Pulse wave velocity and morphological changes associated with early atherosclerosis progression in the aortas of cynomolgus monkeys

Vascular Stiffness in Aging and Disease

The goal of this review is to provide further understanding of increased vascular stiffness with aging, and how it contributes to the adverse effects of major human diseases. Differences in stiffness down the aortic tree are discussed, a topic requiring further research, because most prior work only examined one location in the aorta. It is also important to understand the divergent effects of increased aortic stiffness between males and females, principally due to the protective role of female sex hormones prior to menopause. Another goal is to review human and non-human primate data and contrast them with data in rodents. This is particularly important for understanding sex differences in vascular stiffness with aging as well as the changes in vascular stiffness before and after menopause in females, as this is controversial. This area of research necessitates studies in humans and non-human primates, since rodents do not go through menopause. The most important mechanism studied as a cause of age-related increases in vascular stiffness is an alteration in the vascular extracellular matrix resulting from an increase in collagen and decrease in elastin. However, there are other mechanisms mediating increased vascular stiffness, such as collagen and elastin disarray, calcium deposition, endothelial dysfunction, and the number of vascular smooth muscle cells (VSMCs). Populations with increased longevity, who live in areas called “Blue Zones,” are also discussed as they provide additional insights into mechanisms that protect against age-related increases in vascular stiffness. Such increases in vascular stiffness are important in mediating the adverse effects of major cardiovascular diseases, including atherosclerosis, hypertension and diabetes, but require further research into their mechanisms and treatment.

Aortic distensibility in alkaptonuria

INTRODUCTION

Alkaptonuria (AKU) is a rare inherited disorder of tyrosine metabolism resulting in an accumulation of homogentisic acid oxidation products in the joints and cardiovascular system. Aortic distensibility may be a non-invasive indicator of cardiovascular complications. Descending thoracic aortic distensibility in alkaptonuria has not been studied.

METHODS

Patients diagnosed with alkaptonuria underwent Magnetic Resonance Imaging (MRI) and gated non-contrast and contrast-enhanced cardiovascular computed tomography. Using MRI cine images, aortic distensibility of the descending thoracic aorta was determined.

RESULTS

Seventy-six patients with alkaptonuria were imaged. When compared to literature normal values, aortic distensibility in AKU was impaired (5.2 vs 6.2 × 10^-3, p < .001). Aortic distensibility was inversely related to age (r = -0.6, p = .0001). Hypertensive patients with alkaptonuria had impaired distensibility compared to normotensive patients with alkaptonuria (4.6 vs 5.6 × 10^-3, p = .03), and hyperlipidemic patients with alkaptonuria had impaired distensibility compared to non-hyperlipidemic patients with alkaptonuria (4.1 vs 6.0 × 10^-3, p = .001). Male hypertensive patients with alkaptonuria had greater distensibility than their female counterparts (5.3 vs 2.9 × 10^-3, p = .02). Similarly, male hyperlipidemic patients with alkaptonuria had greater distensibility than their female counterparts (4.8 vs 2.5 × 10^-3, p < .01). Of patients with alkaptonuria, those with a coronary artery calcium (CAC) score greater than 100 had more impaired distensibility than those with a CAC score less than 100 (3.5 vs 5.1 × 10^-3, p = .01) and those with aortic calcium score greater than 100 had impaired distensibility compared to those with an aortic calcium score less than 100 (3.2 vs 4.9 × 10^-3, p = .02). Univariate analysis revealed age, aortic calcification, and hyperlipidemia to be significant factors of distensibility, and multiple regression analysis showed age as the only significant risk factor of distensibility.

CONCLUSIONS

Patients with alkaptonuria have impaired aortic distensibility, which is likely an early marker for reduced cardiovascular health. Variables such as age, hypertension, hyperlipidemia, and aortic and coronary calcification were associated with impaired distensibility.

Diet-induced early-stage atherosclerosis in baboons: Lipoproteins, atherogenesis, and arterial compliance

BACKGROUND

The purpose of this study was to determine whether dietary manipulation can reliably induce early-stage atherosclerosis and clinically relevant changes in vascular function in an established, well-characterized non-human primate model.

METHODS

We fed 112 baboons a high-cholesterol, high-fat challenge diet for two years. We assayed circulating biomarkers of cardiovascular disease (CVD) risk, at 0, 7, and 104 weeks into the challenge; assessed arterial compliance noninvasively at 104 weeks; and measured atherosclerotic lesions in three major arteries at necropsy.

RESULTS

We observed evidence of atherosclerosis in all but one baboon fed the two-year challenge diet. CVD risk biomarkers, the prevalence, size, and complexity of arterial lesions, plus consequent arterial stiffness, were increased in comparison with dietary control animals.

CONCLUSIONS

Feeding baboons a high-cholesterol, high-fat diet for two years reliably induces atherosclerosis, with risk factor profiles, arterial lesions, and changes in vascular function also seen in humans.

Extracellular Matrix Disarray as a Mechanism for Greater Abdominal Versus Thoracic Aortic Stiffness With Aging in Primates

OBJECTIVE

Increased vascular stiffness is central to the pathophysiology of aging, hypertension, diabetes mellitus, and atherosclerosis. However, relatively few studies have examined vascular stiffness in both the thoracic and the abdominal aorta with aging, despite major differences in anatomy, embryological origin, and relation to aortic aneurysm.

APPROACH AND RESULTS

The 2 other unique features of this study were (1) to study young (9±1 years) and old (26±1 years) male monkeys and (2) to study direct and continuous measurements of aortic pressure and thoracic and abdominal aortic diameters in conscious monkeys. As expected, aortic stiffness, β, was increased P<0.05, 2- to 3-fold, in old versus young thoracic aorta and augmented further with superimposition of acute hypertension with phenylephrine. Surprisingly, stiffness was not greater in old thoracic aorta than in young abdominal aorta. These results can be explained, in part, by the collagen/elastin ratio, but more importantly, by disarray of collagen and elastin, which correlated best with vascular stiffness. However, vascular smooth muscle cell stiffness was not different in thoracic versus abdominal aorta in either young or old monkeys.

CONCLUSIONS

Thus, aortic stiffness increases with aging as expected, but the most severe increases in aortic stiffness observed in the abdominal aorta is novel, where values in young monkeys equaled, or even exceeded, values of thoracic aortic stiffness in old monkeys. These results can be explained by alterations in collagen/elastin ratio, but even more importantly by collagen and elastin disarray.

Piecewise Pulse Wave Imaging (pPWI) for Detection and Monitoring of Focal Vascular Disease in Murine Aortas and Carotids In Vivo

Atherosclerosis and Abdominal Aortic Aneurysms (AAAs) are two common vascular diseases associated with mechanical changes in the arterial wall. Pulse Wave Imaging (PWI), a technique developed by our group to assess and quantify the mechanical properties of the aortic wall in vivo, may provide valuable diagnostic information. This work implements piecewise PWI (pPWI), an enhanced version of PWI designed for focal vascular diseases. Localized, sub-regional PWVs and PWI moduli ( EPWI ) were estimated within 2-4 mm wall segments of murine normal, atherosclerotic and aneurysmal arteries. Overall, stiffness was found to increase in the atherosclerotic cases. The mean sub-regional PWV was found to be 2.57±0.18 m/s for the normal aortas (n = 7) with a corresponding mean EPWI of 43.82±5.86 kPa. A significant increase ( (p ≤ 0.001)) in the group means of the sub-regional PWVs was found between the normal aortas and the aortas of mice on high-fat diet for 20 ( 3.30±0.36 m/s) and 30 weeks ( 3.56±0.29 m/s). The mean of the sub-regional PWVs ( 1.57±0.78 m/s) and EPWI values ( 19.23±15.47 kPa) decreased significantly in the aneurysmal aortas (p ≤ 0.05) . Furthermore, the mean coefficient of determination (r(2)) of the normal aortas was significantly higher (p ≤ 0.05) than those of the aneurysmal and atherosclerotic cases. These findings demonstrated that pPWI may be able to provide useful biomarkers for monitoring focal vascular diseases.

