Role of high sensitivity C-reactive protein and other risk factors in intracranial and extracranial artery occlusion in patients with ischaemic stroke

Abstract

Objective

A retrospective case–control study to identify stroke-associated risk factors and quantify serum C-reactive protein in patients with ischaemic stroke, with or without intracranial and/or extracranial artery occlusion (IEAO).

Methods

Patients with ischaemic stroke and internal carotid artery occlusion (ICAO), middle cerebral artery occlusion (MCAO), ICAO + MCAO, or no IEAO (control patients) were retrospectively recruited. Data regarding stroke-associated risk factors were retrieved from medical records. High sensitivity (hs)-CRP was quantified within 3 days of hospital admission.

Results

Patients with ICAO (n = 89), MCAO (n = 74) and ICAO + MCAO (n = 29) had significantly higher serum hs-CRP concentrations, and were significantly more likely to have coronary heart disease, a history of stroke, and more than three stroke-associated risk factors than control patients (n = 84).

Conclusions

Coronary heart disease and a history of stroke are risk factors for ischaemic stroke with IEAO. Hs-CRP may be used as a marker for IEAO.

Keywords

Ischaemic stroke internal carotid artery occlusion middle cerebral artery occlusion risk factors high-sensitivity C-reactive protein

Introduction

Stroke is one of the most common diseases to threaten human health and life. Ischaemic stroke accounts for 70–80% of all cases of stroke, and is associated with high mortality and morbidity rates.¹ Ischaemic stroke is mainly caused by atherosclerosis-induced stenosis of cerebral arteries, leading to decreased or totally occluded cerebral blood flow.^2,3 Age, sex, hypertension, diabetes mellitus, hyperlipidaemia, coronary heart disease and a history of stroke are known risk factors for ischaemic stroke,^4–6 but it is unclear which of these factors are most closely associated with intracranial and/or extracranial artery occlusion (IEAO). Detection of serum biochemical markers associated with IEAO is important for estimating ischaemia, since inflammation has an important role in the development of atherosclerosis and during the ischaemic event.^7–9 Human C-reactive protein (CRP) is an acute-phase reactant that is rapidly produced by the liver after tissue injury or infection.¹⁰ CRP is a sensitive indicator of inflammation and is associated with the development of atherosclerosis,^11,12 as well as being a predictor of ischaemic attacks.^8,9,13,14 However, it remains to be determined whether serum CRP is associated with IEAO in patients with ischaemic stroke.

The aim of this retrospective case–control study was to investigate patients with ischaemic stroke and internal carotid artery occlusion (ICAO), middle cerebral artery occlusion (MCAO), or ICAO + MCAO, to identify risk factors and serum high sensitivity (hs)-CRP concentrations associated with IEAO in these patients, and also in control patients with ischaemic stroke without IEAO.

Patients and methods

Study population

The study retrospectively recruited patients with ischaemic stroke attending the Department of Neurology, Beijing Friendship Hospital, Capital Medical University, Beijing, China between January 2005 and March 2011. Inclusion criteria were: (i) hospitalization for transient cerebral ischaemic attack or acute cerebrovascular disease; (ii) cerebral infarction diagnosed according to World Health Organization criteria¹⁵ and confirmed by computed tomography (CT) or magnetic resonance imaging; (iii) head CT scan used to exclude postinfarction haemorrhage during aggravation of the disease; (iv) patients received standard treatment such as volume expansion, and antiplatelet, antihyperglycaemic, antihypertensive and neuroprotective therapies. Exclusion criteria were: (i) severe renal or hepatic function deficiency, autoimmune disease, cancer, haematological disease and rheumatic disease; (ii) severe trauma, surgery or infection within 2 weeks of disease onset or during hospitalization (including microaspiration); (iii) congenital absence of ICA or MCA. Patients were classified as having ICAO, MCAO, ICAO + MCAO, or neither (control group). The diagnosis of IEAO was confirmed by computed tomography angiography (CTA) or magnetic resonance angiography (MRA).

