Surg TodayJpn J Surg (2000) 30:37–42

The Relationship Between the Angiographic Findings andthe Clinical Features of Carotid Artery Plaque

Dong-Ik Kim1, Sun-Joung Lee1, Byung-Boong Lee1, Yong-il Kim1, Chin-Sang Chung2, Dae-Won Seo2,Kwang-Ho Lee2, Young-Hyeh Ko3, Duk-Kyung Kim4, Young-Soo Do5, and Hong-Sik Byun5

1 Division of Vascular Surgery, 2 Department of Neurology, 3 Department of Diagnostic Pathology, 4 Division of Cardiology,and 5 Department of Radiology, Samsung Medical Center, College of Medicine, Sungkyunkwan University, 50 IL Won Dong, Kangnam-Ku,Seoul 135-710, Korea

Key Words: carotid, atherosclerosis, endarterectomy, stroke,pathology

Introduction

Strokes are responsible for major disabilities among itssurvivors, at an immense cost not only to health care,but also to the quality of life. The composition of carotidartery plaque could affect the preoperative history oftransient ischemic attack, stroke, and the process ofidentifying the endarterectomy layer. Surface ulcer-ation of carotid plaque can be the source of smallemboli which form at the site of exposed plaque con-tents and thereafter cause neurologic symptoms.1 Cal-cium deposits in atheromatous plaque are one of thefeatures of complicated atherosclerotic plaque whichmakes an endarterectomy difficult. In this study, wereviewed the histological characteristics of atheroma-tous carotid plaque and analyzed the relationshipamong the histological, clinical, and angiographicfeatures.

Materials and Methods

We retrospectively reviewed 55 patients who under-went carotid endarterectomy (46 men, 9 women; meanage 58.5 6 4.9 years in men, 71.0 6 1.4 years in women)for extracranial internal carotid artery (ICA) stenosisat our institute from January 1995 to December 1997(Table 1). The degree of ICA stenosis was calculated bycomparing the residual lumen at the point of maximumstenosis to the distal cervical ICA of the arteriogram.2

The degrees of stenosis were categorized into twostrata: those with 30% to 69% stenosis (moderate) andthose with 70% to 99% (severe or high-grade) stenosis.Carotid plaque surface ulcerations were categorized

Abstract: The purpose of this study was to investigate thehistological characteristics of atheromatous carotid plaque,and to analyze the relationship between the angiographic find-ings and the clinical features. We retrospectively reviewed 55cases of carotid endarterectomy for extracranial internal ca-rotid artery stenosis, who were treated at our institute fromJanuary 1995 to December 1997. The histological examinationincluded hematoxylin–eosin staining, Masson-trichrome stain-ing, and immunostaining for antismooth muscle antibody andanti-CD68 antibody. The main compositions of the carotidplaque included synthetic type vascular smooth muscle cellsand extracellular matrix. The histological findings showed ul-ceration in 49 (89.1%) cases, calcium deposits in 42 (76.4%)cases, and an inflammatory reaction in 44 (80.0%) cases. Neu-rological abnormalities were strongly associated with plaqueulceration (P 5 0.045) and an inflammatory reaction (P 50.013), whereas no correlation existed regarding calciumdeposits (P 5 0.173). The angiographic findings showed ulcer-ation in 46 (83.6%) cases. Plaque ulceration in the angiogra-phy findings showed no statistically significant correlationwith the histologic findings (P 5 0.410) and preoperative neu-rologic abnormalities (P 5 0.059). All of the atheroscleroticrisk factors such as hypertension, smoking, diabetes mellitus,hyperlipidemia, and myocardial infarction had no statisticallysignificant correlation with the histological features of thecarotid plaque. In conclusion, the main compositions of ca-rotid plaque were synthetic-type vascular smooth muscle cellsand extracellular matrix. The histological ulceration andinflammatory reaction of the plaque showed a statisticallysignificant correlation with the preoperative neurologic symp-toms, whereas no correlation was seen in the calcium deposits.Angiographic ulceration showed no correlation with the histo-logical findings or preoperative neurologic abnormalities. Inaddition, the histological findings showed no correlation withthe atherosclerotic risk factors.

