Effects of angiotensin-converting enzyme inhibition versus beta-adrenergic blockade on aortic stiffness in essential hypertension

Impact of antihypertensive agents on arterial stiffness in hypertensive patients

AIMS

The present network meta-analysis was performed to comprehensively compare the ability of different types of antihypertensive agents to ameliorate arterial stiffness in hypertensive patients.

METHODS AND RESULTS

To conduct this network meta-analysis, we searched PubMed, the Embase database, and the https://clinicaltrials.gov/ website for all relevant articles concerning clinical trials on hypertension therapy. The last search date was 10 August 2017. As a result, 28 eligible articles were enrolled in our meta-analysis. According to the included studies, there was no significant difference in pulse wave velocity (PWV) between these treatments. The eight types of antihypertension agents outperformed placebo in controlling systolic blood pressure (SBP). Angiotensin-converting enzyme inhibitor (ACEI) outperformed angiotensin II receptor blocker (ARB) in SBP; and angiotensin receptor-neprilysin inhibitor (ARNI) outperformed diuretic (D)in SBP.

CONCLUSIONS

This study found that the eight antihypertensive agents show obvious effect on reducing SBP other than arterial stiffness.

A meta-analytical comparison of atenolol with angiotensin-converting enzyme inhibitors on arterial stiffness, peripheral blood pressure and heart rate in hypertensive patients

OBJECTIVES

This meta-analysis of randomized parallel controlled trials was designed to compare the efficacy of atenolol with angiotensin-converting enzyme inhibitors (ACEIs) in changing pulse wave velocity (PWV), peripheral blood pressure and heart rate (HR) among patients with essential hypertension.

METHODS

This study was conducted according to the PRISMA guideline. Data collection was independently completed by two investigators. Statistical analyses were completed by Stata software (v12.0).

RESULTS

Eight clinical trials were meta-analyzed in this study. Overall changes in PWV (weighted mean difference or WMD = 0.068, 95% confidence interval or CI: -0.487 to -0.623, P = 0.811) and peripheral systolic blood pressure (PSBP) (WMD = -1.281 mmHg, 95% CI: -6.936 to 4.375, P = 0.657) did not differ significantly between atenolol and ACEIs treatment. Relative to ACEIs, atenolol had a more favorable impact on peripheral diastolic blood pressure (PDBP) (WMD = -1.912 mmHg, 95% CI: -3.732 to -0.091, P = 0.040) and HR (WMD = -9.23 bpm, 95% CI: -12.53 to -5.93, P < 0.001). In stratified analyses, particularly by follow-up period, atenolol was observed to be superior over ACEIs within early 3-month treatment in PSBP (WMD = -4.097 mmHg, 95% CI: -6.589 to -1.605, P = 0.001), PDBP (WMD = -6.802 mmHg, 95% CI: -8.517 to -5.087, P < 0.001) and HR (WMD = -14.242 bpm, 95% CI: -16.427 to -12.058, P = 0.028), without heterogeneity (I² = 0.0%). There were low probabilities of publication bias for all comparisons.

CONCLUSIONS

Our findings demonstrate that atenolol and ACEIs were equally effective in reducing PWV and PSBP, while atenolol was superior over ACEIs in improving PDBP and HR, especially within short-term treatment.

Antihypertensive drugs and arterial stiffness

Arterial stiffness is recognized as an important determinant of outcome in the hypertensive population. Although pulse pressure is an indirect index more recently relatively simple non-invasive techniques to measure pulse wave velocity, particularly in the aorta and arterial wave analysis have been developed and applied to clinical trials. There are clear differences in the effects of antihypertensive drugs on these parameters and stiffness is becoming a therapeutic target in its own right.

