Echographical assessment of the early stage of experimental atherosclerosis of the descending aorta in rabbits

The ascending aortic elasticity feature in normotensive subjects: evaluation with coronary CT angiography

To evaluate the ascending aortic elasticity feature, 118 normotensive subjects who underwent coronary computed tomography angiography (CCTA) were enrolled. Two groups of parameters assessing elasticity were calculated based on the measurements of volume and area of ascending aorta. Multivariate analysis revealed that some factors including age, systolic BP, diastolic BP, heart rate, smoking status and hyperlipidemia independently related to decreased aortic elasticity. Both measuring methods are applicable for evaluation of aortic elasticity. As the prevalence of CCTA, it is meaningful that CCTA can provide not only the structural details of ascending aorta but also functional information of the vessel elasticity.

Add-on therapy of EPA reduces oxidative stress and inhibits the progression of aortic stiffness in patients with coronary artery disease and statin therapy: a randomized controlled study

AIM

We examined the anti-oxidant mechanisms of combined therapy of eicosapentaenoic acid (EPA) plus statin on the progression of atherosclerosis.

METHODS

Patients receiving statin therapy for dyslipidemia and with coronary artery disease (CAD) were assigned randomly in an open-label manner to the EPA (1,800 mg/day) -plus-statin group (n= 25; combined-therapy group) or to the statin-only group (n= 25), and followed for 48 weeks. At baseline and 48 weeks after enrollment, oxidative stress, brachial-ankle pulse wave velocity (baPWV) and stiffness parameter β-index of the carotid were measured.

RESULTS

The lipid profile remained unchanged throughout the study. Although the median value of baPWV increased more in the statin-only group than in the combined-therapy group, this difference was not significant (p= 0.29); however, a decrease in baPWV was associated with combined-therapy treatment by multiple regression analysis adjusted for age and mean blood pressure (p= 0.04). In addition, the β-index of the carotid was lower in the combined-therapy group than in the statin-only group (p= 0.02). Furthermore, although the difference in the reduction of the urinary concentration of 8-isoprostane between the two groups did not reach statistical significance, this concentration was significantly lower in the combined-therapy group with higher baseline levels (≥ 183 pg/mL · Cr) of urinary 8-isoprostane (p= 0.004).

CONCLUSIONS

EPA may reduce oxidative stress and inhibit the progression of arterial stiffness more efficiently than statin-only therapy in patients with dyslipidemia and CAD.

Stiffness of the abdominal aorta in beta-thalassemia major patients related with body iron load

OBJECTIVES

Increased iron stores have been implicated in the association with increased risk of cardiovascular events. We evaluated whether the abdominal aortic stiffness was altered in the patients with beta-thalassemia major in relation with body iron load.

METHODS

Sixty-two (32 males and 30 females) beta-thalassemia major patients aged 16.47 +/- 4.8 years were enrolled into the study. Healthy 52 subjects matched for age and sex were recruited as controls. In all subjects, hemoglobin, fasting glucose, cholesterol, high-density lipoprotein-cholesterol, and low-density lipoprotein-cholesterol levels were measured. The average serum ferritin level and liver iron concentration (LIC) were assessed in thalassemia patients. Left ventricular function and mass were evaluated echocardiographically and aortic strain (S), pressure strain elastic modulus (Ep), and normalized Ep (Ep*), aortic distensibility (DIS), and beta stiffness index (beta index) were calculated in all subjects.

RESULTS

There was no statistically significant difference between the study and control groups in sex, mean age, body mass index, heart rate, and systolic blood pressure (P > 0.05). However, pulse pressure and left ventricular mass index (LVMI) were found higher in thalassemia major patients compared with the control group. In beta-thalassemia major patients S (0.21 +/- 0.027 vs. 0.26 +/- 0.017, P < 0.0001) and DIS (1.07 +/- 0.25 vs. 1.56 +/- 0.37, P < 0.0001) were significantly lower compared with the control group. However, Ep (196.9 +/- 44.86 vs. 134.20 +/- 29.10, P < 0.0001), Ep* (3.26 +/- 0.98 vs. 2.04 +/- 0.60, P < 0.0001), and beta index (2.44 +/- 0.58 vs. 1.61 +/- 0.37, P < 0.0001) were significantly higher in beta-thalassemia patients than controls. There was a statistically significant negative correlation between LIC and S, DIS. There was also negative correlation between LVMI and S. However, there was a statistically significant positive correlation between LIC and Ep, Ep*.

