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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 3  |  Issue : 1  |  Page : 16-21

Diagnostic value of carotid intima-media thickness in the investigation of atherosclerosis


1 Department of Radiology, Medicana Hospital, Konya, Turkey
2 Department of Radiology, Akdeniz University, Antalya, Turkey
3 Department of Radiology, Osmangazi University, Eski?ehir, Turkey
4 Department of Biostatistics and Medical Informatics, Akdeniz University, Antalya, Turkey

Date of Web Publication20-Jan-2015

Correspondence Address:
Mehmet S Durmaz
Necip Fazil Mah, Fatih Cad. No. 4/1, Meram, 42090 Konya, Ankara
Turkey
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DOI: 10.4103/1658-631X.149660

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  Abstract 

Objective: The aim of this study was to assess the relationship between intima-media thickness (IMT) and coronary artery disease (CAD), peripheral artery disease (PAD), carotid artery stenosis (CAS) and risk of cerebrovascular disease (CVD) and to evaluate the effectiveness of the measurement of the common carotid artery IMT through ultrasonography (US) screening of asymptomatic CAD, PAD, CAS.
Patients and Methods:
A total of 482 patients (215 females, 267 males) with ages ranging between 65 and 94 years old (mean age: 71.4 years) were examined with ultrasound (US).
Results:
Among the 482 patients, 226 (46.8%) (151 males, 75 females) had increased IMT values. A significant relationship was observed between the increase in the IMT, gender and age. The association between increased IMT and CAS (P = 0.0001), CAD (P = 0.007), PAD (P = 0.0001) and CVD (P = 0.011) was found statistically significant (P < 0.05).
Conclusion:
The increase in the IMT may be used as an independent predictor to foresee the presence and diagnosis of CAD, PAD, CAS and CVD. The results of this study suggest screening for atherosclerosis (CAD, PAD, CAS) patients over 65 years of age using measurement of carotid IMT with US.

  Abstract in Arabic 

ملخص البحث:
تهدف هذه الدراسة إلى تقييم العلاقة بين سماكة البطانة وأمراض الشريان التاجي، والشرايين الطرفية وتضيق الشريان ألسباتي وكذلك أمراض الأوعية الدماغية. شملت الدراسة 284 مريضًا تتراوح أعمارهم بين 49 - 56 عامًا؛ تم فحصهم جميعًا بالموجات فوق الصوتية. ووضحت النتائج علاقة إحصائية بين سماكة البطانة وبين عمر وجنس المريض. خلصت الدراسة إلى إن ازدياد سماكة البطانة يمكن أن يستخدم كمؤشر مستقل لتشخيص أمراض الشريان التاجي، الشرايين الطرفية، تضيق الشريان ألسباتي وأمراض الأوعية الدماغية. يوصي الباحثون بإجراء عملية الفرز لهذه الأمراض لمن تجاوز الخامسة والستين من العمر باستخدام قياس سماكة البطانة بالموجات فوق الصوتية.




Keywords: Carotid artery stenosis, carotid intima-media thickness, coronary artery disease, peripheral artery disease, ultrasound


How to cite this article:
Durmaz MS, Yilmaz S, Keven A, Kara T, Ariöz H, Bozkurt S, Sindel T. Diagnostic value of carotid intima-media thickness in the investigation of atherosclerosis. Saudi J Med Med Sci 2015;3:16-21

How to cite this URL:
Durmaz MS, Yilmaz S, Keven A, Kara T, Ariöz H, Bozkurt S, Sindel T. Diagnostic value of carotid intima-media thickness in the investigation of atherosclerosis. Saudi J Med Med Sci [serial online] 2015 [cited 2019 Sep 21];3:16-21. Available from: http://www.sjmms.net/text.asp?2015/3/1/16/149660


