Correlation of Glycosylated Hemoglobin Levels with Histological and Ultrasound Characteristics of the Carotid Plaque in Diabetic and Nondiabetic Patients

Background: The purpose of this study is to investigate the correlation of glycosylated hemoglobin (HbA1c) levels with histological characters of atherosclerotic plaque that makes it vulnerable, as well as ultrasound (US) criteria that can contribute to the prognosis of carotid disease.

Material and methods: This is a single-center prospective study. Our study population consists of 74 diabetic and nondiabetic patients with carotid atherosclerosis who underwent carotid endarterectomy in our department. Patient categorization was based on the following criteria: levels of HbA1c, gender, and risk factors (smoking, hypertension), carotid stenosis rate, symptomatic or asymptomatic carotid disease, histological examination of the atherosclerotic plaque, and US morphological criteria of the plaque.

Results: The mean age of the patients was 68.2 years (standard deviation = 7.8); 58.1% were smokers, 71.6% had arterial hypertension, 37.8% had symptomatic carotid disease, and 64.9% had atherosclerotic plaque type 6. Futhermore, 95.9% of the patients had a carotid stenosis rate more than 70% and 4.1% had from 50% to 69%. Older patients had more frequent type 7 and 8 atherosclerotic plaque based on American Heart Association scoring system than younger patients (P = 0.041). The relative likelihood of atherosclerotic plaque type 7 and 8 was 1.12 times higher in older patients (Odds ratio [OR] = 1.12, P = 0.029). Patients with higher levels of HbA1cwere more likely to have type 6 atherosclerotic plaque than those with atherosclerotic lesions type 7 and 8 (P < 0.001). Specifically, increasing the level of HbA1c by 1 mg/dl increases the likelihood of the presence of vulnerable plaque by 2.55%. Moreover, the relative likelihood of a type 6 atherosclerotic plaque was 10.4 times higher in the older patients (OR = 10.4, P < 0.001).

Conclusions: This study demonstrates that levels of HbA1c and advanced age are 2 factors that may be correlated with the presence of vulnerable carotid plaques in diabetic population. Moreover, HbA1c is an independent factor that could possibly be used as a prognostic marker for carotid artery disease, although further studies are needed to explore this association to elucidate the precise role of HbA1c.