Aortic distensibility in patients with isolated hypercholesterolaemia, coronary artery disease, or cardiac transplant

Biomechanics of the cardiovascular system: the aorta as an illustratory example

Biomechanics relates the function of a physiological system to its structure. The objective of biomechanics is to deduce the function of a system from its geometry, material properties and boundary conditions based on the balance laws of mechanics (e.g. conservation of mass, momentum and energy). In the present review, we shall outline the general approach of biomechanics. As this is an enormously broad field, we shall consider a detailed biomechanical analysis of the aorta as an illustration. Specifically, we will consider the geometry and material properties of the aorta in conjunction with appropriate boundary conditions to formulate and solve several well-posed boundary value problems. Among other issues, we shall consider the effect of longitudinal pre-stretch and surrounding tissue on the mechanical status of the vessel wall. The solutions of the boundary value problems predict the presence of mechanical homeostasis in the vessel wall. The implications of mechanical homeostasis on growth, remodelling and postnatal development of the aorta are considered.

Validation of a new index for estimating arterial stiffness: measurement of the QPV interval by Doppler ultrasound

BACKGROUND

Pulse wave velocity (PWV), a relevant indicator of arterial stiffness, can be measured noninvasively with a variety of automatic devices, but most are complexly equipped. We developed a novel index for estimating arterial stiffness as "QPV interval," which was determined by means of surface electrocardiogram and Doppler ultrasound of the brachial artery simultaneously.

HYPOTHESIS

This study aimed to validate the QPV interval as an exact and convenient index for estimation of arterial stiffness.

METHODS

Forty-seven patients with untreated essential hypertension and 19 normotensive subjects were enrolled. Brachial-ankle PWV (baPWV) was measured using an automatic volume-plethysmographic apparatus, and Doppler ultrasound was implemented sequentially to measure the QPV interval in each subject. Clinical biochemistry and echocardiography were performed on the same day.

RESULTS

Mean baPWV was significantly higher in hypertensive patients than in normotensive subjects (p = 0.002), whereas mean QPV interval was significantly shorter in hypertensive patients than in the normotensive group (p = 0.019). A simple regression analysis demonstrated an inverse correlation between the QPV interval and baPWV (r = -0.671, p < 0.001) in all enrolled subjects. In a stepwise regression model that adjusted for age, systolic blood pressure, and other determinants of baPWV, the negative association remained between the QPV interval and baPWV (p < 0.001).

CONCLUSION

The QPV interval correlates inversely with baPWV, independent of age and other determinants of baPWV; hence, the QPV interval can serve as a simple and convenient index for assessing arterial stiffness in clinical practice.

Medical application of artificial immune recognition system (AIRS): diagnosis of atherosclerosis from carotid artery Doppler signals

This study was conducted to distinguish between atherosclerosis and healthy subjects. Hence, we have employed the maximum envelope of the carotid artery Doppler sonograms derived from Fast Fourier Transformation-Welch method and Artificial Immune Recognition System (AIRS). The fuzzy appearance of the carotid artery Doppler signals makes physicians suspicious about the existence of diseases and sometimes causes false diagnosis. Our technique gets around this problem using AIRS to decide and assist the physician to make the final judgment in confidence. AIRS has reached 99.29% classification accuracy using 10-fold cross validation. Results show that the proposed method classified Doppler signals successfully.

Systolic, diastolic, and pulse pressures as coronary risk factors in a population with low cholesterol levels: a prospective 10-year evaluation

BACKGROUND

Pulse pressure (PP) has recently been found to be predictive of subsequent cardiovascular, particularly coronary, events in some middle-aged and elderly populations.

HYPOTHESIS

The aim of this prospective population-based study was to evaluate the roles of systolic (SBP), diastolic blood pressure (DBP), and PP in predicting coronary heart disease (CHD) morbidity and mortality in both genders in a population of a wide age span and a setting of low levels of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol.

METHODS

Of participants in the Turkish Adult Risk Factor Study aged > or = 20 years, those free of CHD at baseline examination in 1990 were followed up for a mean of 9.3 years. Coronary heart disease was diagnosed based on clinical findings and Minnesota coding of resting electrocardiograms (ECGs). In 2,601 men and women (mean age at baseline 41.4 +/- 15 years), deaths from CHD developed in 80 and nonfatal CHD in 158 patients.

RESULTS

In a logistic regression analysis for predictors of composite endpoint of coronary mortality and morbidity, individually. DBP was not significantly and independently associated, while SBP was an independent risk predictor in both genders (relative risk [RR] 1.016). When two of three blood pressure components were entered jointly into the multivariable model, PP had a value inferior to that of SBP among men and women, but was of greater value than DBP in men in predicting both the composite endpoint and death from CHD. Among women, the predictive values of PP and DBP were similar. Within the categories of SBP > or = 120 mmHg in men, PP contributed significantly to the predictive power of SBP in overall CHD risk over and above that supplied by SBP, whereas DBP remained noncontributory.

CONCLUSION

Although inferior to the predictive power of SBP, PP was an important determinant of CHD risk in a population of a diverse age span and a better predictor than DBP in men.

Effect of CPAP on brachial-ankle pulse wave velocity in patients with OSAHS: An open-labelled study

Pulse wave velocity (PWV) is a good indicator of arterial stiffness and an important predictor of cardiovascular events. Recent studies have revealed that PWV increases in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) and it also correlates with its severity. However, the therapeutic effect of continuous positive airway pressure (CPAP) on PWV remains undetermined. To clarify this point, we started CPAP treatment on 17 OSAHS patients. Brachial-ankle PWV was measured before starting CPAP, and at 2 months and 4 months after the start of CPAP. Before the CPAP treatment, mean brachial-ankle PWV of the patients was 15.6+/-0.6 m/s, and mean Epworth sleepiness scale (ESS) score was 8.6+/-1.0. Brachial-ankle PWV was found to positively correlate with heart rate, systolic and diastolic blood pressures, mean blood pressure, and arousal index. During the study period, the CPAP treatment did not have a significant effect on heart rate, blood pressures and serum total cholesterol levels. However, it significantly improved ESS score at 4 months after the start of CPAP (P=0.001), while it effectively decreased brachial-ankle PWV at 2 months and at 4 months after the start of CPAP (P=0.010 and P=0.027, respectively). The CPAP treatment was shown to decrease brachial-ankle PWV without affecting blood pressures in OSAHS patients. Although the precise mechanism for this effect is unclear, our finding suggests a close relationship between OSAHS and arterial stiffness, while also reemphasizing the clinical importance of CPAP treatment.

Lipoprotein (a) as a determinant of arterial stiffness in elderly patients with type 2 diabetes mellitus

BACKGROUND

Lipoprotein (a) [Lp(a)] is known to be a risk factor for atherosclerotic disease. However, the relationship between Lp(a) and arterial stiffness has not been clarified. We investigated whether atherosclerotic risk factors, including serum Lp(a), are associated with aortic stiffness in elderly patients with type 2 diabetes mellitus.

