Distension capacity of the carotid artery and ambulatory blood pressure monitoring. Effects of age and hypertension

Physiological basis for longitudinal motion of the arterial wall

As opposed to arterial distension in the radial plane, longitudinal wall motion (LWM) is a multiphasic and bidirectional displacement of the arterial wall in the anterograde (i.e., in the direction of blood flow) and retrograde (i.e., opposing direction of blood flow) directions. While initially disregarded as imaging artifact, LWM has been consistently reported in ultrasound investigations in the last decade and is reproducible beat-to-beat, albeit with large inter-individual variability across healthy and diseased populations. Emerging literature has sought to examine the mechanistic control of LWM to explain the shape and variability of the motion pattern but lacks considerations for key foundational vascular principles at the level of the arterial wall ultrastructure. The purpose of this review is to summarize the potential factors that underpin the causes and control of arterial LWM, spanning considerations from the arterial extracellular matrix to systems-level integrative theories. First, an overview of LWM and relevant aspects wall composition will be discussed, including major features of the multiphasic pattern, arterial wall extracellular components, tunica fiber orientations, and arterial longitudinal pre-stretch. Second, current theories on the systems-level physiological mechanisms driving LWM will be discussed in the context of available evidence including experimental human research, porcine studies, and mathematical models. Throughout, we discuss implications of these observations with suggestions for future priority research areas.

Pulse Wave Imaging in Carotid Artery Stenosis Human Patients in Vivo

Carotid stenosis involves narrowing of the lumen in the carotid artery potentially leading to a stroke, which is the third leading cause of death in the United States. Several recent investigations have found that plaque structure and composition may represent a more direct biomarker of plaque rupture risk compared with the degree of stenosis. In this study, pulse wave imaging was applied in 111 (n = 11, N = 13 plaques) patients diagnosed with moderate (>50%) to severe (>80%) carotid artery stenosis to investigate the feasibility of characterizing plaque properties based on the pulse wave-induced arterial wall dynamics captured by pulse wave imaging. Five (n = 5 patients, N = 20 measurements) healthy volunteers were also imaged as a control group. Both conventional and high-frame-rate plane wave radiofrequency imaging sequences were used to generate piecewise maps of the pulse wave velocity (PWV) at a single depth along stenotic carotid segments, as well as intra-plaque PWV mapping at multiple depths. Intra-plaque cumulative displacement and strain maps were also calculated for each plaque region. The Bramwell-Hill equation was used to estimate the compliance of the plaque regions based on the PWV and diameter. Qualitatively, wave convergence, elevated PWV and decreased cumulative displacement around and/or within regions of atherosclerotic plaque were observed and may serve as biomarkers for plaque characterization. Intra-plaque mapping revealed the potential to capture wave reflections between calcified inclusions and differentiate stable (i.e., calcified) from vulnerable (i.e., lipid) plaque components based on the intra-plaque PWV and cumulative strain. Quantitatively, one-way analysis of variance indicated that the pulse wave-induced cumulative strain was significantly lower (p < 0.01) in the moderately and severely calcified plaques compared with the normal controls. As expected, compliance was also significantly lower in the severely calcified plaques regions compared with the normal controls (p < 0.01). The results from this pilot study indicated the potential of pulse wave imaging coupled with strain imaging to differentiate plaques of varying stiffness, location and composition. Such findings may serve as valuable information to compensate for the limitations of currently used methods for the assessment of stroke risk.

Arterial compliance in a group of normotensive and untreated hypertensive Cameroonian subjects in Yaounde

INTRODUCTION

Arterial compliance is an independent predictor of cardiovascular events. It decreases with age and this decrease is accelerated by hypertension. The objectives were to determine the arterial compliance in a group of normotensive and untreated hypertensive stage 1, 2 and 3 Cameroonian subjects.

METHODS

A cross-sectional study was conducted from August 2012 to February 2013 in Yaoundé. Our sample size was 88 participants. The PulsePen® device was used to determine cfPWV (carotid-femoral Pulse Wave Velocity) and central Augmentation Index % (AIx). Other measurements obtained were: blood pressure (BP), body mass index (BMI), fasting glycaemia, lipid profile and serum creatinine.

