200 Journal of Applied Sciences Research, 8(1): 200-206, 2012 ISSN 1819-544X This is a refereed journal and all articles are professionally screened and reviewed

ORIGINAL ARTICLES

Relation between Obesity and Ischemic Stroke Using Multislice C.T.

1Omar Hussein, 2Wafaa A. Kandeel, 1Ahmed Fathy Abd Elghany, 2Safenaz Y. Youssif

1Radiodiagnosis department, Ain Shams University. 2Biological Anthropology Department, Medical Research Division, National Research Centre, Egypt.

ABSTRACT

Background: Obesity and stroke are two major public health problems all over the world, obesity and in particular abdominal obesity plays a major role in the pathogenesis of several metabolic, cardiovascular and cerebrovascular medical disorders. Obesity is one of the most important risk factors of stroke so maintaining healthy body mass index “BMI” and abdominal fat distribution have a role for prevention. The goal of stroke imaging evaluation is to establish early diagnosis thus guiding the appropriate therapy. The aim of this study was to evaluate the relation between obesity and ischemic stroke using Multislice CT techniques (CT brain perfusion, CT angiography and CT abdomen). Methods: This cross-sectional study involved 120 Egyptian persons. Subjects were divided into cases group (n=60) and control group (n=60). CT brain perfusion or CT angiography and abdominal fat distribution were measured by 16 Multislice CT scans. Anthropometric measurements were taken for all subjects. Results: The cerebral blood flow % was correlated to the total abdominal fat, visceral abdominal fat, BMI, waist and hip circumferences and they showed linear inverse proportion relation. Moreover cerebral blood volume% showed the same linear inverse proportion with visceral fat area, BMI and hip circumference only. Conclusion: The study concludes that the cerebral blood flow% is the most important parameter of CT brain perfusion for early detection of brain ischemia; also abdominal visceral fat could be used as a predictor factor for stroke.

Kew words: Obesity, Ischemic Stroke, Multislice C.T.

Introduction

Obesity represents one of the most serious global health issues. The prevalence of obesity has increased at an alarming rate over the past 2 decades to the extent that it could be considered a pandemic (Abolfotouh M. et al., 2008). In 2008, 1.5 billion adults (aged 20 years and older), were overweight and over 200 million men and nearly 300 million women were obese (www.who.int/mediacentre). The global obesity, mainly central obesity is known to be an important risk factor in development of coronary heart disease, stroke and increased incidence of certain forms of cancers as; colorectal cancer, post-menopausal breast cancer, uterine cancer and kidney cancer-leading causes of death (Robert J. et al., 2009). Generalized obesity results in alteration in total blood volume and cardiac function also lead to difficulty in blood flow and an increased risk of blockage, both of them can cause stroke (Kopelman P. and Grace C., 2004). It is considered that the higher a person's degree of obesity, the higher his risk of stroke regardless of race, gender and how obesity is measured, according to a new study published in stroke (Sarikaya H., et al., 2011). Rapid technological advances had developed in the evaluation of acute stroke as non contrast CT brain can only provide anatomic imaging (Tomandl B. et al., 2003). Nowadays, functional imaging techniques as Multislice CT brain perfusion and CT angiography are used; CT brain perfusion is useful in acute ischemia to assess cerebral haemodynamics as cerebral blood flow (CBF), cerebral blood volume (CBV) and main transit time (MTT) (Mark W., 2008). CT angiography is noninvasive technique used for assessment of both the intracranial and extracranial circulation (Sims J., et al., 2005). Moreover Multislice CT has a role in quantitative assessment of abdominal visceral fat and is considered an optimal accurate technique (Nakamura T., 2009). The aim of this study was to evaluate the relation between obesity and ischemic stroke using recent imaging Multislice CT techniques (CT brain perfusion- CT angiography and CT abdomen).

