|Year : 2019 | Volume
| Issue : 3 | Page : 393-398
Hemoglobin A1c-related histologic characteristics of symptomatic carotid plaques
M Tecellioglu1, S Alan1, S Kamisli1, FS Tecellioglu2, O Kamisli1, C Ozcan1
1 Department Pathology, School of Medicine, Inonu University, Malatya, Turkey
2 Department of Pathology, Malatya State Hospital, Malatya, Turkey
|Date of Acceptance||14-Dec-2018|
|Date of Web Publication||6-Mar-2019|
Dr. M Tecellioglu
Department of Neurology, Inonu University, School of Medicine, Malatya, 44280
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: The aims of our study were to compare the histomorphological characteristics of carotid plaques and glycosylated hemoglobin (HbA1c), which are risk factors for ischemic stroke, in patients who underwent carotid endarterectomy for carotid artery stenosis. Moreover, we aimed to identify the structures that were histologically affected by symptomatic carotid plaques in cases with elevated HbA1c. Materials and Methods: A total of 64 patients who presented with ischemic stroke and had not previously been diagnosed with diabetes were retrospectively evaluated. All stroke risk factors were reviewed. Carotid plaques were graded separately by two different pathologists through microscopic assessment of the following parameters: plaque rupture, lipid core, fibrous cup thickness, inflammation, intraplaque hemorrhage, thrombus, calcification, necrotic core, and neovascularization. An HbA1c value <6.3% was accepted as normal or indicative of prediabetes (group 1), whereas patients with values ranging between 6.3-7.4%, 7.5-8.4%, and >8.4% were categorized into the effectively controlled (group 2), less effectively controlled (group 3), and uncontrolled (group 4) groups, respectively. Results: The mean age of the patients was 73.0 ± 4.5 years in group 1, 69.7 ± 2.3 years in group 2, 66.0 ± 8.5 years in group 3, and 62.7 ± 7.1 years in group 4. A negative correlation was present between age and HbA1c. Smoking, hypertension, low-density lipoprotein cholesterol levels, and triglyceride levels were not significantly different among the four groups. According to the HbA1c classifications, the fibrous cup thickness was 2.64 ± 0.3 mm in group 1, 1.85 ± 0.4 mm in group 2, 1.68 ± 0.5 mm in group 3, and 1.45 ± 0.6 mm in group 4. The fibrous cup became thinner as the HbA1c value increased. Other parameters of unstable carotid plaques did not differ among the HbA1c groups. Conclusions: Increased HbA1c values seem to contribute to plaque instability through the formation of a thin fibrous cup. Thus, of the carotid artery plaque parameters including fibrous cup thickness, plaque rupture, lipid core, inflammation, intraplaque hemorrhage, thrombus, calcification, necrotic core, and neovascularization, fibrous cup thickness is the only histomorphological feature that affected by HbA1c.
Keywords: Carotid plaque, carotid plaque histology, fibrous cup thickness, HbA1c
|How to cite this article:|
Tecellioglu M, Alan S, Kamisli S, Tecellioglu F S, Kamisli O, Ozcan C. Hemoglobin A1c-related histologic characteristics of symptomatic carotid plaques. Niger J Clin Pract 2019;22:393-8
|How to cite this URL:|
Tecellioglu M, Alan S, Kamisli S, Tecellioglu F S, Kamisli O, Ozcan C. Hemoglobin A1c-related histologic characteristics of symptomatic carotid plaques. Niger J Clin Pract [serial online] 2019 [cited 2019 May 21];22:393-8. Available from: http://www.njcponline.com/text.asp?2019/22/3/393/253457
| Introduction|| |
Ischemic stroke and transient ischemic attack (TIA) usually develop because of unstable carotid lesions that lead to thrombus formation or occlusion of the carotid arteries. Carotid endarterectomy (CEA) has been shown to decrease absolute ipsilateral stroke risk by 16% compared to the best medical treatment in symptomatic patients with severe carotid artery stenosis (≥70%).