RESULTS

Our sample's mean age was 35.48 years and ranged from 20 to 60 years. The means of: cfPWV, SBP, DBP, Pulse Pressure (PP) and Heart Rate (HR) showed a statistically significant increase (p-value < 0.05) across the groups from normotensive to severely hypertensive patients. cfPWV was significantly correlated (p-value< 0.05) to: Age, Central SBP, Central DBP, Central PP, HR, BMI and central Augmentation index (AIx). Furthermore, cfPWV was significantly dependent on LVH (p-value <0.05).

CONCLUSION

This study suggests that arterial compliance decreases with increase severity of hypertension, indicating a higher risk of developing cardiovascular events in severely hypertensive patients.

Cardiorespiratory interactions: Noncontact assessment using laser Doppler vibrometry

The application of a noncontact physiological recording technique, based on the method of laser Doppler vibrometry (LDV), is described. The effectiveness of the LDV method as a physiological recording modality lies in the ability to detect very small movements of the skin, associated with internal mechanophysiological activities. The method is validated for a range of cardiovascular variables, extracted from the contour of the carotid pulse waveform as a function of phase of the respiration cycle. Data were obtained from 32 young healthy participants, while resting and breathing spontaneously. Individual beats were assigned to four segments, corresponding with inspiration and expiration peaks and transitional periods. Measures relating to cardiac and vascular dynamics are shown to agree with the pattern of effects seen in the substantial body of literature based on human and animal experiments, and with selected signals recorded simultaneously with conventional sensors. These effects include changes in heart rate, systolic time intervals, and stroke volume. There was also some evidence for vascular adjustments over the respiration cycle. The effectiveness of custom algorithmic approaches for extracting the key signal features was confirmed. The advantages of the LDV method are discussed in terms of the metrological properties and utility in psychophysiological research. Although used here within a suite of conventional sensors and electrodes, the LDV method can be used on a stand-alone, noncontact basis, with no requirement for skin preparation, and can be used in harsh environments including the MR scanner.

Ambulatory blood pressure variability is associated with restenosis after percutaneous coronary intervention in normotensive patients

BACKGROUND

Previous studies have showed that BP variability is associated with cardiovascular events. However, no data were available regarding binary restenosis as an end-point after percutenous coronary intervention (PCI).

METHODS AND RESULTS

This multicenter study included 100 consecutive normotensive patients with stable coronary artery disease who were planned for PCI. Before the index procedure, office BP and 24-h ambulatory BP measurements were performed. BP variability indices including systolic and diastolic 24-h average, the day and the night values of standard deviation (SD) and variation coefficient (VC) were measured and calculated. All patients underwent repeat coronary angiography at 6-month. According to angiographic results, 2 groups were formed; a restenosis group (n=30) with binary restenosis of the stented segment and a control group (n=70) with a stenosis diameter of <50% in stented segment. Systolic SD and VC values for 24-h average (14.0±2.8mmHg vs. 9.5±1.6mmHg, p<0.001 and 16%±3 vs. 11%±2, p<0.001, respectively), the day (15.2±3.9mmHg vs. 10.6±1.7mmHg, p<0.001 and 17%±4 vs. 12%±2, p<0.001, respectively), and the night (12.8±4.1mmHg vs. 8.4±2.4mmHg, p<0.001 and 14%±5 vs. 11%±3, p=0.004, respectively) values were significantly higher in restenosis group compared to control group. Similarly, diastolic SD and VC values for 24-h average (10.6±2.5mmHg vs. 8.1±1.5mmHg, p<0.001 and 12%±3 vs. 9%±2, p=0.001, respectively), the day (11.1±2.9mmHg vs. 9.0±1.8mmHg, p=0.003 and 12%±3 vs. 10%±2, p=0.006, respectively), and the night (10.0±3.6mmHg vs. 7.2±2.0mmHg, p=0.001 and 11%±5 vs. 9%±3, p=0.059, respectively) values were significantly higher in restenosis group compared to no restenosis group except for diastolic VC night. All systolic and diastolic BP variability indices except diastolic VC night were found to be independent predictors of risk of restenosis in multivariate analysis. In addition, the cut-off values of 11.4mmHg and 13% for 24-h systolic SD and VC, respectively, were found to be highly sensitive (93% for both) and specific (94% and 91%, respectively) for predicting binary restenosis at 6-month after PCI.