Subjects and Methods:

Subjects:

This study was designed as a cross-sectional investigation, was conducted on 120 Egyptian persons aged between 20 and 80 years who were classified into two groups; the first group included 60 patients presented with stroke symptoms and the second group included 60 normal individuals as control group.

Corresponding Author: Omar Hussein, Radiodiagnosis department, Ain Shams University.

201 J. Appl. Sci. Res., 8(1): 200-206, 2012

The diseased group included 37 male and 23 female, (CT brain perfusion was done for 48 patients and CT angiography was done for 12 patients). The exclusion criteria were history of head trauma or contrast medium allergy, previous brain surgery and renal failure. The control group included 33 male and 27 female, (CT brain perfusion was done for 22 persons and CT angiography was done for 7 persons).

Methods:

The study extended from November 2009 to December 2011. The examinations were carried out at private radiology center, Cairo, Egypt. Informed consent was obtained from the patients prior to evaluation. 1. Radiological assessment using 16 multidetector CT scanner (GE Medical System); i) Non contrast C.T. brain was done first. ii) Dynamic Multislice CT associated with injection of non ionic low osmolar contrast medium with high concentration [Iopamidol 370 mg I/mL, Scanlux, Sanochemia diagnostics], using an automatic injector (Dual- Shot, Medrad-Stellant) via a venous access. The proper technique selected according to the clinical situation and non contrast CT findings. (a) CT brain perfusion: If symptoms started less than 6 hours (administration of a small amount 40-mL of non ionic contrast material with flow rate 5 mL/sec). (b) CT angiography: If symptoms started more than 6 hours (administration of 100 -120 mL of non ionic contrast with same high flow rate). iii) A single-slice CT scan of the abdomen at L4 – L5 level to assess visceral fat. All scans were sent to an advanced workstation (AW Volumeshare2- version 4.4 Software) where processing by a special software to analysis and obtain;  Perfusion parameters; cerebral blood flow (CBF), cerebral blood volume (CBV), main transit time (MTT), maps and curves.  CT angiography; reconstructions multiplanar reformation (MPR) with 3-dimensional.  The abdominal cut: Measurements of total fat (TFA), subcutaneous fat (SFA) and visceral fat (VFA). 2. Anthropometric measurements were taken for all subjects including weight, height, waist, hip and mid upper arm circumferences. The anthropometric measurements and instruments used followed the International Biological Programme (Hiernaux J. and Tanner J., 1969). Body mass index (BMI) was calculated [weight (kg) / height (m)2] equation. 3. Comparison between stroke patients and control group was done by the Student t-test. Multiple-regression analysis stepwise method was used to determine the correlation of abdominal fat distribution and anthropometric measurements with cerebral blood flow % and cerebral blood volume %.

Results:

Comparisons of anthropometric measurements, abdominal fat distributions between cases (n=60) and control group (n=60) are shown in Table 1. All variables (weight, BMI, waist, hip and mid upper arm circumferences and all abdominal fat data including; total fat, subcutaneous fat and visceral fat as well as visceral/ subcutaneous fat ratio and visceral/total fat ratio) are significantly higher at cases than control group. However, no significant statistically change of height between the two groups. The comparison of the CT brain perfusion parameters in the two groups are shown in Tables 2. The CBF, CBV, Blood Flow% and Blood Volume % are significantly reduced at the stroke patients (cases group) and associated with prolonged MTT compared to normal persons.