METHODS

Aortic stiffness, evaluated by using aortic pulse wave velocity, and major atherosclerotic risk factors were measured in elderly (> or =65 years) patients with type 2 diabetes mellitus. Relationships between aortic pulse wave velocity, Lp(a) and other atherosclerotic risk factors were analyzed.

RESULTS

Among the atherosclerotic risk factors measured, age, pulse pressure, hemoglobin A1c (HbA1c), uric acid, fibrinogen, sialic acid and Lp(a) showed significant positive correlations with aortic pulse wave velocity. Lp(a) also showed significant positive correlations with pulse pressure, fibrinogen, sialic acid, apolipoprotein B and apolipoprotein B/apolipoprotein A-I ratio. The correlation between Lp(a) and aortic pulse wave velocity was independent of age, sex, blood hemoglobin A1c, uric acid and fibrinogen, history of diabetic nephropathy and therapy with lipid-lowering drugs. Apolipoprotein A-II showed a significant negative correlation with both aortic pulse wave velocity and Lp(a). The median level of Lp(a) in the highest tertile group of subjects divided by aortic pulse wave velocity was significantly higher than the median Lp(a) level in the lowest tertile. The middle and highest tertile groups of subjects divided by aortic pulse wave velocity showed significantly high odds ratios of high Lp(a) levels (> or =30 mg/dl) vs the lowest tertile.

CONCLUSIONS

Lp(a) is an independent determinant of aortic stiffness in elderly patients with type 2 diabetes mellitus.

Antecedent left ventricular mass and infarct size in ST-elevation myocardial infarction

BACKGROUND

Increased left ventricular mass index (LVMI) is associated with a greater incidence of acute myocardial infarction (AMI), but there are no data regarding its impact on infarct size.

OBJECTIVES

The objective of this study was to determine whether LVMI impacts on infarct size.

METHODS

We analyzed consecutive patients with a first ST-elevation AMI and successful reperfusion of the culprit artery who underwent an echocardiographic assessment of LVMI and regional wall motion score index (RWMSI) <72 hours post AMI.

RESULTS

Of the 165 patients (76.4% men) with a mean age of 61.0 +/- 13.9 years, 53.9% had anterior wall involvement and 59.3% had increased LVMI. There were no significant differences in baseline characteristics between patients with and without increased LVMI, except for a greater prevalence of hypertension among patients with increased LVMI (44.0% vs 22.4%, P < .001). The distributions of anterior wall AMI location and culprit artery involvement were similar between the groups. Patients with increased LVMI were more likely to present with single-vessel coronary artery disease (P = .04) and heart failure upon presentation (P = .03). There was no significant difference between patients with and without increased LVMI in peak creatine kinase (2106.8 +/- 1642.7 vs 2551.2 +/- 2357.4 U/L, P = .16) or RWMSI (1.62 +/- 0.44 vs 1.61 +/- 0.38, P = .91). In addition, no correlation was observed between LVMI as a continuous variable and RWMSI (r = 0.11, P = .18) or peak creatine kinase values (r = 0.02, P = .81).

CONCLUSIONS

Among patients with a first ST-elevation AMI and successful reperfusion, antecedent increased LVMI was fairly common and did not impact on infarct size.

Impaired coronary flow velocity reserve and aortic distensibility in patients with untreated hypercholesterolemia--an echocardiographic study

INTRODUCTION

Hypercholesterolemia is a primary risk factor for the development of atherosclerosis and leading to severe stages of coronary artery disease (CAD) and aortic atherosclerosis (AA). The objective of this investigation was to measure elastic modulus [(E(p), in 10(3) mmHg] and Young's circumferential static elastic modulus [(E(s), in 10(3) mmHg] as aortic distensibility indices and coronary flow velocity reserve (CFR) in untreated hypercholesterolemic (HC) patients in the course of the same stress transesophageal echocardiography (TEE) and to compare their results to normochole- sterolemic (NC) subjects.

PATIENTS AND METHODS

The following patient populations were compared: 17 NC subjects with negative coronary angiograms, 18 patients with untreated hypercholesterolemia with a negative coronary angiogram and 23 HC patients with significant left anterior descending coronary artery (LAD) disease. All patients underwent coronary angiography, transthoracic and stress TEE examinations.

RESULTS

CFR was significantly reduced in patients of both groups with hypercholesterolemia as compared to NC subjects (1.99+/-0.76 and 1.79+/-0.32 vs. 2.58+/-0.63, P<0.05, respectively). E(p) was significantly increased in HC patients with negative coronary angiograms as compared to NC subjects (0.39+/-0.18 vs. 0.67+/-0.19, P<0.05), while further increase was found in HC patients with LAD disease (0.67+/-0.19 vs. 1.09+/-0.52, P<0.05). E(s) behaved similarly (4.06+/-2.73 vs. 7.60+/-3.70 vs. 11.38+/-6.91, P<0.05, respectively).

CONCLUSION

In conclusion it may be stated that CFR and aortic distensibility indices can be evaluated simultaneously by stress TEE in HC patients. CFR and aortic distensibility were impaired in HC patients as compared to NC subjects.

Brachial Blood Pressure But Not Carotid Arterial Waveforms Predict Cardiovascular Events in Elderly Female Hypertensives

Central arterial waveforms and related indices of large artery properties can be determined with relative ease. This would make them an attractive adjunct in the risk stratification for cardiovascular disease. Although they have been associated with some classical risk factors and the presence of coronary disease, their prospective value in predicting cardiovascular outcomes is unknown. The present study determined the relative predictive value for cardiovascular disease-free survival of large artery properties as compared with noninvasive brachial blood pressure alone in a population of elderly female hypertensive subjects. We measured systemic arterial compliance, central systolic pressure, and carotid augmentation index in a subset of female participants in the Second Australian National Blood Pressure Study (untreated blood pressure 169/88±12/8 mm Hg). There were a total of 53 defined events during a median of 4.1 years of follow-up in 484 women with complete measurements. Although baseline blood pressures at the brachial artery predicted cardiovascular disease-free survival (hazard ratio [HR], 2.3; 95% CI, 1.3 to 4.1 for pulse pressure ≥81 versus <81 mm Hg; P =0.01), no such relation was found for carotid augmentation index (HR, 0.80; 95% CI, 0.44 to 1.44; P value not significant) or systemic arterial compliance (HR, 1.25; 95% CI, 0.72 to 2.16; P value not significant). Blood pressure, but not noninvasively measured central arterial waveforms, predict outcome in the older female hypertensive patient. Thus, blood pressure measurement alone is superior to measurement of arterial waveforms in predicting outcome in this group.

