Carotid intimo-medial thickness in type 2 diabetes and its correlation to coronary risk factors

 

Sanjay T Thorat¹, Mayur Kondewar², Omkar R Patil^3*

 

¹Associate Professor, ^2,3Jr. Resident, Department of Medicine, Krishna Institute of Medical Science, Karad, Maharashtra, INDIA.

Email: mayurkon@gmail.com

 

OBSERVATIONS AND RESULTS

Table 1: Carotid intimo-medial thickness in type-2 DM patients with CHD

In type-2 DM patients with CHD, the mean R-CIMT was 1.06 ±0.20, mean L-CIMT was 1.09 ± 0.18 and mean of M-CIMT was 1.08 ±0.18.

 

Table 2: Carotid intimo-medial thickness in type-2 DM patientswithout CHD

Parameter	N	Mean	SD	Median	Min	Max
R-CIMT	35	0.77	0.13	0.70	0.60	1.10
L-CIMT	35	0.82	0.18	0.80	0.60	1.30
M-CIMT	35	0.80	0.15	0.75	0.60	1.20

 

 

 

 

In type-2 DM patients without CHD, the mean R-CIMT was 0.77 ±0.13, mean L-CIMT was 0.82 ± 0.18 and mean of M-CIMT was 0.80 ±0.15.

 

Table 3: Comparison of demographic characteristics of type-2 DM patients with and without CHD

“t test” is applied. P value is significant if < 0.05.

 

 

Legend

Figure 1: Comparison of demographic characteristics of type-2 DMpatients with and without CHD

Figure 2: Comparison of carotid intimo-medial thickness of type-2DM patients with and without CHD

The age was significantly higher in patients with CHD group as compared to patients without CHD (p=0.001). The weight and BMI were also significantly higher in patients with CHD group as compared to patients without CHD (p=0.001). Height and WHR were comparable in both the groups (p>0.05). Similarly, duration of diabetes was significantly higher in patients with CHD group as compared to patients without CHD (p=0.01).

 

Table 4: Comparison of carotid intimo-medial thickness of type-2DM patients with and without CHD

“t test” is applied. ‘p’ value is significant as (‘p’< 0.05)

R-CIMT, L-CIMT and MCIMT were significantly higher in patients with CHD group as compared to patients without CHD (‘p’=0.001).

 