  Introduction Top


Sonographically, atherosclerotic plaques are first observed as an increase in the combined thickness of the intima and media layers, followed by echogenic material extending towards the arterial lumen. The measurement of the intima-media thickness (IMT) through ultrasonography (US) is a sensitive method of assessing of early-stage atherosclerosis. An IMT over 0.9 mm is an abnormal finding. [1],[2] The increase in the IMT plays an important role as a scanning method for cardiovascular disease (CVD) [1],[2],[3],[4],[5] An increase in IMT is associated with ageing. [6] Various studies have found a significant association between IMT and the presence and extent of the coronary artery disease (CAD) [1],[7],[8],[9],[10] and peripheral arterial disease (PAD). [6] An increase of IMT in the common carotid artery have been associated with a higher risk of stroke and a higher risk of long-term stroke recurrence. [11] The degree of the stenosis in the internal carotid artery is related to the increase in IMT in the common carotid artery. [12] An increase of IMT in the carotid artery is usually accompanied by plaques. The degree of the stenosis caused by the plaques is associated with strokes and transient ischemic attacks (TIA). [12]

Increased IMT is associated with an increase in the risk of vascular mortality and morbidity. [13] The increase in the IMT may be used as an independent variable in order to predict the presence and diagnosis of the CAD, PAD, carotid artery stenosis (CAS) and risk of CVD.

Atherosclerotic disease is common in patients over 65 years of age. This population is recommended to undergo screening methods to identify those who may need prophylactic treatment. The measurement of IMT using US to screen for asymptomatic CAD, PAD, CAS in this subgroup may prove to be cost-effective and have an effect on survival.

The purpose of this study was to assess the relationship between IMT and CAD, PAD, CAS, CVD and to evaluate the effectiveness of the measurement of the common carotid artery IMT through US screening of asymptomatic CAD, PAD, CAS. The results of this study suggest screening for atherosclerosis (CAD, PAD, CAS) for patients over 65 years of age, using measurement of carotid IMT with US, which is a sensitive, simple, economic, non-invasive repeatable method.

[TAG:2]PATIENTS AND METHODS [/TAG:2]

A total of 482 patients over the age of 65 (between 65 and 94) including 267 males (mean age: 71.5) and 215 females (mean age: 71.3), who had presented to our department for various reasons, were enrolled in this study. Patients were provided with detailed information about the procedures and they signed written consent forms. The approval of the ethics committee was obtained before the initiation of the study.

Patients with a history of myocardial infarction diagnosed at a hospital, bypass or stent surgery, and those who were diagnosed with significant (>50%) stenosis in the coronary arteries detected through computed tomography angiography, or digital subtraction angiography were defined as patients with CAD. Patients with clinical findings pointing to the CVD or those who were diagnosed through imaging findings and were under neurological follow-up or treatment due to TIA's were accepted as patients with CVD.

Three radiologists experienced in Doppler US evaluated the patients. The duplex US imaging was carried out with the help of the Aplio (Toshiba, Japan) device, using a 7.5 MHz linear transducer and a 3 MHz convex transducer.

The carotid artery examination was carried out in the supine position, with the head slightly extended and rotated 45° towards the opposite side from the side to be examined. The IMT was measured at the thickest point (usually 1 cm proximally to the bulbus) and in the axial and sagittal planes [Figure 1]. With the help of gray-scale US, both carotid arteries were viewed in the axial and sagittal planes, beginning from the most proximal sections. Then moving the transducer cranially until the most distal section that is visible past the carotid bifurcation in the cranial aspect. The imaging was begun with real time gray-scale in the axial and sagittal planes, followed by Doppler and duplex ultrasounds and concluded with spectral measurements. The stenosis in the CAS was calculated according to the US consensus conference criteria published in 2003. [14]
Figure 1: Measurement of the intima-media thickness with gray-scale ultrasonography.