Physiologic cardiovascular strain and intrinsic wave imaging

Cardiovascular disease remains the primary killer worldwide. The heart, essentially an electrically driven mechanical pump, alters its mechanical and electrical properties to compensate for loss of normal mechanical and electrical function. The same adjustment also is performed in the vessels, which constantly adapt their properties to accommodate mechanical and geometrical changes related to aging or disease. Real-time, quantitative assessment of cardiac contractility, conduction, and vascular function before the specialist can visually detect it could be feasible. This new physiologic data could open up interactive therapy regimens that are currently not considered. The eventual goal of this technology is to provide a specific method for estimating the position and severity of contraction defects in cardiac infarcts or angina. This would improve care and outcomes as well as detect stiffness changes and overcome the current global measurement limitations in the progression of vascular disease, at little more cost or risk than that of a clinical ultrasound.

Heart rate reduction as a therapeutic goal: focus on primary prevention

Recently published studies have demonstrated a direct link between heart rate (HR) and prognosis across various populations and clinical groups, including elderly people, patients with arterial hypertension, myocardial infarction, and coronary artery stenting, overweight patients, or even young people with relatively low cardiovascular risk levels. HR is considered as an additional independent risk factor (RF) of cardiovascular disease (CVD). However, thus far, pharmaceutical HR reduction has been demonstrated to improve prognosis only in patients with coronary heart disease or chronic heart failure. The results in CVD-free patients have been contradictory. The review discusses the potential of different HR-reducing therapeutic regimens, as a part of primary CVD prevention.

A novel noninvasive technique for pulse-wave imaging and characterization of clinically-significant vascular mechanical properties in vivo

The pulse-wave velocity (PWV) has been used as an indicator of vascular stiffness, which can be an early predictor of cardiovascular mortality. A noninvasive, easily applicable method for detecting the regional pulse wave (PW) may contribute as a future modality for risk assessment. The purpose of this study was to demonstrate the feasibility and reproducibility of PW imaging (PWI) during propagation along the abdominal aortic wall by acquiring electrocardiography-gated (ECG-gated) radiofrequency (rf) signals noninvasively. An abdominal aortic aneurysm (AAA) was induced using a CaCl2 model in order to investigate the utility of this novel method for detecting disease. The abdominal aortas of twelve normal and five CaCl2 mice were scanned at 30 MHz and electrocardiography (ECG) was acquired simultaneously. The radial wall velocities were mapped with 8000 frames/s. Propagation of the PW was demonstrated in a color-coded ciné-loop format all cases. In the normal mice, the wave propagated in linear fashion from a proximal to a distal region. However, in CaCl2 mice, multiple waves were initiated from several regions (i.e., most likely initiated from various calcified regions within the aortic wall). The regional PWV in normal aortas was 2.70 +/- 0.54 m/s (r2 = 0.85 +/- 0.06, n = 12), which was in agreement with previous reports using conventional techniques. Although there was no statistical difference in the regional PWV between the normal and CaCl2-treated aortas (2.95 +/- 0.90 m/s (r2 = 0.51 +/- 0.22, n = 5)), the correlation coefficient was found to be significantly lower in the CaCl2-treated aortas (p < 0.01). This state-of-the-art technique allows noninvasive mapping of vascular disease in vivo. In future clinical applications, it may contribute to the detection of early stages of cardiovascular disease, which may decrease mortality among high-risk patients.

Different Effects of Atherogenic Lipoproteins and Blood Pressure on Arterial Structure and Function: The Bogalusa Heart Study

Differential impact of non-high-density lipoprotein cholesterol (total cholesterol minus high-density lipoprotein cholesterol) and blood pressure on arterial wall thickness and stiffness was examined in 900 black and white adults aged 24-43 years. Blacks compared with whites had greater values of pulse wave velocity (5.4 m/sec vs. 5.2 m/sec; p<0.01) and carotid artery intima-media thickness (0.83 mm vs. 0.80 mm; p<0.01). Non-high-density lipoprotein cholesterol was significantly associated with carotid intima-media thickness (standardized regression coefficient [b]=0.21; p<0.01), but not with pulse wave velocity (b=0.03; p=0.37), after adjusting for race, sex, age, body mass index, insulin, glucose, and smoking. Systolic blood pressure was associated significantly stronger with pulse wave velocity (b=0.36; p<0.01) than with carotid intima-media thickness (b=0.15; p<0.01). No race difference in these relationships was found. The results of this study indicate that atherogenic lipoproteins and blood pressure may play different roles in the development of arterial wall stiffness and atherosclerosis.

Cardiovascular functional phenotypes and pharmacological responses in apolipoprotein E deficient mice

This is an overview of recent findings, mainly from our laboratory, describing the cardiovascular functional phenotypes and pharmacological responses in mice genetically deficient in apolipoprotein E (apoE-KO). ApoE-KO mice are hyperlipidemic and spontaneously develop atherosclerosis. We have detected several new cardiovascular functional phenotypes in apoE-KO mice: hyperglycemia, age-dependent aortic stiffening, cardiac hypertrophy and increased cardiac output. Angiotensin II (Ang II) promoted vascular inflammation and atherosclerosis, increased vascular stiffness, and induced abdominal aortic aneurysm (AAA) in apoE-KO mice, in which activation of NF-kappaB mediated pro-inflammatory genes plays an important role. Inhibition of nitric oxide (NO) synthesis with N(omega)-nitro-L-arginine methyl ester (L-NAME) significantly inhibited NO-mediated vascular responses and accelerated atherosclerosis in apoE-KO mice, supporting a protective role of NO against atherosclerosis. Estrogen attenuated atherosclerosis in apoE-KO mice, even in those with atherosclerosis being accelerated by Ang II, hyperglycemia, or L-NAME, demonstrating an anti-atherosclerotic effect of estrogen. Simvastatin paradoxically increased lipid and atherosclerosis in apoE-KO mice, but it decreased lipid and atherosclerosis in LDLR-KO mice, indicating that anti-atherosclerotic effect of simvastatin requires the presence of an intact apoE.

Aortic pulse wave velocity and the degree of atherosclerosis in the elderly: a pathological study based on 304 autopsy cases

INTRODUCTION

Studies examining the correlation between aortic pulse wave velocity (PWV) and atherosclerosis have reported conflicting results. The present paper verifies this correlation by conducting autopsy examination of elderly subjects.

METHODS

A total of 3456 PWV examinations had been performed on 1538 elderly people, as a part of routine physical check-up. During long-term follow-up, many of these subjects died, and autopsy study could be conducted on 304 of these subjects. The average age at death of the subjects was 83 years and the male: female ratio was 6:5. The pathological atherosclerotic index (PAI) was defined as the average pathological degree of atherosclerosis in eight large arteries, including aorta.

RESULTS

Significant positive correlations were observed between the age and PWV (gamma=0.273, P<0.001), and between the systolic blood pressure and PWV (gamma=0.478, P<0.001). There was a significantly positive correlation between the aortic atherosclerotic degree and mean PWV (rho=0.239, P<0.005), and between the PAI and mean PWV (gamma=0.323, P<0.001). The partial regression coefficient between the PAI and mean PWV was 0.209, after adjusting for the mean systolic blood pressure and age at death.

CONCLUSION

The present study proved a weak correlation between the PWV and the pathologically verified degree of the aortic and systemic atherosclerosis.

Aortic stiffness and carotid intima-media thickness: two independent markers of subclinical vascular damage in young adults?

BACKGROUND

Previous reports have shown that carotid intima-media thickness (CIMT) and arterial stiffness are strong predictors of subsequent cardiovascular disease (CVD) morbidity and mortality, and are well related to an unfavourable cardiovascular risk profile in middle-aged and older subjects. These similarities suggest that arterial stiffness may play a role in the development of atherosclerosis or vice versa. However, studies show conflicting results and are limited to elderly subjects. To study this issue further, we evaluated the relation of arterial stiffness to subclinical atherosclerosis in 524 healthy young adults, aged 27-30 years.