CONCLUSIONS

BP variability indices are significantly and independently associated with binary restenosis and higher values can predict restenosis after PCI sensitively and specifically.

Stiffness of the large arteries in individuals with and without Down syndrome

BACKGROUND

Down syndrome is known to cause premature aging in several organ systems. However, it remains unclear whether this aging effect also affects the structure and function of the large arterial trunks. In this controlled study, the possibility of changes in the large arteries due to aging was evaluated in patients with Down syndrome.

METHODS

Eighty-two subjects of both genders were selected. The Down syndrome group had 41 active subjects consisting of 19 males and 22 females (mean age 21 ± 1, range 13-42 years) without cardiovascular complications and who did not use vasoactive drugs. The control group consisted of 41 healthy individuals without trisomy 21 of the same gender and age as the Down syndrome group and who did not use vasoactive medication. Carotid-femoral pulse wave velocity was obtained as an index of aortic stiffness using an automatic noninvasive method.

RESULTS

Individuals with Down syndrome had significantly lower blood pressure than those in the control group. Systolic blood pressure for the Down syndrome group and control group was 106 ± 2 mmHg vs 117 ± 2 mmHg (P < 0.001), respectively; diastolic blood pressure was 66 ± 2 mmHg vs 77 ± 2 mmHg (P < 0.001); and mean arterial pressure was 80 ± 1 mmHg vs 90 ± 1 mmHg (P < 0.001). Only age and systolic blood pressure were shown to correlate significantly with pulse wave velocity, but the slopes of the linear regression curves of these two variables showed no significant difference between the two study groups. Pulse wave velocity, which was initially significantly lower in the Down syndrome group (7.51 ± 0.14 m/s vs 7.84 ± 0.12 m/s; P <0.05), was similar between the groups after systolic blood pressure adjustment (7.62 ± 0.13 m/s vs 7.73 ± 0.13 m/s).

CONCLUSION

Despite evidence in the literature that patients with Down syndrome undergo early aging, this process does not seem to affect the large arterial trunks, given that values of carotid-femoral pulse wave velocity were similar in individuals with or without trisomy 21. Considering that Down syndrome presents with chronic hypotension, it is reasonable to propose that the prolonged reduction of arterial distending pressure may contribute to functional preservation of the arteries in patients with Down syndrome.

Distension of the Carotid Artery and Risk of Coronary Events

Objective— Arterial mechanical properties are of growing interest in the understanding of cardiovascular disease development. We aimed to determine the predictive value of carotid wall mechanics on coronary heart disease (CHD) in the Three-City study.

Methods and Results— At baseline, 3337 participants aged ≥65 years underwent a carotid B-mode ultrasonography. During a median follow-up of 43.4 months, 128 CHD occurred. Increased carotid distension (relative stroke change in lumen diameter) was significantly associated with CHD risk. Comparison of subjects in tertile 3 versus those in tertile 1 (reference) showed a hazard ratio (HR) of 1.80 (95% CI, 1.17 to 2.75). Controlling for various confounders including age, heart rate, brachial (or carotid) pulse pressure, and common carotid intima-media thickness did not alter the association between carotid distension and CHD with a HR of 1.79 (95% CI, 1.12 to 2.86; tertile 3 versus tertile 1). Brachial and carotid pulse pressures were also independently associated with CHD. No association was found between CHD and carotid distensibility coefficient, cross-sectional compliance coefficient, Young’s elastic modulus, or β stiffness index.

Conclusions— In the elderly, increased carotid distension was independently predictive of CHD. This simple and noninvasive parameter might be of particular interest for cardiovascular risk assessment.

Aortic stiffness and pulse pressure amplification in Wistar-Kyoto and spontaneously hypertensive rats