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For the assessment of the arterial system of the lower extremities, the abdominal aorta and the iliac arteries were imaged using a low-frequency convex probe; while high-frequency linear probes were used in the peripheral parts. Both common and external iliac arteries and the common, superficial and deep femoral arteries were imaged in the sagittal and axial planes while the patients were in the supine position. The popliteal arteries were assessed in the supine position, with the knees slightly bent and the lower extremity in external rotation and abduction. The anterior tibial artery was distally followed until the dorsalis pedis artery. The tibioperoneal trunk, posterior tibial artery and the peroneal arteries were followed until the distal aspect as long as they were visible. The flow velocities and wave forms were assessed in terms of arterial stenosis and obstruction using the gray-scale, colour duplex and spectral analysis criteria.

Statistical analysis was performed using PASW 18 (SPSS/IBM, Chicago, IL, USA) and the level of significance was established at the 0.05 level (two-sided). Primarily, the definitive statistics related to the variables were evaluated. The variables were expressed in terms of the mean, minimum and maximum values and the standard deviations. These were observed supporting through cross reference tables and frequency tables. Since the majority of the data related to the variables was categorical, the Chi-square test was employed for the analysis of these variables. This test was performed on the two groups of variables comprising the dependent and independent variables where we searched for a relationship. Also, the influence of the independent variables on the dependent variables was assessed through the logistic regression analysis. In addition, correlations were assessed with Pearson or Spearman coefficients.


  Results Top


In 226 (151 males, 75 females) of the 482 patients enrolled in the study, the IMT was >0.9 mm, which pointed to an increase. The IMT was observed to increase with advancing age. The mean age of those with increased IMT readings was found to be higher than those without an increase. The increase in the IMT which was parallel to advancing age, was observed to be statistically significant (P = 0.0001).

An increase in the IMT was observed in 56.6% of the males and 34.9% of the females ([Table 1]). The association of male sex with the increase in the IMT was found to be statistically significant (P = 0.0001).
Table 1: Rates of the increasing intima-media thickness of according to the sexes

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In patients where the IMT was over 0.9 mm, usually type 2 plaques were observed in the carotid arteries. A significant relationship was observed between the increase in IMT and the presence of the plaques (P = 0.0001).

In 150 of the patients enrolled in the study, no plaque formation or stenosis was observed in the carotid arteries. In 274 patients, stenosis below 50% in at least one of the carotid artery was observed; while in 58 patients (12%) stenosis over 50% in at least one of the carotid arteries was detected. In 28 out of these 58 patients, unilateral stenosis between 50% and 69% was observed in the carotid arteries; while 14 patients had over 70% stenosis; 8 had preocclusive stenosis and 8 further patients had unilateral total occlusions in the carotid artery. In 13.9% of the males and 9.8% of the females in the study, stenosis >50% was present at least unilaterally in the carotid artery. In 48 out of the 226 patients with an IMT over 0.9 mm, a stenosis ≥50% was present at least unilaterally in the carotid artery. The relationship between the increase in the frequency of CAS and the increase in the IMT was statistically significant (P = 0.0001) [Table 2].
Table 2: Increasing of intima-media thickness and carotid artery stenosis

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In 120 of the 162 patients with CAD, there was an increase in the IMT. A statistically significant relationship was observed between the increase in the IMT and the CAD (P = 0.007), [Table 3].
Table 3: Increasing of intima-media thickness and coronary artery disease

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Of the 482 patients enrolled in the study, 110 were symptomatic in terms of CVD, 22 patients (13 males, 9 females) had TIAs, 88 patients (55 males, 33 females) had a history of stroke diagnosed through imaging findings. Of the 226 patients with increased IMT, 60 (26.5%) had a history of CVD. A statistically significant relationship was observed between the increase in IMT and the CVD (P = 0.011), [Table 4].
Table 4: Increasing of intima-media thickness and cerebrovascular disease

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Duplex US findings of PAD were characterised by a disturbance in only the distal, or distal and proximal wave forms in at least one lower extremity. A monophasic, post-stenotic wave decrease in the flow velocities were observed in 59 patients (49 males, 10 females). When the association of the increase in the IMT and PAD was investigated, the IMT was found to have increased in 48 of the 59 patients with PAD (81.3%). A statistically significant relationship was observed between the increase in the IMT and the PAD (P = 0.0001), [Table 5].
Table 5: Increasing of intima-media thickness and peripheral arterial disease

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The IMT was observed to increase statistically significantly in the patients with the findings of at least one out of the CAS (P = 0.002), CVD (P = 0.01), CAD (P = 0.001) or PAD (P = 0.001).