Association of beta-blocker use with increased aortic wave reflection

Studies have found less cardiovascular risk reduction in patients treated with beta-blockers (BBs) compared with other agents. We compared the severity of aortic atherosclerosis, arterial stiffness, and wave reflection in patients treated and not treated with BBs. Seventy-two patients, 37 treated with BBs and 35 not treated, referred for transesophageal echocardiography were studied. Augmentation index (AI), heart-rate-corrected AI (AI-75), aortic systolic (SBP) and diastolic blood pressure, pulse wave velocity (PWV), and aortic intima-media thickness (MAIMT) were measured. There were no differences in MAIMT (2.8 +/- 1.6 mm vs. 2.4 +/- 1.2 mm, P = .20) and PWV (8.9 +/- 2.0 m/s vs. 8.5 +/- 2.6 m/s, P = .46) between the BB and non-BB groups. The BB group had higher AI (28.7 +/-11.9% vs. 22.3 +/- 14.1%, P = .04), AI-75 (27.7 +/- 10.7% vs. 20.1+/- 11.0%, P = .005), aortic SBP (140 +/- 21 mm Hg vs. 125 +/- 21 mm Hg, P = .01), and aortic pulse pressure (62 +/- 20 mm Hg vs. 47 +/- 19 mm Hg, P = .01) than the non-BB group despite similar brachial blood pressure. BB use was associated with increased aortic wave reflection despite similar degree of aortic atherosclerosis.

IN VIVOEVALUATION OF THE HUMAN CAROTID ARTERY COMPLEX ELASTIC MODULUS

The arterial wall dynamics evaluation requires the assessment of its frequency-response. The aim was to apply an original methodology, to evaluate the arterial wall pressure-diameter frequency-response and elastic complex modulus, of human in vivo and in vitro common carotid arteries (CCA). CCA pressure, diameter and wall thickness were recorded. In vitro recordings were performed using pressure microtransducer (Konigsberg) and sonomicrometry, in 14 CCA segments (from donors). The in vivo recordings were obtained non-invasively by tonometry and mode-B echography in 10 normotensive patients, and in 10 hypertensive patients before and after 3 months of treatment with an ACE-inhibitor. A system modeling-identification approach was used to estimate the viscoelastic parameters: elastic, viscous and inertial indexes, and to perform an isofrequency analysis (up to 5Hz) of the incremental elastic modulus Einc(jω) of the arterial wall. The new approach, proposed to evaluate the frequency-dependence of arterial wall mechanics, was applied satisfactorily.

Effect of beta blockers on central aortic pressure in African-Americans

The objective of this study was to evaluate the vascular effects of heart rate (HR) reduction with BB therapy in African Americans (AA). Beta-blockers (BB) offer less cardiovascular protection than other hypertensive drugs. Studies of Caucasian subjects suggest this may be due to an adverse effect of HR lowering on arterial wave reflection. We studied 506 subjects (age 63 ± 14 years, 52% were treated with BB). Central systolic (C-SBP) and pulse pressure (C-PP), augmented pressure (AP), and augmentation index (AI) were obtained via applanation tonometry (Sphygmocor). On univariate analysis, HR correlated inversely with BB use, C-SBP, AP, and AI (all P < .001), but not P-SBP. Multivariate analysis showed P-SBP and HR to be major determinants of C-SBP (R(2) = 0.95). Generalized linear model analysis showed higher C-SBP (P < .05) and C-PP (P = .04), but similar P-SBP (P = .24) in the BB group. After HR adjustment, differences in C-SBP, C-PP, AI, and AP were attenuated, suggesting HR to be a determinant of C-SBP. BB use is associated with higher C-SBP and lower PPA in hypertensive AA despite similar P-SBP. C-SBP is HR-dependent. HR reduction with BB accounts for less effective central blood pressure control in AA, similar to that reported in Caucasians.

The comparative effects of metoprolol and perindopril on aortic elasticity in young patients with prehypertension

OBJECTIVES

It has been recently demonstrated that aortic elasticity is impaired in young patients with prehypertension compared with healthy controls. Accordingly, the purpose of the current study was to analyze the comparative effects of metoprolol and perindopril on aortic elasticity in young patients with prehypertension after 6 months of therapy.