Reprint requests to: D.I. Kim(Received for publication on July 6, 1998; accepted on May 27,1999)

into three strata. The maximal depth and length of theulcer in millimeters on the arteriograms were multipliedto provide the ulcer area, in square millimeters: thosewith 10 or less (type A), those with 10 to 40 (type B),and those with greater than 40 (type C). The indicationsfor a carotid endarterectomy in our institute are: (1)symptomatic stenosis of greater than 70%, (2) symp-tomatic stenosis of 30% to 69% with type C plaqueulcer, (3) asymptomatic stenosis of greater than 70%with contralateral ICA complete occlusion, and (4) as-ymptomatic stenosis of greater than 70% with type Cplaque ulceration.

Pathologic Examination

The atheromatous carotid plaque was endarterec-tomized by two well-trained vascular surgeons. After alongitudinal arteriotomy from common carotid arteryto ICA distal to the stenotic lesion, the surface ofthe atheromatous plaque was observed to determinewhether surface ulceration were present or not. Duringthe endarterectomy procedures, we checked for grosscalcium deposits. Gross photographs of endarterec-tomized specimens were taken. The specimens weredivided longitudinally into two sections: half for trans-mission electron microscopy (TEM) and half for lightmicroscopy. The details of the histological procedureswere identical to those in our previous reports.3,4

For light microscopy, the specimens were fixed in10% buffered formaldehyde solution at room tempera-ture, embedded in paraffin, sectioned, and stained withhematoxylin–eosin and Masson-trichrome. Immunos-taining for antismooth muscle antibody and anti-CD68antibody was performed using the peroxidase-antiperoxidase technique.

For transmission electron microscopy, the specimenswere placed in a 2.5% glutaraldehyde solution and werefurther diced into smaller pieces. These pieces werethen washed in a 0.1M phosphate buffer solution for 2 h,and postfixed with osmium tetroxide for 2h at 4°C.After these double fixations, the pieces were washedwith 0.1M sodium acetate, stained en bloc with 1%uranyl acetate for 15min at 4°C, washed again with0.1M sodium acetate for 10 min at 4°C, dehydratedthrough a graded ethanol series, then were finally em-

bedded in Epon 812. Thin sections, which were stainedwith 0.5% toluidine blue and 0.5% sodium burox, wereprepared for the purpose of orientation, and ultrathinsections were then cut with an ultramicrotome (SorvalMT 1, Harford, CT, USA). The ultrathin sections werestained with 1% uranyl acetate and Raynold’s leadcitrate. Observations were carried out using Hitachi(Tokyo, Japan) HU-11A and HU-11DS electronmicroscopes.

Histological examinations were performed indepen-dently by one pathologist and the first author, whilefocusing on plaque ulcerations, calcium deposits, andinflammation. The prevalences of these features werebased on a consensus opinion between the pathologistand the first author at a joint reevaluation of their pre-viously obtained independent data.

Statistics

All values were expressed as the mean 6 SD. Statisticalsignificance was determined by the Student’s t-test. PValues of less than 0.05 were considered to be statisti-cally significant.

Results

The mean carotid stenosis according to the luminal di-ameter reduction was 89.0% 6 1.4% (Table 1). Therewere 38 (69.1%) cases with symptomatic stenosis and 17(30.9%) cases with asymptomatic stenosis. A histologi-cal examination revealed the main compositions ofthe carotid plaque to be synthetic-type vascular smoothmuscle cells and extracellular matrix (Figs. 1–5).Among the 55 cases with carotid plaque, ulcerationwas found in 49 (89.1%) cases, calcium deposits in 42(76.4%) cases, and an inflammatory reaction in 44(80.0%) cases. The relationship between the histologi-cal features of the carotid plaque and the preoperativehistory of neurological abnormalities is shown in Table2. Neurological abnormalities were strongly associated

Table 1. Characteristics of the patients and the degreea ofinternal carotid artery stenosis

Sex Age (years) StenosisMale Female Male Female (%)

