 mm(3); and Q4 23.4 mm(3); P = 0.01). No similar association was present in diabetic patients. Low adiponectin levels were also associated with IVUS-derived pathological intimal thickening in nondiabetic (r = -0.20, P = 0.03) but not diabetic patients. Low adiponectin levels are associated with atherogenic lipoproteins (elevated triglycerides, small dense LDL cholesterol, and low HDL cholesterol), increased plaque volume, lipid-rich plaque, and IVUS-derived pathological intimal thickening in the total cohort that was driven by the nondiabetic population, suggesting an antiatherogenic role in the early stages of lesion development.

Virtual Histology Intravascular Ultrasound Assessment of Carotid Artery Disease: The Carotid Artery Plaque Virtual Histology Evaluation (CAPITAL) Study

To determine the diagnostic accuracy of virtual histology intravascular ultrasound imaging (VH IVUS) of carotid plaque and to assess the feasibility of VH IVUS to identify plaque with embolic potential in patients undergoing carotid artery stenting (CAS). Thirty patients (17 men; mean age 74+/-7 years) were entered nonrandomly into a single-center, prospective, 2-arm study following FDA and Institutional Review Board approval. In one arm, 15 patients underwent VH IVUS examination of carotid plaque with a cerebral protection device immediately followed by carotid endarterectomy (CEA). A comparison of "virtual" with true histology was then performed, classifying plaque type by VH IVUS and histopathology in a blinded study. In the second arm, 15 patients undergoing CAS had a preliminary VH IVUS scan performed with cerebral protection. Debris collected from the filter following stenting was examined histologically and compared with the VH IVUS data. The diagnostic accuracy of VH IVUS to agree with true histology in different carotid plaque types was 99.4% in thin-cap fibroatheroma, 96.1% for calcified thin-cap fibroatheroma, 85.9% in fibroatheroma, 85.5% for fibrocalcific, 83.4% in pathological intimal thickening, and 72.4% for calcified fibroatheroma. Filter debris was captured in 2 patients prior to CEA and in 4 patients undergoing CAS for restenosis; VH IVUS classification of plaque composition was consistent with the histological evaluation of filter fragments. Calcified nodules projecting into the carotid artery lumen were associated with a higher incidence of previous neurological symptoms (66.7% versus 33.3%, p<0.05), while patients on aspirin has significantly less necrotic lipid core plaque detected by VH IVUS than patients not taking aspirin (6.4%+/-4.7% versus 9.7%+/-2.8%, p<0.05). This study showed a strong correlation between VH IVUS plaque characterization and the true histological examination of the plaque following endarterectomy, particularly in "vulnerable" plaque types. The feasibility study to examine VH IVUS data and the filter debris histology in CAS patients supports a larger prospective study.

Is Pathologic Intimal Thickening the Key to Understanding Early Plaque Progression in Human Atherosclerotic Disease?

The term “ P athologic I ntimal T hickening” (PIT) was recently introduced to define an early stage of atherosclerosis described in human coronary lesions found at autopsies of sudden death victims.1 This descriptive identifier is based on the AHA type III (intermediate) lesion and, as originally presented by Stary and collegues, it’s believed to be the morphological and chemical bridge to more advanced plaques.2 The precise histological features and clinical relevance of PIT remains unsettled, and use of the term is still far from widespread. In short, PIT identifies a lesion with an extracellular lipid pool with intimal smooth muscle cell loss typically adjacent to the medial wall in addition to varying degrees of macrophage infiltration near the lumen. These morphological features indicate a progressive lesion in the earlier stages of atherosclerosis, although there is yet the presence of a necrotic core. As recently studied by Nakashima and colleagues in this issue of Arteriosclerosis, Thrombosis, and Vascular Biology , it may provide a key in settling the chicken-versus-egg debate of atherosclerotic plaque progression: does lipid come first, or do macrophages?3 Is PIT the precursor lesion of fibroatheroma? The study in this issue uses 3-dimensional histology to attempt to address some of these issues, and, in doing so, may raise as many questions as it answers. See page 1159 Although there are many detailed autopsy studies describing various lesion morphologies, little is known how human atherosclerosis progresses from early to more advanced plaques, marked by the formation of a necrotic core. This important question remains, in part, from a lack of direct experimental testing in prospective models of human disease. Moreover, potentially relevant finding in animals are difficult to associate with humans because the pathologic change of atherosclerosis in man cannot be definitely equated with animals. Although …