MATERIAL AND METHODS

Fifty newly diagnosed patients with hypertension, who were in the prehypertension category according to the Joint National Committee seventh report, were enrolled in this blind, randomized, prospective study. After baseline clinical assessment, patients were randomly assigned to 4 mg daily dose of perindopril (group I, n=27, 18 male, median age=35 years) or 100 mg daily dose of metoprolol succinate (group II, n=28, 16 male, median age=33 years) for 6 months. Aortic strain, distensibility, and stiffness indexes were calculated from aortic diameters measured by echocardiography and blood pressures simultaneously measured by sphygmomanometry before and after treatment.

RESULTS

When the median aortic distensibility and strain indexes after 6 months of therapy were analyzed, aortic distensibility and strain indexes of both treatment arms were found to be significantly higher than those of the pretreatment period. In contrast, the posttreatment aortic stiffness indexes of both groups were significantly lower compared with those of pretreatment period. No statistical difference was found between pretreatment and posttreatment aortic elasticity parameters of both groups. Importantly, no statistically significant difference was found between the percentage change from baseline of metoprolol and perindopril groups regarding aortic elasticity parameters (aortic distensibility: 38.1 vs. 37.9%, respectively, P=0.86; aortic strain: 37.7 vs. 37.9%, respectively, P=0.44; stiffness index: -20.0 vs. -23.9%).

CONCLUSION

The current study revealed that early pharmacological intervention had strong beneficial effects on aortic elasticity in patients with prehypertension despite the fact that neither metoprolol nor perindopril was superior to the other.

High aerobic capacity does not attenuate aortic stiffness in hypertensive subjects

BACKGROUND

It is unknown whether increased physical fitness reduces aortic stiffness in hypertensive individuals. The purpose of this cross-sectional study was to examine, in a cohort of community-dwelling subjects with no history of cardiac events, differences in the impact of aerobic capacity on aortic stiffness between normotensive and hypertensive subjects.

METHODS

The study sample included 275 subjects representing a large age range (21-85 years). Of these, 61 subjects (hypertensive cohort) were either hypertensive at enrollment or were taking antihypertensive medication. The remaining 214 subjects (normotensive cohort) had no history of hypertension. The study protocol included maximal cardiopulmonary exercise testing (determination of maximal oxygen consumption, or VO2max) and measurement of aortic wave velocity (AWV) using a novel magnetic resonance-based method.

RESULTS

Overall, the hypertensive cohort exhibited significantly elevated AWV in comparison to a subset of normotensives matched for age, sex, and aerobic fitness. Each cohort was then subdivided according to the percentage of predicted VO2max achieved (< 100% = "unfit," > or = 100% = "fit"). Differences between subgroups were assessed by unpaired t test. In the normotensive cohort, AWV was significantly lower in the fit versus the unfit subgroup. However, in the hypertensive cohort, AWV was not significantly different between fit and unfit subgroups nor between treated and untreated subgroups.

CONCLUSION

Unlike the situation in healthy normotensive subjects, higher peak aerobic capacity is not associated with lower aortic stiffness in hypertensive individuals.

Arterial stiffness: clinical relevance, measurement and treatment

Most traditional cardiovascular risk factors alter the structure and/or function of arteries. An assessment of arterial wall integrity could therefore allow accurate prediction of cardiovascular risk in individuals. The term 'arterial stiffness' denotes alterations in the mechanical properties of arteries, and much effort has focused on how best to measure this. Pulse pressure, pulse wave velocity, pulse waveform analysis, localized assessment of blood vessel mechanics and other methods have all been used. We review the methodology underlying each of these measures, and present an evidence-based critique of their relative merits and limitations. An overview is also given of the drug therapies that may prove useful in the treatment of patients with altered arterial mechanics.