METHODS AND RESULTS

Aortic stiffness was assessed using pulse wave velocity (PWV) and CIMT was used as measure of subclinical atherosclerosis. The positive crude correlation between for mean arterial pressure adjusted PWV and CIMT (Pearson's correlation coefficient: 0.11; P=0.016) attenuated after adjustment for common determinants of both measurements like gender and age (partial correlation coefficient: 0.03; P=0.512). Furthermore, multivariate linear regression models showed that male gender, age and blood pressure were independent determinants of both CIMT and PWV while body mass index and LDL-cholesterol were independent determinants of CIMT only.

CONCLUSIONS

These observations suggest that in healthy young adults arterial stiffness and CIMT reflect two separate entities of vascular damage.

Carotid intima-media thickness, arterial stiffness and risk of cardiovascular disease: current evidence

AIMS

Over recent decades the interest in cardiovascular epidemiology has broadened from studies on causes and consequences of elevated cardiovascular risk factors to include research on causes and consequences of atherosclerosis and associated arterial wall abnormalities. One of the underlying reasons was that established cardiovascular risk factors were insufficiently accurate in identifying those individuals who will suffer from cardiovascular disease in the future and measures of subclinical atherosclerosis may enhance the precision of these predictions and thus enable better-tailored medical care to be provided. The usefulness of measuring subclinical atherosclerosis is conditional on evidence that presence of subclinical atherosclerosis confers an increased risk of cardiovascular disease and that favourable changes in subclinical atherosclerosis parallel reductions in risk. We aimed at providing an overview of epidemiological data on carotid intima-media thickness (CIMT) and arterial stiffness measurements and their relation to risk of cardiovascular disease.

METHODS

We reviewed the published epidemiological data.

RESULTS AND CONCLUSION

CIMT is a good indicator of cardiovascular risk and provides a graded measure of vascular damage: no clear CIMT level above which the cardiovascular risk appears to increase considerably The evidence for arterial stiffness, assessed as carotid distensibility or aortic pulse wave velocity, as an indicator for risk of cardiovascular disease is restricted to subjects with either hypertension or end-stage renal disease or based on small studies in renal transplant patients and elderly. Evidence to indicate that information on carotid intima-media thickness or arterial stiffness, additional to established cardiovascular risk factors, helps to distinguish subjects into those with a high and those with a low absolute risk of cardiovascular disease is limited, but needed. Also, information on the direct comparison of both arterial stiffness measures in their ability to predict cardiovascular disease is needed.

Arterial stiffness in postmenopausal women: determinants of pulse wave velocity

OBJECTIVE To investigate the degree and potential cardiovascular determinants of arterial stiffness, assessed by aortic pulse wave velocity (PWV) measurements, and to relate arterial stiffness to absolute 10-12-year risks of stroke, coronary heart disease and death, as estimated by available risk functions, in postmenopausal women. METHOD We performed a cross-sectional study among 385 postmenopausal women, aged 50-74 years, sampled from the general population. Arterial stiffness was assessed non-invasively by measurement of aortic PWV using applanation tonometry. Information on health was obtained by medical history, registration of current medication, and physical examination. Height, weight, waist and hip circumferences, fasting glucose, total and high-density lipoprotein (HDL) cholesterol, triglycerides, resting blood pressure, and heart rate were measured. Three risk scores were used to estimate, for each individual, the absolute risk of stroke, coronary heart disease, and death within 10-12 years as a function of their cardiovascular risk factor profile. The relationship between PWV and these risk scores was subsequently determined. RESULTS Significant positive relationships with PWV were found for body mass index, fasting glucose, diabetes mellitus, and triglycerides in analyses adjusted for age, mean arterial blood pressure, and heart rate. Height and HDL cholesterol were inversely related to PWV. The risks of stroke, coronary heart disease, and death increased with increasing PWV in a linear graded manner. CONCLUSIONS This cross-sectional study among postmenopausal women provides evidence that most of the established cardiovascular risk factors are determinants of aortic PWV. Increased PWV marks an increased risk of stroke, coronary heart disease, and death within 10-12 years.

Effects of atorvastatin on aortic pulse wave velocity in patients with hypertension and hypercholesterolaemia: a preliminary study

As statins may contribute to plaque stabilisation, it is important to evaluate whether these drugs may modify arterial stiffness. In 23 patients, aged 32-70 years, with hypertension and hypercholesterolaemia, a double-blind randomised study vs placebo was performed to evaluate whether atorvastatin was able to modify aortic stiffness, measured from aortic pulse wave velocity (PWV), after a 12-week treatment. The results revealed that atorvastatin did not change blood pressure, significantly lowered (P<0.003; <0.002) plasma total and LDL cholesterol, and increased aortic PWV by +8% (vs -2% under placebo) (P<or=0.05). The percentage changes in plasma total and LDL cholesterol and in PWV were significantly and negatively correlated, independent of blood pressure level. The finding of increased aortic PWV after 12-week statin treatment agrees with studies in monkeys, indicating that, at the early phase of hypolipidaemic diet but not later, aortic PWV increases transiently as a consequence of the significant reduction of lipid vascular content. In conclusion, the present results support the possibility that statins might contribute to a change in arterial stiffness independent of blood pressure level, and suggest that long-term studies in humans are needed to evaluate the contribution of arterial elasticity to statin-induced vascular remodelling.

Higher usual dietary intake of phytoestrogens is associated with lower aortic stiffness in postmenopausal women

OBJECTIVE

Phytoestrogens have been postulated to protect against cardiovascular diseases, but few studies have focused on the effect of Western dietary phytoestrogen intake.

METHODS AND RESULTS

Four hundred three women with natural menopause either between 1987 and 1989 or between 1969 and 1979 were selected from the baseline data of the PROSPECT study (n=17 395). Isoflavone and lignan intake was calculated from a food-frequency questionnaire. Aortic stiffness was noninvasively assessed by pulse-wave velocity measurement of the aorta. Linear regression analysis was used. After adjustment for age, body mass index, smoking, physical activity, mean arterial pressure, follow-up time, energy intake, dietary fiber intake, glucose, and high density lipoprotein cholesterol, increasing dietary isoflavone intake was associated with decreased aortic stiffness: -0.51 m/s (95% CI -1.00 to -0.03, fourth versus first quartile, P for trend=0.07). Increasing dietary intake of lignans was also associated with decreased aortic pulse-wave velocity: -0.42 m/s (95% CI -0.93 to 0.11, fourth versus first quartile, P for trend=0.06). Results were most pronounced in older women: for isoflavones, -0.94 m/s (95% CI -1.65 to -0.22, P for trend=0.02), and for lignans, -0.80 m/s (95% CI -1.85 to -0.05), fourth versus first quartile.

CONCLUSIONS

The results of our study support the view that phytoestrogens have a protective effect on the risk of atherosclerosis and arterial degeneration through an effect on arterial walls, especially among older women.

Reduction of cardiac functional reserve and elevation of aortic stiffness in hyperlipidemic Yucatan minipigs with systemic and coronary atherosclerosis

To test the hypothesis that cardiac functional reserve is reduced in animals with severe atherosclerosis, Yucatan minipigs were fed a high-cholesterol diet (Chol) for 8 months. Half of them was made diabetic, an additional risk factor for atherosclerosis, with streptozotocin (STZ). Another group of age-matched minipigs were fed a normal diet as controls. At the end of the treatment period, animals were instrumented for the measurement of cardiovascular hemodynamic parameters under isoflurane anesthesia. Cardiac functional reserve was measured by the magnitude of the inotropic response to isoproterenol stress. Hyperlipidemic minipigs developed severe atherosclerotic plaques in the aorta, coronary and iliac artery, accompanied by an increase in the aortic stiffness indexed by increases in pulse wave velocity and augmentation index. These vascular changes were more severe in STZ-induced insulin-dependent diabetes mellitus. The isoproterenol-induced increase in left ventricular contractility (dP/dt) and relaxation (-dP/dt) and, consequently, cardiac output were also significantly reduced in both the Chol groups with or without STZ, compared to control group. Thus, cardiac functional reserve measured by isoproterenol-stimulated responses was reduced in atherosclerotic minipigs, which was further diminished in diabetes.