In humans, increased body weight and arterial stiffness are significantly associated, independently of blood pressure (BP) level. The finding was never investigated in rodents devoid of metabolic disorders as spontaneously hypertensive rats (SHR). Using simultaneous catheterization of proximal and distal aorta, we measured body weight, intra-arterial BP, heart rate and their variability (spectral analysis), aortic pulse wave velocity (PWV), and systolic and pulse pressure (PP) amplifications in unrestrained conscious Wistar-Kyoto (WKY) rats and SHR between 6 and 24 wk of age. Aortic proximal systolic and diastolic pressure, PP, and mean BP were significantly higher in SHR than in WKY rats and increased significantly with age (with the exception of PP). PP amplification increased with age but did not differ between strains. PWV was significantly associated with heart rate variability. PWV was significantly higher (via two-way variance analysis) in SHR than in WKY rats (strain effect) and increased markedly with age in both strains (age effect). Adjustment of PWV to mean BP attenuated markedly both the age and the strain effects. After adjustment for body weight, either alone or associated with mean BP, the age effect was not more significant, but the strain effect was markedly enhanced. In conscious unanesthetized SHR and WKY rats, aortic stiffness is consistently associated with body weight independent of age and mean BP. An intervention study should consider in the objectives systolic BP and PP amplifications measured in conscious animals, central control of body weight, and autonomic nervous system.

Is cardiovascular remodeling in patients with essential hypertension related to more than high blood pressure? A LIFE substudy. Losartan Intervention For Endpoint-Reduction in Hypertension

BACKGROUND

Blocking the renin-aldosterone-angiotensin II system has been hypothesized to induce blood pressure-dependent as well as blood pressure-independent regression of cardiovascular hypertrophy. However, the relative influence of elevated blood pressure (BP) and various neurohormonal factors on cardiovascular remodeling in hypertension is unclear.

METHODS

In 43 untreated patients with hypertension with electrocardiographic left ventricular hypertrophy, we measured relative wall thickness and left ventricular mass index by echocardiography and by magnetic resonance imaging (n = 32), intima-media cross-sectional area, and distensibility of the common carotid arteries by ultrasound, media/lumen ratio of isolated subcutaneous resistance arteries by myography, and median 24-hour systolic BP (n = 40), serum insulin, and plasma levels of epinephrine, norepinephrine, renin, angiotensin II, aldosterone, and endothelin.

RESULTS

In multiple regression analyses, left ventricular mass index by echocardiography (R2 = 0.14, P <.05) and by magnetic resonance imaging (R2 = 0.32, P =.001) were associated with 24-hour systolic BP, whereas relative wall thickness was associated with plasma epinephrine (R2 = 0.12, P <.05) and aldosterone (R2 = 0.10, P <.05). Intima-media cross-sectional area/height was associated with 24-hour systolic BP (beta = 0.40) and plasma epinephrine (beta = 0.43) (adjusted R2 = 0.32, P <.001), whereas carotid distensibility was associated with 24-hour systolic BP (beta = 0.40) and plasma angiotensin II (beta = -0.41) (adjusted R2 = 0.30, P <.001). Media/lumen ratio in subcutaneous resistance arteries was associated with plasma epinephrine (R2 = 0.22, P <.01).

CONCLUSION

Apart from being associated with a high BP burden, cardiovascular remodeling was associated with high levels of circulating epinephrine, aldosterone, as well as angiotensin II, suggesting a beneficial effect above and beyond the effect of BP reduction when using antihypertensive agents blocking the receptors of these neurohormonal factors.

Aortic pulse wave velocity: an independent marker of cardiovascular risk

Aortic pulse wave velocity, a classic index of aortic stiffness, may be easily measured in humans using noninvasive ultrasound methods of high reproducibility. Recent epidemiologic studies have shown that, independently of confounding factors such as age, blood pressure and cardiac mass, aortic pulse wave velocity is a predictor of cardiovascular mortality in populations of hypertensive subjects, whether they have end-stage renal disease or not. Since aortic pulse wave velocity is dominantly influenced by age, this finding may be of major importance for the evaluation of cardiovascular risk in geriatric populations.

Assessment of outcomes other than systolic and diastolic blood pressure: pulse pressure, arterial stiffness and heart rate