Smart Damping Modulation of Carotid Wall Energetics in Human Hypertension

Damping is the conversion of mechanical energy of a structure into thermal energy, and it is related to the material viscous behavior. To evaluate the role of damping in the common carotid artery (CCA) wall in human hypertension and the possible improvement of angiotensin-converting enzyme (ACE) inhibition, we used noninvasive CCA pressure (tonometry) and diameter (B-mode echography) waveforms in normotensive subjects (NT group; n=12) and in hypertensive patients (HT group; n=22) single-blind randomized into HT–placebo (n=10) or HT-treated (ramipril, 5 to 10 mg/d during 3 months; n=12). Vascular smooth muscle (VSM) null tonus condition was achieved from in vitro pressure and diameter waveforms (Konigsberg microtransducer and sonomicrometry) measured in explanted human CCA (n=14). Arterial wall dynamics was described by viscous (η), inertial ( M ), and compliance ( C ) parameters, mean circumferential wall stress, viscous energy dissipation ( W D ), peak strain energy ( W St ), damping ratio (ξ= W D / W St ), and modeling isobaric indexes C Iso and W St(Iso) . The lack of VSM tonus isobarically increased wall stress and reduced η, C Iso , and damping ( P <0.01). Wall stress, η, and W D were greater in HT than in NT ( P <0.015) and arrived near normal in HT-treated ( P <0.032 respect to HT), with no changes in HT–placebo. Whereas C Iso increased in HT-treated ( P <0.01) approaching the NT level, ξ did not vary among groups. During hypertension, because of the W St increase, the arterial wall reacts increasing W D to maintain ξ. ACE inhibition modulates VSM activation and vessel wall remodeling, significantly improving wall energetics and wall stress. This protective vascular action reduces extra load to the heart and maintains enhanced arterial wall damping.

Nebivolol increases arterial distensibility in vivo

Arterial stiffness is a key determinant of cardiovascular risk in hypertensive patients. beta-Blockers appear to be less effective than other drugs in improving outcome in hypertensive patients, and a potential explanation may be that beta-blockers are less effective in reducing arterial stiffness. The aim of this study was to assess the direct effect of beta-blockade on pulse wave velocity (PWV), a robust measure of arterial distensibility, using a local, ovine, hind-limb model. In addition, we hypothesized that the vasodilating beta-blocker nebivolol, but not atenolol, would increase arterial distensibility in vivo. All studies were conducted in anesthetized sheep. PWV was recorded in vivo using a dual pressure-sensing catheter placed in the common iliac artery. Intraarterial infusion of nebivolol reduced PWV by 6+/-3% at the higher dose (P<0.001), but did not alter mean arterial pressure (change of -1+/-3 mm Hg, P=0.1). In contrast, atenolol had no effect on PWV (P=0.11) despite a small drop in mean pressure (change of -5+/-3 mm Hg, P<0.01). Infusion of glyceryl trinitrate led to a dose-dependent fall in PWV, and 2 nmol/min produced a similar reduction in PWV to the higher dose of nebivolol (500 nmol/min). The effect of nebivolol on PWV was significantly attenuated during coinfusion of N(G)-monomethyl-L-arginine (P=0.003) and also during coinfusion of butoxamine (P=0.02). These results demonstrate that nebivolol, but not atenolol, increases arterial distensibility. This effect of nebivolol is mediated through the release of NO via a beta2 adrenoceptor-dependent mechanism. Thus, nebivolol may be of benefit in conditions of increased large artery stiffness, such as isolated systolic hypertension.

Arterial stiffness and the systolic hypertension syndrome

PURPOSE OF REVIEW

This review is intended to provide the background for a new comprehensive hemodynamic view of the syndrome of systolic or wide pulse pressure hypertension and its hallmark abnormality: increased central arterial stiffness.