Effect of hyperhomocysteinemia induced by methionine administration on flow-mediated dilatation of the brachial artery in healthy subjects

Homocysteine may contribute to systolic hypertension and cardiac events by decreasing conduit artery compliance and inducing endothelial dysfunction. The effects of the experimental induction of hyperhomocysteinemia on systemic arterial compliance and pulsewave velocity are unclear, with contradictory results from previous studies. The investigators tested whether oral methionine impairs brachial artery compliance in addition to endothelial function.

Association between serum C-reactive protein levels and pulse wave velocity: a population-based cross-sectional study in a general population

Arterial stiffness as determined by aortic pulse wave velocity (PWV) has been shown to predict cardiovascular events in high-risk subjects such as those with hypertension or end-stage renal disease. Although it is suspected that low-grade inflammation as represented by increased C-reactive protein (CRP) plays an important role in the progression of atherosclerosis, it is not yet known whether serum CRP levels are associated with PWV. To examine the relationship between brachial-ankle PWV (baPWV) and serum CRP levels, several cardiovascular risk factors including these two markers (baPWV and CRP) were measured in 870 participants (mean age 59 years) randomly selected from a general population. Age, male gender, systolic blood pressure, heart rate, diabetes, and serum CRP levels increased with the quartiles divided by baPWV (all, p<0.01). By multiple regression analysis, age (p<0.001), systolic blood pressure (p<0.001), heart rate (p<0.001), body mass index (p<0.001), and CRP (p<0.01) were significant and independent predictors for baPWV. In conclusion, this cross sectional study has demonstrated in the general population that the arterial stiffness marker baPWV was independently correlated with serum CRP levels after adjustment for other established cardiovascular risks factors. This result suggests that baPWV may be a surrogate marker for atherosclerotic vascular damages including an inflammatory component.

Assessment of Arterial Stiffness Index as a Clinical Parameter for Atherosclerotic Coronary Artery Disease

BACKGROUND

The aim of the present study was to assess the feasibility and usefulness of the arterial stiffness index (ASI) measured non-invasively by computerized oscillometry and by comparing it with the pulse wave velocity (PWV).

METHODS AND RESULTS

The study group comprised 60 consutive patients who underwent coronary angiography and whose aorto-femoral PWV were obtained with a Judkins catheter. The ASI was obtained using Cardio Vision MS-2000 (IMDP, Las Vegas, NV, USA): (i) baseline (ASI-B); (ii) hyperemia induced by compression of the arm with cuff pressure for 5 min (ASI-H); and (iii) sublingual nitroglycerin (ASI-N). In total, 34 patients had significant coronary artery disease (CAD). The PWV and all ASI were higher in patients with CAD than in those without CAD (ASI-B, 85.9+/-57.8 vs 48.2+/-24.5, p=0.001; ASI-H, 98.1+/-49.8 vs 48.1+/-21.3, p<0.01; ASI-N, 66.7+/-55.7 vs 33.2+/-27.9, p=0.002). However, only ASI-B and ASI-H were positively correlated to the PWV (ASI-B, r=0.27, p=0.03; ASI-H, r=0.49, p=0.001; ASI-N, r=0.19, p=0.16). The ASI was increased after hyperemia in patients with CAD (ASI-H, 85.9+/-57.8 to 98.1+/-49.8, p=0.01), but not in patients without CAD (ASI-H, 48.2+/-24.5 to 48.1+/-21.3, p>0.01). After adjusting their age, only ASI-H was correlated to the presence of CAD (r=0.33, p<0.01).

CONCLUSIONS

It is feasible and useful to use the ASI for detection of atherosclerotic coronary disease. The findings of ASI-H suggests that in addition to stiffening of the arterial wall itself, the impairment of flow mediated vasodilation, because of endothelial dysfunction, further increases the arterial stiffness.

C-reactive protein and arterial stiffness in older adults: the Rotterdam Study

Arterial stiffness is one of the characteristics of vascular aging. Increases in pulse pressure, which reflect an increase in the stiffness of the large arteries, are associated with elevated C-reactive protein (CRP) levels. This may suggest a role of inflammation in the development of arterial stiffness. We investigated the relation between measures of arterial stiffness and CRP within the framework of the Rotterdam Study, a population-based cohort study including subjects aged 55 years and older. The carotid-femoral pulse wave velocity and the distensibility coefficient of the carotid artery were used as measures of arterial stiffness. Data on both arterial stiffness and CRP were available for 866 participants. In adjusted models, levels of CRP were linearly associated with pulse wave velocity (regression coefficient 0.088, 95% CI 0.006-0.170). Adjusted mean values of pulse wave velocity were significantly different across tertiles of CRP, being higher in the highest tertile of CRP. However, no significant association between CRP and carotid distensibility was observed.

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.

Large-artery stiffness contributes to the greater prevalence of systolic hypertension in elderly women

OBJECTIVES

To determine whether sex differences in large-artery stiffness contribute to the greater prevalence of systolic hypertension in elderly women than in elderly men.

DESIGN

During a single visit arterial stiffness was assessed in the unmedicated state using four parameters.

PARTICIPANTS

Three hundred seventy-four women with a mean age+/-standard deviation of 72+/-5 and 296 men aged 71+/-5 participated.

SETTING

Hypertensive patients were recruited from general practice as part of the second Australian National Blood Pressure Study in Melbourne, Australia.

MEASUREMENTS

Large-artery stiffness was assessed using multiple methodologies, including aortic arch stiffness (beta-index) using M-mode ultrasound and arterial compliance and augmentation index using noninvasive carotid pressure and aortic flow measurements.

RESULTS

Women had greater carotid and brachial pulse pressure (PP) than men (P<.001), despite higher mean arterial pressure in men. Mean arterial compliance was lower in women (0.20+/-0.12 vs 0.28+/-0.16 mL/mmHg, P<.001) even after correction for aortic area, and aortic arch stiffness was higher (30+/-36 vs 23+/-22; P<.01). Consistent with both a stiffer proximal circulation and a shorter distance to reflection sites, women had higher augmentation index (38+/-11% vs 29+/-12%, P<.001). In multivariate analysis, sex was an independent determinant of all arterial stiffness indices.

CONCLUSION

Independently of known confounders, elderly hypertensive women have stiffer large arteries, greater central wave reflection, and higher PP than elderly men. Stiffer large arteries likely contribute to the greater prevalence of systolic hypertension in elderly women and may partly explain the acceleration in postmenopausal cerebrovascular and cardiac complications.