The histologic characteristics of unstable carotid plaques have been identified in numerous studies., A thin or ruptured fibrous cup, intraplaque hemorrhage, large lipid-rich necrotic core, inflammation, thrombus, intimal smooth muscle cells, calcification, and neovascularization are unstable plaque characteristics associated with stroke development.,,,
Diabetes is one of the classic risk factors of stroke. Stroke is more common in patients with diabetes and is responsible for approximately 25% of diabetes-related deaths. The majority of strokes in diabetic patients are ischemic. The elevation of glycosylated hemoglobin (HbA1c) is reported to be a risk factor for ischemic stroke.
The aim of this study was to compare the post-CEA histomorphological characteristics of the carotid plaques of patients who experienced a stroke due to carotid artery stenosis and to determine HbA1c values, one of the risk factors for ischemic stroke.
| Materials and Methods|| |
A total of 64 patients without a previous diagnosis of diabetes, and who presented to the Inonu University Neurology Department with ischemic stroke and underwent CEA, were retrospectively evaluated. CEA was performed in patients with ≥70% stenosis according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria. Carotid stenosis was determined by intra-arterial cerebral angiography. All patients were symptomatic. Routine cardiologic and medical evaluations were conducted and possible cardioembolism or systemic infectious diseases were ruled out before CEA. Antiplatelet treatment and oral anticoagulants were discontinued at least 6 days before surgery, and the routine coagulation parameters on the day of surgery were normal in all patients. Only patients who had undergone surgery within 30 days after the stroke were included, whereas patients who had undergone CEA for restenosis or carotid stenosis because of radiotherapy were excluded.
Patients were stratified into groups according to five long-term randomized controlled studies conducted to determine treatment strategies in adults with diabetes, as follows: HbA1c <6.3%, normal or prediabetic (group 1); HbA1c 6.3-7.4%, effectively controlled (group 2); HbA1c 7.5-8.4%, less effectively controlled (group 3); and HbA1c >8.4%, uncontrolled (group 4).
Routine procedures for carotid plaques were performed in all patients. All carotid plaques were excised en bloc. The plaques were washed with saline and fixed with 10% formalin after the surgery, and the calcified lesions were decalcified. Transverse macroscopic specimens of 2-mm thickness were obtained. Each 2-mm tissue was embedded in a separate paraffin block. Sections 4-5 μm thick were taken from the paraffinized blocks, transferred to slides, and stained with the elastica van Gieson (EVG) and hematoxylin & eosin (H&E) tissue stains, followed by quantitative analysis. The slides were evaluated with light microscopy (BX50®; Olympus).
The following characteristics were then graded separately by two pathologists on microscopic examination using simple and repeatable semi-quantitative scales, as previously described: plaque rupture, lipid core, fibrous cup thickness, inflammation (macrophage infiltration), intraplaque hemorrhage, thrombus (platelet and macrophage adhesion), calcification, necrotic core, and neovascularization. A lipid core was defined as amorphous material containing cholesterol crystals and was considered “large” when it accounted for 50% of the plate thickness or 25% of the total cross-sectional area. Intraplaque hemorrhage was defined as erythrocyte accumulation within the plaque causing deterioration of the plaque structure or iron- or hemosiderin-loaded macrophages within the plaque connective tissue. Calcification was defined as nodular or calcific nodules. Inflammation was defined as groups of more than 50 macrophages in the plaque or core. Plaque rupture was recorded if there was a clear association between the lipid core and the lumen. Thrombus was defined as the organization of fibrin and red blood cells in the lumen [Figure 1]. For evaluating the thickness of the fibrous cup, the thickest fibrous cup section between the necrotic core and the lumen was used and measured in mm [Figure 2].
This study was approved by the ethics review committee of the University of Inonu.
