Aortic and large artery stiffness: current methodology and clinical correlations

The Emerging Role and Clinical Applications of Morphomics in Diagnostic Imaging

Analytic morphomics refers to the accurate measurement of specific biological markers of human body composition in diagnostic medical imaging. The increasing prevalence of disease processes that alter body composition including obesity, cachexia, and sarcopenia has generated interest in specific targeted measurement of these metrics to possibly prevent or reduce negative health outcomes. Typical morphomic measurements include the area and density of muscle, bone, vascular calcification, visceral fat, and subcutaneous fat on a specific validated axial level in the patient's cross-sectional diagnostic imaging. A distinct advantage of these measurements is that they can be made retrospectively and opportunistically with pre-existing datasets. We provide a narrative review of the current state of art in morphomics, but also consider some potential future directions for this exciting field. Imaging based quantitative assessment of body composition has enormous potential across the breadth and scope of modern clinical practice. From risk stratification to treatment planning, and outcome assessment, all can be enhanced with the use of analytic morphomics. Moreover, it is likely that many new opportunities for personalized medicine will emerge as the field evolves. As radiologists, embracing analytic morphomics will enable us to contribute added value in the care of every patient.

Abdominal aortic calcification volume (AACV) is a predictive factor for postoperative complications associated with biliary tract cancer

PURPOSE

Curative surgical treatment of biliary tract cancer is highly invasive and involves postoperative complications. Abdominal aortic calcification is a parameter that is reportedly linked to systemic arteriosclerosis. We measured the abdominal aortic calcification volume (AACV), assessed the correlation between AACV and postoperative complications, and evaluated the clinical utility of AACV.

METHODS

We retrospectively evaluated 97 patients (ampullary carcinoma, n = 21; distal bile duct cancer, n = 43; hilar bile duct cancer, n = 33). We assessed the calcification volume of the abdominal aorta from the renal artery ramification to the common iliac artery bifurcation. The correlation between AACV, clinical factors, and postoperative complications was evaluated.

RESULTS

The average AACV was 5.02 cm³, and the median AACV was 3.74 (range 0-27.4) cm³. The AACV was significantly related to age (P = 0.009), Brinkman index (P = 0.007), and history of cardiovascular disease (P = 0.015). The AACV was strongly correlated with postoperative complications (P < 0.001) and Clavien-Dindo grade > III postoperative complications (P < 0.001). The AACV was also correlated with pancreatic fistula in pancreatectomy cases (P < 0.001). A multivariate analysis revealed that the AACV was an independent predictor of postoperative complications.

CONCLUSION

The AACV was significantly associated with postoperative complications. The AACV could be used for the preoperative assessment of surgical risk.

Assessment of arterial stiffness to predict blood pressure response to renal sympathetic denervation

BACKGROUND

Recent trials support the efficacy of renal sympathetic denervation (RDN) to reduce blood pressure (BP). Nevertheless, about one third of patients are considered non-responders to RDN. Previous retrospective analyses suggest arterial stiffness could predict BP response to RDN.

AIMS

We prospectively assessed the potential of invasive pulse wave velocity (iPWV) to predict BP response to RDN. Additionally, we aimed to establish non-invasive models based on arterial stiffness to predict BP response to RDN.

METHODS

 iPWV, magnetic resonance imaging-based markers of arterial stiffness and the carotid-femoral pulse wave velocity were recorded prior to RDN in patients with treatment resistant hypertension. Changes in daytime BP after 3 months were analysed according to the prespecified iPWV cut-off (14.4 m/s). Regression analyses were used to establish models for non-invasive prediction of BP response. Results were compared to iPWV as reference and were then validated in an external patient cohort.

RESULTS

Eighty patients underwent stiffness assessment before RDN. After 3 months, systolic 24h and daytime BP were reduced by 13.6±9.8 mmHg and 14.7±10.6 mmHg in patients with low iPWV, versus 6.2±13.3 mmHg and 6.3±12.8 mmHg in those with high iPWV (p<0.001 for both). Upon regression analysis, logarithmic ascending aortic distensibility and systolic baseline BP independently predicted BP change at follow-up. Both were confirmed in the validation cohort.

CONCLUSIONS

 iPWV is an independent predictor for BP response after RDN. In addition, BP change prediction following RDN using non-invasive measures is feasible. This could facilitate patient selection for RDN treatment.

Aortic Agatston score correlates with the progression of acute type A aortic dissection

Aortic calcification in the tunica media is correlated with aortic stiffness, elastin degradation, and wall shear stress. The study aim was to determine if aortic calcifications influence disease progression in patients with acute type A aortic dissection (ATAAD). We retrospectively reviewed a total of 103 consecutive patients who had undergone surgery for ATAAD at our institution between January 2009 and December 2019. Of these, 85 patients who had preoperatively undergone plain computed tomography angiography (CTA) for evaluation of their aortic calcification were included. Moreover, we assessed the progression of aortic dissection after surgery via postoperative CTA. Using a classification and regression tree to identify aortic Agatston score thresholds predictive of disease progression, the patients were classified into high-score (Agatston score ≥ 3344; n  =   36) and low-score (<3344; n  =   49) groups. Correlations between aortic Agatston scores and CTA variables were assessed. Higher aortic Agatston scores were significantly correlated with the smaller distal extent of aortic dissection (p < 0.001), larger true lumen areas of the ascending (p  =  0.009) and descending aorta (p =   0.002), and smaller false lumen areas of the descending aorta (p =  0.028). Patients in the high-score group were more likely to have DeBakey type II dissection (p =  0.001) and false lumen thrombosis (p  =  0.027) than those in the low-score group, thereby confirming the correlations. Aortic dissection in the high-score group was significantly less distally extended (p < 0.001). A higher aortic Agatston score correlates with the larger true lumen area of the ascending and descending aorta and the less distal progression of aortic dissection in patients with ATAAD. Interestingly, the findings before and after surgery were consistent. Hence, aortic Agatston scores are associated with aortic dissection progression and may help predict postoperative residual dissected aorta remodeling.

A correction score to compare aortic calcification in contrast enhanced and non-contrast measurements from computed tomography scans

BACKGROUND

Aortic wall calcification shows strong promise as a cardiovascular risk factor. While useful for visual enhancement of vascular tissue, enhancement creates heterogeneity between scans with and without contrast. We evaluated the relationship between aortic calcification in routine abdominal computed tomography scans (CT) with and without contrast.

METHODS

Inclusion was limited to those with abdominal CT-scans with and without contrast enhancement within 120 days. Analytic Morphomics, a semi-automated computational image processing system, was used to provide standardized, granular, anatomically indexed measurements of aortic wall calcification from abdominal CT-scans. Aortic calcification area (ACA) and aortic wall calcification percent (ACP) and were the outcomes of interest. Multiple linear regression was used to evaluate the relationship of aortic measurements. Models were further controlled for age and sex. Stratification of measurements by vertebral level was also performed.

RESULTS

A positive association was observed for non-contrast calcification in ACP β 0.74 (95% CI 0.72, 0.76) and ACA β 0.44 (95% 0.43, 0.45). Stratified results demonstrated the highest coefficient of determination at L2 for percent and L3 for area models [R² 0.91 (ACP) 0.74 (ACA)]. Adjusted lumber-level associations between non-contrast and contrast measurements ranged from (β 0.69-0.82) in ACP and (β 0.37-0.54) in ACA.

CONCLUSION

A straightforward correction score for comparison of abdominal aortic calcification measurements in contrast-enhanced and non-contrast scans is discussed. Correction of aortic calcification from CT scans can reduce scan heterogeneity and will be instrumental in creating larger cardiovascular cohorts as well as cardiovascular risk surveillance programs.

Evaluation of metabolic parameters and aortic elasticity in normotensive children with premature adrenarche

OBJECTIVES

Premature adrenarche may be associated with an intrauterine programmed metabolic syndrome which should be considered as a warning sign for coronary heart disease due to accelerated atherosclerosis, hypertension, type 2 diabetes mellitus (DM), and polycystic ovary syndrome.

METHODS

Seventy-three patients with premature adrenarche were evaluated for metabolic parameters and aortic elasticity to evaluate the susceptibility to atherosclerosis and compared with a control group. The patients were examined in two groups as overweight and nonoverweight, and metabolic and cardiac parameters were also compared among these groups. Strain, distensibility, and stiffness index parameters were used to evaluate aortic elasticity.

RESULTS

Biochemical parameters and cardiac measurements were not statistically different between patients and controls. They also did not differ between patients with normal weight and overweight groups. Atherogenic index and insulin resistance were closely related and a positive correlation between cholesterol and triglyceride, and ascending aortic stiffness was found.