Beat-to-beat oscillations in pulse pressure

We compared 5-min standard deviations (SD) and frequency domain measures of beat-to-beat pulse pressure (PP) variability with those of RR-interval, systolic (SBP) and diastolic (DBP) blood pressure variabilities, and with cross-spectral baroreflex sensitivity (BRS) in a population-based sample of 150 healthy individuals, aged 35-64 years. Beat-to-beat variability of PP was composed of similar frequency components as the other spectral variabilities, and was closely related to SBP variability. The proportion of high frequency (HF) component from overall variability was higher in PP variability than in SBP and DBP variabilities. The low frequency (LF) component and the SD of beat-to-beat PP correlated inversely with BRS (-0.48 and -0.32, respectively; P<0.001 for both). To test a hypothesis that arterial stiffening is associated with increased beat-to-beat oscillation in PP, we examined associations of beat-to-beat PP variability with risk factors of atherosclerosis, i.e. with age, gender, smoking, blood pressure, body mass index, serum lipids, glucose, insulin and homeostasis model assessment of insulin resistance. The SD of beat-to-beat PP variability correlated with age (0.21, P = 0.010), PP (0.31, P<0.001) and body mass index (0.22, P = 0.008). The LF component of PP variability correlated not only with age (0.17, P = 0.041), PP (0.27, P = 0.001) and body mass index (0.22, P = 0.007), but also with serum insulin (0.17, P = 0.042), homeostasis model assessment of insulin resistance (0.18, P = 0.031) and serum triglycerides (0.16, P = 0.048). Our findings suggest that increased beat-to-beat oscillation of PP reflects arterial stiffening and impaired baroreflex function.

The effect of diabetes on heart rate and other determinants of myocardial oxygen demand in acute coronary syndromes

AIMS

To compare major determinants of myocardial oxygen demand (heart rate, blood pressure and rate pressure product) in patients with and without diabetes admitted with acute coronary syndromes.

METHODS

A cross-sectional study of the relation between diabetes and haemodynamic indices of myocardial oxygen demand in 2542 patients with acute coronary syndromes, of whom 1041 (41.0%) had acute myocardial infarction and 1501 (59.0%) unstable angina.

RESULTS

Of the 2542 patients, 701 (27.6%) had diabetes. Major haemodynamic determinants of myocardial oxygen demand were higher in patients with than without diabetes: heart rate 80.0 +/- 20.4 vs. 75.2 +/- 19.2 beats/minute (P < 0.0001); systolic blood pressure 147.3 +/- 30.3 vs. 143.2 +/- 28.5 mmHg (P = 0.002); rate-pressure product 11533 +/- 4198 vs. 10541 +/- 3689 beats/minute x mmHg (P < 0.0001). Multiple regression analysis confirmed diabetes as a significant determinant of presenting heart rate [multiplicative coefficient (MC) 1.05; 95% confidence interval (CI) 1.03-1.07; P < 0.0001], rate pressure product (MC 1.09; CI 1.05-1.12; P < 0.0001) and systolic blood pressure, which was estimated to be 3.9 mmHg higher than in patients without diabetes (P=0.003). These effects of diabetes were independent of a range of baseline variables including acute left ventricular failure and mode of presentation (unstable angina or myocardial infarction).

CONCLUSIONS

In acute coronary syndromes, heart rate and other determinants of myocardial oxygen demand are higher in patients with than without diabetes, providing a potential contributory mechanism of exaggerated regional ischaemia in this high-risk group.

Preclinical changes in the mechanical properties of abdominal aorta in obese children

Obesity in childhood has been associated with the development of early cardiovascular abnormalities. The aim of the present study was to investigate whether preclinical functional changes are detectable in the abdominal aorta of obese children. One hundred consecutively seen obese children and 50 healthy controls were studied. The groups were matched in terms of age and gender. The pulsatile wall-motion of the abdominal aorta was determined using a B-mode ultrasound technique. The following mechanical property parameters were measured or computed: lumen diastolic and systolic diameters, relative aortic strain, elastic modulus, and stiffness. Compared to controls, obese children had higher blood pressure values and higher concentrations of total cholesterol, triglycerides, insulin, and C-reactive protein. Homeostasis model assessment (HOMA) score, a parameter of insulin resistance, was significantly higher in obese children than in controls (3.2 +/- 1.9 v 1.4 +/- 0.5, P <.001). Aortic mechanical parameters were significantly different in obese children as compared to controls: stiffness was higher (3.00 +/- 1.45 v 2.22 +/- 0.87, P <.001) as was elastic modulus (0.38 +/- 0.18 v 0.24 +/- 0.10 N/m(2), P <.001). Obese girls with insulin resistance (ie, in the highest tertile of HOMA, >3.7) had increased aortic stiffness (3.79 +/- 2.25) compared to obese girls in the lowest tertiles of HOMA (2.67 +/- 1.09, P =.045), even after adjustment for traditional cardiovascular risk factors (P =.031). The present findings suggest that preclinical changes in the aortic elastic properties are detectable in obese children. Insulin resistance seems to play an important role in the increased rigidity of the aortic wall in obese girls.

Impaired elastic properties of ascending aorta in patients with giant cell arteritis

OBJECTIVE

To investigate the elastic properties of the ascending aorta in untreated patients with giant cell arteritis compared with age and sex matched normal controls.

METHODS

Distensibility of the ascending aorta and aortic strain were measured in 22 patients with a recent diagnosis of giant cell arteritis (documented by a positive temporal artery biopsy) before initiation corticosteroid treatment, and in 44 age and sex matched healthy subjects. Aortic distensibility was calculated as 2x[pulsatile change in aortic diameter]/[(diastolic aortic diameter)x(aortic pulse pressure)], and aortic strain as [pulsatile change in aortic diameter]/[diastolic aortic diameter]. Aortic diameters were measured by echocardiography. Aortic pressures were obtained by external sphygmomanometry.

RESULTS

Distensibility of the ascending aorta and aortic strain were both lower in patients with giant cell arteritis than in the controls (p<0.01). In the patients with giant cell arteritis, aortic distensibility was inversely correlated with white blood cell count (p<0.05), but not with erythrocyte sedimentation rate or C reactive protein.

CONCLUSIONS

Compared with healthy subjects, aortic distensibility and aortic strain are decreased in patients with giant cell arteritis before initiation of corticosteroid treatment. There was an association between the degree of reduction of aortic distensibility and the white blood cell count in the patient group.

Large Artery Stiffness Is Not Related to Plasma Cholesterol in Older Subjects with Hypertension

OBJECTIVE

Previous studies have demonstrated a prognostic role of large artery stiffness in hypertensive subjects and increased stiffness in subjects with coronary artery disease. Although plasma cholesterol is an established risk factor for cardiovascular disease, its relationship with large artery properties in a hypertensive population is unclear.

METHODS AND RESULTS

Plasma cholesterol and large artery properties were measured at baseline in a subset of participants of a randomized controlled trial (ANBP2) evaluating hypertension treatment in older (65 to 84 years) subjects. Noninvasive measures of large artery behavior were central augmentation index (AI), systemic arterial compliance (SAC), and transverse expansion of the aortic arch (aortic distensibility). Arterial waveforms acceptable for analysis were obtained in approximately 80% of cases yielding valid measurements of AI in 868, SAC in 846, and aortic distensibility in 680 subjects. Mean total and high-density lipoprotein (HDL) concentrations were 5.5+/-1.0 and 1.4+/-0.5 mmol L(-1). Total and HDL cholesterol and AI were greater in females than males, whereas SAC and aortic distensibility were greater in males. In multiple regression analyses there were no significant associations between stiffness parameters and total or HDL cholesterol. Significant independent associations in such analyses were found for mean arterial blood pressure, gender, age, height, and heart rate, in keeping with previous findings.