In recent years, studies have shown that parameters derived from the arterial pressure wave other than systolic and diastolic blood pressure provide important information on cardiovascular status. Among these parameters, pulse pressure, arterial stiffness and heart rate have emerged as independent markers of cardiovascular risk in different populations. Although a number of studies have used casual measurements of these parameters in a clinic setting, others have focused on their assessment under ambulatory conditions. The pulse pressure represents the amplitude of the pressure wave signal (systolic minus diastolic blood pressure), higher pulse pressure values having been reported in patients possessing cardiovascular risk factors. Close associations between a high pulse pressure and several surrogate end-points have been described. Furthermore, epidemiological studies have shown that a high pulse pressure is an independent predictor of hard end-points in several populations. Arterial stiffness represents one of the major haemodynamic factors determining pulse pressure. Pulse wave velocity, measured from the initial upstroke of the pressure wave, constitutes an established index of arterial stiffness. Studies have reported stiffer arteries in patients with cardiovascular pathology even at an early stage of disease. Close correlations between arterial stiffness and several surrogate markers have been reported, and arterial stiffness and its changes have recently been shown to be an independent predictor of hard end-points in patients with a high cardiovascular risk. Methods to evaluate arterial stiffness under ambulatory conditions are emerging. Heart rate represents the frequency of the cyclical strain of the arterial wall, clinical studies having shown that ambulatory heart rate is correlated to several surrogate markers. A few epidemiological studies have analysed the value of ambulatory heart rate as an independent predictor of hard end-points, but their positive findings need to be confirmed. The analysis of the pressure wave thus allows the determination of several haemodynamic indices other than systolic and diastolic blood pressure. Pulse pressure, arterial stiffness and heart rate constitute other outcomes that may be useful as additional factors in risk assessment for future therapeutic decision-making.

Relation of blood pressure variability to carotid atherosclerosis and carotid artery and left ventricular hypertrophy

The relationship of blood pressure (BP) variability to cardiovascular target-organ damage is controversial. Studies examining BP variability and left ventricular (LV) hypertrophy have been contradictory, and only limited data on the relation of BP variability to carotid atherosclerosis and carotid artery hypertrophy exist. BP variability was assessed as the standard deviation and coefficient of variation of awake and asleep pressures in 511 normotensive or untreated hypertensive subjects who underwent ambulatory BP monitoring and cardiac and carotid ultrasonography. Although the presence of focal carotid plaque was associated with an increase in ambulatory pressures and pressure variability, the differences in variability were eliminated by adjustment for age and absolute pressures. Similarly, LV mass was significantly related to BP variability, but the significance of this finding was eliminated after adjustment for important covariates. In multivariate analyses, age was the primary determinant of carotid artery cross-sectional area, with a weak but independent contribution from awake systolic and diastolic BP variability in addition to absolute pressure. BP variability was not independently related to either carotid or LV relative wall thickness, both measures of concentric remodeling. In the present study, awake BP variability was weakly but independently associated with carotid artery cross-sectional area, a measure of arterial hypertrophy. However, neither systolic nor diastolic BP variability was independently associated with carotid atherosclerotic plaque or LV mass.

[Nephropathy, nycthemeral variability and pulse pressure in patients with type 2 diabetes mellitus]

BACKGROUND

The loss of the blood pressure nictemeral rhythm and the elevated pulse pressure are considered independent cardiovascular risk factors that can be related with the microvascular damage of patients with type 2 diabetes mellitus.

PATIENTS AND METHOD

We carried out an observational, tranverse study, of a population of patients with type 2 diabetes mellitus. The variables are calculated by means of 24 hour ambulatory registry of blood pressure. The results are compared with the diverse degrees ofnephropathy.

RESULTS

A total of 61 patients is studied; 31 have a behavior "non dipper". The "non dipper" proportion increased with the urinary albumin excretion (p = 0.024). The pulse pressure was higher inpatients with macroalbuminuria (p = 0.004).

CONCLUSIONS

Theresults demonstrate a more frequent loss of the nictemeral rhythm and higher pulse pressure among the patients with type 2 diabetes mellitus and nephropathy.

[Factors associated with arterial distensibility in hypertension]

OBJECTIVE

To find out what variables affect changes in arterial compliance in subjects with hypertension by measuring their pulse wave velocity (PWV).

DESIGN

Cross-sectional, descriptive study.

SETTING

Rural health centre.

PATIENTS

156 hypertense patients under 76, chosen by simple random sampling from those on the hypertension register.

MEASUREMENTS AND INTERVENTIONS

We determined the degree of hypertension, years of evolution, systolic pressure (SBP), diastolic pressure (DBP), body mass index (BMI), glucaemia, whether lipaemia existed, diabetes or glucose intolerance, tobacco habit, age, sex and PWV (measured automatically by computer). We performed multivariate analysis by means of multiple linear regression, with PWV as the dependent variable, and age, SBP, DBP, BMI, years of evolution of hypertension, cholesterol, triglycerides and glucaemia as independent variables.