CONCLUSIONS

The results may suggest that cholesterol and triglyceride-related arterial involvement is more involved in the pathogenesis of arterial stiffness. It can be considered that 'being overweight' or 'having metabolic profile characterized by insulin resistance and dyslipidemia' are the major coexisting factors influencing the vascular structure, rather than increased androgens and premature adrenarche itself.

Experimental investigation into the effect of compliance of a mock aorta on cardiac performance

Demand for heart transplants far exceeds supply of donated organs. This is attributed to the high percentage of donor hearts that are discarded and to the narrow six-hour time window currently available for transplantation. Ex-vivo heart perfusion (EVHP) provides the opportunity for resuscitation of damaged organs and extended transplantation time window by enabling functional assessment of the hearts in a near-physiologic state. Present work investigates the fluid mechanics of the ex-vivo flow loop and corresponding impact on cardiac performance. A mechanical flow loop is developed that is analogous to the region of the EVHP system that mimics in-vivo systemic circulation, including the body’s largest and most compliant artery, the aorta. This investigation is focused on determining the effect of mock aortic tubing compliance on pump performance. A custom-made silicone mock aorta was developed to simulate a range of in-vivo conditions and a physiological flow was generated using a commercial ventricular assist device (VAD). Monitored parameters, including pressure, tube distension and downstream velocity, acquired using time-resolved particle imaging velocimetry (PIV), were applied to an unsteady Bernoulli analysis of the flow in a novel way to evaluate pump performance as a proxy for cardiac workload. When compared to the rigid case, the compliant mock aorta case demonstrated healthier physiologic pressure waveforms, steadier downstream flow and reduced energetic demands on the pump. These results provide experimental verification of Windkessel theory and support the need for a compliant mock aorta in the EVHP system.

Rise and fall of elastic fibers from development to aging. Consequences on arterial structure-function and therapeutical perspectives

In the arteries of vertebrates, evolution has given rise to resilient macromolecular structures, elastin and elastic fibers, capable of sustaining an elevated blood pressure and smoothening the discontinuous blood flow and pressure generated by the heart. Elastic fibers are produced only during development and childhood, before being progressively degraded by mechanical stress and enzymatic activities during adulthood and aging. During this period, arterial elastic fiber calcification and loading of lipids also occur, all of these events conducting to arteriosclerosis. This leads to a progressive dysfunction of the large elastic arteries inducing elevated blood pressure as well as altered hemodynamics and organ perfusion, which induce more global malfunctions of the body during normal aging. Additionally, some arterial conditions occur more frequently with advancing age, such as atherosclerosis or aneurysms, which are called age-related diseases or pathological aging. The physiological or pathological degradation of elastic fibers and function of elastic arteries seemed to be rather inevitable over time. However, during the recent years, different molecules - including several ATP-dependent potassium channel openers, such as minoxidil - have been shown to re-induce elastin production and elastic fiber assembly, leading to improvements in the arterial structure and function or in organ perfusion. This review summarizes the changes in the arterial elastic fibers and structure from development until aging, and presents some of the potential pharmacotherapies leading to elastic fiber neosynthesis and arterial function improvement.

Pronounced Coronary Arteriosclerosis in Cirrhosis: Influence on Cardiac Function and Survival?

BACKGROUND

The relation between excessive alcohol consumption and coronary arteriosclerosis has remained controversial. The etiology of cirrhosis has been considered a substantial risk factor for development of arteriosclerotic lesions. The coronary artery calcium-score derived from coronary CT angiography is a robust marker of coronary arteriosclerosis.

AIMS

To study the burden of coronary arteriosclerosis in cirrhotic patients of various etiologies and association to cardiac dysfunction and survival.

METHODS

Fifty-seven patients with cirrhosis without cardiovascular disease underwent coronary CT angiography, tissue Doppler echocardiography, electrocardiogram and registration of clinical and biochemical characteristics.

RESULTS

In patients with cirrhosis the median coronary artery calcium-score was increased in comparison with age and race-adjusted healthy reference values (men: 328 vs. 9 HU and women: 136 vs. 0 HU; p < 0.001). Moreover, the coronary artery calcium-score in alcohol-related cirrhosis was significantly higher than in nonalcohol-related cirrhosis (362 vs. 46 HU, p < 0.001). Coronary artery calcium-score correlated with age (p = 0.002) but not with established cardiovascular risk factors including smoking, type 2 diabetes, hypertension, gender, or hypercholesterolemia. Coronary artery calcium-score was associated with diastolic dysfunction, lateral e´ (p = 0.025), but not with other markers of cardiac dysfunction. During a median follow-up of 25 months 12 patients (21%) died but coronary artery calcium-score was not associated with survival.

CONCLUSIONS

Coronary arteriosclerosis was particular extensive in patients with alcoholic cirrhosis. However, the current results suggest that coronary arteriosclerosis only have limited influence on cardiac function and survival. Surprisingly, no other established risk factors apart from age seemed to interfere with coronary arteriosclerosis in cirrhotic patients.

Biomechanical properties and microstructure of human ventricular myocardium

In the multidisciplinary field of heart research it is of utmost importance to identify accurate myocardium material properties for the description of phenomena such as mechano-electric feedback or heart wall thickening. A rationally-based material model is required to understand the highly nonlinear mechanics of complex structures such as the passive myocardium under different loading conditions. Unfortunately, to date there are no experimental data of human heart tissues available to estimate material parameters and to develop adequate material models. This study aimed to determine biaxial extension and triaxial shear properties and the underlying microstructure of the passive human ventricular myocardium. Using new state-of-the-art equipment, planar biaxial extension tests were performed to determine the biaxial extension properties of the passive ventricular human myocardium. Shear properties of the myocardium were examined by triaxial simple shear tests performed on small cubic specimens excised from an adjacent region of the biaxial extension specimens. The three-dimensional microstructure was investigated through second-harmonic generation (SHG) microscopy on optically cleared tissues, which emphasized the 3D orientation and dispersion of the myofibers and adjacent collagen fabrics. The results suggest that the passive human LV myocardium under quasi-static and dynamic multiaxial loadings is a nonlinear, anisotropic (orthotropic), viscoelastic and history-dependent soft biological material undergoing large deformations. Material properties of the tissue components along local microstructural axes drive the nonlinear and orthotropic features of the myocardium. SHG microscopy investigation revealed detailed information about the myocardial microstructure due to its high resolution. It enabled the identification of structural parameters such as the fiber and the sheet orientations and corresponding dispersions. With this complete set of material data, a sophisticated material model and associated material parameters can be defined for a better description of the biomechanical response of the ventricular myocardium in humans. Such a model will lead to more accurate computational simulations to better understand the fundamental underlying ventricular mechanics, a step needed in the improvement of medical treatment of heart diseases.

STATEMENT OF SIGNIFICANCE

Unfortunately, to date there are no experimental data of human heart tissues available for material parameter estimation and the development of adequate material models. In this manuscript novel biaxial tensile and shear test data at different specimen orientations are presented, which allowed to adequately capture the direction-dependent material response. With these complete sets of mechanical data, combined with their underlying microstructural data (also presented herein), sophisticated material models and associated material parameters can be defined for the description of the mechanical behavior of the ventricular myocardium in humans. Such models will lead to accurate computational simulations to better understand the fundamental underlying ventricular mechanics, a step needed in the improvement of medical treatment of heart diseases.

Computed tomography of aortic wall calcifications in aortic dissection patients

Objectives

To investigate the frequency of aortic calcifications at the outer edge of the false lumen and the frequency of fully circular aortic calcifications in a consecutive series of patients with aortic dissection who underwent contrast-enhanced CT.

Methods

The study population compromised of 69 consecutive subjects aged 60 years and older with a contrast-enhanced CT scan demonstrating an aortic dissection. All CT scans were evaluated for the frequency of aortic calcifications at the outer edge of the false lumen and the frequency of fully circular aortic calcifications by two experienced observers. Between observer reliability was evaluated by using Cohen’s Kappa. Differences between groups were tested using unpaired T test and Chi-square test.

Results

Presumed media calcifications were observed in 22 (32%) patients of 60 years and older and were found more frequently in chronic aortic dissection (N = 12/23, 52%) than in acute aortic dissection (N = 10/46, 22%).

Conclusion

As the intima has been torn away by the aortic dissection it is highly likely that CT scans can visualize the calcifications in the tunica media of the aorta.

Determinants of Arterial Stiffness in Female Patients with Takayasu Arteritis

Objective.

The assessment of pulse wave velocity (PWV) in Takayasu arteritis (TA) is complex because of many confounding factors. We evaluated PWV in female patients with TA and controls with comparable anthropometric and clinical variables and assessed a possible association of TA with disease variables.

Methods.