All analyses were performed using SSPS for Windows statistical software (ver. 17.0; SSPS Inc., Chicago, IL, USA). A power analysis indicated that at least 60 patients were required. Parametric statistical tests were used because our variables conformed to a normal distribution. Analysis of variance (ANOVA) was used to compare more than two groups, and the post-hoc Tukey test was used for multiple comparisons. The Chi-square test was used to compare qualitative variables. The Pearson correlation coefficient was calculated to determine the direction and strength of the relationship between constant variables. A P value <0.05 was considered to indicate statistical significance.
| Results|| |
The study participants consisted of 24 females (37.5%) and 40 males (62.5%). The mean age was 67.3 ± 7.2 years. A small lipid core was found in 44 (68.8%) patients, and a large lipid core in 20 (31.2%) patients. There was no macrophage infiltration in two (3.1%) patients, <50 macrophages in 28 (43.8%) patients, and ≥50 macrophages in 34 (53.1%) patients. Plaque rupture, calcification, intimal smooth muscle cells, and a necrotic core were present in all patients. Intraplaque hemorrhage was also present in all patients and was mild in 16 (25%), moderate in 36 (56.2%), and severe in 12 (18.8%) patients. A thrombus was present in 62 (96.1%) patients, and absent in 2 (3.1%) patients. Neovascularization was present in 60 (93.8%) patients, and absent in 4 (6.2%) patients. The mean fibrous cup thickness was 1.85 ± 0.6 mm [Table 1].
According to the HbA1c classification, 14 (21.9%) patients were in group 1, 14 (21.9%) patients were in group 2, 16 (25%) patients were in group 3, and 20 (31.2%) patients were in group 4. The mean HbA1c value was 7.2% ± 1.2%. The mean age of the patients was 73.0 ± 4.5 years in group 1, 69.7 ± 2.3 years in group 2, 66.0 ± 8.5 years in group 3, and 62.7 ± 7.1 years in group 4. A negative correlation was present between age and HbA1c (P = 0.042). Smoking, hypertension, low-density lipoprotein (LDL) cholesterol levels, and triglyceride levels were not significantly different among the groups (P > 0.5 for all). The fibrous cup value was 2.64 ± 0.3 mm in group 1, 1.85 ± 0.4 mm in group 2, 1.68 ± 0.5 mm in group 3, and 1.45 ± 0.6 mm in group 4. The fibrous cup became thinner as the HbA1c value increased (P = 0.021) [Table 2]. The parameters other than a thin fibrous cup were not significantly different among the groups according to HbA1c values.
|Table 2: Comparison of HbA1c values, mean age, and mean fibrous cup thickness|
Click here to view
| Discussion|| |
In this study, when evaluating carotid plaque histomorphological characteristics according to HbA1c values, fibrous cup thickness was inversely associated with HbA1c and directly correlated with age in stroke patients.
Advanced age is an unmodifiable risk factor for both hemorrhagic and ischemic stroke. The risk of stroke doubles in women and men every 10 years after the age of 55 years. It has been reported that approximately 75-80% of strokes occur in individuals >65 years, whereas 50% occur in those >70 years, and 25% in those aged >85 years., In patients with diabetes, age at the time of stroke is lower, and the overall prognosis is worse. In the current study, age at the time of stroke decreased as HbA1c values increased. Other risk factors for stroke such as smoking, hypertension, LDL levels, and triglyceride levels were not different among the groups according to HbA1c values.
