Measurement of the intimal thickness of the carotid artery: comparison between 40 MHz ultrasound and histology in rats

Non-Invasive Vascular Very-High Resolution Ultrasound to Quantify Artery Intima Layer Thickness: Validation of the Four-Line Pattern

Preliminary findings suggest that very-high resolution ultrasound (VHRU, 55 MHz) could differentiate arterial intima layer thickness (IT) non-invasively in vivo. We aimed to validate ultrasound-derived IT measurements and describe a four-line pattern consistent with intimal thickening. VHRU was applied to temporal arteries of 37 patients with suspected giant cell arteritis without inflammation on histology. Anatomically matched ultrasound-derived measurements of arterial layer thickness with the leading-edge method was compared to histology. Intimal thickening (IT >0.06 mm on histology) was identified as a four-line pattern in VHRU with a sensitivity of 96.3% and a specificity of 100%. Histologic and VHRU IT measurement agreement was excellent (mean difference 0.007 mm; 95% limits of agreement, -0.043 to 0.057) and intra-class coefficient (ICC) 0.923 (95% confidence interval [CI], 0.833-0.964). Intra- and inter-observer agreements for VHRU IT were high: ICC 0.946 (95% CI, 0.877-0.976) and 0.872 (95% CI, 0.773-0.943). VHRU utilizing the leading-to-leading edge method allows accurate and reliable measurements of arterial IT in patients with IT >0.06 mm. Measurements of IT will provide the opportunity to explore early subclinical structural intimal changes in the arterial wall increasing with age.

Vascular impact of quercetin administration in association with moderate exercise training in experimental type 1 diabetes

Hyperglycemia and oxidative stress have a major role in the pathogenesis of diabetic vascular complications. In this study, we investigated the efficacy of combining quercetin treatment with moderate exercise training in reversing diabetes-induced oxidative stress and ultrasound modifications in rat carotid arteries. The diabetic Wistar rats were divided into sedentary groups and trained groups. The trained animals went through a regular moderate exercise by swimming (5 weeks). Some non-diabetic and diabetic rats were daily treated with quercetin (30 mg/kg, for 5 weeks). At the end of the study, the imaging evaluation required to assess the effects of diabetes on carotid arteries was performed by micro-ultrasound (MU). The diabetic rats presented atherosclerotic plaques, with an increase in the echogenicity of the carotid artery wall, carotid intima-media thickness (CIMT), and carotid wall thickness, while the diabetic trained rats treated with quercetin presented normal values of these parameters. Malondialde-hyde (MDA) levels, superoxide dismutase (SOD) antioxidant enzyme activity, reduced glutathione (GSH) levels and the reduced (GSH) to oxidized (GSSG) glutathione ratio were determined in the carotid artery tissue. Diabetes caused elevated MDA levels and a decrease in SOD activity, GSH levels and GSH/GSSG ratio in the carotid artery tissue. Treating diabetic rats with quercetin combined with moderate exercise training reversed all these oxidative stress parameters. Our results show that this combination, quercetin and moderate exercise training, can be a good treatment strategy for the vascular complications of diabetes by attenuating hyperglycemia-mediated oxidative stress.

Is Carotid Artery Ultrasound Still Useful Method for Evaluation of Atherosclerosis?

Carotid ultrasound is an imaging modality that allows non-invasive assessment of vascular anatomy and function. Carotid intima-media thickness (IMT) has been shown to predict cardiovascular (CV) risk in multiple large studies. However, in 2013, American College of Cardiology/American Heart Association guidelines designated that the carotid IMT as class III evidence level was not recommended for use in clinical practice as a routine measurement of risk assessment for a first atherosclerotic CV event. Following the announcement of this guideline, combined common carotid IMT and plaque, including plaque tissue characterization and plaque burden, using 3D ultrasound was reported to be better than either measurement alone in a variety of studies. Moreover, changes in the intima thickness were related to aging and early atherosclerosis, and remodeling of the media thickness was associated with hypertension. Separate measurement is useful for evaluating the effects of different atherosclerotic risk factors on the arterial wall; however, a more detailed and elaborate technique needs to be developed. If so, separate measurement will play an important role in the assessment of atherosclerosis and arterial wall change according to a variety of risk factors, such as metabolic syndrome. In addition, although carotid blood flow velocity is a useful tool for risk classification and prediction in clinical practice, further clinical research is needed. The value of carotid IMT by ultrasound examination for risk stratification remains controversial, and groups developing future guidelines should consider the roles of plaque presence and burden and hemodynamic parameters in additional risk stratification beyond carotid IMT in clinical practice.