46 (83.6%) 9 (16.4%) 58.5 6 4.9 71.0 6 1.4 89.0 6 1.4

a Internal carotid artery (ICA) stenosis was calculated by comparingthe residual lumen at the point of maximun stenosis to the distalcervical ICA

Table 2. Relationship between the histological features ofcarotid plaque and preoperative neurologic symptoms

Asymptomatic Symptomatic

Ulceration (1) 13 36(2) 4 2

P 5 0.045Calcium deposit (1) 11 31

(2) 6 7P 5 0.173

Inflammation (1) 17 27(2) 0 11

P 5 0.013

38 D.I. Kim et al.: Histological Features of Carotid Artery Plaque

Fig. 1. a Central lipid core of atheromatous plaque with anoverlying fibrous cap. Dystrophic calcification is present in thelipid core showing a cholesterol cleft (H&E, 3400). b Well-developed atheromatous plaque showing massive dystrophic

calcification in the superficial intimal layer (H&E, 340). cDiffuse calcification (H&E, 3100). d Higher magnification ofc (H&E, 3400)

Fig. 2a,b. Masson-trichrome stain. aFibrosis of the intimal fibrous capand the media is high lighted (340).b Diffuse fibrosis of the entire layer isshown (340)

D.I. Kim et al.: Histological Features of Carotid Artery Plaque 39

with plaque ulceration (P 5 0.045) and inflammatoryreaction (P 5 0.013), whereas no such correlation ex-isted for calcium deposits (P 5 0.173). Angiographicfindings showed ulceration in 46 (83.6%) cases (Table3). Plaque ulceration in angiography showed no statisti-cally significant correlation with the histologic findings(P 5 0.410) or preoperative neurologic abnormalities(P 5 0.059). The relationship between the histologicalfeatures of carotid plaque and the atherosclerotic riskfactors is shown in Table 4. None of the atheroscleroticrisk factors had any statistically significant correlation

Fig. 3. a Immunostaining for anti-smooth muscle antibody (PAP withDAB, 3100). b Higher magnificationof a (PAP with DAB, 3400)

Fig. 4. Immunostaining for anti-CD68 antibody showingstrong cytoplasmic staining of the macrophages infiltrated inthe periphery of the lipid core (PAP with DAB, 3400) Fig. 5. Ultrastructure of vascular smooth muscle cells in the

atheromatous plaque showing well-developed dense bodiesand pinocytotic vesicles (TEM, 310 000)

with ulceration, calcium deposits, or the inflammatoryreaction of the carotid plaque.

Discussion

The differences in the composition of carotid plaqueplay an important role in determining the course ofplaque growth and its subsequent embolic potential.

40 D.I. Kim et al.: Histological Features of Carotid Artery Plaque

Table 3. Relationship between plaque ulceration in the an-giography and histologic examinations and between plaqueulceration in the angiography findings and the preoperativeneurologic symptoms

Ulcer in angiography

(1) (2)

Ulcer in (1) 42 7histology (2) 4 2

P 5 0.410Neurologic (2) 12 5

abnormality (1) 34 4P 5 0.059

Ulceration, subintimal hemorrhage, and calcium depo-sition of carotid plaque increase the risk of ischemicneurologic events more than the smooth uncomplicatedcarotid plaque.5 The pathophysiology of carotid plaqueis the consequence of a natural growth and rupture thatare followed by repair.6,7 The early focal lesions con-tained a large number of foam cells, fat components,and extracellular matrix. By increasing the plaque size,neovascularization extends from the vasa vasorum inthe media of the arterial wall and develops in the baseof the plaque. The plaque’s growth depends on thenutrient supply. The occlusion of this nutrient arteryresults in an inflammatory reaction, plaque ischemia,and plaque degeneration. As the expanding plaquestretches the overlying endothelium, it may rupture intothe arterial lumen, thus releasing the emboli and form-ing an ulcer.8 The endothelial layer above the plaqueundergoes degenerative changes and the infarctedplaques are thereafter exposed to the bloodstream. Thisexposed ulcerated plaque represents a thrombotic sur-face. The pathogenesis of cerebral ischemia due to em-bolism has been reported by several investigators.9–11