RECENT FINDINGS

Studies of the pathogenesis of systolic hypertension have lagged. This review describes the systolic hypertension syndrome as a complex set of hemodynamic maladaptations that include stiff central arteries, normal peripheral arteries with variable pressure amplification characteristics, arteriolar constriction, microcirculatory rarefaction, metabolic abnormalities, cardiac hypertrophy, and increased blood pressure variability. Because the structural and functional properties of arteries of different caliber are highly heterogeneous and vary with aging and disease, simple measurements such as standard brachial artery blood pressure, brachial pulse pressure, or mean arterial pressure are inadequate to provide meaningful insight into the pathophysiology of the syndrome. Additional parameters developed to describe changes in arterial mechanics (arterial compliance or stiffness, elastic modulus, impedance, pulse wave velocity, augmentation index, and pulse pressure amplification) are intrinsically limited and are directly or indirectly pressure-dependent. Quantitation of central arterial stiffness provides a modest increment in cardiovascular and renal risk stratification.

SUMMARY

Better clinical management of systolic hypertension depends on greater insight into the syndrome as a whole, more critical analysis of existing techniques, and the development of new approaches.

Noninvasive assessment of arterial stiffness and risk of atherosclerotic events

Investigation of arterial stiffness, especially of the large arteries, has gathered pace in recent years with the development of readily available noninvasive assessment techniques. These include the measurement of pulse wave velocity, the use of ultrasound to relate the change in diameter or area of an artery to distending pressure, and analysis of arterial waveforms obtained by applanation tonometry. Here, we describe each of these techniques and their limitations and discuss how the measured parameters relate to established cardiovascular risk factors and clinical outcome. We also consider which techniques might be most appropriate for wider clinical application. Finally, the effects of current and future cardiovascular drugs on arterial stiffness are also discussed, as is the relationship between arterial elasticity and endothelial function.

Serum hepatocyte growth factor concentration is correlated with the forearm vasodilator response in hypertensive patients

To evaluate the clinical importance of serum hepatocyte growth factor (HGF) concentration, we designed two clinical investigations. The first study analyzed the correlation between serum HGF concentration and clinical arterial stiffness or the vasodilator response to reactive hyperemia in hypertensive patients. The second study investigated the correlation between changes in serum HGF concentration and clinical arterial stiffness or reactive hyperemia during treatment with cilazapril or atenolol. A total of 210 hypertensive patients were analyzed in the first study, and 25 patients with essential hypertension were evaluated in the second study. Pulse wave velocity (PWV), strain gauge plethysmography, and serum HGF concentration were measured in the first study. We also evaluated these factors before and after treatment with either cilazapril (2.0 mg/day) or atenolol (25 mg/day) for 6 months in the second study. Serum HGF concentration was negatively correlated to reactive hyperemia in overall (r = 0.434, P < .0001) and nontreatment (r = 0.452, P < .0001) hypertensive patients. Arterial stiffness was weakly related to serum HGF concentration (P < .05) after adjusting for age and mean blood pressure (BP). By multiple regression analysis, only serum HGF concentration showed a strong independent correlation with reactive hyperemia, age and mean BP with PWV. Moreover, a relationship between endothelium-dependent vasodilation and serum HGF concentration was observed during treatment with cilazapril or atenolol (r = 0.406, P < .005). These results suggest that in evaluation of serum HGF concentration, the forearm vasodilator response to reactive hyperemia and PWV might be useful for managing hypertension in patients who are receiving antihypertensive therapy.