The Clinical Significance of Separate Measurements of Carotid Arterial Wall to Assess the Risk Factor for Atherosclerosis

Background

Carotid intima-media thickness (CIMT) is associated with several risk factors for atherosclerosis and has been consistently linked to cardiovascular and cerebrovascular disease. The clinical significance of separate measurements of CIMT, which is the sum of the intima (IT) and media thickness (MT), to use as an assessment of risk for atherosclerosis has not yet been fully established.

Methods

Among 3377 patients who underwent B-mode ultrasound of carotid arteries and coronary angiography in the Medical Department of St. Mary's Hospital from September 2003 to March 2009, 1146 subjects (M:F = 616:530; mean age, 57.7 ± 12.1 years) who were diagnosed with normal coronary arteries were enrolled in this study. IT, MT, and CIMT of the enrolled patients were manually measured using high-frequency ultrasonography (15 MHz linear array transducer).

Results

In multivariate logistic regression analysis, age (β = 0.063, p < 0.0001), body mass index (BMI) (β = 0.028, p = 0.018), and hypertension (HTN) (β = 0.046, p = 0.0002) were associated with MT (R² = 0.256) and the IT/MT ratio (R² = 0.209). Age (β = 0.065, p < 0.0001), BMI (β = 0.025, p = 0.038), hemoglobin A1c (β = 0.045, p = 0.045), and HTN (β = 0.043, p = 0.0006) correlated with mean CIMT (R² = 0.230). Age (β = -0.071, p < 0.0001) and BMI (β = -0.046, p = 0.002) were associated with the IT/MT ratio (R² = 0.219) on the left side. Age (β = 0.093, p < 0.0001) was related to MT (R² = 0.265) and mean CIMT (R² = 0.243) on the left side.

Conclusion

We noted different atherosclerotic risk factors were related to measurements of the arterial wall in different ways. Therefore, separate measurements of CIMT might be a useful method to assess the risk for atherosclerosis.

Carotid intima-media thickness is not related with clinical outcomes in young hypertensives

INTRODUCTION

Careful observations of long- and short-term outcomes associated with carotid intima-media thickness (IMT) are relatively limited.

METHODS

A total of 2,972 patients (male:female = 1,960:1,012; mean age = 62 ± 12 years) who underwent carotid IMT measurements from September 2003 to March 2009 were divided into four groups. Group I (n = 271; mean age, 42 ± 7.8 years) included normotensive younger subjects (males, <45 years and females <55 years), group II (n = 992; mean age, 63 ± 9 years) included normotensive elderly subjects, group III (n = 177; mean age, 46 ± 7.8 years) was hypertensive younger subjects, and group IV (n = 1,532; mean age, 63 ± 10.2 years) was hypertensive elderly subjects. We analyzed the clinical and cardiovascular events in the younger hypertensive subjects based on IMT measurements.

RESULTS

The baseline characteristics of the subjects showed that carotid IMT increased in the elderly subjects and in patients with hypertension. Poor clinical outcomes, such as all-cause death and major adverse cardiac events, were related with age, not with hypertension. Among the conventional risk factors, age and the highest quartile level of right maximum carotid IMT were related with major adverse events (young: odds ratio [OR], 0.47; 95% confidence interval [CI], 0.25 to 0.9 vs. OR, 1.73; 95% CI, 1.20 to 2.49). The patients in the highest quartile of carotid IMT had worse survival outcomes than those with the lowest IMT (p = 0.03).

DISCUSSION

Subjects with hypertension had increased carotid IMT levels. Controlling hypertension and carefully evaluating carotid IMT are important to prevent cardiovascular events even in younger subjects with hypertension.