RESULTS

Mean age 62.5 (SD 8.8). 28.2% male. Mean SBP 153 (SD 18.9). Mean DBP 87 (SD 10.3). Mean years of evolution 10.4 (SD 7.4). Mean BMI 31.2 (SD 4.9). Hyperglucaemia 24.4%. Mean glucaemia 111.3 (SD 29). Mean PWV 11.82 (SD 2.37). PWV was above the theoretically normal figures in 69.2% of cases. Multiple linear regression showed that the variables which affected PWV significantly were age, SBP and hyperglucaemia.

CONCLUSIONS

Arterial compliance can be improved by controlling SBP, given that the other related factors cannot be changed.

Static versus dynamic distensibility of the carotid artery in humans

In clinical studies, the elastic behavior of central arteries is usually assessed by measuring dynamic distensibility. In this study, we aimed to investigate how dynamic and static distensibility of the common carotid artery (D(dyn) and D(stat), respectively) are related in 28 healthy volunteers of 20-71 years. The carotid diameter and its change with the pressure pulse were measured using an ultrasound echo-tracking device. Arterial blood pressure was measured by Finapres and carotid pressure was determined by applanation tonometry. D(dyn) was determined at rest using the pressure pulse, while D(stat) was determined during pressor responses induced by handgrip or cold pressor test. Data are given as mean +/- 1 SD. In younger subjects (<35 years), D(stat) did not differ from D(dyn) (7.0 +/- 3.4 vs. 6.5 +/- 2.1 x 10(-3) x mm Hg(-1), respectively), whereas in older subjects (>35 years), D(stat) was significantly higher than D(dyn) (3.8 +/- 1.4 vs. 2.1 +/- 0.9 x 10(-3) x mm Hg(-1), p < 0.001). For all subjects, D(stat) and D(dyn) decreased with increasing age and mean arterial pressure (MAP). Using stepwise multiple regression analysis, the strongest predictor of D(stat) proved to be MAP, while that of D(dyn) was age. D(stat) was found to be linearly related to the hysteresis loop area of the pressure-diameter relation (r = 0. 94), i.e. to vessel wall viscosity. It is concluded that, with increasing age, static distensibility overestimates the distension capacity of large arteries.

Relative influence of insulin resistance versus blood pressure on vascular changes in longstanding hypertension. ICARUS, a LIFE sub study. Insulin Carotids US Scandinavia

BACKGROUND

Insulin resistance is associated with hypertension. The relative influences of hyperinsulinaemia and high blood pressure on vascular hypertrophy and carotid distensibility is unclear in patients with longstanding hypertension.

METHODS

In 88 unmedicated patients with stage II-III hypertension and left ventricular hypertrophy on electrocardiogram we measured blood pressure, minimal forearm vascular resistance (MFVR) using plethysmography, intima-media thickness (IMT) and the wall distensibility of the common carotid arteries using ultrasound, and insulin sensitivity using a 2-h isoglycaemic hyperinsulinaemic clamp.

RESULTS

IMT was positively correlated to systolic blood pressure (r= 0.26, P < 0.05), whole body glucose uptake index (M/IG; r= 0.22, P< 0.05), age (r= 0.24, P< 0.05) and negatively correlated to body mass index (r= -0.24, P < 0.05); IMT did not correlate to fasting serum insulin (r= -0.14, NS). In men (n = 64) MFVR was positively correlated to systolic blood pressure (r = 0.30, P < 0.05), but was unrelated to M/G and serum insulin. The distensibility of the common carotid arteries was negatively correlated to systolic blood pressure (r = -0.40, P< 0.001) and in untreated patients (n = 22) positively correlated to M/IG (r = 0.47, P < 0.05).

CONCLUSIONS

High systolic blood pressure was related to vascular hypertrophy, whereas hyperinsulinaemia and insulin resistance were not, suggesting that longstanding high blood pressure is a far more important determinant for structural vascular changes than insulin resistance at this stage of the hypertensive disease. However, hyperinsulinaemia and insulin resistance were associated with low distensibility of the common carotid arteries in the subgroup of never treated hypertensive patients.

