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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 5  |  Issue : 2  |  Page : 63-68

Relationship of carotid artery intima media thickness to blood pressure, age and body mass index of hypertensive adult patients


1 Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria
2 Department of Radiology, Jos University Teaching Hospital, Jos, Nigeria
3 Department of Radiology, Federal Medical Centre, Gusau, Nigeria
4 Department of Medical Microbiology, University of Abuja, Abuja, Nigeria

Date of Web Publication16-Jun-2015

Correspondence Address:
Dr. P O Ibinaiye
Department of Radiology, Ahmadu Bello University Teaching Hospital, Zaria
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2278-9596.158816

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  Abstract 

Background: The intima-media thickness (IMT) has been established as an early predictor of general arteriosclerosis in patients with hypertension. The aims of this study were to establish the relationship between carotid IMT (CIMT) and blood pressure of hypertensive adult patients and to correlate CIMT with age and body mass index (BMI) in hypertensive adult patients.
Patients and Methods: This prospective study was carried out from November 2012 to February 2013 on 200 hypertensive patients aged 21-70 years. The common carotid artery (CCA) was scanned using an ALOKA SSD-3500 ultrasound scanner with Doppler facility and a 7.5MHz linear transducer. Three measurements of the CIMT were obtained at 1cm proximal to the right and left carotid bulb and the mean value of the three measurements was recorded.
Results: There were 200 patients comprising 67 males and 133 females. Their ages ranged 21-70 years, mean of 50.62 ± 10.46 years. The right and left mean CIMT was 0.99 ± 0.13 and 0.99 ± 0.18, respectively; while the overall mean CIMT for both sides was 0.99 mm ± 0.13. The mean BMI for the studied group was 29.09 ± 5.68. The mean systolic and diastolic blood pressure (SBP and DBP) was 157.0 ± 15.5 and 97.6 ± 11.2 mmHg, respectively. There was a significant difference in the mean CIMT value for each SBP and DBP groupings. CIMT correlated positively with age and blood pressure, but had a negative correlation with BMI. Carotid plaques were seen in the CCA wall of 20 patients (10%).
Conclusion: In hypertensives, age and blood pressureare the most important determinants of CIMT. The incidence of carotid plagues in our patients was high; therefore, good control of blood pressure in hypertensives may reduce the incidence of carotid plaques and stroke.

Keywords: Blood pressure, BMI, carotid intima-media thickness, hypertension


How to cite this article:
Ibinaiye P O, Kolade-Yunusa H O, Abdulkadir A, Yunusa T. Relationship of carotid artery intima media thickness to blood pressure, age and body mass index of hypertensive adult patients. Arch Int Surg 2015;5:63-8

How to cite this URL:
Ibinaiye P O, Kolade-Yunusa H O, Abdulkadir A, Yunusa T. Relationship of carotid artery intima media thickness to blood pressure, age and body mass index of hypertensive adult patients. Arch Int Surg [serial online] 2015 [cited 2020 Oct 21];5:63-8. Available from: https://www.archintsurg.org/text.asp?2015/5/2/63/158816


  Introduction Top


Hypertension is a chronic medical condition in which the systemic arterial blood pressure is elevated; greater than or equal to 140/90 mmHg. It is the most common noncommunicable cardiovascular problem worldwide afflicting humans. Approximately 15-37% of the world's adult population is afflicted [1] and in Nigeria its prevalence is documented as 11.1%. [2] In more than 95% of hypertensive patients, there is no specific underlying cause of hypertension and such patients are said to have essential/primary hypertension or idiopathic/unknown etiology; whereas, only a small percentage have an identifiable cause (secondary hypertension). [3]

Hypertension causes thickening of the intima media of large vessels with subsequent atheroma formation. Therefore, hypertension is a risk factor for development of atherosclerosis, a systemic condition primarily affecting elastic arteries (carotid, aorta, and iliac arteries) as well as large and medium-sized muscular arteries. Arterial wall modifications represent an early involvement of the target organs in patients with hypertension. [4],[5],[6],[7] Atherosclerotic plaques start developing in the carotid arteries and aorta simultaneously, actually preceding plaque occurrence in the coronary arteries. [8],[9]