  Discussion Top


Measurement of the IMT using US is one of the most sensitive techniques to evaluate early-stage atherosclerosis. [1],[2],[3],[4] IMT was initially measured by Pignoli et al. in 1986. [15] It is recommended to perform the measurement 1 cm proximally to the carotid bulb and in the longitudinal plane that shows the intimal reflection and the medial layer. Since the intimal, medial and adventitial transition lines are difficult to distinguish in near-wall measurement, even if they are clearly visible, the images are gain-dependent. The generally accepted view in carotid IMT assessments is to conduct the measurement on the far wall. [16] For the purposes of our study, we have conducted the IMT measurements in the longitudinal plane, on the far wall and 1 cm proximally to the carotid bulb. An IMT reading over 0.9 mm is an abnormal finding and at this thickness, the intima-media layer is usually accompanied by a sonographically detectable plaque. [1],[2] In our study, a statistically significant relationship was observed between an increase in the IMT and the presence of plaques (P = 0.0001).

Carotid IMT measurement may have clinical significance in predicting the presence of plaques in the carotid arteries, coronary arteries and the arteries in the lower extremities. The increase in IMT is the precursor lesion of atherosclerosis and the presence of plaques must be predicted when there is an increase in the IMT.

The Edinburgh Artery Study revealed that IMT increases parallel to patient age. [6] Indeed, it has been observed that IMT is associated with advancing age and that it is greater in males of all age groups. [6] Furthermore in our study, the association of the increase in IMT with the male sex was observed to be statistically significant (P = 0.0001). The mean age of those with an increase in IMT was found to be higher than those without an increase. A statistically significant relationship was observed between advancing age and the increase in IMT (P = 0.0001). Based on these results, focussing the atherosclerotic scanning programs primarily on males sex and on those advanced in age may be more efficient in terms of the scanning costs.

Increased carotid artery IMT readings have been related to a higher risk of ischemic vascular events. [17] The IMT increase measured in the carotid artery is associated with an increased risk for strokes and the stroke rate has been reported to increase in parallel to the annual increase in IMT. [18] In our study a statistically significant relationship was observed between the increase in the IMT and CVD (P = 0.011). However, in 21.2% of those with an increase in the IMT, 50% or greater stenosis was observed in at least one side of the CAS. The relationship between the frequency of the CAS and the increase in IMT was observed to be statistically significant (P = 0.0001). North American Symptomatic Carotid Endarterectomy Trial [19] and Asymptomatic Carotid Atherosclerosis studies [20] have demonstrated a significant decrease in the risk of CVD following the treatment of the CAS. Therefore, since a statistically significant relationship was observed between an increase in IMT and CAS, CVD was more frequently observed in those with an increase in IMT in our study and IMT may be used as a sonographic indicator of atherosclerosis which may predict the risk for CVD.