We evaluated 27 patients with TA consecutively. Exclusion criteria were menopause, smoking, diabetes, renal insufficiency, poorly controlled hypertension, cardiac arrhythmias, obesity, inflammatory comorbidities, pregnancy, and surgical procedures involving the aorta. Disease activity was determined by clinical and laboratory variables. As healthy controls, 27 subjects with comparable age, blood pressure, height, and weight were selected. Carotid-femoral PWV measurements were obtained using the Complior system.

Results.

The mean PWV in patients with TA was higher than in healthy controls (9.77 ± 3.49 vs 7.83 ± 1.06 m/s; p = 0.009). Despite our strict selection criteria, patients with TA had an average systolic blood pressure (SBP) 8 mmHg higher than controls (p = NS), and significantly higher pulse pressure values. The multivariate linear regression model shows that 93.8% of the PWV variability is explained by the variables age, mean BP, and the disease itself (adjusted R2= 0.938). Stepwise logistic analysis using the PWV cutoff value established by the receiver-operator characteristic curve (> 8.34 m/s) as dependent variable, and measures with significance in univariate analysis as independent variables revealed that TA (OR 4.69; 95% CI 1.31–16.72; p = 0.017) and mean BP (OR 1.06; 95% CI 1.00–1.12; p = 0.048) were independently associated with higher PWV. Further analysis of disease variables revealed that PWV values were not correlated with erythrocyte sedimentation rate, C-reactive protein, cumulative dose of glucocorticoid, or ejection fraction (p > 0.05).

Conclusion.

In our cohort of female patients with TA, the disease itself and mean BP were the strongest determinants associated with arterial stiffness.

The influence of gender on carotid artery compliance and distensibility in children and adults

PURPOSE

Given the role of arterial wall elasticity in the development of cardiovascular disease, carotid artery compliance and distensibility have been used commonly over the last decade as predictors of cardiovascular risk, although their gender differences remain unknown. The purpose of our study was to evaluate the impact of gender on carotid arterial elasticity in a large sample of children and adults.

METHODS

Carotid artery compliance and distensibility were measured with ultrasonography in 294 children (157 boys, 137 girls; ages 6-18 years) and 604 adults (291 men, 311 women; ages 18-49 years) previously recruited for a study investigating cardiovascular risk factors. An independent sample t test was used to compare demographic and carotid artery elasticity values by age and gender.

RESULTS

No significant gender difference in carotid arterial compliance and distensibility was observed in children. Women had significantly greater cross-sectional compliance than men (0.004 ± 0.000 versus 0.003 ± 0.000 1/mmHg, p = 0.041).

CONCLUSIONS

We found significant gender difference in carotid compliance in adults, but not in children, suggesting that gender differences in arterial stiffness are not present early in life but emerge later in adulthood.

Autonomic dysfunction in ischemic stroke with carotid stenosis

OBJECTIVES

Impaired autonomic function is common in acute ischemic stroke. Previous limited studies have suggested that atherosclerosis may affect the distensibility of the carotid sinus and then impair the cardiovascular autonomic function. This study sought to investigate cardiovascular autonomic function in patients with ischemic stroke with carotid stenosis.

METHODS

Eighty-five patients with ischemic stroke (58 ones without carotid stenosis and 27 ones with carotid stenosis, average 6 months after stroke onset) and 37 elderly controls were recruited. All performed Ewing's battery autonomic function tests.

RESULTS

From Ewing's battery of autonomic function tests, atypical, definite, or severe autonomic dysfunction was identified in 69.0% patients without carotid stenosis and 88.9% with carotid stenosis, with significant difference between the two groups, and the prevalence of autonomic dysfunction in both groups was higher than that in controls (21.6%). Patients with carotid stenosis showed impairment of all parasympathetic tests (all P < 0.05) and one of the sympathetic tests [Mean fall in systolic blood pressure (BP) on standing: P = 0.051], and those without carotid stenosis only showed impairment in two parasympathetic tests (Valsalva ratio: P = 0.014; heart rate response to deep breathing: P < 0.001) in comparison with controls. Patients with carotid stenosis had significantly more impairment than those without carotid stenosis in some autonomic parameters (Valsalva ratio: P < 0.05; mean fall in systolic BP on standing: P < 0.05).

CONCLUSIONS

Cardiovascular autonomic function is impaired in patients with ischemic stroke, but patients with carotid stenosis show more severely impaired parasympathetic and sympathetic functions.

A constituent-based model of age-related changes in conduit arteries

In the present report, a constituent-based theoretical model of age-related changes in geometry and mechanical properties of conduit arteries is proposed. The model was based on the premise that given the time course of the load on an artery and the accumulation of advanced glycation end-products in the arterial tissue, the initial geometric dimensions and properties of the arterial tissue can be predicted by a solution of a boundary value problem for the governing equations that follow from finite elasticity, structure-based constitutive modeling within the constrained mixture theory, continuum damage theory, and global growth approach for stress-induced structure-based remodeling. An illustrative example of the age-related changes in geometry, structure, composition, and mechanical properties of a human thoracic aorta is considered. Model predictions were in good qualitative agreement with available experimental data in the literature. Limitations and perspectives for refining the model are discussed.

Feasibility of dual Doppler velocity measurements to estimate volume pulsations of an arterial segment

If volume flow was measured at each end of an arterial segment with no branches, any instantaneous differences would indicate that volume was increasing or decreasing transiently within the segment. This concept could provide an alternative method to assess the mechanical properties or distensibility of an artery noninvasively using ultrasound. The goal of this study was to determine the feasibility of using Doppler measurements of pulsatile velocity (opposed to flow) at two sites to estimate the volume pulsations of the intervening arterial segment. To test the concept over a wide range of dimensions, we made simultaneous measurements of velocity in a short 5 mm segment of a mouse common carotid artery and in a longer 20 cm segment of a human brachial-radial artery using a two-channel 20 MHz pulsed Doppler and calculated the waveforms and magnitudes of the volume pulsations during the cardiac cycle. We also estimated pulse wave velocity from the velocity upstroke arrival times and measured artery wall motion using tissue Doppler methods for comparison of magnitudes and waveforms. Volume pulsations estimated from Doppler velocity measurements were 16% for the mouse carotid artery and 4% for the human brachial artery. These values are consistent with the measured pulse wave velocities of 4.2 m/s and 10 m/s, respectively, and with the mouse carotid diameter pulsation. In addition, the segmental volume waveforms resemble diameter and pressure waveforms as expected. We conclude that with proper application and further validation, dual Doppler velocity measurements can be used to estimate the magnitude and waveform of volume pulsations of an arterial segment and to provide an alternative noninvasive index of arterial mechanical properties.

Microstructural and biomechanical alterations of the human aorta as a function of age and location

While it is known that the aorta stiffens with location and age, little is known about the underlying mechanisms that govern these alterations. The purpose of this study was to investigate the relationship between the anisotropic biomechanical behavior and extracellular matrix microstructure of the human aorta and quantify how each changes with location and age. A total of 207 specimens were harvested from 5 locations (ascending n = 33, arch n = 38, descending n = 54, suprarenal n = 52, and abdominal n = 30) of 31 autopsy donor aortas (aged 3 days to 93 years). Each specimen underwent planar biaxial testing in order to derive quantitative biomechanical endpoints of anisotropic stiffness and compliance. Quantitative measures of fiber alignment and degree of fiber alignment were also generated on the same samples using a small-angle light scattering (SALS) technique. Circumferential and axial stiffening occurred with age and increased from the proximal to distal aorta, and the abdominal region was found to be more stiff than all others (p ≤ 0.006). Specimens from donors aged 61 and above were drastically more stiff than younger specimens (p < 0.001) and demonstrated greater circumferential compliance and axial stiffening (p < 0.001). Fiber direction for all ages and locations was predominantly circumferential (p < 0.001), and the degree of fiber alignment was found to increase with age (p < 0.001). Our results demonstrate that the aorta becomes more biomechanically and structurally anisotropic after age 60; with significant changes occurring preferentially in the abdominal aorta, these changes may play an important role in the predisposition of disease formation (e.g., aneurysm) in this region with age.

Aortic arch calcification detectable on chest X-ray is a strong independent predictor of cardiovascular events beyond traditional risk factors

OBJECTIVES

Arterial calcification makes the management of hemodynamics more difficult. Some reports have previously shown that simple assessment of aortic calcification using plain radiography is associated with cardiovascular (CV) events; however, these studies simply assessed whether aortic calcification was present or absent only, without considering its extent. Here, we evaluated validity of grading aortic arch calcification (AAC) to predict new CV events.