Racial differences in aortic stiffness in normotensive and hypertensive adults

OBJECTIVE

To investigate whether differences exist in the mechanical properties of large arteries between white and black subjects.

DESIGN

Eighty-two white (49 normotensive and 33 untreated hypertensive) and 38 black (24 normotensive and 14 untreated hypertensive) adult male volunteers were studied in a cross-sectional study.

METHODS

Carotid-femoral pulse wave velocity was measured as an index of arterial stiffness, using a recently developed non-invasive automatic device, and compared between white and black subjects before and after the adjustment for age. The slope of regressions for pulse wave velocity and systolic blood pressure were also compared between racial groups.

RESULTS

In the normotensive group, white subjects presented higher mean values of pulse wave velocity than blacks while the opposite behavior was found in the hypertensive group. After adjustment for age, significant differences in pulse wave velocity between whites and blacks became evident in the normotensive (whites 8.15 +/- 0.04 versus blacks 7.75 +/- 0.02 m/s; P < 0.001) and hypertensive (whites 8.88 +/- 0.02 versus blacks 9.30 +/- 0.17 m/s; P < 0.001) groups. Linear regression analysis for age-adjusted pulse wave velocity and systolic blood pressure showed that the slope was significantly greater in blacks than in whites (0.040 +/- 0.002 versus 0.019 +/- 0.001 m/s; P < 0.001).

CONCLUSION

These data indicate that there is a greater pressure-dependent increase in aortic stiffness in blacks than in whites. This finding points towards major differences in mechanical properties of large arteries between these racial groups.

Arterial mechanics predict cardiovascular risk in hypertension

Systolic and diastolic blood pressures are the exclusive mechanical factors considered as predictors of cardiovascular risk for members of populations of normotensive and hypertensive subjects. However, if hypertension is considered as a mechanical factor acting on the arterial wall with deleterious consequences, the totality of the blood pressure curve should be considered in order to investigate the risk. The purpose of this review is to show that in addition to systolic and diastolic blood pressures, other hemodynamic indexes with particular relevance for cardiac complications and that originate from pulsatile pressure should be taken into account, namely brachial pulse pressure, pulse pressure amplification, early wave reflections, and pulse wave velocity.

Age-related differences of blood pressure profile in essential hypertension

The purpose was to assess age-related circadian changes of blood pressure profile (BPP) employing a truncated Fourier series with four harmonics (tFs) in patients with essential hypertension. The study was performed on 32 patients with essential hypertension divided in two groups: (A) 15 patients younger than 55 years and (B) 17 patients older than 60 years. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were monitored every 20 minutes for 24 h with a noninvasive portable device (SpaceLabs 90202). To evaluate the existence of SBP and DBP circadian rhythms a one-sample runs-test was performed and the mesor, amplitude, and acrophase from the overall curve of each patient were obtained by tFs. In both groups, SBP and DBP profiles showed a first peak in the late morning and a second peak in the early evening around the same hours. The two peaks in the SBP profile were higher and the two peaks in the DBP profile were lower in older patients than in younger ones (p < .01, p < .05, p < .3, p < .05). The truncated Fourier series with four harmonics evidences different age-related BP profiles characterized by two peaks with higher SBP and lower DBP in elderly patients. These changes of BPP are in accordance with the reported higher risk of cardiovascular events observed around the same hours.

Effects of short-term administration of sublingual nifedipine on coronary arterial wall elastic properties: evaluation by intravascular ultrasound