Clinical data including age, smoking history, medical history (diabetes mellitus, hypertension, hyperlipidaemia, coronary heart disease and stroke) and stroke severity (National Institutes of Health Stroke Scale [NIHSS] score¹⁶) were retrospectively retrieved from medical records.

The study was approved by the Institutional Review Board of Beijing Friendship Hospital, Capital Medical University, Beijing, China. The requirement for patient consent was waived due to the retrospective nature of the study.

Blood sampling and CRP assay

Venous blood (3 ml) was drawn on the third day after admission between 8.00 h and 11.00 h after an overnight fast. Blood was centrifuged at 3500g for 5 min at 4℃, and the resulting serum was stored at –80℃ until use. Serum hs-CRP was quantified via immunoturbidimetric assay using a Modular P800 analyser (Roche Diagnostics GmbH, Mannheim, Germany), according to the manufacturer’s instructions.

Statistical analyses

Normally distributed numerical data were presented as mean ± SD and analysed using one-way analysis of variance. Non-normally distributed numerical data were presented as median (25th, 75th percentiles) and analysed using Wilcoxon test. Categorical data were expressed as n (%) and compared using χ²-test. Multivariate logistic regression analysis was used to evaluate the relationship between risk factors, hs-CRP, and the development of IEAO. Statistical analyses were performed using SPSS® version 13.0 (SPSS Inc., Chicago, IL, USA) for Windows®. P-values <0.05 were considered statistically significant.

Results

The study included 192 patients with ischaemic stroke and IEAO (139 male/53 female; mean age 65.50 ± 11.26 years; age range 35–91 years). Of these, 89 had ICAO (71 male/18 female; mean age 65.28 ± 10.77 years; age range 40–91 years), 74 had MCAO (54 male/20 female; mean age 65.36 ± 11.99 years; age range 35–87 years), and 29 had both ICAO and MCAO (18 male/11 female; mean age 60.00 ± 12.34 years; age range 41–85 years). The control group comprised 84 patients with ischaemic stroke without IEAO (59 male/25 female; mean age 61.18 ± 8.90 years; age range 44–77 years).

Data regarding stroke-associated risk factors stratified by study group are shown in Table 1. Patients in each of the three IEAO groups (ICAO, MCAO, or ICAO + MCAO) were significantly more likely to have heart disease or a history of stroke than those in the control group (P < 0.01 for each comparison). Serum hs-CRP concentrations were significantly higher in patients with ICAO, MCAO or ICAO + MCAO than those in the control group (P < 0.001 for each comparison). Hs-CRP concentrations did not differ significantly between the three IEAO groups. There were no significant between-group differences in sex, age, hypertension, diabetes mellitus, hyperlipidaemia or smoking history.

Table 1.

Stroke-associated risk factors in patients with ischaemic stroke with internal carotid artery occlusion (ICAO), middle cerebral artery occlusion (MCAO), or both ICAO and MCAO, and in control patients with ischaemic stroke alone.

Characteristic	ICAO group n = 89	MCAO group n = 74	ICAO + MCAO group n = 29	Control group n = 84
Sex, male/female	71/18	54/20	18/11	59/25
Age, years	65.28 ± 10.77	65.36 ± 11.99	66.00 ± 12.34	61.18 ± 8.90
Hypertension	63 (70.8)	58 (78.4)	18 (62.1)	51 (60.7)
Diabetes mellitus	23 (25.0)	25 (33.8)	10 (34.5)	18 (21.4)
Coronary heart disease	26 (29.2)**	15 (20.3)**	8 (27.6)**	4 (4.8)
Hyperlipidaemia	20 (22.5)	10 (13.5)	6 (20.7)	7 (8.3)
History of stroke	36 (40.4)**	27 (36.5)**	10 (34.5)**	6 (7.1)
History of smoking	46 (51.7)	44 (59.5)	16 (55.2)	34 (40.5)
hs-CRP, mg/l	7.10 (1.37, 8.62)***	5.33 (1.18, 9.90)***	6.71 (2.23, 9.95)***	2.72 (0.70, 3.08)

Data presented as n (%), mean ± SD, or median (25th, 75th percentile).