METHODS AND RESULTS

We retrospectively reviewed chest X-rays in 239 asymptomatic out-patients who underwent measurement of endothelial function at the 1994-2000 without past history of CV events. The extent of AAC was divided into four grades (0-3). Among these subjects, the follow-up of CV events in 209 patients was completed. At baseline, AAC grade was positively related to age, pulse pressure, diabetes and renal dysfunction. Impairment of endothelial function, as determined by flow-mediated dilation (FMD), was also correlated to increasing AAC grade. Fifty-seven CV events in total occurred during a mean follow-up period of 69+/-45 months. With multivariate adjustment, Kaplan-Meier analysis showed that the incidence was significantly higher in patients with higher AAC grade (grades 2 and 3) than in those with grade 0 or 1 (p<0.01, log-rank test). Two kinds of multivariate Cox-proportional hazards analyses showed the predictive values of AAC grade were significant (hazard ratio, 2.49; p=0.01, 2.56; p<0.01, respectively), and the predictive power was superior to that of renal dysfunction or FMD. In addition, the prediction was valuable even in patients without CKD.

CONCLUSIONS

AAC detectable on chest X-ray is a strong independent predictor of CV events beyond traditional risk factors including endothelial dysfunction. Risk stratification by assessment of AAC may provide important information for management of atherosclerotic disease.

Potassium Magnesium Supplementation for Four Weeks Improves Small Distal Artery Compliance and Reduces Blood Pressure in Patients with Essential Hypertension

It has been postulated that the loss of arterial compliance may precede cardiovascular diseases, and that arterial compliance is an important parameter to consider when evaluating arterial diseases such as essential hypertension (EH) and the effects of antihypertensive treatment. In all, 133 EH patients and 147 healthy subjects were enrolled in this study. Large arterial compliance (C1) and small arterial compliance (C2) were measured by the CVProfilor DO-2020 CardioVascular Profiling System. Thirty-five patients randomly received magnesium potassium supplementation (magnesium, 70.8 mg/d; potassium, 217.2 mg/d) for four weeks, and 32 patients received lacidipin (4 mg/d) as a control. Before and after the four weeks, blood pressure, C1, and C2 were measured. It was found that arterial compliance was significantly lower in EH patients compared with healthy subjects (C1: 12.53 +/- 0.33 vs. 15.63 +/- 0.30 ml/mmHg x 10, p < 0.01;C2: 3.79 +/- 0.17 vs. 5.69 +/- 0.25 ml/mmHg x 100, p < 0.01). On lacidipine, systolic and diastolic BP decreased 13.27 +/- 1.76 mm Hg and 6.33 +/- 1.55 mm Hg, and C1 and C2 compliance values increased 25.05% +/- 4.49% and 34.50% +/- 7.40%, respectively. On K+ and Mg2+ supplementation, systolic and diastolic BP decreased 7.83 +/- 1.87 mm Hg and 3.67 +/- 1.03 mm Hg, and C1 and C2 compliance values increased 12.44% +/- 4.43% and 45.25% +/- 6.67%, respectively. Decreases in systemic vascular resistance (mean arterial pressure divided by cardiac output) by 11.9% and 16.6 % (p < 0.01) were seen between the drug-induced changes, respectively. Both large arterial compliance and small arterial compliance were decreased in essential hypertension patients. In essential hypertension patients, magnesium and potassium supplementation could improve small arterial compliance, while lacidipine improved large arterial compliance significantly.

The long-term effects of tibolone on aortic stiffness and endothelial function

OBJECTIVE

To investigate the effect of 10 years of treatment with tibolone on aortic stiffness and endothelial function.

DESIGN

Cross-sectional study of women currently participating in an open-label, non-randomized study of the long-term efficacy of tibolone. A total of 113 recently postmenopausal women were recruited in 1988. Fifty-eight agreed to take tibolone 2.5 mg daily and 55 were followed during the study as matched controls (who chose not to take any form of hormone replacement therapy (HRT) for the duration of the study). The groups were matched for age, weight and time since last menstrual period.

SETTING

A Central London Teaching Hospital.

SUBJECTS

After 10 years, 60 women remained in the study, 32 in the tibolone group and 28 in the control group. All of these women were invited to participate in this pilot study and attend the Menopause Research Unit. Fourteen women from each group agreed to attend. The main outcome measures were aortic stiffness, measured by pulse wave velocity, and endothelial function, as assessed by flow-mediated dilatation of the brachial artery.

RESULTS

Pulse wave velocity was significantly lower in the tibolone group (10.4 +/- 1.2) than in the control group (11.6 +/- 1.2), p = 0.042. The flow-mediated dilatations were similar in both groups.

CONCLUSION

In this study, long-term use of tibolone over 10 years has a beneficial effect on aortic stiffness. The differences seen in brachial artery vasoreactivity failed to reach statistical significance. Whether this is a true indication of the effects of long-term tibolone on brachial artery vasoreactivity will only be determined by performing a larger, placebo-controlled, randomized study.

Validity and usefulness of aortic arch calcification in chest X-ray

BACKGROUND

Arterial calcification is associated with cardiovascular (CV) disease, to be leading to vessel wall stiffness and causing the management of hemodynamics in the elderly more difficult. Here, we compared the extent of calcification in the aortic arch by reviewing chest X-rays to that in the abdominal aorta as assessed by more detailed examinations. In addition, the validity of the grading and the relationship of this useful grading to clinical risk factors were evaluated.

METHODS AND RESULTS

The extent of aortic arch calcification (AAC) on a postero-anterior plain chest X-ray was divided into four grades (0 to 3). First, AAC grade was assessed in patients who underwent two quantitative examinations for abdominal aortic calcification; lateral radiograph of lumbar spine and/or computer tomography, and was positively correlated with the abdominal aortic calcification level. Subsequently, AAC grade in 239 out-patients (115 men; mean age, 61.9 years) was also evaluated, and was 0, 1, 2, and 3 in 46%, 22%, 29%, and 4% of the population, respectively, was significantly associated with pulse pressure and intima-media thickness. AAC grade in patients with diabetes or renal dysfunction was significantly higher than in those without each risk, but there was no association with other risk factors. In addition, AAC grade was positively correlated with risk factor clustering.

CONCLUSION

Assessment of AAC detectable on a chest X-ray is very useful and its grade reflects the magnitude of calcified change in the whole aorta. In addition, AAC evaluation may provide supportive information for atherosclerotic risk stratification.

Ageing of the conduit arteries

Conduit arteries become stiffer with age due to alterations in their morphology and the composition of the their major structural proteins, elastin and collagen. The elastic lamellae undergo fragmentation and thinning, leading to ectasia and a gradual transfer of mechanical load to collagen, which is 100-1000 times stiffer than elastin. Possible causes of this fragmentation are mechanical (fatigue failure) or enzymatic (driven by matrix metallo proteinases (MMP) activity), both of which may have genetic or environmental origins (fetal programming). Furthermore, the remaining elastin itself becomes stiffer, owing to calcification and the formation of cross-links due to advanced glycation end-products (AGEs), a process that affects collagen even more strongly. These changes are accelerated in the presence of disease such as hypertension, diabetes and uraemia and may be exacerbated locally by atherosclerosis. Raised MMP activity, calcification and impaired endothelial function are also associated with a high level of plasma homocysteine, which itself increases with age. Impaired endothelial function leads to increased resting vascular smooth muscle tone and further increases in vascular stiffness and mean and/or pulse pressure. The effect of increased stiffness, whatever its underlying causes, is to reduce the reservoir/buffering function of the conduit arteries near the heart and to increase pulse wave velocity, both of which increase systolic and pulse pressure. These determine the peak load on the heart and the vascular system as a whole, the breakdown of which, like that of any machine, depends more on the maximum loads they must bear than on their average. Reversing or stabilising the increased arterial stiffness associated with age and disease by targeting any or all of its causes provides a number of promising new approaches to the treatment of systolic hypertension and its sequelae, the main causes of mortality and morbidity in the developed world.

Pulse hypertension: a new component of the metabolic syndrome in elderly women?

The classification of arterial hypertension (HT) to define metabolic syndrome (MS) is unclear in that different cutoffs of blood pressure (BP) have been proposed. We evaluated the categorization of HT most qualified to define MS in relationship with coronary heart disease (CHD) mortality at a population level. A total of 3257 subjects aged > or =65 years were followed up for 12 years. MS was defined according to the criteria of the National Education Cholesterol Program using three different categories of HT: MS-1 (systolic blood pressure (SBP) > or =130 and diastolic blood pressure (DBP) > or =85 mm Hg), MS-2 (SBP > or =130 or DBP > or =85 mm Hg) and MS-3 (pulse pressure (PP) > or =75 mm Hg in men and > or =80 mm Hg in women). Gender-specific adjusted hazard ratio (HR) with 95% confidence intervals (CI) for CHD mortality was derived from Cox analysis in the three MS groups, both including and excluding antihypertensive treatment. In women with MS untreated for HT, the risk of CHD mortality was always significantly higher than in those without MS, independent of categorization; the HR of MS was 1.73 (CI 1.12-2.67) using MS-1, 1.75 (CI 1.10-2.83) using MS-2 and 2.39 (CI 3.71-1.31) using MS-3. In women with MS treated for HT, the HR of CHD mortality was significantly increased only in the MS-3 group (1.92, CI 1.1-2.88). MS did not predict CHD in men. In conclusion, MS can predict CHD mortality in elderly women with untreated HT but not in those with treated HT; in the latter, PP is the most predictive BP value.