Table 1: Comparison of anthropometric measurements and the abdominal fat distributions between cases and control groups. Parameter Cases ( Stroke) Control ( Normal) (n=60) (n=60) mean ± SD mean ± SD Age 56.7 ± 11.9** 41.5±16.8 Weight (kg) 86.1 ± 12.9** 68.6±13.9 Height (cm) 164.6 ±8.8 165.6±8.8 BMI(kg/m2) 31.9±4.6** 24.9±3.9 Waist circumference (cm) 96.2±10.4** 86.1±6.7 Hip circumference (cm) 110.1±10.3** 95.7±7.7 Waist hip ratio (WHR) 0.87±0.05** 0.90±0.02 Mid upper arm (cm) 28.7±2.4* 27.7±2.8 Total abdominal fat (cm2) 823.92± 215.5** 582.19±146.7 Subcutaneous Abdominal fat (cm2) 341.54 ± 191.9** 233.23 ± 116.6 Visceral Abdominal fat (cm2) 170.10 ± 61.79** 66.23 ± 32.32 Visceral / Subcutaneous fat Ratio 0.59 ± 0.26** 0.42 ± 0.43 Visceral / Total fat % 20.75 ± 6.24** 11.08 ± 4.33 Values are the mean ± S.D. Student t-test was used to compare mean value between case and control groups. *P <0.05; **P <0.01.

202 J. Appl. Sci. Res., 8(1): 200-206, 2012

Table 2: Comparison of brain perfusion parameters between cases and control groups. Parameter Cases ( Stroke) Control ( Normal) (n=48) (n=22) mean ± SD mean ± SD Blood Flow (CBF) mL/100g/min 43.7± 24.3* 64.6 ±29.2 Blood Volume (CBV) mL/100g 2.1±1.1** 2.9±1.6 Main transient time( MTT) 4.7±2.8* 3.5±1.5 Blood Volume% 84.5%± 22.6%** 96.5±7.2 Blood Flow% 75.3%± 22.1%** 96.9%±6.7 Values are the mean ± S.D. Student t-test was used to compare mean value between case and control groups. *P <0.05; **P <0.01.

Fig. 1: 56 years old male presented by right side weakness 3 hours ago (a) non contrast CT revealed no abnormality, (b-c) CT perfusion; (b) MTT, prolonged at left basal ganglia (6.5 seconds) as compared to right normal side (4 seconds) & (c) CBF, reduced at left basal ganglia (21 mL/100g/min) as compared to normal side (30 mL/100g/min) and (d) abdominal fat ( subcutaneous fat =364.40 cm2 and visceral fat = 166.60 cm2).

The multiple correlations regression analysis between CT brain perfusion parameters and abdominal fat distribution and anthropometric measurements are shown in Tables 3. As regards correlation between CT brain perfusion parameters and abdominal fat distribution. The reduction of cerebral blood flow% was highly significantly correlated with increased total and visceral abdominal fat area. Moreover the reduction of cerebral blood volume% was only significantly correlated with increased visceral abdominal fat area. Concerning the correlation between CT brain perfusion parameters with each others; the reduction of CBF was highly significantly correlated with reduction of CBV; cerebral blood flow% and cerebral blood volume% also associated with prolonged MTT. Moreover the reduction of cerebral blood flow% and cerebral blood volume% were highly correlated with reduction of the CBF and prolonged MTT. Correlation between CT brain perfusion parameters and anthropometric measurements showed reduction of cerebral blood flow% and cerebral blood volume% in relation to increased weight, BMI, and hip circumferences. In addition increased waist circumference correlated only with reduction of cerebral blood flow%. The multiple regression analysis showed that total abdominal fat and visceral fat were correlated to blood flow % (figure 2). From all CT brain perfusion parameters, the cerebral blood flow% was the most important parameter for early detection of ischemic stroke. Also abdominal visceral fat could be used as a predictor factor for stroke.

203 J. Appl. Sci. Res., 8(1): 200-206, 2012

Fig. 2: Correlations between blood flow % and total abdominal fat (a), visceral abdominal fat (b) and subcutaneous fat (c).

204 J. Appl. Sci. Res., 8(1): 200-206, 2012

The correlations between positive findings of CT Angiography and abdominal fat distributions as well as anthropometric measurements are shown in Table 4. It shows high significant correlation between positive CT angiographic findings and visceral abdominal fat area, visceral / total fat % and increased waist and hip circumferences. However there is no statistic significant difference with other parameters.