P < 0.01 versus control group; ***P < 0.001 versus control group; χ²-test for categorical variables, one-way analysis of variance for normally distributed continuous variables, Wilcoxon test for non-normally distributed categorical data.

hs-CRP, high sensitivity C-reactive protein.

Table 2 includes data regarding the number of risk factors per patient in each study group. Patients in each of the three IEAO groups were significantly more likely to have more than three stroke-associated risk factors than those in the control group (P < 0.01 for each comparison). Patients in the control group were significantly more likely to have a single risk factor than those in each of the three IEAO groups (P < 0.05 for each comparison).

Table 2.

Number of stroke-associated risk factors in patients with ischaemic stroke with internal carotid artery occlusion (ICAO), middle cerebral artery occlusion (MCAO), or both ICAO and MCAO, and in control patients with ischaemic stroke alone.

Risk factors, n	ICAO group n = 89	MCAO group n = 74	ICAO + MCAO group n = 29	Control group n = 84
1	13 (14.6)*	14 (18.9)*	5 (17.2)*	31 (36.9)
2	20 (22.5)	18 (24.3)	6 (20.7)	22 (26.2)
3	25 (28.1)	19 (25.7)	6 (20.7)	15 (18.0)
>3	21(23.6)**	22 (29.7)**	9 (31.0)**	3 (3.6)

Data presented as n (%).

P < 0.05 versus control group; **P < 0.01 versus control group; χ²-test.

Multivariate logistic regression analysis found that history of stroke (odds ratio [OR] 0.424; 95% confidence intervals [CI] 0.202, 0.888) and serum hs-CRP concentration (OR 1.183; 95% CI 1.092, 1.283) were significantly associated with IEAO. History of coronary heart disease was not associated with IEAO risk.

Data regarding stroke severity (NIHSS score) are shown in Table 3. Patients in each of the three IEAO groups had significantly higher NIHSS scores than those in the control group (P < 0.05 for each comparison). Patients in the MCAO and MCAO + ICAO groups had significantly higher NIHSS scores than those in the ICAO group (P < 0.01 for each comparison). There was no significant difference in NIHSS score between the ICAO + MCAO and MCAO groups.

Table 3.

Stroke severity (National Institutes of Health Stroke Severity [NIHSS] score¹⁶) in patients with ischaemic stroke with internal carotid artery occlusion (ICAO), middle cerebral artery occlusion (MCAO), or both ICAO and MCAO, and in control patients with ischaemic stroke alone.

Stroke severity	ICAO group n = 89	MCAO group n = 74	ICAO + MCAO group n = 29	Control group n = 84
NIHSS score	3.92 (0.00, 8.50)*	6.90 (3.00, 12.00),*	8.18 (2.75, 13.00),*	1.91 (0.00, 3.00)

Data presented as median (25th, 75th percentiles).

P < 0.05 versus control group; Wilcoxon test.

P < 0.01 versus ICAO group; Wilcoxon test.

***

P < 0.001 versus control group; Wilcoxon test.

Discussion

This case–control study of patients with ischaemic stroke found that those with IEAO were significantly more likely to have coronary heart disease, a history of stroke, and more than three stroke-associated risk factors than control patients without IEAO. In addition, patients with IEAO had significantly higher hs-CRP levels than controls in the present study. Our finding that serum hs-CRP concentration and history of stroke were significantly associated with IEAO suggests that these factors may be involved in IEAO pathogenesis. Patients in the ICAO, MCAO, and ICAO + MCAO groups had significantly higher NIHSS scores than those in the control group.