Differentiation of mild and severe stenosis with motion estimation in ultrasound images

Doppler ultrasound technique is now recognized as the best noninvasive screening test for carotid artery stenosis. Ultrasound does not calculate directly the degree of arterial narrowing, but relies on extrapolating the changes in blood flow parameters to an anatomical stenosis. This paper deals with the estimation of the stiffness indices of mild and severe stenosis of common carotid artery by motion estimation algorithm, focusing on their changes with the progression of atherosclerosis. 145 men with the mean age of 55 +/- 12 y who were healthy or had mild stenosis or severe stenosis were studied. For each ultrasound examination, matching longitudinal views of the common carotid artery were located, the frames were grabbed and processed with motion estimation algorithm and then diameter, cross-section changes and intima-media thickness of the right common carotid artery were estimated. The blood pressure was recorded in the right brachial artery using a semiautomatic device. The arterial diameter and cross-section changes and intima-media thickness were used together with the blood pressure measurements to estimate standard arterial stiffness indices. Relative diameter changes in carotid arteries with mild and severe stenosis were decreased by 22% to 48%, respectively, compared with healthy carotid artery. Systolic blood pressure in mild stenosis was approximately 4.4% lower and in severe stenosis was 2.0% higher compared with the healthy carotid. The stiffness indices were significantly different in the group of patients with severe stenosis (p-value < 0.05) compared with the healthy and mild stenosis subjects. It is concluded that, regarding the influence of atherosclerosis on the stiffness indices of right common carotid artery, we can differentiate mild and severe stenosis in carotid artery, through processing the sequential color Doppler ultrasound images by optical flow tracking algorithm.

Assessment of test repeatability of arterial stiffness index

BACKGROUND

Increased arterial stiffness is an early indicator of vascular disease. Several methods may be used to determine arterial stiffness. One method obtains an arterial stiffness index from the vascular dynamics of oscillometric-derived brachial artery pressure.

METHODS

To determine the test-retest repeatability of the CardioVision MS-2000, 47 healthy hospital employees had five consecutive measurements of arterial stiffness index measured after a 5-10 min period of rest and then repeated after an average of 146.8 days. Their mean age was 37 years and 71% were women.

RESULTS

The mean arterial stiffness index was 39.6+/-9.7 and 37.2+/-10.5 mmHg x10 (P=0.22) for the first and second time period, respectively. We computed an intraclass correlation coefficient of 0.31 and 0.33 for the first and second time periods, which is the measure of consistency or agreement of arterial stiffness index values within cases. The intraclass correlation coefficient for systolic blood pressure, diastolic blood pressure, heart rate and arterial stiffness index were 0.68 (P=0.0001), 0.70 (P=0.0001), 0.35 (P=0.02) and 0.25 (P=0.08), respectively.

CONCLUSION

The results of this study suggest poor test-retest repeatability if consecutive measurements are used. The intraclass correlation coefficient, however, could be improved by eliminating the highest and lowest value from a set of measurements.

Determination of layer-specific mechanical properties of human coronary arteries with nonatherosclerotic intimal thickening and related constitutive modeling

At autopsy, 13 nonstenotic human left anterior descending coronary arteries [71.5 +/- 7.3 (mean +/- SD) yr old] were harvested, and related anamnesis was documented. Preconditioned prepared strips (n = 78) of segments from the midregion of the left anterior descending coronary artery from the individual layers in axial and circumferential directions were subjected to cyclic quasi-static uniaxial tension tests, and ultimate tensile stresses and stretches were documented. The ratio of outer diameter to total wall thickness was 0.189 +/- 0.014; ratios of adventitia, media, and intima thickness to total wall thickness were 0.4 +/- 0.03, 0.36 +/- 0.03, and 0.27 +/- 0.02, respectively; axial in situ stretch of 1.044 +/- 0.06 decreased with age. Stress-stretch responses for the individual tissues showed pronounced mechanical heterogeneity. The intima is the stiffest layer over the whole deformation domain, whereas the media in the longitudinal direction is the softest. All specimens exhibited small hysteresis and anisotropic and strong nonlinear behavior in both loading directions. The media and intima showed similar ultimate tensile stresses, which are on average three times smaller than ultimate tensile stresses in the adventitia (1,430 +/- 604 kPa circumferential and 1,300 +/- 692 kPa longitudinal). The ultimate tensile stretches are similar for all tissue layers. A recently proposed constitutive model was extended and used to represent the deformation behavior for each tissue type over the entire loading range. The study showed the need to model nonstenotic human coronary arteries with nonatherosclerotic intimal thickening as a composite structure composed of three solid mechanically relevant layers with different mechanical properties. The intima showed significant thickness, load-bearing capacity, and mechanical strength compared with the media and adventitia.

Anisotropic Mechanical Properties of Tissue Components in Human Atherosclerotic Plaques

Knowledge of the biomechanical properties of human atherosclerotic plaques is of essential importance for developing more insights in the pathophysiology of the cardiovascular system and for better predicting the outcome of interventional treatments such as balloon angioplasty. Available data are mainly based on uniaxial tests, and most of the studies investigate the mechanical response of fibrous plaque caps only. However, stress distributions during, for example, balloon angioplasty are strongly influenced by all components of atherosclerotic lesions. A total number of 107 samples from nine human high-grade stenotic iliac arteries were tested; associated anamnesis of donors reported. Magnetic resonance imaging was employed to test the usability of the harvested arteries. Histological analyses has served to characterize the different tissue types. Prepared strips of 7 different tissue types underwent cyclic quasistatic uniaxial tension tests in axial and circumferential directions; ultimate tensile stresses and stretches were documented. Experimental data of individual samples indicated anisotropic and highly nonlinear tissue properties as well as considerable interspecimen differences. The calcification showed, however, a linear property, with about the same stiffness as observed for the adventitia in high stress regions. The stress and stretch values at calcification fracture are smaller (179±56 kPa and 1.02±0.005) than for each of the other tissue components. Of all intimal tissues investigated, the lowest fracture stress occurred in the circumferential direction of the fibrous cap (254.8±79.8 kPa at stretch 1.182±0.1). The adventitia demonstrated the highest and the nondiseased media the lowest mechanical strength on average.

Age-dependent relation of serum sialic acid concentration to aortic pulse wave velocity in type 2 diabetes

OBJECTIVE

The purpose of this study was to determine whether age affects the significance of serum sialic acid concentration as a marker of atherosclerosis in patients with diabetes.

METHODS

In this cross-sectional study, we investigated the relationship of serum sialic acid concentration to aortic pulse wave velocity (a-PWV) and the effects of age on this relationship in patients with type 2 diabetes.

RESULTS

In the elderly (70 years or over) diabetic patients, a-PWV showed a significant positive correlation with serum sialic acid. This relationship was also significant after adjustment for age, duration of diabetes, body mass index, systolic blood pressure, LDL cholesterol, HDL cholesterol and fibrinogen levels. In elderly diabetic patients, a-PWV also showed a significant positive correlation with age and duration of diabetes and a significant negative correlation with serum HDL cholesterol level. On the other hand, in the younger (31-60 years) diabetic patients, there was no significant correlation between serum sialic acid level and a-PWV, while a-PWV showed significant positive correlations with age, duration of diabetes and plasma fibrinogen level.

CONCLUSIONS

Serum sialic acid level reflects atherosclerosis in elderly diabetic patients but not in younger diabetic patients. This may explain recent controversial findings regarding the relationship between serum sialic acid level and incidence of coronary heart disease in diabetes.

C-reactive protein is associated with arterial stiffness in apparently healthy individuals

OBJECTIVE

C-reactive protein (CRP) levels predict outcome in healthy individuals and patients with atherosclerosis. Arterial stiffness also independently predicts all-cause and cardiovascular mortality and may be involved in the process of atherosclerosis. The aim of this study was to investigate the relationship between stiffness and inflammation in a cohort of healthy individuals.