Effect of antihypertensive agents on arterial stiffness as evaluated by pulse wave velocity: clinical implications

Structural and functional properties of the arterial wall have been reported to be altered in hypertension, even at early stages of the disease. Morbidity and mortality associated with hypertension are primarily related to arterial damage that may affect one or several organs. Considering the potential implications of arterial assessment in the prevention of cardiovascular disease, evaluation of the arterial effects of antihypertensive agents is recommended by numerous authorities. Among the noninvasive and simple methods to evaluate large arteries, pulse wave velocity (PWV) measurement is widely used as an index of regional arterial stiffness. This method is related to the arterial geometry and wall function, simple and reproducible, and thus, can easily be applied in clinical trials. Several studies performed in various populations showed significant powerful interactions between PWV and cardiovascular risk factors. In addition, aortic PWV was shown to be a forceful marker and predictor of cardiovascular risk in normotensive individuals and patients with hypertension. Furthermore, aortic PWV was shown to be an independent predictor of all-cause mortality in patients with essential hypertension. In comparison with placebo, clinical studies have shown that in short and long term trials, antihypertensive agents improved arterial stiffness (as evidenced by a reduction in PWV) independently of blood pressure reduction. The decrease of PWV was more pronounced with long term treatment than with short term treatment. Whether antihypertensive agents differ in their arterial effects independently of blood pressure changes remains unclear. Pharmacological studies, generally performed in small numbers of patients, indicate that the effects of long term treatment with ACE inhibitors, calcium channel antagonists and some beta-blockers on arterial stiffness are generally similar. The effectiveness of an antihypertensive agent in reducing arterial stiffness may also be influenced by the genetic background of the patient. Recently, the Complior Study has shown the feasibility to assess arterial stiffness in clinical trials involving large populations using an automatic device for measuring PWV. Long term treatment with an ACE inhibitor, perindopril, was associated with a decrease in blood pressure and aortic PWV in patients with essential hypertension. In high risk patients with end-stage renal failure, ACE inhibitors effectively decreased arterial stiffness and had a favorable effect on survival which was independent of changes in blood pressure. The correlation between reversion of arterial stiffness and decrease in cardiovascular morbidity and mortality needs to be confirmed in populations of patients with lower cardiovascular risk.

An alteration in arterial compliance associated with elevated aerobic fitness

OBJECTIVE

To identify a nonpharmacologic method of enhancing arterial compliance, a correlate of atherogenesis; to determine the relationship between aerobic fitness levels and arterial compliance; and to identify a characteristic Doppler analog waveform associated with elevated levels of aerobic fitness.

DESIGN

A cross-sectional design was used to compare the Doppler studies of sedentary subjects and aerobically trained subjects. The trained subjects were divided into a moderately trained group and a highly trained group.

SETTING AND PARTICIPANTS

One hundred subjects consisting of 50 sedentary control subjects and 50 aerobically trained subjects in a university-based setting. The mean age of the total group of subjects was 36.0+/-8.6 years. Each group had an equal number of male and female subjects. Control subjects were sedentary, with normal vascular risk factor profiles and a mean aerobic capacity (maximum oxygen consumption) of 25.8+/-3.0 mL x kg(-1) x min(-1). Trained subjects were divided into a moderately trained group and a highly trained group. The mean aerobic capacity for the moderately trained group was 46.0+/-4.4 mL x kg(-1) x min(-1), and that for the highly trained group was 63.3+/-6.7 mL x kg(-1) x min(-1). A standard Doppler examination, including ankle pressure index was performed on each subject.

MAIN OUTCOME MEASURE

Arterial compliance measurements were recorded by using A-mode Doppler ultrasonography and analyzed by diastolic flow analysis.

RESULTS

Control subjects had a mean arterial compliance level of 21.1%+/-2.5%. The moderately trained subjects had a mean compliance level of 34.8%+/-4.9%, and the highly trained subjects had a mean compliance level of 46.0%+/-6.7%. An analysis of variance was used for this comparison and was significant at a P value of less than .01.

CONCLUSION

These results demonstrate that elevated aerobic fitness levels are associated with an augmentation in arterial compliance. A linear relationship existed in our data between aerobic fitness levels and arterial compliance. This study suggests that enhanced arterial compliance is another beneficial cardioprotective effect associated with aerobic training.