Table 3: Correlation between CT brain perfusion parameters and abdominal fat distributions as well as anthropometric measurements. Parameter Blood Flow Blood MTT Blood. Flow% Blood. (CBF) Volume Volume% (CBV) Total Abdominal fat -0.108 -0.033 0.126 -0.416** -0.210 Subcutaneous Abdominal fat 0.095 0.000 -0.068 0-.148 0.033 Visceral Abdominal fat -0.209 -0.174 0.181 -0.384** -0.255* Visceral/Subcutaneous Fat Ratio -0.164 -0.120- 0.117 -0.205- -0.203 Visceral / Total Fat % -0.139 -0.143 0.144 -0.218 -0.158- Blood Flow (CBF) NS .738** -0.489** 0.519** 0.332** Blood. Volume (CBV) 0.738** NS 0.020 0.195 0.147 MTT -0.489** 0.020 NS -0.463** -0.316** Blood Flow% 0.519** 0.195 -0.463** NS 0.733** Blood Volume% 0.332** 0.147 -0.316** 0.733** NS Weight -0.104 -0.054 0.197 0-.447** -0.316** Height 0.205 0.198 0.081 -0.002 -0.053 BMI -0.226 -0.172 0.148 0-.463** -0.309** Waist circumference -0.161 -0.158 0.184 -0.321** -0.142 Hip Circumference -0.182 0-.169 0.161 -0.382** -0.238* Waist / Hip ratio 0.035 0.018 0.046 0.120 0.202 **. Correlation is significant at the 0.01.

Table 4: Correlation between CT angiography and abdominal fat distributions as well as anthropometric measurements. Parameter Positive CT Angiographic findings Normal CT angiography (n=11) mean ± SD (n=8) mean ± SD Total abdominal fat (cm2) 862.8± 247.4 679.2 ± 221.3 Subcutaneous Abdominal fat (cm2) 347.9 ± 157.1 275.3 ± 170.9 Visceral Abdominal fat (cm2) 195.7 ± 84.5** 88.4 ± 53.3 Visceral / Subcutaneous fat Ratio 0.59 ± 0.19 0.39 ± .26 Visceral / Total fat % 22.3 ± 5.8** 12.7 ± 6.9 Waist circumference (cm) 99.6 ± 7.0* 89.5 ± 10.0 Hip circumference (cm) 110.7 ± 7.6* 100.2 ± 10.6 Mid upper arm (cm) 29.7 ±1.8 27.8 ± 2.6 Waist hip ratio (WHR) 0.90 ± .033 .89 ± .016 BMI (kg/m2) 32.8 ± 4.8 27.8 ± 5.9 Values are the mean ± S.D. Student t-test was used to compare mean value between case and control groups. *P <0.05; **P <0.01.

Discussion:

Obesity is an established risk factor for cardiovascular and cerebrovascular diseases especially ischemic stroke (Bosnar-Puretić M. et al., 2009). General adiposity, more specific abdominal adiposity suggest that it is a strong predictor of stroke and increased risk of ischemic stroke, which is measured by BMI, waist circumference and waist-hip ratio respectively (Gang H. et al., 2007). Recently, Multislice CT proved to be an optimal technique for the accurate quantitative assessment of abdominal visceral fat (Nakamura T., 2009). Stroke is the commonest neurological cause of morbidity and mortality all over the world and being the third leading cause of death. Estimation of stroke risks in population is not only helpful for healthcare providers but also important to identify persons at elevated risk and to select proper treatments in clinical trials (Khan N. et al., 2009). Non contrast computed tomography (CT) was the first image modality of the brain and its pathology as it is widely available and can be performed quickly in acute stroke to identify hemorrhage, infarction and neoplasm (Tomandl B. et al., 2003). Numerous imaging techniques have been developed and applied to evaluate brain function as Multislice CT brain perfusion. It is useful in acute ischemia and can be performed immediately following non contrast CT to assess brain haemodynamics in the form of cerebral blood flow (CBF), cerebral blood volume (CBV) and main transit time (MTT). This technique has a unique advantage to differentiate irreversible brain tissue damage "infarcted core" from reversible tissue "penumbra" for the usage of thrombolytic agents (Ashok S. et al., 2006). Moreover CT angiography is now a widely available noninvasive technique. Its importance in acute stroke lies in its capabilities for demonstrating thrombi within intracranial vessels and for evaluating the carotid and vertebral arteries in the neck which may detect the cause of the ischemic event and can guide further management (Sims J. et al., 2005).