These emboli consisted of platelets, thrombotic par-ticles, cholesterol crystals, semiliquid lipids, breakdown

products of intraplaque hemorrhages, or atheroscleroticplaque itself, including calcific materials. Seeger andKlingman12 reported that carotid plaques removed frompatients with ipsilateral TIAs or embolic strokes con-tained more lipid and more cholesterol than the plaqueremoved from asymptomatic patients. They also stud-ied the relationship between carotid plaque composi-tion, plaque morphology, and neurologic symptoms.They concluded that the significant difference in plaquelipid levels between the plaques removed from symp-tomatic and asymptomatic patients suggested that theplaque lipid concentration may be an important factorin the pathogenesis of ischemic neurologic symptomsdue to carotid atherosclerosis.13 Carotid plaque surfaceulceration is an important factor in the pathogenesis ofneurologic symptoms. Moore et al. reported three typesof ulcer according to the ulcer size.14 They measured themaximal depth and length of the ulcer in millimeterson the arteriograms. These dimensions were then multi-plied to express the ulcer area in square millimeters.Ulcers whose products were 10 or less were called typeA; between 10 to 40, type B; greater than 40, type C.They reported an annual stroke rate of 0.9%, type A;4.5%, type B; and 7.5%, type C. Zukowski et al.15 re-ported a macroscopic plaque ulceration in 26 of the 36(72%) patients with TIA. Bassiouny et al.5 found thatthe rates of the plaque surface ulceration were signifi-cantly higher in severe carotid stenosis patients than inthose with minimal stenosis. However, the associationbetween the surface ulceration and the neurologicsymptoms has not yet been uniformly observed.5,16

Calcium deposits in carotid plaque is one of the fea-tures of a complicated atherosclerotic lesion.6,17,18 Seegeret al.12,13 studied the calcium contents from 78 carotidplaques and found the calcium values in the symptom-atic and asymptomatic groups of carotid plaque to besimilar.

O’Donnell et al.19 reported that 16 out of 27ulcerations were detected on arteriography (sensitivity

Table 4. Relationship between the histological features and atherosclerotic risk factors

Hypertension Smoking DM Hyperlipidemia MI

Yes No Yes No Yes No Yes No Yes No

Ulceration (1) 31 18 31 18 21 28 13 36 19 30(2) 3 3 2 4 2 4 1 5 3 3

P value 0.528 0.158 0.655 0.601 0.596Calcium deposit (1) 26 16 26 16 20 22 12 30 13 24

(2) 8 5 7 6 3 10 2 11 4 9P value 0.981 0.604 0.117 0.340 0.437

Inflammation (1) 27 17 26 18 16 28 9 35 17 27(2) 7 4 7 4 7 4 5 6 5 6

P value 0.890 0.783 0.101 0.089 0.680

DM, diabetes mellitus; MI, myocardial infarction

D.I. Kim et al.: Histological Features of Carotid Artery Plaque 41

59%). In our study, 42 out of 49 ulcerations were de-tected on arteriography (sensitivity 85.7%). The highsensitivity in our study might be the result of the broadcriteria used to determine the ulcers in arteriography.

Various risk factors are known to contribute to theatherosclerosis of the carotid artery. Hypertension,20

diabetes mellitus,21 smoking,17 and hyperlipidemia18

promote atherosclerosis. Sueyoshi et al.22 reported thatserum cholesterol is an important risk factor in the pro-gression of carotid atherosclerosis.

Conclusion

The results of our study suggest that the main composi-tions of carotid plaque were synthetic-type vascularsmooth muscle cells and the extracellular matrix. Theplaque ulceration and inflammatory reaction of theplaque showed a statistically significant correlation withthe preoperative neurologic symptoms, but no correla-tion with calcium deposits. The angiographic ulcerationof the plaque showed no correlation with either thehistological findings or the preoperative neurologicalabnormalities. The plaque ulceration, calcium deposits,and inflammtory reaction also showed no correlationwith such atherosclerotic risk factors as hypertension,smoking, diabetes mellitus, hyperlipidemia, and myo-cardial infarction.

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