Carotid pressure is a better predictor of coronary artery disease severity than brachial pressure

The mechanisms relating pulse pressure to cardiovascular outcome may include surrogacy for coronary disease severity. Although pulse pressure is typically measured at the brachial artery, central pulse pressure and its principal determinant, large-artery stiffness, may relate more closely to disease severity. This study aimed to determine the relationships between large-artery stiffness and carotid and brachial blood pressures and coronary artery disease severity. One hundred fourteen male patients with coronary artery disease (age 60+/-8 years, mean+/-SD) and 57 age-matched healthy male controls (age 59+/-9 years) were recruited. Patients were classified into 2 groups based on the magnitude of their maximum coronary stenosis: moderate (50% to 89%) and severe (>/=90%). Large-artery stiffness was assessed as systemic arterial compliance and carotid-femoral pulse wave velocity. Mean pressure was not different between the 3 groups. Systemic compliance and carotid pulse pressure were significantly different between all 3 groups, with compliance lowest and pressure highest in the severe group (P<0.05). Pulse wave velocity was higher in patients with severe stenosis than in those with moderate stenosis (P<0.01) and those in the control group (P<0.001). Brachial pulse pressure was higher in patients than in controls (P<0.05), but there was no difference between the 2 disease groups. In separate multivariate analyses, carotid pressures and systemic arterial compliance were determinants of coronary artery disease severity, independent of age, smoking status, body mass index, mean arterial pressure, heart rate, cholesterol levels (total, LDL, and HDL), triglycerides, and beta-antagonist and lipid-lowering therapy (P<0.001), whereas brachial pressures and pulse wave velocity were not. In conclusion, central blood pressures and systemic arterial compliance are more sensitive markers of coronary artery disease severity than brachial pressures.

Aerobic exercise training does not modify large-artery compliance in isolated systolic hypertension

The present study characterized large-artery properties in patients with isolated systolic hypertension (ISH) and determined the efficacy of exercise training in modifying these properties. Twenty patients (10 male and 10 female) with stage I ISH and 20 age- and gender-matched control subjects were recruited, and large-artery properties were assessed noninvasively. Ten ISH patients (5 male and 5 female) were enrolled in a randomized crossover study comparing 8 weeks of moderate intensity cycling with 8 weeks of sedentary activity. Brachial and carotid systolic, diastolic, mean, and pulse pressures were higher in the ISH group than in the control group. Systemic arterial compliance (0.43+/-0.04 versus 0.29+/-0.02 arbitrary compliance units for the control versus ISH groups, respectively; P=0.01) was lower, and carotid-to-femoral pulse-wave velocity (9.67+/-0.36 versus 11.43+/-0.51 m. s(-1) for the control versus ISH groups, respectively; P=0.007), input impedance (2.39+/-0.19 versus 3.27+/-0.34 mm Hg. s. cm(-1) for the control versus ISH groups, respectively; P=0.04), and characteristic impedance (1.67+/-0.17 versus 2.34+/-0.27 mm Hg. s. cm(-1) for the control versus ISH groups, respectively; P=0.05) were higher in the ISH group than in the control group. Training increased maximal oxygen consumption by 13+/-5% (P=0.04) and maximum workload by 8+/-4% (P=0.05); however, there was no effect on arterial mechanical properties, blood lipids, or left ventricular mass or function. These results suggest that the large-artery stiffening associated with ISH is resistant to modification through short-term aerobic training.

Parameters for the preoperative evaluation of arteriosclerosis for free-flap transfers in head and neck surgery

The microsurgical transfer of free tissue has become essential for reconstructive surgery in the head and neck, and arteriosclerosis is one of the risk factors for microvascular anastomosis. In order to detect severe arteriosclerosis and to determine the parameters useful for evaluating arteriosclerosis preoperatively, the grade of arteriosclerosis was investigated with respect to age, PWV (Aortic Pulse Wave Velocity), ocular fundus findings, and histopathological findings of the recipient arteries in 40 patients with malignant tumours. Severe arteriosclerosis was detected in 2/40 patients by the PWV, in the same 2/40 patients by the ocular fundus findings and in the same 2/40 patients by histopathological findings. The current observations indicate that the PWV and ocular fundus findings are useful parameters for the preoperative evaluation of the grade of arteriosclerosis.

Increased aortic stiffness assessed by pulse wave velocity in apolipoprotein E-deficient mice

Atherosclerosis develops and progresses spontaneously in apolipoprotein E-knockout (apoE-KO) mice. A direct consequence of atherosclerosis is an increase in vascular stiffness. Pulse wave velocity (PWV) has been used to assess the stiffness of large vessels and was found to be increased in patients with atherosclerosis. In the present study, aortic stiffness was assessed by PWV in 4- and 13-mo-old apoE-KO mice and age-matched controls (C57BL/6J). In 13-mo-old apoE-KO mice with extensive atherosclerotic lesions in the aorta (61 +/- 4%), PWV increased significantly (3.8 +/- 0.2 m/s) compared with controls (2.9 +/- 0.2 m/s). Endothelial nitric oxide (EDNO)-mediated vasorelaxation in response to ACh was markedly diminished in the aortic rings isolated from 13-mo-old apoE-KO mice compared with age-matched controls. In contrast, in 4-mo-old apoE-KO mice with only moderate atherosclerotic lesions in the aorta (23 +/- 5%), there were no significant changes in PWV and EDNO-mediated relaxation compared with controls. Blood pressure was not different among the four groups of mice. There were no significant differences in endothelium-independent vascular responses to sodium nitroprusside among different groups investigated. Histological evaluation revealed focal fragmentation of the elastic laminae in the aortic walls of 13-mo-old apoE-KO mice. These results demonstrate for the first time that aortic stiffness determined by PWV increases in 13-mo-old apoE-KO mice. Endothelial dysfunction and elastic destruction in vascular wall caused by atherosclerosis may have contributed.

The relationship between modified pulse wave transit time and cardiovascular changes in isoflurane anesthetized dogs

OBJECTIVE

To clarify the relationship between blood pressure and pulse wave transit time at the peripheral artery from the R wave of the electrocardiogram (m-PWTT), the effects of cardiovascular interventions on this relationship was evaluated.

METHODS

Ten mongrel dogs were anesthetized by isoflurane inhalation, and catheter tip pressure transducers were inserted into the ascending aorta and at the bifurcation of abdominal aorta to measure central and peripheral pulse wave arrival. Pulse wave arrival at the ascending aorta from the R wave represents pre-ejection period (PEP) and pulse wave arrival between the ascending aorta and bifurcation of aorta represents pulse wave transit time (PWTT), thus m-PWTT = PEP + PWTT. Hypertension was induced by the continuous infusion of dobutamine and phenylephrine, and hypotension was induced by deepening isoflurane anesthesia, acute blood loss and nitroglycerine infusion. The relationship between timing components (PWTT, PEP, and m-PWTT) and blood pressure was recorded and analyzed by using the least squares method.

RESULTS

The relationship between timing components (PWTT, PEP and, m-PWTT) and blood pressure was significant and highly correlated. When the change in blood pressure was due to the myocardial contractility, such as after dobutamine infusion, the relationship between all timing components and blood pressure was consistent and negative. However, when the change in blood pressure was due to the vasoactive agents, such as phenylephrine, the relationship between timing components and blood pressure was dependent on the reflex change in PEP.

CONCLUSIONS

Change in m-PWTT is a good parameter to predict blood pressure changes, although the absolute blood pressure value cannot be obtained.