METHODS AND RESULTS

Pulse wave velocity (PWV) and blood pressure were assessed in 427 individuals. Subjects with cardiovascular disease, diabetes, hypercholesterolemia and those using medication were excluded. CRP correlated with age, mean arterial pressure (MAP), brachial and aortic PWV, and pulse pressures. In multiple regression models, aortic PWV correlated independently with age, CRP, male gender, and MAP (R2=0.593; P<0.001). CRP was also independently associated with brachial PWV. Aortic augmentation index correlated with age, gender, MAP, and inversely with heart rate and height, but not with CRP (R2=0.794; P<0.001). Aortic, carotid, and brachial pulse pressures were also independently associated with CRP levels.

CONCLUSIONS

Aortic and brachial PWV, and pulse pressure, relate to levels of inflammation in healthy individuals, suggesting that inflammation may be involved in arterial stiffening. Anti-inflammatory strategies may, therefore, be of benefit in reducing arterial stiffness and thus cardiovascular risk, especially in patients with premature arterial stiffening.

Pioglitazone: cardiovascular effects in prediabetic patients

Pioglitazone is the second thiazolidine derivative used clinically in the type 2 diabetes mellitus (DM). In the prediabetic stage, hyperinsulinemia or insulin resistance has been suggested to be closely associated with the oxidative stress. The first thiazolidine derivative used to treat DM, troglitazone, is chemically related to alpha-tocopherol, a known antioxidant. Troglitazone prevents tissue damage, but has been reported to produce hepatotoxicity. Pioglitazone strongly increases insulin sensitivity, improves glucose and lipid metabolism and showed no evidence of hepatotoxicity. The mechanism of the antidiabetic action of pioglitazone involves activation of insulin receptors and/or high affinity for peroxisome proliferator-activated receptor gamma (PPARgamma). Hydroxylation of the phenyl and pyridine rings in the chemical structure of pioglitazone may facilitate the scavenging of hydroxyl radicals. The direct antioxidant effect of pioglitazone may contribute to its effect on insulin resistance. The hypoglycemic and hypolipidemic effects of pioglitazone are likely to reduce the expression of TNFalpha. The reduction in the oxidative stress may lead to the suppression of TGFbeta and of collagen accumulation. A decrease in collagen content is likely to improve left ventricular diastolic function and distensibility of the aortic wall. Reduction in the oxidative stress may prevent the proliferation of vascular smooth muscle cells and contribute to the decrease in the aortic wall stiffness.

Passive biaxial mechanical response of aged human iliac arteries

Inflation and extension tests of arteries are essential for the understanding of arterial wall mechanics. Data for such tests of human arteries are rare. At autopsy we harvested 10 non-diseased external iliac arteries of aged subjects (52-87 yrs). Structural homogeneity was ensured by means of ultrasound imaging, and anamneses of patients were recorded. We measured the axial in situ stretches, load-free geometries and opening angles. Passive biaxial mechanical responses of preconditioned cylindrical specimens were studied in 37 degrees C calcium-free Tyrode solution under quasistatic loading conditions. Specimens were subjected to pressure cycles varying from 0 to 33.3 kPa (250 mmHg) at nine fixed axial loads, varying from 0 to 9.90N. For the description of the load-deformation behavior we employed five "two-dimensional" orthotropic strain-energy functions frequently used in arterial wall mechanics. The associated constitutive models were compared in regard to their ability of representing the experimental data. Histology showed that the arteries were of the muscular type. In contrast to animal arteries they exhibited intimal layers of considerable thickness. The average ratio of wall thickness to outer diameter was 7.7, which is much less than observed for common animal arteries. We found a clear correlation between age and the axial in situ stretch lambda is (r = -0.72, P = 0.03), and between age and distensibility of specimens, i.e. aged specimens are less distensible. Axial in situ stretches were clearly smaller (1.07 +/- 0.09, mean +/- SD) than in animal arteries. For one specimen lambda is was even smaller than 1.0, i.e. the vessel elongated axially upon excision. The nonlinear and anisotropic load-deformation behavior showed small hystereses. For the majority of specimens we observed axial stretches smaller than 1.3 and circumferential stretches smaller than 1.1 for the investigated loading range. Data from in situ inflation tests showed a significant increase of the axial stretch with intraluminal pressure. Thus, for this type of artery the axial in situ stretch of a non-pressurized vessel is not representative of the axial in vivo stretch. None of the constitutive models were able to represent the deformation behavior of the entire loading range. For the physiological loading range, however, some of the models achieved good agreement with the experimental data.

Uniaxial strain upregulates matrix-degrading enzymes produced by human vascular smooth muscle cells

Arteries remodel in response to environmental changes. We investigated whether mechanical strain modulates production of matrix metalloproteinase (MMP)-2 and -9 by cultured vascular smooth muscle cells (SMC). MMP-2 and MMP-9 expression were tested using human saphenous vein SMC cultured on silicone membranes at rest or subjected to physiological levels (5%) of stationary or cyclical (1 Hz) uniaxial strain. Compared with control, stationary strain significantly increased MMP-2 mRNA levels at all time points, whereas cyclic strain decreased it after 48 h. Both secreted and cell-associated pro-MMP-2 levels were increased by stationary strain at all times (P < 0.01), whereas cyclic strain decreased secreted levels after 48 h (P < 0.02). MMP-9 mRNA levels and pro-MMP-9 protein were increased after 48 h of stationary stretch (P < 0.01) compared with both no strain and cyclic strain. Our study indicates that vascular SMC show a selective response to different types of strain. We suggest that local increases in stationary mechanical strain resulting from stenting, hypertension, or atherosclerosis may lead to enhanced matrix degradation by SMC.

Evaluation of regional aortic distensibility using color kinesis

Regional aortic stiffness cannot be evaluated by conventional methods. Regional aortic wall velocity during systole in the descending aorta was evaluated by using transesophageal echocardiography with color kinesis. The authors defined regional aortic distensibility (RAD) by considering pulse pressure, with RAD (microm/s/mm Hg) = (regional aortic wall velocity)/(pulse pressure). RAD was evaluated in 38 patients who had coronary artery disease (CAD) and 10 who did not. RAD decreased depending on aging (partial regression coefficient was -5.39 x 10(-1), p<0.001), and RAD was lower in the CAD group than that in the no-CAD group (p<0.05). In the CAD group, 19 patients had a single fixed plaque (4 calcified and 15 noncalcified plaques). RAD in the calcified plaque was lower than that in the noncalcified plaque (p<0.01), and RAD was lower in the noncalcified plaque than that in the no-plaque region (p<0.05). In noncalcified plaques, the relation between RAD and maximum intimal thickness had a significant correlation, r=0.7, p<0.001. The residual of RAD from the regression line was significantly larger in the calcified plaque than that in the noncalcified plaque (p<0.001). In conclusion, RAD can express increasing regional aortic wall stiffness brought about by arteriosclerosis quantitatively. Color kinesis provides information on characteristic difference between calcified and noncalcified plaque.

Differentiation of primary and secondary Raynaud's disease by carotid arterial stiffness

INTRODUCTION

primary Raynaud's disease may be difficult to differentiate clinically from the secondary form with an underlying connective tissue, haematological, neurovascular or drug-induced disorder. We undertook a study to determine the elastic carotid and muscular femoral arterial biomechanical properties and intima-media thickness (IMT) in subjects with primary and secondary Raynaud's disease, to assess whether these parameters could differentiate the two conditions.

METHODS

twenty patients with primary Raynaud's disease and 53 subjects with secondary Raynaud's associated with scleroderma (systemic sclerosis, SSc) had measurements of their carotid and femoral wall mechanics with a duplex scanner coupled to a Wall Track system. Their age, gender, body mass index, heart rate, systolic and diastolic blood pressures, presumed cardiovascular load, plasma creatinine, fasting cholesterol, triglyceride and glucose concentrations were also measured.

RESULTS

the carotid elastic properties [mean (SD): elastic modulus: 560 (180) vs 1204 (558) mmHg,p <0.001 and stiffness index: 5.69 (1.35) vs 11.92 (6.4), p<0.001 for primary and secondary Raynaud's respectively] were significantly impaired in patients with secondary Raynaud's disease even after adjustment for potentially influencing physiological and biochemical variables. There were no statistical differences in the femoral elastic properties or the carotid and femoral IMTs between the two groups.

CONCLUSION

Duplex determination of the carotid elasticity or stiffness is different in primary Raynaud's phenomenon compared with secondary Raynaud's associated with SSc. This may be a useful non-invasive tool, in addition to autoantibody markers and nail-fold capillaroscopy, to differentiate between the two forms of Raynaud's phenomenon.