CONCLUSIONS

Increased abdominal aortic stiffness was detected in beta-thalassemia major patients and this increase in arterial stiffness correlated with LIC and LVMI.

Early endothelial dysfunction in cholesterol-fed rabbits: a non-invasive in vivo ultrasound study

Background

Endothelial function in hypercholesterolemic rabbits is usually evaluated ex vivo on isolated aortic rings. In vivo evaluation requires invasive imaging procedures that cannot be repeated serially.

Aim

We evaluated a non-invasive ultrasound technique to assess early endothelial function in rabbits and compare data with ex vivo measurements.

Methods

Twenty-four rabbits (fed with a cholesterol diet (0.5%) for 2 to 8 weeks) were given progressive infusions of acetylcholine (0.05–0.5 μg/kg/min) and their endothelial function was assessed in vivo by transcutaneous vascular ultrasound of the abdominal aorta. Ex vivo endothelial function was evaluated on isolated aortic rings and compared to in vivo data.

Results

Significant endothelial dysfunction was demonstrated in hypercholesterolemic animals as early as 2 weeks after beginning the cholesterol diet (aortic cross-sectional area variation: -2.9% vs. +4% for controls, p < 0.05). Unexpectedly, response to acetylcholine at 8 weeks was more variable. Endothelial function improved in 5 rabbits while 2 rabbits regained a normal endothelial function. These data corroborated well with ex vivo results.

Conclusion

Endothelial function can be evaluated non-invasively in vivo by transcutaneous vascular ultrasound of the abdominal aorta in the rabbit and results correlate well with ex vivo data.

Intravascular ultrasound imaging in the assessment of atherosclerotic plaques in rabbit abdominal aorta: comparison with histologic findings

RATIONALE AND OBJECTIVES

To examine the correlation between the echogenicity and the components of atherosclerotic plaques in rabbit.

METHODS

The atherosclerotic plaque formation in the abdominal aortas of hyperlipidemic or normolipidemic rabbits was stimulated by inserting polyethylene tubing. Intravascular ultrasound (30-MHz, 4.5 F catheter) investigation was performed at locations in the vessel. The intravascular ultrasound images of the plaques were evaluated and compared with the histologic findings.

RESULTS

Ultrasound images delineated areas showing hyperechoic or hypoechoic ultrasound beams in the plaques. Histologic studies revealed that the hyperechoic areas were closely associated with a dense fibrous extracellular matrix, whereas the hypoechoic areas corresponded to lesions showing a marked accumulation of foamy macrophages or proteoglycan-rich loose myxoid extracellular matrix with smooth muscle cell proliferation.

CONCLUSION

A good correlation between ultrasound images and histologic features was observed. These results suggest that intravascular ultrasound imaging could provide useful information for assessing the tissue characteristics of atherosclerotic lesions.

Importance of NAD(P)H oxidase-mediated oxidative stress and contractile type smooth muscle myosin heavy chain SM2 at the early stage of atherosclerosis

BACKGROUND

Increased vascular oxidative stress induced by hyperlipidemia may alter the phenotype of vascular smooth muscle (SM) cells and play a crucial role in the progression of atherosclerosis. To clarify the mechanisms underlying vascular dysfunction and oxidative stress in hypercholesterolemia, we compared the effects of antioxidant probucol with those of pravastatin on aortic stiffness, phenotypic modulation, oxidative stress, and NAD(P)H oxidase essential subunit p22(phox) expression in aortic medial SM cells of cholesterol-fed rabbits by using color image analysis of immunostained sections.