Assessment by transesophageal echography of atherosclerosis of the descending thoracic aorta in patients with hypercholesterolemia

This study assesses atheromatous lesions and aortic stiffness of the descending thoracic aorta (DTA) in patients with hyperlipidemia by transesophageal echography (TEE) and investigates the relations between atherosclerotic lesions and aging or serum cholesterol levels in these patients. Subjects included 16 patients with familial hypercholesterolemia (FH), 15 non-FH hyperlipidemic patients (non-FH), and 17 age-matched normal subjects. With use of TEE, the DTA was divided into 4 longitudinal portions of equal length, and the atheromatous lesions of each portion of DTA were scored according to their character and extension by biplane 2-dimensional TEE. The scores of atheromatous lesions from all 4 portions were added together to give the total atheromatous score. Then, after measuring the instantaneous dimensional changes of DTA in a cardiac cycle by M-mode TEE and blood pressure (BP) by a cuff method, we calculated the aortic stiffness parameter beta = ln(systolic BP/diastolic BP)/([Dmaximum - Dminimum]/Dminimum). The beta was significantly higher in FH and non-FH subjects than in normal subjects. In both FH and non-FH subjects, the total atheromatous score correlated with total serum cholesterol levels (r = 0.64 [p <0.01]; r = 0.58 [p <0.05], respectively). There were significant correlations between age and beta in all 3 groups (FH, r = 0.67 [p <0.005]; non-FH, r = 0.53 [p <0.05]; normal subjects, r = 0.49 [p <0.05]), and the slopes of the regression lines of FH and non-FH subjects were much steeper than those of normal subjects. The incidence of atherosis in the DTA was significantly higher in hyperlipidemic patients than in normal subjects, even among the younger members of the hyperlipidemic population with progressive aortic stiffness.

Effect of timing of blood pressure measurement in the assessment of arterial stiffness: the SMART Study

In the assessment of arterial stiffness, pulse pressure is measured. Presently, there is no consensus on how pulse pressure should be measured. Distensibility of the left and right common carotid arteries was measured noninvasively in 224 patients participating in the Second Manifestations of ARTerial disease (SMART) study. Blood pressure was recorded every 4 min, using a semiautomatic oscillometric device. Distensibility coefficients (DC) were calculated with pulse pressure obtained as an average of (A) all measurements during the session; (B) the second, third, and fourth measurement; (C) measurements before and after distensibility assessment; and (D) three measurements nearest to distensibility assessment. Associations of cardiovascular risk factors with the four calculated DCs were evaluated with linear regression analysis. DC estimates were slightly more precise with methods A and B than with C or D. The magnitude of the associations showed a slight trend to higher precision for methods A and B. Pulse pressures obtained as an average of all or the second, third, and fourth blood pressure measurements during an arterial stiffness measurement session yield slightly more precise estimates of DC. However, the differences between the methods are small; therefore, we suggest that pragmatic arguments dominate the choice between the methods.

Aortic stiffness in young patients with heterozygous familial hypercholesterolemia

BACKGROUND

Dyslipidemia is a primary risk factor for the development of atherosclerosis. Aortic distensibility is an important determinant of left ventricular function and coronary blood flow whose possible alterations in patients with dyslipidemia have not been fully investigated.

METHODS

To assess the effect of dyslipidemia on the elastic properties of the aorta, we studied 60 patients (mean age 37+/-11 years) with heterozygous familial hypercholesterolemia and no manifest arterial disease and compared them with 20 of their normolipidemic siblings (mean age 34+/-10 years). Two indexes of the aortic elastic properties were measured: aortic distensibility was calculated by use of the formula: 2 x (AoS-AoD)/PP x AoD, and aortic stiffness index was calculated by use of the formula: In (SBP/DBP)/(AoS-AoD)/AoD, where AoS and AoD are aortic root end-systolic and end-diastolic diameters, respectively, SBP and DBP are systolic and diastolic arterial pressure, respectively, and PP is pulse pressure. Internal aortic root diameters were measured at 3 cm above the aortic valve by use of two-dimensional guided M-mode transthoracic echocardiography, and arterial pressure was measured simultaneously at the brachial artery by sphygmomanometry.

RESULTS

The mean aortic systolic and diastolic diameter index did not differ significantly between the two groups. In contrast, aortic distensibility was found to be significantly reduced in subjects with isolated familial hypercholesterolemia compared with that in the control group (2.15+/-1.72 cm2.dynes(-1).10(-6) vs 3.18+/-1.58 cm2.dynes(-1).10(-6), p < 0.02). In addition, the mean aortic stiffness index was double in patients with familial hypercholesterolemia compared with that in normolipidemic subjects.

CONCLUSIONS

Severe dyslipidemia does not overtly influence aortic dimensions but leads to impairment of aortic elastic properties before the occurrence of clinical manifestations of atherosclerotic disease.

The heart and conduit vessels in hypertension

The heart and conduit vessels, integral components of a pulsatile pumping system, undergo complex adaptive and degenerative changes in response to the increased load of hypertension. Over the last two decades, great technological strides have been made with regards to further discovering the role of the heart and conduit vessels in hypertension. This article reviews the adaptation of the heart and vessels to hypertension, the clinical implications of these structural and functional changes, and the effects of therapy on cardiovascular function.

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

To assess the early stage of atherosclerosis of the thoracic descending aorta, we evaluated morphological atheromatous lesions (atherosis) and the stiffness parameter of the artery (beta; sclerosis) in 24 male rabbits using echography. Male Japanese white rabbits weighing 2.5-3.0 kg were fed a diet containing 1% cholesterol for 7 (n = 8) or 14 weeks (n = 8). Rabbits fed a normal diet were used as controls (n = 8). Atheromatous lesions were evaluated with intravascular ultrasound (IVUS: Aloka, 20 MHz, 6F). We also calculated beta using M-mode echography (7.5 or 10 MHz) and direct aortic pressure measurement. Thickening of the intima-media complex was clearly observed with IVUS in the 14-week group but was not detected in the others. Histologically, only a thin layer of foamy cells on the intima (thickness < 20 microns) was observed in the 7-week group. The value of beta was significantly increased in both the 7-week (4.7 +/- 2.2) and 14-week groups (4.5 +/- 0.8) compared with controls (1.7 +/- 0.9, both p < 0.01). These results suggest that the development of atherosis might be preceded by vascular sclerosis during the early stage of atherosclerosis when the serum cholesterol level is high: at a time when the thin layer of foamy cells could not be detected by conventional IVUS.

Improvement of atherosclerosis and stiffness of the thoracic descending aorta with cholesterol-lowering therapies in familial hypercholesterolemia

The thoracic aorta is frequently involved in atherosclerotic lesions associated with familial hypercholesterolemia (FH). Transesophageal echocardiography (TEE) allows quantitative evaluation of the wall properties of the thoracic aorta. Using TEE, we tested whether atherosclerosis of the thoracic aorta in FH could be improved by cholesterol-lowering therapies. The subjects investigated were 22 FH patients and 22 age-matched normal subjects. The descending aorta (DA) was divided into four longitudinal portions of equal length. Atheromatous lesions of each portion of the DA were scored by character and extension of lesions by biplane two-dimensional TEE. The scores of atheromatous lesions from all four portions of the DA were added together to give the total atheromatous score (TAS). We also measured instantaneous dimensional changes of the DA in a cardiac cycle by M-mode TEE and blood pressure by a cuff method and calculated the stiffness parameter beta (In[SBP/DBP]/[Dmax-Dmin]/Dmin), where SBP is the systolic arterial blood pressure, DBP is the diastolic arterial blood pressure, Dmax is the maximum aortic dimension during the ejection period, and Dmin is the minimum aortic dimension during the preejection period. TAS was higher in FH (3.70 +/- 1.32) than normal (0.62 +/- 0.54, P < .0001) subjects. Beta in FH (10.35 +/- 4.87) was greater than in normal (5.10 +/- 1.25, P < .0001) subjects, but there were no significant differences of DA dimensions between the groups. In both normal subjects and FH patients, beta correlated with age (r = .52, P < .02 and r = .59, P < .005, respectively). In FH patients, beta and TAS correlated well with pretreatment total cholesterol levels (r = .43, P < .05 and r = .60, P < .005, respectively). In 12 of 22 FH patients, strict cholesterol-lowering therapies with diet and cholesterol-lowering drugs (pravastatin and probucol) were undertaken for 13 months. Cholesterol levels were significantly decreased from 333 +/- 45 to 219 +/- 39 mg/dL (P < .0001); this was associated with significant decreases in beta and TAS (from 9.88 +/- 5.03 to 7.88 +/- 3.92, P < .005, and from 3.61 +/- 1.50 to 2.94 +/- 1.22, P < .0005, respectively). In FH patients, the incidence and severity of morphological and physiological atherosclerosis of the DA were significantly higher than in age-matched normal subjects. A significant regression of atherosclerosis was achieved by strict cholesterol-lowering therapies in relatively young FH patients.