It is well known that atherosclerosis attributes to ischaemic stroke.^2,3 A study found that 6.9% of an asymptomatic population aged ≥40 years had intracranial atherosclerosis, and that hypertension, glycosuria, coronary heart disease and family history of stroke were risk factors for intracranial artery stenosis in these individuals.⁴ Age, sex, hypertension, diabetes mellitus, hyperlipidaemia, coronary heart disease and a history of stroke are known risk factors for ischaemic stroke.^4–6 In the present study, we investigated these risk factors in 192 patients with ischaemic stroke with ICAO, MCAO, or ICAO + MCAO, and compared them with 84 patients without IEAO. We found that coronary heart disease and a history of stroke occurred more frequently in patients with IEAO than in those without. Transcranial Doppler ultrasonography of 3057 patients with at least one vascular risk factor (hypertension, diabetes mellitus or hyperlipidaemia) found that 12.6% of patients had middle cerebral artery (MCA) stenosis.¹⁷ Advanced age, hypertension, diabetes mellitus and hyperlipidaemia were associated with MCA stenosis, and its prevalence increased with the number of risk factors.¹⁷ This is in accordance with the present finding that patients with IEAO were significantly more likely to have more than three stroke-associated risk factors than control patients, suggesting that the increasing number of risk factors contributes to intracranial/extracranial artery occlusion. MCA stenosis is known to increase the risk of vascular disease mortality in patients with type 2 diabetes mellitus,¹⁸ and patients with stroke or transient ischaemic attack attributed to stenosis of a major intracranial artery have a 12–14% risk of recurrence during the following 2 years, despite antithrombotic treatment.¹⁹ Early control of these risk factors is therefore vital to effectively prevent the occurrence of stenosis and occlusion of the intra- and extracranial arteries, reducing the incidence of ischaemic stroke.

C-reactive protein is an indicator of inflammation and a marker of atherosclerosis,^11,12 and is associated with ischaemic attacks in patients with ischaemic stroke.^8,9,13,14 Serum hs-CRP concentrations have been shown to correlate with morphological features of rapidly progressive carotid atherosclerosis, suggesting that hs-CRP is a sensitive marker for the presence of active atherosclerotic disease.²⁰ In addition, in a case–control study of 600 patients with ischaemic stroke and 600 matched controls, serum CRP concentrations were significantly higher for all ischaemic subtypes than controls, both in the acute phase and at 3-month follow-up examinations.²¹ Elevated serum CRP has been found to significantly predict the risk of future ischaemic stroke in elderly patients.⁹ Furthermore, increased hs-CRP is associated with the presence of macrophages and T lymphocytes in plaques, reflecting plaque instability that can lead to an ischaemic event.²² Patients with ischaemic stroke and IEAO had significantly higher serum hs-CRP concentrations than controls in the present study, further suggesting that hs-CRP is a sensitive marker for the presence of vascular occlusion in these patients. There was no significant difference in hs-CRP concentrations between the three IEAO groups, however.

Serum hs-CRP has prognostic significance; elevated hs-CRP successfully predicted poor outcomes 1 year after acute stroke.²³ It has been reported that hs-CRP and homocysteine were independent predictors of short-term outcome and mortality after acute ischaemic stroke.²⁴ In contrast, others found that hs-CRP concentration could predict neither functional disability 3 months after stroke onset,²⁵ nor the severity of short-term functional disability.²⁶ We are planning a prospective study to determine the correlation between hs-CRP concentration and prognosis in patients with IEAO.

The present study had some limitations. First, due to the retrospective nature of this study, selection bias may occur and our findings may therefore not be applicable to the general population. An alternative and more efficient matching technique would eliminate this possibility. Secondly, stroke severity was assessed via NIHSS score rather than actual infarct volumes. Thirdly, we examined serum hs-CRP only, and did not include other inflammatory markers. Further studies are required to evaluate other inflammatory markers in this patient group. Finally, hs-CRP was quantified on one occasion only. Future studies should include multiple measurements.

In conclusion, coronary heart disease and a history of stroke are risk factors for ischaemic stroke with IEAO. Patients with IEAO were more often associated with more than stroke-associated risk factors and had increased serum hs-CRP levels compared with control patients. Hs-CRP may be used as a marker for IEAO, but could not differentiate between patients with ICAO, MCAO, or ICAO + MCAO.

Footnotes

Declaration of conflicting interest

The authors declare that there are no conflicts of interest.

Funding

This work was supported by a grant from the National Natural Science Foundation of China (No. 81371355) and the Beijing Municipal Health System High-Level Technician Cultivation Project (No. 2009-3-07).

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