Increased carotid intima-media thickness in hypertensive patients is caused by increased medial thickness

Won, Hee Kwan; Kim, Wuon Shik; Kim, Ki Young; Hyun, Dae Woo; Kwon, Taek Geun; Bae, Jang Ho

Abstract

BACKGROUNDS/AIMS: It has been suggested that there is a differential response of the vasculature to systemic risk factors for atherosclerosis. We sought to evaluate the impact of hypertension on the carotid arterial wall using new methods that can measure each arterial wall layer.
METHODS
The study subjects consisted of 163 patients who underwent carotid arterial scanning using high-resolution ultrasound that could measure the left carotid intima-media, intima, and media separately. The individual carotid arterial wall thickness was measured off-line by a new method using the Canny edge-detection algorithm.
RESULTS
Hypertensive patients (n=79, mean age 61.8 years) had a higher prevalence of diabetes (31.6% vs 11.9%, p=0.004) and a lower level of HDL-cholesterol than did normotensive patients (41.8+/-11.0 mg/dL vs 45.7+/-10.0 mg/dL, p=0.019). Hypertensive patients had higher carotid intima-media thickness (CIMT, 0.81+/-0.21 mm vs 0.74+/-0.18 mm, p=0.003) and carotid medial thickness (CMT, 0.46+/-0.12 mm vs 0.42+/-0.09 mm, p=0.007) than did normotensive patients, whereas carotid intimal thickness (CIT) was not significantly different (0.34+/-0.04 mm vs 0.34+/-0.04 mm, p=0.196). Multivariate analysis revealed that the independent factors of CIMT were CMT (beta=0.915, p<0.001), hypertension (beta=0.076, p=0.008), age (beta=0.074, p=0.010), and sex (beta=-0.079, p=0.005). Pearson correlation coefficient between CIMT and CMT was higher (r=0.932, p<0.001 vs r=0.445, p<0.001) than that between CIMT and CIT. The correlation between CIMT and CMT was higher (r=0.940, p<0.001 vs r=0.910, p<0.001) in hypertensive patients than in normotensive patients, whereas that between CIMT and CIT was lower (r=0.344, p=0.002 vs r=0.583, p<0.001) in hypertensive patients.
CONCLUSIONS
The increased CIMT is caused by increased CMT in hypertensive patients, and this finding is compatible with the medial hypertrophy seen in hypertension. The carotid medial layer should be the focus of attention in future studies looking at hypertensive patients.