Therapeutic effects of nitric oxide-donor isosorbide dinitrate on atherosclerosis-induced alterations in hemodynamics and arterial viscoelasticity are independent of the wall elastic component

Whether the arterial elastic structures are involved in the beneficial effects of long-term treatment with organic nitrates on atherosclerosis-induced changes in hemodynamics and arterial wall viscoelastic properties, are case for angiotensin-converting enzyme (ACE) inhibitors, is not known. In the present study, atherogenic (A) diet, and isosorbide dinitrate (ISDN) (I) (60 mg Risordan LP, daily dose) were given concomitantly for 4 months to adult Pitman-Moore minipigs (A + I animals, n = 8), which were compared with A (n = 8) or control (C, n = 8) animals. Blood flow was investigated by hemodynamics in the hindlimb arterial bed; and wall rheology, histomorphometry and elastin; and desmosine (DES) and isodesmosine (IDE) contents in the abdominal aorta. Atherosclerosis prominently impaired the function of capacitance and resistance arteries, altered blood pressure contours, increased aortic stiffness and wall tension, and reduced parietal viscoelasticity through viscous component blunting. The treatment with ISDN significantly improved aortic pulsatility, arteriolar opposition to blood flow, and blood pressure (BP) contours by restoring, at least in part, the wall viscoelastic properties. However, there was no significant change in the area of the pressure-diameter curve hysteresis between the three animal groups. In contrast, ISDN reduced neither the cross-sectional area of lesions nor the losses in wall elastin content and had no influence on lipid accumulations in vessels and in the blood. The present results demonstrate that the beneficial hemodynamic and wall viscoelastic effects elicited by ISDN in atherosclerotic minipigs are not accounted for by therapeutic properties of the nitric oxide (NO) donor against alterations of elastic structures, but by the viscoelastic properties in the arterial wall.

George Lyman Duff Memorial Lecture. Arterial imaging and atherosclerosis reversal

This review explores evidence for the reversibility of atherosclerosis and augmentation of angiography with non-invasive arterial wall imaging. Meta-analysis from coronary angiographic trials demonstrates that regression and stabilization are 1.5 to 2 times more common in treated than placebo subjects, and progression is reduced by half in treated subjects. Odds ratios for clinical coronary events are significantly reduced with treatment. Lesion improvement occurs more readily in women than men and more so in women receiving concomitant estrogen replacement therapy. Lesions with > or = 50% diameter stenosis (%S) at baseline respond more readily to lipid lowering than those < 50% S, whereas reduction in coronary events is related to stabilization of lesions < 50% S. Lipoproteins have a differential effect on lesion progression according to lesion size, and triglyceride-rich lipoproteins play an important role in the progression of coronary artery lesions < 50% S. Improved therapeutic regimens to alter progression of atherosclerosis may require adjunctive therapy, such as with antioxidants or hormone replacement therapy, in concert with low-density lipoprotein cholesterol reduction to prevent new lesion formation or early lesion progression. Sequential coronary angiographic determination of progression evaluated by both quantitative coronary angiography and global change score, a visual assessment of overall lesion change, predicts clinical coronary events. Only inferences about the state of the arterial wall can be made from angiography, because it delineates only the lumen. Therapy testing and study of atherosclerosis progression can be improved with noninvasive B-mode ultrasonographic imaging of the distal common carotid artery far-wall intima-media thickness (IMT), a reliable measure of early preintrusive atherosclerosis. Measurement of common carotid IMT is useful for the study of coronary artery risk factors and can augment studies of coronary artery intrusive lesions, because it is associated with coronary artery disease. B-mode measurement of common carotid IMT has the potential of serving as a noninvasive surrogate end point for clinical coronary events. Screening for peripheral vessel changes indicative of high risk for coronary artery disease is possible and cost-effective with the noninvasive procedures now available.

Aortic compliance measurements using Doppler ultrasound: in vivo biochemical correlates

A noninvasive Doppler ultrasound technique for the assessment of aortic compliance based on the in vivo measurement of pulse wave velocity along the thoraco-abdominal aortic pathway is described. An approach for correcting for the effect of blood pressure on aortic distensibility is considered. The derivation of an index of intrinsic distensibility, Cp, which is independent of blood pressure, is provided and applied to data collected from normal, healthy volunteers. Overviews are provided of studies utilising the technique to determine aortic compliance in medical disorders, which are known to predispose to premature cardiovascular disease, such as diabetes mellitus, familial hypercholesterolaemia and growth hormone deficiency. The significance of correlations between in vivo aortic compliance measurements and plasma concentrations of total cholesterol, low-density-lipoprotein cholesterol, high-density-lipoprotein cholesterol and insulin-like growth factor-I are discussed. It is proposed that the measurement of aortic compliance in normal, healthy individuals may potentially be a useful in vivo research tool for investigating the effects of biochemical factors on the biophysical properties of the aortic wall. Furthermore, we believe that the routine measurement of blood pressure-corrected aortic distensibility may prove a useful, noninvasive clinical tool for assessing patients' susceptibility to atherosclerosis, as well as for monitoring their response to therapeutic interventions.

Hypercholesterolaemia alters arterial and blood factors related to atherosclerosis in hypertension

To evaluate the influence of hypercholesterolaemia on arterial and blood factors related to cardiovascular disease in hypertension, 20 normocholesterolaemic and 31 hypercholesterolaemic hypertensive patients underwent determinations of whole blood filterability (WBF), plasma fibrinogen concentration (PF) and aortic pulse wave velocity (PWV). Both of the groups had similar age, body mass index, cumulative smoking dose and blood pressure. Hypercholesterolaemics had lower WBF (P less than 0.02), higher PF (P less than 0.02) and higher PWV (P less than 0.01) than normocholesterolaemics. In the whole population WBF correlated with age (P less than 0.005), mean blood pressure (P less than 0.01), total cholesterol (P less than 0.05) and plasma fibrinogen (P less than 0.01). However, in a multivariate analysis where age and pressure were controlled as variables, only the association between WBF and PF remained significant (P less than 0.001). Thus, the higher fibrinogen affects whole blood filterability in hypercholesterolaemic hypertensive patients. In the whole population PWV correlated positively with HDL cholesterol (P less than 0.01) and age (P less than 0.001) and the association with HDL cholesterol remained significant in a multivariate analysis (P less than 0.001) where age was controlled. The effect of ageing on arterial rigidity seems to be similar in both hypertensive groups as deduced from the identical regression slopes relating pulse wave velocity to age. So in hypertension with high cholesterol, arterial rigidity was increased without changes in arterial stiffening with age.