The measurement of intima-media thickness is of great importance as a scanning method for CAD. [1],[2],[3],[4] The European Society of Cardiology accepts IMT >0.9 mm a risk factor in terms of target organ damage. [21] A statistically significant relationship between IMT and the presence and extent of CAD has been observed in a number of studies. [2],[4],[7],[8],[9],[10] Thus, IMT was suggested as an independent variable in predicting an angiographic diagnosis of CAD. [7],[8],[9] In those with coronary artery stenosis, a significant relationship was observed between the number of the diseased coronary arteries and the increase in IMT. [9] In the Cardiovascular Health Study, it was underlined that CAD developed parallel to the annual increase in the IMT measured in the main coronary artery. Furthermore, the IMT measured from the internal carotid artery was observed to be associated with an increased risk of heart attack. [18] In a study that investigated the relationship between the extent of atherosclerosis in the carotid arteries and the increase in the IMT and CAD, a significant association was observed between the increase in IMT and CAD. The results of this study have pointed out a 94% probability of CAD in the patients with an IMT of over 1.15 mm with a 65% sensitivity and 80% specificity. [9] In our study, 74% of patients with CAD showed an increase in IMT and a statistically significant relationship was observed between this increase and CAD (P = 0.007). Our study has demonstrated that IMT can be used as an independent variable in predicting CAD in scanning programs.

In the study of the risk of artherosclerosis risk in communities, [4] the increase in IMT and symptomatic PAD were reported to be associated. Relationship between IMT increase and asymptomatic PAD was reported by Bots et al. [5] Also, in the age range of 60-80 years, the increase in the IMT was found to be closely related to both symptomatic and asymptomatic PAD in The Edinburgh Artery Study. [6] In our study, an increase in IMT was detected in 48 out of the 59 patients with PAD (81.3%). The association of the increase in IMT and PAD was found to be statistically significant (P = 0.0001). Our study has demonstrated that an increase in IMT may be used as an independent variable in predicting the presence and diagnosis of PAD.

We have defined increased IMT as a reading over 0.9 mm in our study. Of the 482 patients enrolled in our study, 226 patients (151 males, 75 females) (46.8%) were found to have increased IMT values. A significant relationship was observed between the increase in IMT and male sex. The association of advancing age and the increase in IMT was also found to be statistically significant. In 21.2% of those with increased IMT, 50% or greater stenosis was observed in at least one side of the CAS and a statistically significant relationship was found between the increase in IMT and CAS (P = 0.0001). CVD is more frequently observed in those with increased IMT and statistically significant relationship was found between the increase in IMT and CVD in our study (P = 0.011). Also, CAD was observed in 53% of the patients with increased IMTs; while increased IMT was detected in 74% of those with CAD. The frequency of CAD in those with increased IMT was observed to be statistically significantly higher. Increased IMT was detected in 81.3% of the patients with PAD and the relationship between the increase in IMT and PAD was found to be statistically significant (P = 0.0001). In the patients with the findings of at least one of the following: CAS (P = 0.002), CAD (P = 0.001), CVD (P = 0.01) or PAD (P = 0.001), the increasing of IMT was observed to be statistically significant (P < 0.05).

The main limitation of our study was the small number of patients compared to the studies in the literature with larger populations. Also, the patient group only included the patients who presented to the hospital. The patients with CAD had previously received this diagnosis and were under treatment for the condition, whereas there could have been patients who were unaware of their CAD. Thus, the number of our patients with CAD may be higher than specified and this may have affected our results. Still, we are of the opinion that in spite of these limitations, the fact that our study was conducted on a heterogeneous population including both symptomatic and asymptomatic patients, and the fact that it demonstrated the statistically significant association between the increase in the IMT and the CAS, CAD, CVD and PAD may contribute to the literature.


  Conclusion Top


The measurement of IMT through US is a sensitive, simple, economic, non-invasive and repeatable method for the assessment of early atherosclerosis. Thus, the measurement of IMT using US may be employed to detect atherosclerotic CVDs in the early stages, as well as for atherosclerotic risk stratification. An increase in IMT is the precursor lesion of atherosclerosis and the presence of plaques should be predicted in case of increased IMT readings. Since the relationship of IMT increase with the CAD, PAD, CAS and CVD is statistically significant, our study has shown that IMT increase may serve as an independent variable in predicting the presence and diagnosis of CAD, PAD, CAS and CVD. Our study has shown that populations with high risk for atherosclerosis who are over 65 years of age, measurement of carotid artery IMT with US can be used as a screening program for CAD, PAD, CAS.

 
  References Top

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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