205 J. Appl. Sci. Res., 8(1): 200-206, 2012

The relation between CT brain perfusion parameters and obesity parameters as; abdominal fat including total, visceral and subcutaneous fat areas is an interesting issue. The aim of this study was to evaluate this relation. CT brain perfusion was evaluated by the percentage of the CBF and CBV comparing with the healthy side to overcome any technical errors. The results revealed that, the reduction of the cerebral blood flow% was highly significantly correlated with the increase in both total and visceral abdominal fat as well as with prolonged MTT. Also the reduction of the blood volume% was significantly correlated with only increased visceral abdominal fat area and highly correlated with prolonged MTT. Our results show agreement with Junko N. et al, 2004, who reported that accumulation of abdominal visceral fat was associated with lacunar infarcts among the middle-aged Japanese men in 859 patients. Concerning the CT brain perfusion, a review study by Sajjad Z., at 2008, proved that, CT perfusion imaging enables the physician to directly estimate the tissue at risk which can be salvaged with reperfusion, enabling appropriate patient selection. Wintermark M. et al. (2005), conducted a clinical trial to determine the prognostic accuracy of CT perfusion, performed in acute stroke patients at the time of emergency room admission. Accuracy was determined by comparison of CT perfusion with delayed magnetic resonance (MR) performed after 3 days of admission and by monitoring the evolution of each patient's clinical condition. He proved that the perfusion CT maps were significantly more accurate in detecting stroke, despite limited spatial coverage, the perfusion CT is highly reliable to assess the stroke extent and allows the accurate prediction of the final infarct size and the extent of the penumbra. He concluded that perfusion CT could therefore be a valuable tool in the early management of acute stroke patients. The relation between CT brain perfusion parameters and anthropometric measurements showed reduction of cerebral blood flow% and cerebral blood volume% in correlation with increased weight, BMI, waist and hip circumferences. This relation was studied by Gang H. et al., 2007, and Jood k. et al., 2004; they found that general adiposity, measured by BMI, was associated with an increased risk of ischemic or hemorrhagic stroke in both sexes. Abdominal adiposity, measured by waist circumference or waist-hip ratio, was associated with an increased risk of stroke. Other prospective studies (Kurth T. et al., 2002, Song Y., et al., 2004 and Kurth T. et al., 2005) have found that a high BMI may increase the risk of stroke, especially ischemic stroke. On the other hand few studies have found no association (Curb J. 1991 and Shaper A. et al., 1997) or even a low BMI associated with a higher risk of stroke (Cui R. et al., 2005). In the Nurses’ Health Study (Rexrode K. et al., 1997) and the Women’s Health Study (Kurth T. et al. 2005), BMI was a risk factor for ischemic and hemorrhagic stroke, but this association was highly mediated by hypertension, diabetes mellitus, and elevated serum cholesterol level. Several studies (Gang H. et al., 2007 and Walker S. et al., 1996) have also suggested that the indicators of abdominal adiposity, such as waist-hip ratio, may be a stronger predictor of stroke than general adiposity, measured by BMI.

Conclusion:

Non contrast CT and CT perfusion or CT angiography can be used in combination for a quick and accurate evaluation of acute stroke. The cerebral blood flow% is the most important parameter of CT brain perfusion for early detection of brain ischemia; also abdominal visceral fat could be used as a predictor factor for stroke.

Acknowledgements

Special thanks to every staff member at Misr Radiology Center, Cairo, Egypt for their great help and sincere support.

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