The Marfan syndrome: abnormal aortic elastic properties

Aortic distensibility and aortic stiffness index were measured at the ascending aorta (3 cm above the aortic valve) and the mid-portion of the abdominal aorta from the changes in echocardiographic diameters and pulse pressure in 14 patients with the Marfan syndrome and 15 age- and gender-matched normal control subjects. The following formulas were used: 1) Aortic distensibility = 2(Changes in aortic diameter)/(Diastolic aortic diameter) (Pulse pressure); and 2) Aortic stiffness index = ln(Systolic blood pressure)/(Diastolic blood pressure)(Changes in aortic diameter)/Diastolic aortic diameter. Pulse wave velocity was also measured. Compared with normal subjects, patients with the Marfan syndrome had decreased aortic distensibility in the ascending and the abdominal aorta (2.9 +/- 1.3 vs. 5.6 +/- 1.4 cm2 dynes-1, p less than 0.001 and 4.5 +/- 2.1, vs. 7.7 +/- 2.5, cm2 dynes-1, p less than 0.001, respectively) and had an increased aortic stiffness index in the ascending and the abdominal aorta (10.9 +/- 5.6 vs. 5.9 +/- 2.2, p less than 0.005 and 7.1 +/- 3.1 vs. 3.9 +/- 1.2, p less than 0.005, respectively). Aortic diameters in the ascending aorta were larger in these patients than in normal subjects, but those in the abdominal aorta were similar in the two groups. Linear correlations for both aortic distensibility and stiffness index were found between the ascending and the abdominal aorta (r = 0.85 and 0.71, respectively). Pulse wave velocity was more rapid in the patients than in the normal subjects (11.6 +/- 2.5 vs. 9.5 +/- 1.4 m/s, respectively, p less than 0.01). Thus, aortic elastic properties are abnormal in patients with the Marfan syndrome irrespective of the aortic diameter, which suggests an intrinsic abnormality of the aortic arterial wall.

Anatomic correlates of aortic pulse wave velocity and carotid artery elasticity during atherosclerosis progression and regression in monkeys

We noninvasively measured changes in average aortic stiffness in 79 cynomolgus monkeys being fed cholesterol progression, regression, and control diets by measuring pulse wave velocity (PWV) in 260 experiments during a 30-month period. Every 6 months, a group of monkeys was studied with invasive aortic PWV techniques and with ultrasonically determined pressure-strain elastic modulus (Ep) of the carotid artery, and then the group was killed so that morphometric evaluation of atherosclerosis severity could be made. After 6 months of a cholesterol progression diet, PWV decreased slightly from 6.2 +/- 0.1 to 5.7 +/- 0.1 m/sec, followed by an approximate linear increase to 8.8 +/- 1.2 m/sec after 30 months on the diet. The corresponding ratio of intimal (plaque) area to medial area (IA/MA) measured on perfusion-fixed cross-sections of the abdominal and thoracic aortas increased from 0.16 +/- 0.07 at 6 months to 1.23 +/- 0.22 at 30 months. Monkeys in the regression groups were fed the cholesterol progression diet for 18 months, followed by a chow diet for 6 or 12 months. In the first 6 months of the cholesterol regression diet, PWV continued to increase from 7.0 +/- 0.2 to 8.1 +/- 0.4 m/sec, and IA/MA was 1.24 +/- 0.18. However, after 12 months of the cholesterol regression diet, PWV decreased to 6.8 +/- 0.4 m/sec, and IA/MA was 0.90 +/- 0.18. The variability of the data demonstrates that PWV is not a simple function of atherosclerosis severity, and the best simple correlation was r = 0.69 (r2 = 0.48) between PWV and intimal area. However, multiple regression analysis of aortic PWV, systolic (SP) and diastolic (DP) blood pressures, and total plasma cholesterol concentration (TPC), all of which can be measured with minimally invasive techniques, improved the prediction of the IA/MA ratio through the following equation: IA/MA = 0.127 PWV-0.039 DP+0.023SP+0.0003TPC-0.292 (r = 0.81, r2 = 0.66). These data suggest that arterial stiffness in combination with minimally invasive parameters can be used to predict the severity of diffuse asymptomatic atherosclerosis in monkeys. However, more widespread application of these data to humans is uncertain because of biological variability and differences between animal models and human subjects.

Noninvasive measurement of compliance of human leg arteries

Electrical impedance plethysmography has been evaluated for early detection of peripheral atherosclerosis. A pressure cuff was wrapped around the lower leg and the cuff pressure increased. Two circumferential electrodes glued in the middle of the cuff recorded the impedance pulse, from which the arterial pulse volume was calculated. The ratio of maximal arterial volume change to the pulse pressure was determined as a measure of maximal compliance Cp. Based on the data from 118 human subjects, Cp was found to correlate well with known cardiovascular risk factors. For example, Cp decreased on the average from 3.08 to 1.92 microL.mm Hg-1.cm-1 (1 microL.mm Hg-1.cm-1 = 7.5 x 10(-10) m4.N-1) in groups of subjects of increasing age from 22 to 70 years. Subjects on a regular exercise program had an average value of 3.86, while those with proven peripheral vascular disease had a value of 0.70. In a related pathologic validation study on 15 monkeys fed a cholesterol-control diet a good correlation was found between the limb peak compliance and morphometric data obtained from iliac and carotid arteries.

Correlation of noninvasive arterial compliance with anatomic pathology of atherosclerotic nonhuman primates

Fifteen cynomolgus monkeys were fed a control (n = 3) or cholesterol-containing diet (n = 12) for 26 months. An impedance plethysmograph and a calibrated volume plethysmograph were used to determine femoral arterial volume change, delta V, from femoral arteries. Abdominal aorta pulse pressure was measured directly. The ratio of delta V to pulse pressure, delta P, defined femoral artery compliance. At necropsy, sections of pressure fixed common iliac, external iliac, femoral and carotid arteries were obtained for measurements. The site of the largest atherosclerotic lesion was chosen for histologic measurement. The percentage intima in arterial tissue (PIAT) was determined at the site of the largest atherosclerotic lesions in iliac arteries and averaged. Peak compliance was inversely correlated with the PIAT (Pearson correlation -0.39, P less than 0.10, n = 21) which improved to r = -0.52, P less than 0.01 (n = 27) when the PIAT also included the carotid atherosclerosis. The correlation coefficients were comparable to those obtained for total plasma cholesterol concentration, and direct systolic and diastolic blood pressure. Peak compliance and alpha-cholesterol concentrations provided the best multiple linear regression fit for the prediction of PIAT.

Effect of two week lymphatic occlusion on the mechanical properties of dog femoral arteries

In order to study the long-term effect of impaired lymphatic drainage on the mechanical properties of the arterial wall, cylindrical femoral artery segments from 10 mongrel dogs after 2 weeks of hindlimb lymphatic occlusion were subjected to in vitro mechanical test and compared with the contralateral, sham-operated segments. Smooth muscle contraction was induced by norepinephrine (7.4 X 10(-6) M) and smooth muscle relaxation by papaverine (1.6 X 10(-4) M). As a result of 2 weeks of lymphatic occlusion, wall thickness increased from 243 +/- 18 to 343 +/- 35 microns (P less than 0.02), inner radius decreased from 1.69 +/- 0.11 to 1.42 +/- 0.12 mm (P less than 0.01) and elastic modulus decreased from 1.23 X 10(6) to 0.55 X 10(6) N/m2 (P less than 0.01), when determined at 100 mm Hg (13.3 kPa) intraluminal pressure and with relaxed smooth muscle. The contractile apparatus was able to produce active strain in the vessels with lymphostasis and at physiological pressures not significantly different from the controls (0.89 +/- 0.02 vs. 0.91 +/- 0.02), but at significantly lower levels of tangential stress. Active stress decreased significantly. This study shows that a reorganization of the vessel wall mechanical force-bearing elements occurs in lymphostasis, which, in some respects, resembles the mechanical alterations found in different forms of atherosclerosis.