CONCLUSIONS

In the largest cohort of elderly hypertensive subjects studied to date, plasma cholesterol per se was not associated with large artery stiffness. Such independence from cholesterol increases the potential for artery stiffness measurements to additionally contribute to cardiovascular risk assessment in this population.

Arterial function after successful renal transplantation

BACKGROUND

Renal transplantation is increasingly the preferred method of renal replacement therapy. Cardiovascular disease is the major barrier to long-term survival for transplant recipients. The aim of this study was to determine whether the increased arterial stiffness of patients with chronic renal failure is improved after successful renal transplantation.

METHODS

The study involved a group of 36 patients, aged 27 to 68 years (mean +/- SD, 46 +/- 11 years) who had cardiovascular risk assessment and measurements of carotid artery intima-media thickness (IMT), arterial pulse wave velocity [aorto-femoral (PWV a-f) and femoral-dorsalis pedis (PWV f-d)], systemic arterial compliance (SAC), and arterial wave reflection (augmentation index, AI(x)) performed before and 12 months after successful renal transplantation. B-mode ultrasound measurements were used to determine mean carotid IMT and applanation tonometry techniques to determine SAC, AI(x), PWV (a-f), PWV (f-d), and central pressures. On each occasion the following were also measured: fasting lipids, homocysteine (tHcy), red cell folate, cobalamin, and fibrinogen levels.

RESULTS

One year after transplantation, mean serum creatinine was 143 +/- 47 micromol/L, and creatinine clearance 60 +/- 16 mL/min/1.74m(2) (range 25 to 104 mL/min/1.74m(2)). Total and low-density lipoprotein (LDL) cholesterol were significantly reduced. tHcy was decreased by 38% and normalized in 45%. Systolic and diastolic blood pressure and mean arterial pressure were all improved. From baseline to 12 months' post-transplantation, there was no significant change in carotid IMT (mean IMT 0.76 +/- 0.11 vs. 0.75 +/- 0.14 mm, P= 0.28) or SAC (0.45 +/- 0.23 vs. 0.46 +/- 0.22 units, P= 0.95), but PWV [PWV (a-f) 9.6 +/- 2.6 vs. 8.8 +/- 2.2 m/sec, P= 0.007; PWV (f-d) 10.7 +/- 1.8 vs. 8.4 +/- 1.7 m/sec, P < 0.001] and AI(x) (24.3 +/- 13.4 vs. 15.9 +/- 11.4%, P= 0.003) improved. After adjusting for the differences in blood pressure, the changes in PWV (a-f) were no longer significant, but the differences in PWV (f-d) persisted. The change in AI(x) remained significant after adjusting for differences in heart rate, and the fall in AI(x) was greater in patients on immunosuppression with tacrolimus compared with those on cyclosporine.

CONCLUSION

One year after successful renal transplantation, improvement in cardiovascular risk factors was associated with improvement in indices of arterial stiffness.

High brachial-ankle pulse wave velocity is an independent predictor of the presence of coronary artery disease in men

Pulse wave velocity (PWV) is an index of arterial stiffness, and a simple device for measuring brachial-ankle PWV (baPWV) has recently been developed. However, the clinical application of baPWV in patients with coronary artery disease (CAD) remains to be fully evaluated. This cross-sectional study was conducted to evaluate whether a higher baPWV predicts the presence of CAD. The baPWV was measured in 123 patients (77 males, 46 females; 63.5+/-11.8 years) who were undergoing coronary angiography. CAD was defined as >50% diameter stenosis. Hemodynamic data and cardiovascular risk factors were examined according to the presence or absence of CAD. Patients with CAD were significantly older across both sexes. The presence of hypertension and chest pain, but not baPWV, was correlated with CAD in females. The baPWV, and the presence of diabetes, hyperlipidemia, and chest pain were related to the presence of CAD in males. Multivariate logistic regression analysis in male patients showed that baPWV, diabetes, hyperlipidemia, and chest pain were independent risk factors for the presence of CAD. Furthermore, high baPWV in males with or without chest pain had a positive predictive value of 81.8% and 71.7% for the presence of CAD, respectively. In conclusion, high baPWV was shown to be a good independent predictor for the presence of CAD in men.

Increased pulse pressure is associated with reduced baroreflex sensitivity

Although pulse pressure (PP), heart rate variability (HRV) and baroreflex sensitivity (BRS) have been shown to predict cardiovascular events and mortality in various populations, their relationships have not been clarified. We examined these associations in two separate population-based samples of healthy middle-aged subjects. In population 1, data were obtained from 149 subjects (71 men and 78 women) aged 35-64 (mean 47.7) years, and in population 2, from 214 subjects (88 men and 126 women) aged 40-62 (mean 50.5) years. Increased 24-h ambulatory PP was related to decreased cross-spectral BRS independent of age and gender (beta=-0.28, P<0.001 for population 1; beta=-0.22, P=0.003 for population 2). This association remained significant when 24-h ambulatory diastolic blood pressure, body mass index, smoking and alcohol intake were added as covariates in the multivariate analysis. Increased ambulatory PP was also associated with increased beat-to-beat systolic arterial pressure variability. Associations between ambulatory PP and HRV were not significant after controlling for age and gender. Our results suggest that elevated PP does not affect overall HRV, but it interferes with baroreflex-mediated control of the heart rate. This association may be due to a common denominator, such as arterial stiffness, for PP and BRS.

Variation of mechanical properties along the length of the aorta in C57bl/6 mice

The objective of the present study is to obtain a systematic set of data on the mechanical properties along the entire length of the mouse aorta. The ascending aorta of seven mice was cannulated near the aortic valve, and the aorta was preconditioned with several cyclic changes in pressure. The perfusion pressure was then increased in 30-mmHg increments from 0 to 150 mmHg. Cab-O-Sil, colloidal silica, was mixed into the perfusate to prevent flow through the microvessels and hence attain zero-flow distensions. Our results show that the residual circumferential strain leads to a uniformity of transmural strain of the aorta in the loaded state along the entire length of the aorta. This uniformity is attained in the range of 60–120 mmHg. At pressures <60 mmHg, the outer strain is greater than the inner strain, whereas at pressures >120 mmHg, the converse is true. Furthermore, we found that the circumferential and longitudinal stress-strain relationships are linear in the pressure range of 30–120 mmHg. Finally, the circumferential modulus is greatest (most rigid) near the diaphragm, and the majority of volume compliance (85%) is in the thoracic compared with the abdominal aorta. These findings are important for an understanding of the hemodynamics of the cardiovascular system of the normal mouse and will serve as a reference state for the study of various diseases in knock-in and knock-out models of this species.