Hypertension is one of the risk factors for stroke, myocardial infarction, heart failure, peripheral vascular disease, and arterial aneurysm; and a leading cause of chronic kidney disease. Assessment of subclinical and clinical target organ damage is a key element in the management of patients with hypertension. Practical and applicable examination for predicting the damage has been long-sought. One of such practical examination for predicting organ damage is the B-mode ultrasonic measurements of intima-media thickness (IMT) in the carotid arteries. Other practical examination includes fundoscopy to check changes in the retinal and 24-h urinary excretion of protein and albumin.

The B-mode ultrasonic measurements of IMT of the carotid arteries have been used extensively for evaluating the presence and progression of arteriosclerosis in patients with hypertension. Ultrasound measurements of IMT and plaque occurrence in the carotid arteries are important not only for the assessment of structural alterations but also because the extent of atherosclerosis in these vessels reflects the severity of arterial damage in other vascular territories. [10],[11]

High resolution B-mode ultrasonography is a noninvasive, simple, safe, inexpensive, precise, and reproducible method of examining and evaluating the walls of common carotid arteries for arterial wall thickening and atherosclerotic progression and regression. It also provides a measure of carotid IMT (CIMT) and detects presence of stenosis and plaques in patients with hypertension. This technique permits accurate quantification of the CIMT, which is generally considered as an early marker of atherosclerosis sonographically. Thickening of intima-media complex alsoreflects generalized atherosclerosis [12] and assessment of CIMT has been proposed as a noninvasive measure of cardiovascular disease burden in adults. [13] Extracranial carotid arteries provide excellent and reproducible sites for IMT assessment because of their accessibility, adequatesize, and limited movement. [14]

The aim of this study was to establish the relationship between CIMT and blood pressure levels, age, and body mass index (BMI) of hypertensive adult patients.


  Patients and Methods Top


Study design

This hospital-based, prospective, cross-sectional study was carried from 1 st November, 2012 to 27 th February, 2013 at Department of Radiology, Jos University Teaching Hospital, Jos, Nigeria. An informed written consent was obtained from the subjects before enlistment into the study. Approval to carry out the study was obtained from the ethical committee of the Jos University Teaching Hospital, Jos, Nigeria.

Inclusion criteria

Adult patients attending Cardiology Clinic with confirmed primary hypertension with blood pressure ≥140/90, aged 18-70 years. The subjects were poorly controlled hypertensive patients who defaulted or not compliant with medications.

Exclusion criteria

Subjects below 18 years of age and above 70 years and patients with other associated cardiovascular risk factors such as diabetes, smoking, and hypercholesterolemia. Hypertensives on medication with blood pressure level <140/90 mmHg, patients with diagnosed secondary hypertension (this information was obtained from the patient's hospital record file), unwillingness to participate, pregnant women because of physiological changes, and accompanying dilation of CCA; [6] subjects in whom imaging circumstances were very poor, with limited boundary visualization of CCA or where there is anatomical constraint either a high carotid artery bifurcation or a short neck.

Methodology

Brief history was taken and general physical examination of the subjects was done. All patients had their fasting blood sugar level and fasting total cholesterol level checked. The blood pressure of the patients were measured by the same senior physician or senior registrar in the cardiology clinic at presentation in sitting position on the left arms using standard mercury sphygmomanometer (Accosson, cuff 12 cm × 15 cm). Hypertension was defined as blood pressure levels higher than or equal to 140/90 mmHg in at least two consecutive measurements. [15] Hypertension was classified using World Health Organization (WHO) classification as Grade 1 hypertension (systolic blood pressure (SBP) 140-159 mmHg, diastolic blood pressure (DBP) 90-99 mmHg); Grade 2 hypertension (SBP 160-179 mmHg, DBP 100-109 mmHg), and Grade 3 hypertension (SBP ≥ 180 mmHg, DBP ≥ 110 mmHg). [15] The height (in meters) and weight (in kilograms) of each subject was taken. The BMI was calculated as ratio of measured weight to square of the measured height (kg/m 2 ). BMI was classified using WHO classification as underweight (BMI <18.5); normal (BMI 18.5-24.9); overweight (BMI 25.0-29.9); and obese (BMI ≥30). [16]