Automatic measurements of diameter, distension and intima media thickness of the aorta in premature rabbit pups using B-mode images

To improve cardiovascular research, there is a growing need for arterial characterization in small animals. We developed a method, ARTIC (arterial characterization) for measuring lumen diameter, distension and intima media thickness (IMT). In this study ARTIC was used to automatically characterize the aorta of premature rabbit pups. Automatic measurements were compared with manual measurements, both performed by three observers. Diameter was 769 ± 140 μm (manual) and 766 ± 142 μm (automatic), distension was 35 ± 15 μm (manual) and 40 ± 12 μm (automatic) and IMT was 84 ± 11 μm (manual) and 88 ± 8 μm (automatic) (mean ± standard deviation). The variation in the measured diameter, distension and IMT ranged from 1.1% to 26.0% (manual) and from 1.0% to 9.0% (automatic). The intra-class correlation coefficient ranged from 33.0% to 99.3% (manual) and from 76.9% to 99.6% (automatic). The evaluation revealed that it is feasible to use ARTIC on B-mode images of arteries with small dimensions, which makes it a useful tool for arterial characterization in small animals.

Repeatability and reproducibility of ultrasonographic measurement of carotid intima thickness

PURPOSE

To evaluate the repeatability and reproducibility of intima thickness (IT) measurements at different sites along the common carotid artery and compare with intima-media thickness (IMT) measurements.

METHODS

Ultrasound examinations of common carotid artery were performed in 30 healthy subjects and 20 patients with diabetes mellitus. Carotid IT and IMT were measured at 10 mm, 13 mm, and 16 mm upstream from the carotid bulb. Each subject was scanned by three operators to evaluate inter-operator reproducibility. Each operator scanned the subjects twice to evaluate intra-operator repeatability. Inter-equipment reproducibility of the measurements was evaluated.

RESULTS

The inter-operator reproducibility for measuring carotid IT at the three sites was 81.5%, 81.9% and 69.1%, respectively, slightly lower than carotid IMT measurement (89.7%, 86.5%, 75.2%, respectively). The intra-operator repeatability for carotid IT measurement at the three sites ranged 76.9-89.5%, 67.4-90.3%, and 55.2-70.5%, respectively, and was lower than for IMT measurement (86.5-96.9%, 87.6-95.7%, 79.9-86.5%, respectively). The inter-equipment reproducibility of IMT (75.7-86.6%) was slightly better than for IT measurement (71.4-75.9%).

CONCLUSIONS

Ultrasonographic measurement of carotid IT is repeatable and reproducible, although not as good as IMT. Measurements preformed 10 mm to 13 mm upstream from the carotid bulb yield more repeatable and reproducible results.

High-resolution ultrasound showing increased intima and media thickness of the radial artery in patients with end-stage renal disease

OBJECTIVE

Although clinically relevant atherosclerosis of the upper limb arteries is rarely seen, intimal hyperplasia of the arteries may reflect global atherosclerosis and increased intima-media thickness of the brachial artery has been linked to an increased risk of cardiovascular events and to early failure of the radiocephalic arteriovenous fistula. We speculated that patients with ESRD have thickening of both the radial intimal and medial layers compared to healthy subjects.

METHODS

Ultrasound biomicroscopy is a novel very high frequency (55 MHz) ultrasound technique that could accurately measure the intima and media thickness of the vessel wall. No previous study has measured intima and media thickness separately in patients with end-stage renal disease and hence, the aim of the current study was to investigate the radial arterial wall layers in patients with chronic renal failure.

RESULTS

Thirty-one patients with end-stage renal disease and 41 healthy subjects underwent ultrasound biomicroscopy of the radial arteries. Blood pressures did not differ except for pulse pressures which were elevated among patients with end-stage renal disease (p<0.01). Patients with end-stage renal disease showed 39% thicker intima and 18% greater media in the radial artery compared to healthy subjects (0.117+/-0.031 mm versus 0.084+/-0.02 mm for the IT, p<0.01 and 0.205+/-0.062 mm versus 0.174+/-0.044 mm for the MT; p<0.05).

CONCLUSIONS

Both the intima and the media layers of the radial arteries are increased in patients with end-stage renal disease. Whether measurements of the radial arterial intima thickness may convey valuable information on the risk of future cardiovascular events and early arteriovenous fistula failure in end-stage renal disease remain to be elucidated in future studies.