Clustered features of the metabolic syndrome and the risk for increased aortic pulse wave velocity in middle-aged Japanese men

The association between different features of the metabolic syndrome (MS) (obesity, hypertension, hypercholesterolemia, low high-density lipoprotein cholesterol level, hypertriglyceridemia, high fasting plasma glucose level, and hyperuricemia) and the risk for increased aortic pulse wave velocity (PWV) of > or = 8.0 m/sec was examined in 2431 Japanese men aged 35 to 54 years who were not taking antihypertensive medication. After controlling for age, cigarette smoking, and alcohol intake, the odds ratios for increased aortic PWV in subjects with 1, 2, 3, and > or = 4 features of the MS, compared with those without features of the MS, were 1.35 (95% CI, 0.86 to 2.11), 1.90 (95% CI, 1.18 to 3.06), 1.57 (95% CI, 0.89 to 2.76), and 2.38 (95% CI, 1.26 to 4.49), respectively (p for trend = 0.003). A 9-year longitudinal study was also performed to prospectively examine the association between clustered features of the MS and the development of increased aortic PWV in 2073 men without aortic stiffness with a PWV < 8.0 m/sec and without antihypertensive medication during the follow-up period. The multivariate-adjusted hazard ratios for the incidence of increased aortic PWV in subjects with 1, 2, 3, and > or = 4 features of the MS, compared with those without features of the MS, were 1.39 (95% CI, 1.10 to 1.77), 1.46 (95% CI, 1.1 1 to 1.92), 1.75 (95% CI, 1.27 to 2.40), and 2.22 (95% CI, 1.52 to 3.25), respectively (p for trend < 0.001). These results suggest that clustered features of the MS are closely associated with the risk for increased aortic PWV in middle-aged Japanese men.

Gender differences in large artery stiffness pre- and post puberty

Age-related large artery stiffening is more pronounced in women compared with men and is an important cause of isolated systolic hypertension. This study aimed to investigate whether such gender differences are inherent or the result of sex steroid influences. Healthy children prepuberty [26 female (10.3 +/- 0.1 yr), 32 male (10.3 +/- 0.1 yr), mean age +/- SD] and post puberty [30 female (15.9 +/- 0.2 yr), 22 male (15.9 +/- 0.4 yr)] were studied. Large artery stiffness was assessed globally via systemic arterial compliance and regionally via pulse wave velocity. Prepubertal males and females did not differ in body size, cardiac output, or heart rate. Prepubertal females had stiffer large arteries and higher pulse pressure than age-matched males (P < 0.05). Postpubertal males were taller and heavier and had a greater cardiac output and lower heart rate compared with similarly aged females. In relation to pubertal status, females developed more distensible large arteries post puberty whereas males developed stiffer large vessels (P < 0.05). These changes where such that central large artery stiffness was similar between genders in the postpubertal group. Together these data suggest that large artery stiffness varies intrinsically between genders but is also modulated by both male and female sex steroids.

Low HDL cholesterol concentration is associated with increased intima-media thickness independent of arterial stiffness in healthy subjects from families with low HDL cholesterol

BACKGROUND

Low high-density lipoprotein cholesterol (HDL-C) is associated with increased risk for developing coronary artery disease. Cardiovascular disease is characterized by increased intima-media thickness (IMT) and arterial stiffness, but the effect of low HDL on these measurements has not been reported.

MATERIALS AND METHODS

We studied 18 apparently healthy subjects from families with low HDL-C and 18 control subjects, which were pair-matched to maximize statistical power. Intima-media thickness was assessed using ultrasound examination of the carotid arteries. Arterial stiffness was measured using applanation tonometry on the radial artery and pulse-wave analysis to obtain central aortic pulse-pressure waveform, from which the augmentation index, a measure of global large artery stiffness, was calculated.

RESULTS

Low HDL subjects (age 41 +/- 3 years, BMI 26.6 +/- 1.0 kg m(-2) had significantly lower HDL-C than the control subjects (age 41 +/- 3 years, BMI 26.5 +/- 1.0 kg m-2; 1.00 +/- 0.05 vs. 1.49 +/- 0.09 mmol L-1, low HDL vs. control subjects, P < 0.0001). Subjects with low HDL-C had significantly thicker mean IMTs than the control subjects (0.77 +/- 0.03 vs. 0.70 +/- 0.02 mm, low HDL vs. control subjects, P < 0.01). The maximal (0.99 +/- 0.04 vs. 0.89 +/- 0.03 mm, P < 0.01), far wall (0.76 +/- 0.04 vs. 0.69 +/- 0.02 mm, P < 0.05) and carotid bulb (1.11 +/- 0.06 vs. 0.97 +/- 0.04 mm) IMTs were also significantly increased, whereas the mean common carotid and the internal artery IMT were not. The age-related increase in mean IMT was more pronounced in the low HDL subjects than the control subjects (P < 0.01 for difference between elevations of age vs. IMT slopes). There were no differences in central pressure augmentation, the augmentation index, peripheral or central blood pressures between the groups.

CONCLUSIONS

A low HDL-C concentration is associated with thickening of carotid IMT independent of other risk factors in healthy affected members of low HDL families.

Analysis of the regional pulse wave velocity by Doppler: methodology and reproducibility

Increased arterial stiffness is observed in a number of cases. The analysis of the regional functional arterial properties is of interest to determine the role of a given risk factor on the vascular wall and in some diseases such as atherosclerosis. We analysed the pulse wave velocity (PWV) measured by the Doppler method with 2D guidance and its reproducibility in different arterial segments in 15 men with coronary artery disease. Regional Doppler PWV was defined as the distance between the extremities of a given segment divided by the transit time calculated by Doppler. Intra- and interobserver reproducibilities of the Doppler measurements were studied in all of the subjects. The variation coefficients were low, maximum at the level of ascending aorta and minimal at the level of iliac segment. This good reproducibility was validated by the Bland-Altman method. Moreover, using this Doppler technique, we found a progressive increase in PWV from the ascending aorta to the iliac segment. These data demonstrate that noninvasive Doppler analysis is a feasible and reproducible method to determine regional PWV.