METHODS AND RESULTS

Japanese white male rabbits were fed either normal chow or 1% cholesterol diet for 14 weeks. After the first 7 weeks, cholesterol-fed rabbits were further divided into 3 groups: those fed with cholesterol feed only and those additionally given pravastatin (10 mg/d) or probucol (1.3 g/d) for the last 7 weeks. Within 7 weeks of treatment, probucol improved aortic stiffness more effectively than did pravastatin, inhibiting phenotypic modulation by selectively upregulating contractile-type SM myosin heavy chain isoform SM2 and by reducing both p22(phox) and superoxide content in medial SM cells of cholesterol-fed rabbit aorta. No significant differences in cholesterol levels, superoxide content, and endothelial NO synthase levels in the intima, aortic morphology and fibrosis, and synthetic-type myosin heavy chain in medial SM cells were observed between the 2 drug-treated groups.

CONCLUSIONS

These results suggest that oxidative stress and SM2 in medial SM cells might be important factors for vascular dysfunction, and strategies aimed at blocking NAD(P)H oxidase and upregulating SM2 may have therapeutic potential against the progression of atherosclerosis in hypercholesterolemia.

Influence of baroreflex on volume elasticity of heart and aorta in the rabbit

Optimal ventriculoaortic coupling includes tuning of elastic properties. The ratio of effective arterial elastance and left ventricular endsystolic elastance is often taken as a measure for mechanical and energetical efficiency. The present study determined the time course of ventricular and aortic volume elasticity (VE = dp/dV) throughout a complete heartbeat. This was achieved by using changes of eigenfrequency of two catheter-transducer systems under closed chest conditions in rabbits. Short-term VE modulation was studied by a baroreflex response, as induced by pressure changes applied to the carotid sinus. Long-term changes were studied in atherosclerotic rabbits (12 wk of high-cholesterol feeding). The time course and mean values of ventricular and aortic VE were changed by the baroreflex stimulus. Cholesterol feeding diminished the response. The degree of ventriculoaortic coupling, as quantified by VE(Aorta)/VE(Ventricle) ratio, varied during a single ejection period. The large span allows either maximal energetical efficiency or maximal stroke work. Although normal rabbits adjusted their ventriculoaortic coupling during baroreflex input, the cholesterol-fed rabbits failed to do so.

Pulse pressure--a review of mechanisms and clinical relevance

The goal of this study was to review the origin, clinical relevance and treatment of pulse pressure (PP). Elevated PP is increasingly being recognized as a risk factor for cardiovascular, particularly coronary, disease. Pulse pressure is discussed in terms of both Windkessel and distributive models of the arterial circulation. Pulse pressure arises from the interaction of cardiac ejection (stroke volume) and the properties of the arterial circulation. An increased stiffness of the aorta and large arteries leads to an increase in PP through a reduction in arterial compliance and effects on wave reflection. A number of factors are known to influence arterial wall behavior and, therefore, PP. In addition to the effects of aging and blood pressure on arterial wall elasticity, there is some evidence that atherosclerosis, per se, amplifies these effects. Thus, the relationship between PP and coronary disease may be bidirectional. A number of dietary and lifestyle interventions have been shown to modify large artery behavior. These include aerobic exercise training and consumption of n-3 fatty acids. Conversely, strength training is associated with an increase in arterial stiffness and a higher PP. The effects of antihypertensive medication have been extensively studied, but many studies are difficult to interpret because of concomitant change in blood pressure, and to a lesser degree, heart rate. However a number of studies do suggest direct arterial wall effects, particularly for angiotensin-converting enzyme inhibitors. A distributed compliance model of the arterial circulation provides a framework for understanding the causes, effects and potential treatment of elevations in PP.

Risk Factors for Stiffness of the Wall of the Thoracic Aorta in Patients With Mild Atherosis

Previous studies have suggested that aging is associated with progressive arterial stiffness and widening of the pulse pressure, and pulse pressure has been found to be a risk factor of cardiovascular diseases. However, the effects of age, blood pressure (including pulse pressure) or atherogenic factors on thoracic aortic wall stiffness in patients with mild atherosis are unclear, so the present study used transesophageal echocardiography to examine 103 consecutive patients with various cardiovascular diseases. The extent of atherosis was evaluated in terms of intima-medial thickness (IMT), and 2 indices of wall stiffness in the aorta were calculated: elastic modulus and stiffness parameter (beta). In subjects with mild atherosis (IMT <1.0mm), age, body mass index, systolic blood pressure, pulse pressure, triglyceride level, and hypertension were factors significantly associated with high wall stiffness, and multiple logistic stepwise analysis revealed that age, pulse pressure, and triglyceride level were particularly significant.