Examination of the CIMT was performed using 7.5 MHz linear transducer ALOKA SSD-3500 ultrasound scanner equipped with Doppler facility. The technic of measurements of CIMT used was as described by Lee et al. [12] [Figure 1] shows the site of measurement.
Figure 1: Showing the anatomy of carotid artery. It also shows the site of measurement of intima-media thickness of CCA. CCA = Common carotid artery, ICA = Internal CA, ECA = External CA

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The data obtained was recorded in the data sheet and analyzed using Statistical Package for Social Sciences (SPSS) for windows version 19.0 (SPSS Inc, Chicago, Illinois, USA). Mean ± standard deviation was used to summarize the variables. Comparison of mean and proportion was considered statistically significant if P-value was equal to or less than 0.05. The results were presented in form of tables and figures.


  Results Top


There were 200 patients comprising of 67 males and 133 females. Their ages ranged from 21 to 70 years, mean of 50.62 ± 10.46 years. The predominant age group of the patients was 51-60 years accounting for 57 (28.5%) [Table 1]. The right and left mean CIMT was 0.99 ± 0.13 and 0.99 ± 0.18 mm, respectively, while the overall mean CIMT for both sides was 0.99 ± 0.13 mm. There was no statistically significant difference between the two sides (P = 0.386). The mean CIMT for male and female patients were 1.02 ± 0.16 and 0.977 ± 0.12 mm, respectively (P = 0.11). Males CIMT values were higher than females; however, gender difference in CIMT was not statistically significant (P = 0.11) [Table 2].
Table 1: Age distribution among hypertensive subjects


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Table 2: Mean CIMT of hypertensive


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The mean CIMT for age group 21-30 and 61-70 was 0.80 and 1.05 mm, respectively. The CIMT progressively increased with age in hypertensives and this increase was statistically significant (P = 0.000). Age has a strong correlation with CIMT (Pearson correlation = 0.35) [Table 3].
Table 3: Mean CIMT value with age group in hypertensives


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The mean SBP and DBP was 157.0 ± 15.5 and 97.6 ± 11.2 mmHg, respectively. The CIMT values for hypertensives with SBP of 140-159, 160-179, and ≥180 mmHg were 0.97, 1.01, and 1.09 mm, respectively; while CIMT values for DBP 90-99, 100-109, and ≥110 mmHg were 0.98, 1.00, and 1.07 mm, respectively. The mean CIMT increased progressively with increasing SBP and DBP. These findings were statistically significant (P = 0.007 for SBP and P = 0.002 for DBP). Both SBP and DBP had a positive correlation with CIMT (Pearson correlation for SBP is 0.22 and DBP is 0.21). In hypertensives; age, DBP, and SBP are the most important determinants of CIMT.

The mean BMI for the hypertensive patients studied was 29.09 ± 5.68. We also found that BMI had a negative correlation with CIMT in hypertensives (Pearson correlation = -0.23) and this correlation was statistically significant (P = 0.020) [Figure 2]. Carotid plaques were seen in the CCA wall of 20 hypertensive patients (10%) in this study. Twelve plaques were seen in the right CCA, while eight plaques were found in the left CCA [Figure 3].
Figure 2: Graph showing relationship between BMI and CIMT in hypertensives. CIMT = Carotid intima-media thickness, BMI = body mass index

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Figure 3: Showing a homogenous plague casting acoustic shadowing in the carotid bulb