Stroke is 2-6-fold more common in patients with diabetes, and the majority of cases are of the ischemic type. Metabolic and hemodynamic abnormalities in diabetic patients are associated with risk of stroke. Diabetes plays an important role in stroke pathogenesis by increasing peripheral resistance and atherosclerosis progression, and thus also atherosclerotic complications due to diabetic microangiopathy.,,
HbA1c levels are an alternative diagnostic method for diabetes, as they are associated with diabetes-related retinopathy. In addition, they are independent of fasting status and reflect the glycemic level in the last 3 months. HbA1c elevation is accepted as a risk factor for stroke and is associated with a two-fold higher stroke rate. HbA1c levels are also an independent indicator of cardiovascular mortality in patients who have not been diagnosed with diabetes. They are believed to be related not only to microvascular but also to macrovascular results. In fact, carotid intima media thickness was found to be high in patients with low HbA1c values. HbA1c is also associated with coronary and peripheral atherosclerosis in non-diabetic patients with normal fasting blood glucose., Among patients with type 2 diabetes, the incidence of coronary artery disease and unstable atherosclerotic coronary plaque are higher in those with HbA1c levels ≥7% compared to individuals with lower values. Moderate HbA1c elevation has also been reported to contribute to the development of carotid plaques. Similarly, previous studies reported a strong association between HbA1c and carotid atherosclerosis. The HbA1c level can, therefore, be said to be an independent and modifiable risk factor for carotid and coronary atherosclerosis. The main aim of our study was to determine the components of symptomatic carotid plaques that are histomorphologically affected by HbA1c elevation.
Ischemic strokes and TIA usually develop because of unstable carotid lesions. Plaque rupture, a thin fibrous cup, calcification within the fibrous cup, plaque thrombus, macrophage infiltration, and intraplaque neovascularization are independent risk factors for symptomatic unstable carotid plaques.,
A necrotic core has been found in 94% of symptomatic carotid plaques. Plaque rupture is more common in symptomatic carotid plaques than in asymptomatic plaques, and its prevalence is higher in patients presenting with stroke than in those with TIA or who are asymptomatic., Microcalcifications within the fibrous cup increase structural stress on the plaque and are reported to be an independent risk factor for symptomatic plaques., Atherosclerotic plaque intimal smooth muscle cell content is associated with plaque instability. Neovascularization, intraplaque hemorrhage,, lipid core, and macrophage infiltration , have been reported to be among the major characteristics of unstable atherosclerotic plaques in previous studies. However, parameters other than a thin fibrous cup did not show a statistically significant difference among the groups according to HbA1c values in our study. In other words, fibrous cup thickness is the only unstable plaque characteristic affected by HbA1c levels independent of other stroke risk factors.
The lipid index was higher, and a thin fibrous cup and macrophage infiltration were more common, among diabetic patients with HbA1c values ≥8% in a study evaluating coronary artery plaque characteristics. A thin fibrous cup together with a necrotic lipid core in coronary arteries of patients with type 2 diabetes was associated with increased plaque instability. Minimum fibrous cup thickness was reported as the most accurate pathologic factor when evaluating plaque instability in a previous study. The mean maximal fibrous cup diameter was also found to be significantly lower in symptomatic carotid plaque patients than in asymptomatic ones. Moreover, the fibrous cup was reported to be thinner in symptomatic patients with macroscopically high levels of carotid stenosis on carotid ultrasonography and magnetic resonance imaging compared to asymptomatic patients. Although the incidence of a thin fibrous cup was high in our patient group, who were all symptomatic, it increased even further with increasing HbA1c values.
In conclusion, among fibrous cup thickness, plaque rupture, lipid core, inflammation, intraplaque hemorrhage, thrombus, calcification, necrotic core, and neovascularization, fibrous cup thickness was the only histological parameter of unstable carotid plaques associated with HbA1c levels. In other words, HbA1c elevation was independently associated with carotid plaque instability using a thin fibrous cup.
| Limitations of the Study|| |
This study was retrospective in nature, and the number of patients included was low. Our results should be supported by studies including a larger number of patients. Although the patients included herein were operated on within 30 days after the last clinical stroke-related event, guidelines suggest an optimal time period of 14 days. Moreover, all patients were symptomatic, and we did not include an asymptomatic patient group. In addition, this study was quantitative in nature and included a morphological analysis of carotid plaque specimens but no enzymatic tests, such as for matrix metalloproteinase. Other carotid plaque characteristics useful for predicting plaque instability, such as wall shear stress, were not evaluated, and plaque instability evaluation was limited to pathology indices.
Financial support and sponsorship
This study was supported by the İnönü University Scientific Project Unit (Project no. 2016-64).
Conflict of interest
There is no conflict of interest
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (name of institute/committee) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]