Assessment of aortic atherosclerosis and carotid atherosclerosis in coronary artery disease

The present study investigated the relationship between aortic atherosclerosis and carotid atherosclerosis, and studied the effects of coronary risk factors for these arteries. The subjects consisted of 78 patients with coronary artery disease (CAD) and 69 patients without CAD. All subjects underwent enhanced computed tomography and B-mode ultrasonography within a short time period to determine the extent of aorta and carotid atherosclerosis. Significant correlations between maximal aortic wall thickness (MAWT) and aortic wall volume (AWV) with carotid intima-media thickness (IMT) were demonstrated. MAWT, AWV and IMT were significantly higher in patients with CAD compared with controls (p=0.009, p=0.024, p=0.001, respectively). Furthermore, there were significant differences in MAWT, AWV and IMT among groups classified by the number of coronary artery stenoses, and no significant differences among groups classified by risk factors, but it was shown that MAWT, AWV and IMT increased gradually as the risk factors increased in number. MAWT, AWV and IMT had positive correlations with age, systolic blood pressure and triglyceride, and a negative correlation with high density lipoprotein-cholesterol. This study demonstrated that both aortic atherosclerosis and carotid atherosclerosis are closely correlated with coronary atherosclerosis, and that the atherosclerosis indices are independently associated with age and hyperlipidemia.

Effect of olprinone, a phosphodiesterase III inhibitor, on arterial wall distensibility: differentiation between aorta and common carotid artery

Although the effects of phosphodiesterase III (PDE III) inhibitors as vasorelaxants have been well documented, there are only few data on the wall response of different arteries. We evaluated the artery-specific effect of olprinone (OP), one of the PDE III inhibitors, on the major branches of human arteries and peripheral circulation. In 14 healthy subjects (average age: 57.5 +/- 21.2 years), systolic and diastolic diameters (Ds and Dd, respectively) and the time velocity integral (VI) of flow velocity patterns were measured by M-mode and Doppler echocardiography in the carotid artery (CA), the ascending aorta (asAo), the abdominal aorta (abAo), and the left ventricular outflow tract. Blood pressure (BP) was simultaneously measured using a cuff sphygmomanometer. Measurements were taken before and 20min after a bolus injection of OP (0.2 microg/kg). Distensibility (Ds - Dd), stiffness parameter beta (In(systolic BP/diastolic BP)/(Ds/Dd - 1)), cardiac output (CO: (Flow Area) x VI x HR at left ventricular outflow), selective flow volume (FV: (Flow Area) x VI x HR at CA or abAo), and vascular resistance (VR: mean BP/(CO or FV)) were then calculated. The distensibility increased significantly after OP administration (P = 0.0015), but that of the asAo or abAo did not change. Although there was a significant increase in CO (P = 0.001) and a significant decrease in systemic VR (P = 0.001) following OP administration, the FV and VR of both CA and abAo did not change significantly. The selectiveness of the effect of OP was demonstrated in terms of the CA wall distensibility. This was thought to be attributable to the differences in the structural components or the reactivity of smooth muscle cells to OP.

A quantitative study of the aorta of the New Zealand rabbit (Oryctolagus cuniculus L.)

Ten segments of the aorta of the rabbit were studied quantitatively. The thoracic and abdominal aorta of the rabbit were measured from proximal to distal and parallel to the reduced diameter, demonstrating a decreasing thickness of the tunica intima and tunica media that becomes physiologically apparent during adulthood in these commonly used laboratory animals. The ratio of intimal to medial thickness, multiplied by 100, was calculated and found to be between 2.56 and 3.74 for the thoracic aorta and 4.03 and 5.62 for the abdominal aorta of the rabbit. These findings are important for the better understanding of the development of atherosclerosis.