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  Discussion Top


There was progressive increase in CIMT from 21 to 70 years in hypertensive patients. Other studies also consistently showed increased CIMT with age. [17],[18],[19],[20],[21] Our study also showed that age has a strong correlation with CIMT values recorded in hypertensive subjects (Pearson correlation 0.35). In hypertensives, higher CIMT value with age could probably be due to the combined effect of increase blood pressure levels and aging process on the intima media. Also the impact of blood pressure levels on the intima media has been considered as an accelerated form of aging and hypertensive patients develop aging process in their arterial walls earlier in life than normotensives. [21]

In this study, CIMT correlated positively with SBP and DBP of hypertensive patients (Pearson correlation for SBP is 0.22 and DBP 0.21). This was consistent with several other studies [18],[20],[22] despite differences in the methodology employed in measurement of blood pressure. While blood pressure was taken at presentation in this study; other studies used 24h SBP and DBP measurement method. [18],[20] Also, CIMT was noticed to increase with increasing blood pressure levels. In hypertensives, elevated blood pressure level can cause injury to the endothelium of blood vessels with subsequent thickening of intima media complex via medial hypertrophy, [21],[23] a process specifically related to the disease. This thickening of the arterial wall is probably an adaptive mechanism to compensate for the persistent increase in blood pressure levels [20] and the thickening of the vessel wall have been demonstrated in vivo and in vitro. [24] Therefore, increase in blood pressure has a significant effect on the IMT.

In this study, the overall mean CIMT of 0.99 ± 0.13 mm in hypertensive subjects were higher compared to values from previous studies; Honzikova et al., [18] and Plavnik et al., [20] recorded 0.60 and 0.67mm, respectively, and Lemne et al., [25] in Sweden had an overall value of 0.73 mm. The differences in CIMT observed in various studies in hypertensives could be due to sampling methods, sampling size, and racial differences. The sample size in this study was comparably larger than in other studies. [18],[20],[25] Differences in lifestyles, diet, and social habits, for instance high alcohol intake as well as chronic intake of potato chips in the study environment (Jos) is known to induce a pro-inflammatory state which is a risk factor for atherosclerosis [23] and may be responsible for the differences in the CIMT observed in this study and other studies.

In this study, the method used at arriving at CIMT value involved taking three measurements 1cm proximal to right and left carotid bulb and the mean value of the three measurements were recorded for each side; this was different from the method employed in some other studies. [20],[25] This method is simple, reliable, and reproducible. There is minimal inter- and intraobserver error. [26] Using this method allows rapid identification of the target area and ensures that an identical area is assessed on follow-up. [26] Certain infections such has viral hepatitis and human immunodeficiency virus infection have been shown to be associated with increased CIMT probably due to presence of pro-inflammatory cells which are risk factor in artherogenesis. [21],[23]

We also found that BMI had a negative correlation with CIMT in hypertensives (Pearson correlation = -0.23) and this correlation was statistically significant (P = 0.020). Similar finding was demonstrated in the studies by Honzikova et al., and Planvik et al. [18],[20] BMI has been shown to influence the CIMT, but the role of BMI in arterial wall thickening is poorly understood and its influence is probably independent of age. [27] A plaque is defined as a focal structure arising from the intima media layer of the arterial wall and encroaching into the arterial lumen. [28] Plaques are sometimes found in the wall of the vessel of hypertensive patients. Carotid plaques were seen in the vascular wall of 20 hypertensive patients (10%) in this study. These plaques were more evident in right CCA. This finding is similar to what was recorded by Lemne et al., [25] study where they also recorded high number of plaques in hypertensives which were also evident in the right carotid arteries. Umeh et al., [19] also recorded a high number of plaques among hypertensive subjects in Ibadan.


  Conclusion Top


In hypertensives, age and blood pressure (SBP and DBP) are the most important determinants of CIMT. The incidence of carotid plagues in hypertensive subjects studied is high; therefore, good control of blood pressure in hypertensives may reduce the incidence of carotid plaques and stroke.

 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]


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