Intravascular ultrasound is suited to measure coronary cross-sectional anatomy. Therefore the regional coronary wall elasticity was evaluated by examining the response to nifedipine. In 20 patients, coronary ostial pressure (P) and intravascular ultrasound images were simultaneously recorded before and after sublingual administration of 10 mg nifedipine. We identified the perimeter of the vessel wall, with normal or atherosclerotic plaque, on ultrasound image. At the atherosclerotic site, we measured segmental perimeter (S) for each normal or plaque segment. The ratio of the individual segment length (delta S/delta P) and cyclic variation of cross-sectional area (delta A/delta P) per mm Hg increase in P were calculated. Nifedipine decreased pressure (133/79-120/73 mm Hg) and increased heart rate (79-82 beats/min). After nifedipine, delta A/delta P increased from 8.5 +/- 10.2 x 10(-3) to 16.5 +/- 14.4 x 10(-3) mm2/mm Hg at 20 normal sites (p = 0.005) but was unchanged at 17 atherosclerotic sites (6.6 +/- 7.0 x 10(-3) to 6.7 +/- 7.1 x 10(-3) mm2/mm Hg). Nifedipine increased delta S/delta P in normal segments (4.5 +/- 8.7 x 10(-3) to 9.9 +/- 10.9 x 10(-3) mm/mm Hg; p = 0.02) but produced no change in segments with calcified or soft plaque (-1.1 +/- 0.3 x 10(-3) to 1.4 +/- 1.6 x 10(-3) mm/mm Hg and 5.0 +/- 3.6 x 10(-3) to 6.1 +/- 4.8 x 10(-3) mm/mm Hg, respectively). This study demonstrated that nifedipine increases regional coronary arterial elasticity at normal segments but not at that containing mildly atherosclerotic segment, and likely that the arterial wall function indicated by the response to nifedipine was impaired at an early stage of atherosclerosis.

Assessment of antihypertensive treatment by ambulatory blood pressure

ADVANTAGES OF AMBULATORY BLOOD PRESSURE MONITORING: Ambulatory blood pressure monitoring is now used widely to assess the efficacy of antihypertensive drugs in daily life conditions. These 24-h measurements have a number of advantages compared to conventional sphygmomanometric readings. Although a small placebo effect is observed in the first few hours after placebo administration, 24-h average blood pressure is substantially devoid of any placebo effect. Moreover, ambulatory blood pressure is not affected by the alerting reaction usually observed during the doctor's visit. When the 24-h average value is considered, ambulatory blood pressure is more reproducible than clinic blood pressure. Finally, ambulatory blood pressure is prognostically more important than clinic blood pressure, since the end-organ damage associated with hypertension is more closely related to 24-h than to clinic blood pressure. Ambulatory blood pressure monitoring is therefore particularly useful when testing the efficacy of new antihypertensive agents on 24-h blood pressure. TESTING THE COMBINATION OF VERAPAMIL AND TRANDOLAPRIL: In a recent study we evaluated the efficacy of a fixed combination of verapamil and trandolapril using both clinic and ambulatory blood pressure measurements. Ambulatory blood pressure monitoring showed that the effect of the combination of verapamil and trandolapril was greater than the effect of either of the two drugs administered alone. However, the clinic blood pressure measurements failed to show any systemically greater effect with the combination versus monotherapy. This further indicates that ambulatory blood pressure is superior to conventional blood pressure in the assessment of antihypertensive drugs.

Non-invasive evaluation of arterial abnormalities in hypertensive patients

ARTERIAL ABNORMALITIES IN HYPERTENSION: Morbidity and mortality in hypertension are mainly determined by arterial lesions which may occur in different regional circulations (e.g. kidney, cerebral, coronary circulations, causing nephro-angiosclerosis, stroke or myocardial infarction, respectively). Despite arterial heterogeneity, structural and functional abnormalities are usually observed at an early stage of hypertension in both large and small arteries. These alterations modify physiological and mechanical properties of the arterial wall, which may become clinically evident by increasing arterial pulsatility or pulse pressure; the alterations facilitate the establishment and progression of atherosclerosis and arteriosclerosis.

METHODS OF ASSESSING ARTERIAL ABNORMALITIES

Several non-invasive techniques can be used to assess haemodynamic properties of arteries: (1) casual and ambulatory blood pressure measurements can be used to evaluate pulse pressure; (2) pulse pressure can be measured directly in different sites of the arterial tree using the Tonometer device; (3) ultrasound techniques can be applied, including Doppler signals to assess the arterial flow, video-echo signals to analyse the arterial structure such as the intimal-medial thickness and echo-tracking systems for direct measurements of arterial wall distension and thickness; (4) pulse wave velocity is widely used as index of arterial distensibility; this parameter, assessed by the Complior device, has shown that hypertensive patients have decreased arterial distensibility and that antihypertensive treatment does not always reverse this abnormality.

TREATMENT

It is important to evaluate the effect of cardiovascular risk-reduction measures on the arterial wall. Large therapeutic trials are necessary to show whether an evaluation of arterial abnormalities can identify patients with a high cardiovascular risk and contribute to their treatment and prognostic improvement.