Relation between coronary artery disease, risk factors and intima-media thickness of carotid artery, arterial distensibility, and stiffness index

Atherosclerosis is a diffuse process that involves vessel structures. In recent years, the relation of noninvasive parameters such as intima-media thickening (IMT), arterial distensibility (AD), and stiffness index (SI) to cardiovascular diseases has been researched. However, we have not found any study that has included all these parameters. The aim of this study is to examine the relation between the presence of coronary artery disease (CAD) and its risk factors to AD, SI, and IMT, which are the noninvasive predictors of atherosclerotic process in the carotid artery. Included in the study were 180 patients who were diagnosed as having CAD by coronary angiography (those with at least > or = 30% stenosis in the coronary arteries) and, as a control group, 53 persons who had normal appearing coronary angiographies. IMT, AD, and SI values of all the patients in the study were measured by echo-Doppler imaging (AD formula = 2 x (AoS - AoD)/PP x AoD, SI formula = (SBP/DBP)/([AoS - AoD]/AoD). Significantly increased IMT (0.82 +/- 0.1, 0.57 +/- 0.1, p<0.05), decreased AD (0.25 +/- 0.9, 0.37 +/- 0.1, p<0.05), and increased SI (13 +/- 4, 8 +/- 3, p<0.05) values were detected in the CAD group compared to the control group. A significant correlation was found between IMT and presence of diabetes mellitus (DM), systolic blood pressure, total cholesterol, and presence of plaque in carotids, and age. In the coronary artery disease group there was a significant correlation between AD and age, systolic blood pressure, and HDL cholesterol levels, while there was no significant correlation with plaque development. A significant correlation was also found between stiffness index and systolic blood pressure and age; however, there was no relation between number of involved vessels and IMT, AD, and SI. We found sensitivity, specificity, and positive predictive and negative predictive values for CAD diagnosis to be 70%, 75%, 77%, and 66%, respectively. In CAD cases, according to data in this study, IMT and SI increased while AD decreased, and this was detected by carotid artery Doppler ultrasonography. Therefore, it was concluded that these cheaper, noninvasive, and easily available parameters could be used in early diagnosis of CAD.

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.

Arterial distensibility: acute changes following dynamic exercise in normal subjects

The time course of acute changes in large artery distensibility immediately and for 60 min following maximum treadmill exercise in normal subjects was characterized by simultaneously measuring upper and lower limb pulse wave velocity (PWV). A new oscillometric technique was used, which has proven to be sensitive to changes in distensibility induced by acute changes in vascular tone independently of blood pressure. The observed changes in PWV are attributable to changes in vascular tone corresponding to recovery from a systemic net constrictor response and a local net dilator response to exercise with persisting postexercise vasodilatation. They are inadequately explained by associated changes in blood pressure and cannot be attributed to changes in heart rate or viscosity. Modeled as a system of n coupled linear differential equations, the minimum (and adequate) order required to reproduce these patterns was n = 1 for the upper and n = 2 for the exercising lower limb. The economy of the solution suggests entrainment among the multiple interactive mechanisms governing vasomotor control.

Effects of Low and High Doses of Atorvastatin on Arterial Compliance

At the beginning of atherosclerosis before evidence of morphological lesions or plaques, vascular distensibility or arterial compliance decreased gradually. This endothelial dysfunction is regarded as an early feature of atherosclerosis. In a randomized, double-blind study design, group 1 (12 patients; 7 males, 5 females) with serum LDL-C levels higher than 170 mg/dL and without any other risk factor for atherosclerosis received three months of 20 mg/day atorvastatin treatment while group 11 (8 males, 4 females) with the same characteristics received 80 mg/day. Baseline and posttreatment serum lipid fractions and arterial compliance were measured. Arterial compliance was measured noninvasively in the left common carotid artery with color Doppler ultrasound. Atorvastatin reduced total cholesterol (TC), LDL-C, and triglyceride levels by 32% (P < 0.001), 40.8% (P < 0.001), and 19% (P < 0.001), respectively, and increased HDL-C by 6.9%, (P = 0.002) in the first group. In the second group these reductions were 38.5% (P < 0.001), 46.2% (P < 0.001), and 26.78% (P < 0.001), respectively, and the increase in HDL was 7.8% (P = 0.03). It was observed that the decrease in serum TC, LDL-C and triglyceride levels were significantly higher in the second group than the first group. With atorvastatin, the distensibility coefficient (DC) and compliance coefficient (CC) increased from 18.7 +/- 3.4 to 21.3 +/- 2.9 10(-3) x kPa(-1) (P < 0.001) and from 0.69 +/- 0.05 to 0.77 +/- 0.03 mm2 x kPa(-1) (P < 0.001) in the first group while they changed from 18.3 +/- 3.6 to 21.9 +/- 3.0 10(-3) x kPa(-1) (P < 0.001) and from 0.70 +/- 0.04 to 0.81 +/- 0.01 mm2 x kPa(-1) (P < 0.001) respectively, in the second group. DC and CC increased in both groups, but the differences between the groups were not significant. High doses of atorvastatin reduce blood lipid levels more than conventional doses, however, the change in compliance is not dose-dependent. As endothelial dysfunction is regarded as an early feature of atherosclerosis, there would be no need to administer aggressive doses in a patient without any risk factors other than hyperlipidemia.

Morphologic rather than functional or mechanical sonographic parameters of the brachial artery are related to angiographically evident coronary atherosclerosis

OBJECTIVES

The purpose of this study was to determine the relationship among coronary atherosclerosis and functional, morphologic, and mechanical parameters assessed noninvasively within the brachial artery (BA).

BACKGROUND

Flow-mediated vasodilation (FMD) of the BA, intima-media thickness (IMT) of the carotid artery, and distensibility of the aorta have been correlated with the presence of coronary artery disease (CAD).

METHODS

The BA was examined with high-resolution ultrasound (13 MHz) in 117 male patients, in whom coronary angiography was performed. Coronary artery disease (> or =30% diameter stenosis in > or =1 major branch) was found in 84 patients, and 33 patients had smooth coronary arteries (non-CAD). Wall cross-sectional area (WCSA) was calculated from resting diameter and IMT.

RESULTS

The BA-WCSA (5.3 +/- 1.5 mm(2) vs. 4.4 +/- 1.4 mm(2), p = 0.002) and IMT (0.37 +/- 0.07 mm vs. 0.31 +/- 0.07 mm, p < 0.001) were significantly greater in patients with CAD compared with non-CAD patients. Flow-mediated vasodilation and distensibility were similar among groups. Using logistic regression analyses adjusting for age, positive family history, hypertension, hypercholesterolemia, smoking, FMD, and distensibility, only WCSA (p < 0.01) and IMT (p < 0.001) correlated independently with the presence of CAD.

CONCLUSIONS

Morphologic but not functional and mechanical parameters of the BA are associated with the presence of CAD. Among BA sonographic parameters, IMT and WCSA seem to be the most accurate ones for the estimation of coronary atherosclerotic risk.

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.

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.

Large artery stiffness predicts ischemic threshold in patients with coronary artery disease

OBJECTIVES

The goal of this study was to determine whether large artery stiffness contributes to exercise-induced myocardial ischemia in patients with coronary artery disease (CAD).

BACKGROUND

Large artery stiffness is an independent predictor of cardiovascular mortality and a major determinant of pulse pressure and, thus, cardiac afterload and coronary perfusion. Clinical relevance of the hemodynamic consequences of large artery stiffening has not previously been demonstrated in relation to myocardial ischemia.