Mechanisms and consequences of large artery rigidity

In this review paper, the classical and more recently described mechanisms responsible for the structural and functional characteristics of large artery rigidity are described. Mostly important, these characteristics appear to be non-specific to the primary disease process involved in arterial hypertension, diabetes mellitus, dyslipidemia, congestive heart failure, chronic uremia, and perhaps senescence, including vascular dementia. Nonspecific in terms of aetiology, the vasculopathy encountered in these diseases exhibits common structural and functional abnormalities. The identification of such abnormalities could well become the target of potent nonpharmacological and (or) pharmacological interventions capable of preventing or retarding morbidity and mortality. The structural characteristics responsible for large artery rigidity include smooth muscle cell hypertrophy, matrix collagen deposition, and recently described, dysfunction in proteoglycan metabolism. Functional abnormalities, such as bradykinin-dependent hyper-reactivity of smooth muscle cells and vasa vasorum microcirculation network disturbances, also appear to alter aortic wall rigidity. The physiopathology of target organ damage is then revisited, based on endothelial dysfunction, documented in large and resistance arteries, as well as in microcirculation networks, where altered permeability to macromolecules leads to interstitial matrix disorganization and cell damage. The clinical evaluation of large artery rigidity is described, and one of the noninvasive methods, evaluation of pulse-wave velocity, is validated in normal conditions and in disease processes. Finally, non-pharmacological and pharmacological therapeutic measures are presented, and includes physical exercise to reduce insulin resistance, and renin-angiotensin-II-aldosterone modulators.

Angiotensin II injures the arterial wall causing increased aortic stiffening in apolipoprotein E-deficient mice

Cardiovascular diseases, such as atherosclerosis and hypertension, are associated with arterial stiffening. Previous studies showed that ANG II exacerbated atherosclerosis and induced hypertension and aneurysm formation in apolipoprotein E-deficient (apoE-KO) mice. The aim of the present study was to examine the effects of chronic treatment of ANG II on the arterial elastic properties in apoE-KO mice. We hypothesized that ANG II will injure the arterial wall resulting in increased arterial stiffening. Male apoE-KO mice were infused with either ANG II (1.44 mg. kg(-1). day(-1)) or vehicle (PBS) for 30 days. ANG II treatment accelerated atherosclerosis in the carotid artery by sixfold (P < 0.001) and increased blood pressure by 30% (P < 0.05). Additionally, our data demonstrated that ANG II increased arterial stiffening using both in vivo and in vitro methods. ANG II significantly increased pulse wave velocity by 36% (P < 0.01) and decreased arterial elasticity as demonstrated by a more than 900% increase in maximal stiffening (high strain Young's modulus) compared with vehicle (P < 0.05). These functional changes were correlated with morphological and biochemical changes as demonstrated by an increase in collagen content (60%), a decrease in elastin content (74%), and breaks in the internal elastic lamina in the aortic wall. In addition, endothelium-independent vasorelaxation to sodium nitroprusside was impaired in the aortic rings of ANG II-treated mice compared with vehicle. Thus, the present data indicate that ANG II injures the artery wall in multiple ways and arterial stiffening may be a common outcome of ANG II-induced arterial damage.

Osteopontin transcription in aortic vascular smooth muscle cells is controlled by glucose-regulated upstream stimulatory factor and activator protein-1 activities

The expression of the matrix cytokine osteopontin (OPN) is up-regulated in aortic vascular smooth muscle cells (VSMCs) by diabetes. OPN expression in cultured VSMCs is reciprocally regulated by glucose and 2-deoxyglucose (2-DG; inhibitor of cellular glucose metabolism). Systematic analyses of OPN promoter-luciferase reporter constructs identify a CCTCATGAC motif at nucleotides -80 to -72 relative to the initiation site that supports OPN transcription in VSMCs. The region -83 to -45 encompassing this motif confers basal and glucose- and 2-DG-dependent transcription on an unresponsive promoter. Competition and gel mobility supershift assays identify upstream stimulatory factor (USF; USF1:USF2) and activator protein-1 (AP1; c-Fos:c-Jun) in complexes binding the composite CCTCATGAC element. Glucose up-regulates both AP1 and USF binding activities 2-fold in A7r5 cells and selectively up-regulates USF1 protein levels. By contrast, USF (but not AP1) binding activity is suppressed by 2-DG and restored by glucose treatment. Expression of either USF or AP1 activates the proximal OPN promoter in A7r5 VSMCs in part via the CCTCATGAC element. Moreover, glucose stimulates the transactivation functions of c-Fos and USF1, but not c-Jun, in one-hybrid assays. Mannitol does not regulate binding, transactivation functions, USF1 protein accumulation, or OPN transcription. Thus, OPN gene transcription is regulated by USF and AP1 in aortic VSMCs, entrained to changes in cellular glucose metabolism.

Arterial elastic properties and cardiovascular risk/event

Cardiovascular disease is a major cause of morbidity and mortality in the western world. There is convincing evidence that the elastic properties, particularly of large arteries, are impaired in the presence of cardiovascular disease and risk factors such as cigarette smoking, hypertension, diabetes and ageing. Evidence is also emerging that treatment of these risk factors is associated with an improvement in the elastic properties, mirrored by a reduction in the cardiovascular risk and events. The main problems associated with arterial elasticity are the multiple definitions and methods of measurement and the problem of obtaining reliable nearby blood pressure measurement. Nevertheless, duplex estimation appears to be a non-invasive, accurate and reliable method of defining these properties. This method is broadly used as a research tool, but there is a good case for its use in clinical practice, particularly in the screening of patients at risk of cardiovascular events.

Validation of a device to measure arterial pulse wave velocity by a photoplethysmographic method

We aimed to validate a new method for measuring arterial pulsewave transit time and pulsewave velocity (a measure of arterial elasticity), based on the principle of photoplethysmography (PPG), and to compare transcutaneous values with those obtained by intra-arterial measurements. Three validation experiments are described. (a) PPG pulse wave delay times (defined as the time interval between the ECG R wave and the foot of the arterial pulse wave measured at the wrist or ankle) were compared to values obtained simultaneously from an established methodology (Doppler ultrasound). (b) Aortic pulsewave delay times in 17 subjects obtained non-invasively by the PPG method were compared with those obtained from the intra-arterial pressure wave. (c) Repeatability measurements of PWV on the same subjects were carried out over two timescales (minutes and hours) in the arm, the leg and the trunk. The Doppler and PPG delay times correlated well, as did intra-arterial and transcutaneous values. Repeatability at short timescales was good (coefficients of variation (CV) < 6% for all measurement sites) and, at the longer timescale, was satisfactory (CVs in the aorta, the arm and leg were 6.3, 13.1 and 16.0, respectively). The PWV values agreed well with others in the literature. We conclude that the PPG technique provides a complement to existing methods for the non-invasive measurement of arterial compliance. Its simplicity and ease of use make it suitable for large-scale epidemiological studies.

Relation of drinking alcohol to atherosclerotic risk in type 2 diabetes

OBJECTIVE

The effects of drinking alcohol on atherosclerotic risks were investigated in 194 type 2 diabetic patients to determine whether drinking alcohol influences risk of atherosclerosis in diabetic subjects.

RESEARCH DESIGN AND METHODS

The subjects were divided by the degree of their average weekly alcohol consumption into three groups: nondrinkers, light drinkers (ethanol consumption <210 g/week), and heavy drinkers (ethanol consumption > or = 210 g/week). The degree of atherosclerotic progression was evaluated using aortic pulse wave velocity (a-PWV), and possible atherosclerotic risks were evaluated using known atherosclerotic risk factors.

RESULTS

a-PWV was significantly lower in light drinkers than in nondrinkers and heavy drinkers, but there was no significant difference in a-PWV between nondrinkers and heavy drinkers. Systolic blood pressure, HDL cholesterol, and triglyceride levels were significantly higher in heavy drinkers than in nondrinkers and light drinkers, whereas there was no significant difference in these levels between nondrinkers and light drinkers. The mean levels of BMI and blood HbA(1c), uric acid, and fibrinogen were not different between the three groups. There were significant positive correlations of a-PWV with age and systolic blood pressure and weak but significant negative correlations of a-PWV with alcohol consumption and HDL cholesterol level.

CONCLUSIONS

Light drinking, but not heavy drinking, has preventive effects on atherosclerosis in type 2 diabetic subjects. The known beneficial effects of drinking alcohol on blood lipids and fibrinogen may not be involved in the preventive effect of light drinking on atherosclerosis in diabetic subjects.

Hormone replacement therapy with estradiol valerate and cyproterone acetate: effects on endothelium-dependent vasodilatation and arterial wall compliance

OBJECTIVE

to evaluate changes in vasomotor endothelium function and elastic properties of the brachial artery in postmenopausal women beginning hormone replacement therapy (HRT) with Climen(R), a 28-day sequential therapy combining estradiol valerate (E2V) 2 mg/day D1-D21 with cyproterone acetate (CPA) 1 mg/day D12-D22, followed by a 7-day treatment-free interval.