Stiffness of systemic arteries in patients with myocardial infarction. A noninvasive method to predict severity of coronary atherosclerosis

The static elastic properties of arterial tree (abdominal aorta and common carotid artery) were studied in 19 normal subjects and in 49 patients with myocardial infarction with an ultrasonic phase-locked echo-tracking system that allows continuous transcutaneous measurement of the arterial diameter. The stiffness index beta, which represented the mechanical properties in the arterial wall, was calculated from the relation between systemic blood pressure and the diameter of the artery. Patients with myocardial infarction underwent coronary angiography in their convalescent period to determine involved vessels. In 11 patients, coronary artery was patent; 15 patients had one-vessel disease, 12 had two-vessel disease, and the remaining 11 patients had three-vessel disease. In normal subjects, increasing age was associated with an increase in arterial stiffness. An average value of the stiffness index of the abdominal aorta was 8.58 +/- 3.02 (mean +/- SD) and that of common carotid artery was 9.17 +/- 2.22. In patients with three-vessel disease, these values were significantly higher (22.37 +/- 4.29 in abdominal aorta and 13.17 +/- 4.56 in common carotid artery) than those in normal subjects. Stiffness index of patients with two- or one-vessel disease was also increased but lower than those in patients with three-vessel disease (p less than 0.05). Forty-four of 49 patients with infarction had an arterial stiffness index of abdominal aorta higher than the 95% confidence limits of the normal data (p less than 0.05). Twenty-eight patients were outside the nomogram of common carotid artery (p less than 0.05). The mechanical properties of these elastic arteries provided sufficiently reliable information on changes caused by atherosclerosis.

Flow pattern and structural changes at carotid bifurcation in hypertensive cynomolgus monkeys

Blood flow pattern and morphological changes within the extracranial carotid system were studied in M. fascicularis before, immediately after, and at various intervals (4 hours, 4 days, 10 days, and 4 weeks) after the introduction of systemic hypertension by surgical coarctation of the thoracic aorta. Intra-arterial hemodynamics were assessed by means of both continuous-wave Doppler signal spectrum analysis and multigate pulsed-wave Doppler flow velocity profile processing. Diminished peak frequencies throughout the carotid system and enlargement of the lumen diameter in the common carotid artery and the carotid bulb were major findings and were suspected to be due to cerebral autoregulation at high levels of intracranial vascular resistance. In the internal carotid artery of pure muscular type, the lumen diameter was diminished so the carotid bulb became an area of structural and hemodynamic transition. As a consequence, flow irregularities already observed in this region before surgery considerably increased during hypertension. In addition, endothelial disarray and leucocytic adherence and activation were associated with these hemodynamic alterations within the carotid bulb. Their mutual role in early atherogenesis is discussed.

Reversal of atherosis and sclerosis. The two components of atherosclerosis

In 1904, Marchand recognized the consistent association of fatty degeneration and vessel stiffening and introduced the term "atherosclerosis" to indicate this combination. Current research is focused principally on the lipid component, but there is evidence that both aspects are reversible. Atheromatous lipids add significantly to the volume of lesions and thus contribute to vascular obstruction and end-organ damage. Reversal of atherosis has been observed in all the major species used in atherosclerosis research; rabbits, swine, dogs, chicks, pigeons, and subhuman primates. Direct evidence for reversal in humans is based on angiographic trials and is less extensive. One femoral artery and one coronary artery trial indicate that the lesions can be stabilized. CLAS, the largest angiographic trial to date, indicates that coronary lesion reversal is possible. Clinical effects of sclerosis are more subtle, and there is little evidence that sclerosis alone leads to end-organ damage. However, it should be noted that atherosclerotic lesions producing end-organ damage invariably have a major fibrous component. Sclerotic vessels have reduced systolic expansion and abnormally rapid pulse wave propagation, which can be measured noninvasively. Primate studies indicate that sclerosis is induced by hypercholesterolemic diets and is reversible when these diets are withdrawn. Changes in sclerosis may be another useful indicator of the formation and reversal of lesions and may involve changes in EDRF. Future studies of atherosclerosis reversal should use a combination of measures to evaluate both atherosis and sclerosis.

Reversion of cardiac hypertrophy and reduced arterial compliance after converting enzyme inhibition in essential hypertension

Blood pressure, forearm arterial hemodynamics (with a pulsed Doppler flowmeter), and echocardiographic parameters were studied in 16 patients with sustained essential hypertension before and 3 months after administration of the converting enzyme inhibitor perindopril. In a single-blind study versus placebo, it was shown that perindopril significantly reduced blood pressure (p less than 0.01), whereas there was an increase in brachial blood flow (p less than 0.01) because of a simultaneous increase in blood flow velocity (p less than 0.01) and arterial diameter (p less than 0.01). During a 5-minute period of wrist occlusion, blood flow velocity was reduced to a greater extent with perindopril than with placebo (p less than 0.001), whereas corresponding reductions in arterial diameter were equivalent, indicating that the increase in diameter after perindopril could not be explained simply on the basis of flow-dependent dilatation. During active treatment, brachial artery compliance increased (p less than 0.01) and pulse wave velocity decreased (p less than 0.01), whereas there was no change in the tangential tension of the arterial wall, defined as the product of mean arterial pressure and arterial diameter. Four weeks after treatment was stopped, blood pressure and forearm arterial hemodynamics returned toward baseline values. Cardiac mass was significantly decreased after perindopril (p less than 0.01) and remained decreased 4 weeks after cessation of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of elastase on the stiffness and elastic properties of arterial walls in cholesterol-fed rabbits

The effect of cholesterol feeding and elastase administration on the arterial stiffness and elastic properties was investigated in rabbits by pressure-diameter tests on excised thoracic aortas, common carotid and femoral arteries. Rabbits in groups RA and RB were fed 1% cholesterol diet for 14 weeks. Groups RC and RD were fed the cholesterol diet for the first 7 weeks, and then given regular chow for the last 7 weeks. In addition, rabbits in groups RB and RC were administered elastase daily for the last 7 weeks. Rabbits in group RE were fed the regular chow for 14 weeks and served as the control group. The arterial stiffness and the elastic modulus of wall material in the RA rabbits were generally higher than those in the control rabbits. Administration of elastase and/or feeding of the regression diet decreased the wall stiffness and elastic modulus significantly, although the effect of elastase did not appear clearly when used in combination with the regression diet. The cholesterol feeding decreased the ratio of thickness to wall radius, whereas the ratio was more or less increased by the elastase administration and/or the regression diet.

Cardiovascular dynamics in relation to presentation and postural changes in normal fetuses

The role of fetal cardiovascular function in the reduced intrauterine growth rate of breech pregnancy was studied in fetuses with different presentations. Hemodynamic responses to postural changes were also investigated in fetuses in horizontal and vertical positions. Thirty-one normal pregnancies, with 15 fetuses presenting by the breech and 16 fetuses by the vertex, were included in the study. Diameter pulse waves from the fetal descending aorta were measured using equipment combining real-time ultrasound imaging with phase-locked echo-tracking. No differences in basal pulse wave parameters were demonstrated between breech and vertex fetuses nor did any differences appear when maternal posture was changed from horizontal to upright or vice versa. The present observations suggest that fetal circulatory factors are less likely to be a primary cause of the reduced intrauterine growth in breech presentation. Tilting of the fetus in late gestation seems to produce neither a redistribution of its blood volume nor secondary adaptations to an orthostatic challenge. The hydrostatic effect of amniotic fluid presumably precludes the requirement of fetal circulatory adaptation to postural changes.

Interdependence of pulse wave variables in the human fetal aorta

The problem of inferring the state of fetal circulation from diameter pulse waves in the descending aorta was studied with the aid of statistical methods in 12 fetuses in late uncomplicated gestation. By means of a phase-locked, echo-tracking ultrasound technique, aorta diameter-time waveforms and pulse propagation velocities were measured. In a factor analysis, three independent factors explained 75% of the total variance of variables in the waveforms. Relationships between some of the variables and biophysical events are suggested; they await confirmation from animal experiments, in order to develop a practical method for assessing fetal circulation.