METHODS

We hypothesized that stiffer large arteries would reduce myocardial ischemic threshold as assessed by time to ST-segment depression of 0.15 mV during a treadmill exercise test in patients with CAD. Ninety-six patients with CAD (78 men) age 62 +/- 9 years (mean +/- SD) were classified as having single (52 patients), double (31 patients), or triple (13 patients) coronary vessel disease, based on angiographically confirmed stenoses >50%. Systemic arterial compliance, distensibility index, aortic pulse wave velocity, and carotid augmentation index were measured using carotid applanation tonometry and Doppler velocimetry of the ascending aorta, at rest.

RESULTS

In univariate analysis, all large artery stiffness/compliance indexes correlated with time to ischemia (p = 0.01 to 0.009). Both carotid (p = 0.007) and brachial (p = 0.001) pulse pressure also correlated inversely with time to ischemia. In multivariate analysis including other major risk factors plus severity of coronary stenosis, indexes of arterial stiffness were significant independent predictors of ischemic threshold.

CONCLUSIONS

Within a patient group with moderate CAD, large artery stiffness was a major determinant of myocardial ischemic threshold.

Impact of aortic stiffness on ischemic stroke in elderly patients

BACKGROUND AND PURPOSE

Large atherosclerotic plaques in the aortic arch detected by transesophageal echocardiography (TEE) are associated with increased risk of ischemic stroke in the elderly. The atherosclerotic process also affects aortic distensibility, which can also be assessed by TEE. The purpose of this study was to evaluate the possible association of aortic stiffness by TEE with ischemic stroke in elderly patients.

METHODS

We performed TEE in 40 consecutive elderly patients aged > or =55 years with acute ischemic stroke and in 42 consecutive control subjects aged > or =55 years. Aortic stiffness index beta, which has been used in the literature to express the stiffness of the aortic wall, was calculated as follows: beta=ln (systolic blood pressure/diastolic blood pressure)/([D(max)-D(min)]/D(min)), where ln is natural logarithm, D(max) is maximum aortic lumen diameter, and D(min) is minimum aortic lumen diameter by TEE. The association of index beta with ischemic stroke was evaluated by logistic regression analysis after adjustment for potential confounders, including thickness of aortic arch plaques.

RESULTS

Index beta was significantly greater in stroke patients than in controls (9.7+/-5.0 versus 5.3+/-3.5; P<0.0001). When aortic plaque thickness and other stroke risk factors were entered in multivariate analysis, index beta was found to be independently associated with ischemic stroke (odds ratio, 1.28 per unit increase; 95% CI, 1.10 to 1.52).

CONCLUSIONS

Aortic stiffness by TEE is associated with ischemic stroke, independent of thickness of aortic arch plaques and other stroke risk factors. This suggests that aortic stiffness by TEE may add prognostic information when assessing the risk of ischemic stroke in the elderly.

Methods and devices for measuring arterial compliance in humans

This review analyses methods and devices used worldwide to evaluate the arterial stiffness. Three main methodologies are based upon analysis of pulse transit time, of wave contour of the arterial pulse, and of direct measurement of arterial geometry and pressure, corresponding to regional, systemic and local determination of stiffness. They are used in clinical laboratory and/or in clinical departments. Particular attention is given to the reproducibility data in literature for each device. This article summarizes the discussion of the dedicated Task Force during the first Conference of Consensus on Arterial Stiffness held in June 2000 (Paris, France).

Determinants of coronary artery compliance in subjects with and without angiographic coronary artery disease

OBJECTIVES

The goal of this study was to determine factors contributing to the biomechanical properties of coronary arteries in people with and without angiographic coronary artery disease (CAD).

BACKGROUND

The stiffness of the aorta is known to increase with increasing age and in the presence of CAD. However, little is known about the mechanics of coronary arteries, which may have important clinical consequences.

METHODS

Intravascular ultrasound was used to determine the mechanical properties of coronary arteries and plaque behavior in subjects with CAD (n = 38), those with chest pain but angiographically normal coronary arteries (N) (n = 9) and those early (<2 weeks) after cardiac transplant (T) (n = 14).

RESULTS

Coronary arteries dilated during systole in all groups, but cross-sectional compliance and distensibility were lowest in the proximal left anterior descending artery (LAD) in the subjects with CAD compared with the N and T groups (compliance: 1.2 +/- 0.2 vs. 1.7 +/- 0.5 and 2.7 +/- 0.6 x 10(-2) mm(2) mm Hg(-1) [mean +/- SEM] respectively, p < 0.02 CAD vs. T; distensibility: 0.8 +/- 0.2 vs. 1.7 +/- 0.5 and 1.7 +/- 0.3 x 10(-3) mm Hg(-1), p < 0.05 CAD vs. T). There was extensive plaque in the CAD group, and plaque was also present in the N group, but minimal atheroma was present in the T group. Plaque cross-sectional area diminished significantly during systole in both the LAD and circumflex arteries. Absolute changes were: 0.50 +/- 0.30, 0.33 +/- 0.11 and 0.68 +/- 0.13 mm(2) in the proximal LAD, distal LAD and proximal circumflex arteries, respectively. In subjects with atheroma, there was a significant correlation between cross-sectional compliance and plaque compression at all sites, and plaque compression was a significant determinant of cross-sectional compliance at both proximal sites in multiple regression analyses with age, mean arterial pressure and extent of plaque as the other independent variables.

CONCLUSIONS

A major determinant of the systolic increase in coronary luminal area in patients with atheroma is a reduction in plaque cross-sectional area during systole.

Increased central pulse pressure and augmentation index in subjects with hypercholesterolemia

OBJECTIVES

The goal of this study was to investigate the relation between serum cholesterol, arterial stiffness and central blood pressure.

BACKGROUND

Arterial stiffness and pulse pressure are important determinants of cardiovascular risk. However, the effect of hypercholesterolemia on arterial stiffness is controversial, and central pulse pressure has not been previously investigated.

METHODS

Pressure waveforms were recorded from the radial artery in 68 subjects with hypercholesterolemia and 68 controls, and corresponding central waveforms were generated using pulse wave analysis. Central pressure, augmentation index (AIx) (a measure of systemic stiffness) and aortic pulse wave velocity were determined.

RESULTS

There was no significant difference in peripheral blood pressure between the two groups, but central pulse pressure was significantly higher in the group with hypercholesterolemia (37 +/- 11 mm Hg vs. 33 +/- 10 mm Hg [means +/- SD]; p = 0.028). Augmentation index was also significantly higher in the patients with hypercholesterolemia group (24.8 +/- 11.3% vs. 15.6 +/- 12.1%; p < 0.001), as was the estimated aortic pulse wave velocity. In a multiple regression model, age, short stature, peripheral mean arterial pressure, smoking and low-density lipoprotein cholesterol correlated positively with AIx, and there was an inverse correlation with heart rate and male gender.

CONCLUSIONS

Patients with hypercholesterolemia have a higher central pulse pressure and stiffer blood vessels than matched controls, despite similar peripheral blood pressures. These hemodynamic changes may contribute to the increased risk of cardiovascular disease associated with hypercholesterolemia, and assessment may improve risk stratification.