METHODS

Thirty-one women with natural or surgical menopause were included in an open multicenter study. Before treatment, at the end of the estrogen-only phase of cycle 1, and after the combined phase in cycles 1 and 3, endothelium-dependent vasodilatation (EDVD%) in the brachial artery was measured by the post-ischemia increase of the inner diameter, and pulse wave velocity (PWV) was measured in the same artery by simultaneous continuous wave Doppler and photo-plethysmography.

RESULTS

compared to pre-treatment values, the median increase in EDVD was 14.3% after cycle 1 (P=0.0001) and 27.9% after cycle 3 (P=0.0001). CPA did not alter the effect of E2V on EDVD in cycle 1. Median arterial systolic pressure was unchanged, but median diastolic pressure fell from 70 to 67.5 mmHg (P=0.04) after cycle 3. Median PWV was reduced by 0.76 m/s after cycle 3 (relative reduction -9.3%) (P=0.035). There was a significant correlation between PWV and EDVD changes from pre-treatment values at the end of the 3rd cycle.

CONCLUSION

treatment of postmenopausal women with E2V/CPA led to an immediate and significant improvement in endothelium-dependent vasodilatation. The estrogen-related vasomotor effect was not suppressed by the progestogen CPA. The WV changes are consistent with slower improvement of arterial compliance in some women. The non-invasive measurement of EDVD and PWV is a convenient method for the evaluation of both mechanical and functional effects of combination HRT on the arterial wall.

The heart, kidney, and brain as target organs in hypertension

The heart, kidney, brain, and arterial blood vessels are prime targets of hypertensive damage. Uncontrolled hypertension accelerates the damage to these organs and results in eventual organ failure and cardiovascular death and disability. Current guidelines for the appropriate treatment and control of hypertension requires an assessment of the presence of target organ damage. When present, evidence of target organ damage determines the urgency and intensity of drug treatment and may also dictate the choice of initial antihypertensive drug class. Thus, evaluation of persons with suspected or established hypertension must include a meticulous search for evidence of target organ damage. Fortunately, treatment with all antihypertensive medications that results in significant BP reductions also reduces fatal and nonfatal hypertensive complications and significantly slows down the progression to organ failure. Because of the important role that adverse activation of the renin-angiotensin-aldosterone system plays in target organ damage, drugs that antagonize this system have provided consistent and compelling proof of organ protection in both primary and secondary prevention of adverse outcomes. The challenge now is to use these and all other antihypertensive agents effectively to control BP to target levels in patients with hypertension. Continued emphasis on the adoption of lifestyle changes for prevention of hypertension in the first place or as adjunctive therapy in hypertensive patients is essential.

Left ventricular mass and arterial compliance: relation to coronary heart disease and its risk factors in South Indian adults

BACKGROUND

Rates of coronary heart disease (CHD) in India are rising, and are now similar to those in Western countries. The prevalence of conventional CHD risk factors such as hypercholesterolaemia, hypertension, smoking and obesity, tend to be lower in Indian than Western populations, and fail to explain these high rates of disease. Increased left ventricular (LV) mass and decreased arterial compliance predict a higher risk of CHD in Western populations, but there are no published data from India. We have measured LV mass and arterial compliance, and examined their relation to CHD and other known risk factors, in men and women living in Mysore, South India.

METHODS

We examined 435 men and women born in Mysore during 1934-1953. LV mass was measured by echocardiography and arterial compliance (derived from pulse wave velocity, PWV) was measured by a non-invasive optical method in three arterial segments.

RESULTS

The mean LV mass was 149 g (S.D. 37) in men and 125 g (S.D. 32) in women. The mean PWV was 4.14 m/s in the aorto-radial, 3.28 m/s in the aorto-femoral and 13.59 m/s in the femoro-popliteal-posterior tibial segments. LV mass and PWV were positively correlated with each other and with systolic and diastolic blood pressures, non-insulin dependant diabetes mellitus, fasting plasma glucose, insulin, proinsulin concentrations and serum triglyceride concentrations (p<0.05 for all), independently of age, sex and body size. In addition, LV mass correlated negatively with fasting serum HDL-cholesterol (p=0.02). Higher LV mass was associated with an increased risk of CHD (p=0.05).

CONCLUSIONS

The mean LV mass in this Indian population is low compared with Western populations, though as in the West, increased LV mass is associated with an increased risk of CHD. Greater LV mass and reduced arterial compliance are associated with higher levels of many known CHD risk factors especially with those which form the Insulin Resistance Syndrome.

Arterial elasticity among normotensive subjects and treated and untreated hypertensive subjects

OBJECTIVE

The aim of this study was to determine arterial elasticity in normotensive and hypertensive individuals.

BACKGROUND

In addition to blood pressure, other parameters serve as markers for vascular disease. Arterial elasticity is one parameter that can be determined by a modified Windkessel model of the circulation. This model estimates, from a computerized pulse contour analysis, the proximal (capacitive) elasticity of the large arteries and the distal (reflective) elasticity of the small arteries.

METHODS

A prospective, multi-center, controlled clinical study evaluated large-artery and small-artery elasticity indices in four groups: (1) normotensives without a family history of hypertension; (2) normotensives with a family history of hypertension; (3) treated and controlled hypertensives; and (4) untreated and uncontrolled hypertensives. Blood pressure, using a mercury manometer, and arterial elasticity, using a CVProfilor DO-2020 CardioVascular Profiling System (Hypertension Diagnostics, Inc., Eagan, MN, USA), were measured supine in triplicate 3 min apart in a randomized sequence.

RESULTS

There were 212 evaluable subjects of mean age 46 years; 57% were women, 51% Caucasian and 33% African-American. Comparing normotensives without a family history and untreated hypertensives, both large-artery and small-artery elasticity indices were significantly different (P < 0.0001). After controlling for age and body surface area, a significant linear trend (P = 0.0001) across the four groups was detected for both large- and small-artery elasticity indices.

CONCLUSION

As the hypertension status worsened, large- and small-artery elasticity indices decreased, suggesting a potential for the diagnostic use of arterial elasticity determinations.

Infinite number of solutions to the hemodynamic inverse problem

Investigators have had much success solving the "hemodynamic forward problem," i.e., predicting pressure and flow at the entrance of an arterial system given knowledge of specific arterial properties and arterial system topology. Recently, the focus has turned to solving the "hemodynamic inverse problem," i.e., inferring mechanical properties of an arterial system from measured input pressure and flow. Conventional methods to solve the inverse problem rely on fitting to data simple models with parameters that represent specific mechanical properties. Controversies have arisen, because different models ascribe pressure and flow to different properties. However, an inherent assumption common to all model-based methods is the existence of a unique set of mechanical properties that yield a particular pressure and flow. The present work illustrates that there are, in fact, an infinite number of solutions to the hemodynamic inverse problem. Thus a measured pressure-flow pair can result from an infinite number of different arterial systems. Except for a few critical properties, conventional approaches to solve the inverse problem for specific arterial properties are futile.

Carotid arterial distensibility is an important determinant of improvement in autonomic balance after successful coronary angioplasty

OBJECTIVE

To determine whether arterial distensibility influences improvement of autonomic imbalance after left ventricular wall motion (LVWM) abnormality has been improved by percutaneous transluminal angioplasty (PTCA) in patients with ischemic heart disease (IHD).

METHODS AND RESULTS

The following variables were assessed before and 3 months after PTCA in 63 patients with IHD who had a successful PTCA: heart rate variability (standard deviation of all normal R-R intervals [SDNN] measured from 24 h Holter electrocardiograms), baroreceptor sensitivity (determined by the phenylephrine injection method), and carotid artery distensibility (determined by ultrasonography). Abnormalities of LVWM were assessed by cineventriculography. In a multivariate analysis, carotid artery distensibility before PTCA and changes in LVWM abnormality before and after PTCA were independently associated with changes in baroreceptor sensitivity and SDNN (P< 0.05). Patients were divided into two groups: one with impaired and one group with unimpaired initial carotid artery distensibility. After PTCA, LVWM was improved significantly in both groups, but baroreceptor sensitivity and SDNN were improved significantly (respectively from 5.0 +/- 3.3 to 5.9 +/- 3.9 ms/mmHg, P< 0.01 and from 111 +/- 47 to 128 +/- 54 ms, P < 0.01) only in patients with well-preserved carotid artery distensibility.

CONCLUSIONS

The beneficial effect of PTCA on autonomic balance was greater in patients with well-preserved carotid artery distensibility than in those with impaired carotid artery distensibility. These results suggest that the pathophysiological state of arterial distensibility may modify the autonomic balance even after myocardial ischemia-related LVWM abnormalities are improved.