Early Human Atherosclerosis

The present study was designed to clarify the morphological features of early human atherosclerosis and to determine whether specific extracellular matrix proteoglycans play a role in early atherogenesis. Step and serial sections were obtained from right coronary arteries with no or early atherosclerosis. Atherosclerosis was classified into 4 grades according to the amount of lipid deposition. Coronary arteries with Grade 0 showed diffuse intimal thickening (DIT) with no lipid deposits. The extracellular matrix proteoglycans, biglycan and decorin, were localized in the outer layer of DIT. Most cases of Grade 1 and Grade 2 exhibited fatty streaks with extracellular lipids colocalizing with biglycan and decorin in the outer layer of the intima. As lipid grades increased, macrophages increased in number and were present in the deeper layers. Most cases of Grade 3 exhibited pathologic intimal thickening (PIT) with extracellular lipids underneath a layer of foam cell macrophages. In early human coronary atherosclerosis, fatty streaks develop via extracellular deposition of lipids associated with specific types of proteoglycans in the outer layer of preexisting DIT. As the amount of the lipid increases in fatty streaks, macrophages infiltrate toward the deposited lipid to form PIT with foam cells.

Characterization of Intimal Changes in Coronary Artery Specimens with MR Microscopy

To determine if magnetic resonance (MR) microscopy can yield images sufficient for discriminating early progressive atherosclerotic lesions from nonprogressive atherosclerotic lesions in human coronary arteries. Institutional review board approval and informed consent were not required. Seventeen coronary artery segments (mean diameter, 2.8 mm +/- 1.0 [standard deviation]) were collected within 36 hours after death from 11 cadavers (six men, five women; age range at death, 33-65 years). Quantitative T1, T2, intensity-weighted (IW), and magnetization transfer (MT) maps were acquired with a 9.4-T vertical-bore magnet. Coronary artery lesions were classified as adaptive intimal thickening (AIT), pathologic intimal thickening (PIT), or intimal xanthoma (IXA). Internal anatomic fiducial landmarks and stains were applied to proximal and epicardial vessel surfaces and used to register histologic sections with MR images and thus enable comparison of MR images and Movat pentachrome-stained histologic specimens. Unique 0.0012-0.0287-cm(2) regions of interest were visually identified on quantitative T1, T2, MT, and IW maps of AIT, IXA, and PIT lesions. Distributions of T1, T2, MT, and IW values were compared with Student t and Wilcoxon two-sample tests. MR microscopic images of nonprogressive AIT and IXA lesions revealed two intimal layers. The luminal intima had higher T1 and T2 values and lower MT values than did the medial intima; these findings were consistent with compositional differences observed in histologic sections. In the IXA lesion, T2 values of both intimal layers were markedly reduced when compared with T2 values of AIT lesions because of the accumulation of lipid-laden macrophages in both layers. Progressive PIT lesions had a typical multilayered appearance or foci with a short T2 relaxation time and low IW values; these features were not observed in AIT or IXA lesions. MR microscopy enabled identification of morphologic arterial wall features that enable discrimination of progressive PIT lesions from nonprogressive AIT or IXA lesions.

Lipoprotein-Associated Phospholipase A 2 Protein Expression in the Natural Progression of Human Coronary Atherosclerosis

Although lipoprotein-associated phospholipase A2 (Lp-PLA2) has received recent attention as a biomarker of inflammation and risk for acute coronary events, its relative expression in coronary plaque phenotypes, including unstable lesions, has not been established. Coronary segments (n=30) were prospectively collected from 25 sudden coronary death patients for immunolocalization of Lp-PLA2. Lesion morphologies were classified as pathologic intimal thickening, fibroatheromas, thin-cap fibroatheromas (fibrous cap thicknesses <65 microm), and rupture. The expression of Lp-PLA2 was detected using a specific monoclonal antibody. Apoptosis was identified by DNA end-labeling using terminal deoxynucleotidyl transferase (TdT). Lp-PLA2 staining in early plaques was absent or minimally detected. In contrast, thin-cap fibroatheromas and ruptured plaques showed intense Lp-PLA2 expression within necrotic cores and surrounding macrophages including those in the fibrous cap. The degree of macrophage apoptosis was greater in thin-cap fibroatheroma and ruptures compared with less advanced plaques with additional double labeling studies showing Lp-PLA2 present in apoptotic cells in regions of high macrophage density. Lp-PLA2 is strongly expressed within the necrotic core and surrounding macrophages of vulnerable and ruptured plaques, with relatively weak staining in less advanced lesions. These findings together with the association of Lp-PLA2 in apoptotic macrophages suggest a potential role in promoting plaque instability.