DISCUSSION

Patients with diabetes mellitus suffer unduly from premature and severe atherosclerosis. The Framingham study pointed out that diabetic individuals have higher serum concentrations of lipids and more hypertension, obesity, and thus are more prone to advanced atherosclerosis and it’s sequelae, namely coronary artery disease (CAD), cerebrovascular disease, aortic atherosclerosis, and peripheral vascular disease. Ultrasonographic assessment of easily accessible arteries has been advocated as a surrogate marker for less accessible vessels, such as coronary and cerebral arterial systems. Ultrasound imaging, which can provide information on intimal-medial thickness (IMT), plaque presence and type, calcification, and wall diameter, offers the ability to examine pre-symptomatic lesions, assess atherosclerotic burden and hence the risk of cardiovascular events. Intimal-medial thickness of the common carotid artery is considered to be an excellent non-invasive measure of generalizedatherosclerosis^D-1,D-5 and also a surrogate marker of coronary arterydisease.^D-6,D-7 It is also extensively used to examine the stage of atherosclerosis and to evaluate the regression of atherosclerotic lesions. following intervention therapies.^[D-8,D-10] The international atherosclerosis project has suggested that the carotid and cerebral arteries and the aorta undergo the atherosclerotic process approximately at the same age as the coronary arteries.^[D-11] Moreover, there is good agreement between histological examination and the ultrasonographic evaluation of the carotid arteries.^D-12 The current study was undertaken primarily to determine the carotid intimomedial thickness in Type II Diabetes Mellitus patients with coronary heart disease (CHD) as compared to Type II Diabetes Mellitus patients without coronary heart disease (CHD). The correlation of carotid intimomedial thickness with coronary risk factors in patients with Type II Diabetes Mellitus was the secondary objective. The mean CIMT in our study group of a total of 102 cases with type 2 diabetes was 0.98 ± 0.21 mm. The value was higher than the non-diabetic patients. The age, weight, BMI were significantly higher in patients with CHD group as compared to patients without CHD (p=0.001). Height and WHR were comparable in both the groups (p>0.05). Similarly, duration of diabetes was significantly higher in patients with CHD group as compared to patients without CHD (p=0.01). The finding was in the line with the published literature. Mohan et al^D-13 in the Chennai Urban Population Study (CUPS) in 2000 studied IMT of the carotid artery in South Indian diabetic and non-diabetic subjects and observed that the mean IMT value of the diabetic subjects (0.95 ± 0.31 mm) was significantly higher than those of the non-diabetic subjects (0.74 ± 0.14 mm) (p<0.001). Both in the normal and diabetic subjects, these values increased with age. At any given age, the diabetic subjects had higher values than the non-diabetic subjects but the difference reached statistical significance after the age of 50 years (p<0.05). IMT showed a correlation with age and duration of diabetes in the diabetic subjects. In a study by Aggarwal et al, the mean CIMT in study group of a total of 111 cases with type 2 diabetes was 0.840 ± 0.18 mm. This was lower than the value reported by Mohan et al in the CUPS study (0.95 ± 0.31 mm), yet higher than normal. Multivariate regression analysis showed that age and diabetes were the major risk factors for IMT. Kawamori et al^D-3 (1992) in their study on the prevalence of carotid atherosclerosis in diabetic subjects concluded that IMT is linearly related with age in diabetic subjects (IMT = [0.0155 x age] + 0.32450). Multivariate regression analysis of 275 type 2 diabetic cases indicated that smoking, hyperlipidaemia, duration of diabetes, hypertension and age were factors determining thickness of the carotid arterial wall. In our study, in type-2 DM patients with CHD, the mean R-CIMT was 1.06 ± 0.20, mean L-CIMT was 1.09 ± 0.18 and mean of M-CIMT was 1.08 ± 0.18. In type-2 DM patients without CHD, the mean R-CIMT was 0.77 ± 0.13, mean L-CIMT was 0.82 ± 0.18 and mean of M-CIMT was 0.80 ± 0.15. We found significantly higher R-CIMT, L-CIMT as well as Mean CIMT in patients with CHD group as compared to patients without CHD (p=0.001). In a study in 2001 by Jadhav et al,^[D-14] an IMT greater than 0.8 mm was observed in CAD patients (whether diabetic only, hepertensive only, or both), as against those without CAD; this difference was most marked in the hypertensive group (22.2% vs. 3.6%) and contributed to the increased arterial thickness in diabetics with concomitant hypertension. Multivariate regression analysis revealed CIMT to be associated with CAD with an odds ratio of 2.40. In a study by Aggarwal, CIMT was found to be very strongly and significantly correlated with the prevalence of CAD (p<0.0001). Among the CAD patients, hypertriglyceridaemia (HTG) was significantly correlated to mean CIMT (p<0.001). Temelkova-Kurktschieu et al^D-15 observed that postprandial HTG correlates with increased IMT in type 2 diabetics. In our study, the SBP and DBP were significantly higher in patients with CHD group as compared to patients without CHD (p=0.001). Further, though, the parameters like BSLF, BSLPP, HbA1c, BUL, creatinine, total cholesterol, LDL, VLDL and HDL were comparable in both the groups (p>0.05); TRG and M-ALB were significantly higher in patients with CHD group as compared to patients without CHD (p=0.001). In type-2 DM patients with CHD, mean of total cholesterol was 171.55 ± 43.54, and the mean M-ALB was 158.42 ± 182.22. In type-2 DM without CHD, the mean of total cholesterol was162.63 ± 30.57, and the mean value of M-ALB was 26.95 ± 25.77. The findings are in the line with published literature. Chen et al^D-16 investigated the association of fasting and postprandial triglyceride levels with CIMT among type 2 diabetic patients in Southeast China. The CIMT in patients with postprandial HTG was significantly greater than that in patients with postprandial normo-triglyceridaemia (p<0.05). The cardiovascular health study collaborative research group has recently observed, in 4476 subjects without clinical cardiovascular disease followed over 6 years, that the relative risk for myocardial infarction (MI) or stroke for the quantile with the highest IMT as compared with the lowest quantile was 3.87. IMT is a strong independent predictor for new cardiovascular events, even after statistical adjustment for other traditional risk factors. In a case control study of 772 persons selected from the ARIC population to evaluate adults free of clinical cardiovascular disease, case subjects, identified on the basis of carotid arterial wall thickness, had consistently higher values for atherogenic risk factors (age, body mass index, systolic and diastolic blood pressure, pack years of smoking, total triglycerides, low-density lipoprotein (LDL cholesterol), and low high density lipoprotein (HDL cholesterol) than control subjects. Carotid IMT (CIMT) has been shown to be independently associated with CAD in Indian subjects. This fact was reinforced by our study wherein CIMT was found to be very strongly and significantly correlated with the prevalence of CAD (p<0.0001). In our study, among the CAD patients, triglyceride and micro-albuminuria was significantly correlated to mean CIMT (p<0.001). Nagai et al,^D-17 in 1998, compared CIMT in asymptomatic older subjects with exercise - induced myocardial ischaemia. They observed that exercise induced ST-segment depression was associated with increased IMT (p<0.0001) independent of age and manifest CAD. After adjustment for age, IMT values progressively increased from healthy subjects to asymptomatic subjects with positive exercise ECG alone to those with concordant positive ECG and thallium scintigraphic findings who had virtually identical IMT to subjects with manifest CAD. Each 0.1 mm increase in IMT was associated with a 1.91 fold increased risk for concordant positive exercise tests or manifest CAD, independent of other significant predictors of CAD. Aggarwal et al., also found a strong and significant correlation between mean CIMT and prevalence of silent ischaemia, (p<0.001). On multivariate regression analysis, keeping mean CIMT as the dependent variable, the predictors that were seen to affect IMT included serum creatinine, total cholesterol levels, serum triglyceride levels and microalbuminuria. Jadhav et al^D-18 in their study on association of microalbuminuria with IMT and CAD observed that microalbuminuria had a strong association with high IMT in diabetic subjects. Aggarwal et al., also found in diabetics with silent ischemia are similar to their observations, as microalbuminuria had a significant correlation (p<0.05) with IMT in this subgroup.

 

CONCLUSION

The present study comprised of 102 patients with type-2 diabetes. A high mean CIMT (>0.9 mm) was seen in the study. Comparison of type 2 diabetic patients with and without CAD revealed that the presence of CAD was significantly associated with age (p<0.001), weight (p<0.001), BMI (p<0.001), duration of DM (p<0.001), triglycerides (p<0.001), microalbuminuria (p<0.001), and mean CIMT (p<0.0001). There is a correlation of carotid intimomedial thickness with coronary risk factors particularly triglyceride and micro-albuminuria. As we can seen here, the patients having known hypertensive, high triglycerides and high microalbuminuria are shown to have high carotid intimomedial thickness. IMT of the common carotid artery is an excellent non-invasive measure of generalized atherosclerosis and is also a surrogate marker of coronary artery disease and is a strong independent predictor for new cardiovascular events.

 

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