Flow-mediated vasodilation and distensibility of the brachial artery in renal allograft recipients

BACKGROUND

Alterations of large artery function and structure are frequently observed in renal allograft recipients. However, endothelial function has not yet been assessed in this population.

METHODS

Flow-mediated vasodilation is a useful index of endothelial function. We measured the diameter and distensibility of the brachial artery at rest using high-resolution ultrasound and Doppler frequency analysis of vessel wall movements in the M mode. Thereafter, changes in brachial artery diameter were measured during reactive hyperemia (after 4 min of forearm occlusion) in 16 cyclosporine-treated renal allograft recipients and 16 normal controls of similar age and sex ratio. Nitroglycerin-mediated vasodilation was measured to assess endothelium-independent vasodilation. Brachial artery blood pressure was measured using an automatic sphygmomanometer, and brachial artery flow was estimated using pulsed Doppler.

RESULTS

Distensibility was reduced in renal allograft recipients (5.31 +/- 0. 74 vs. 9.10 +/- 0.94 x 10-3/kPa, P = 0.003, mean +/- sem), while the brachial artery diameter at rest was higher (4.13 +/- 0.14 vs. 3.25 +/- 0.14 mm, P < 0.001). Flow-mediated vasodilation was significantly reduced in renal allograft recipients (0.13 +/- 0.08 vs. 0.60 +/- 0.08 mm or 3 +/- 2 vs. 19 +/- 3%, both P < 0.001). However, nitroglycerin-mediated vasodilation was similar in renal allograft recipients and controls (0.76 +/- 0.10 vs. 0.77 +/- 0.09 mm, NS, or 19 +/- 3 vs. 22 +/- 2%, NS). There were no significant differences in brachial artery flow at rest and during reactive hyperemia between both groups. The impairments of flow-mediated vasodilation and distensibility in renal allograft recipients remained significant after correction for serum cholesterol, creatinine, parathyroid hormone concentrations, end-diastolic diameter, as well as blood pressure levels, and were also present in eight renal allograft recipients not treated with cyclosporine. Flow-mediated vasodilation was not related to distensibility in either group.

CONCLUSIONS

The results show impaired endothelial function and reduced brachial artery distensibility in renal allograft recipients. The impairments of flow-mediated vasodilation and distensibility are not attributable to a diminished brachial artery vasodilator capacity, because endothelium-independent vasodilation was preserved in renal allograft recipients.

Total arterial compliance in ambulatory hypertension during selective beta1-adrenergic receptor blockade and angiotensin-converting enzyme inhibition

Aortic root flow and pressure estimates were obtained noninvasively with Doppler echocardiography and calibrated subclavian artery pulse tracing in 30 subjects with ambulatory hypertension in a randomized, crossover study with 4 weeks' treatment and washout periods. Total arterial compliance, assessed by use of a three-element Windkessel model of the arterial tree, increased 42% with atenolol (50-100 mg once daily), and 7% (p = NS) with captopril (25-50 mg twice daily). Atenolol reduced mean arterial pressure by 15%, heart rate by 22%, and cardiac output by 14%, and increased acceleration time of aortic root flow by 17% and stroke volume and ejection time each by 11%. Captopril reduced mean arterial pressure and total peripheral resistance each by 7%. Acceleration time of aortic root flow, ejection time, heart rate, stroke volume, and cardiac output were not significantly changed by captopril. We conclude that total arterial compliance, at the operational blood pressure, increases during selective beta1-adrenergic receptor blockade in subjects with ambulatory hypertension. Although the main mechanism may be a reduction in mean arterial pressure, it should be considered whether reduced heart rate may play an additional role. The nonsignificant increase in total arterial compliance during angiotensin-converting enzyme inhibition may primarily be a consequence of a modest reduction of the mean arterial pressure.

Protective effect of chronic garlic intake on elastic properties of aorta in the elderly

BACKGROUND

Epidemiological studies have suggested that garlic may have protective effects against cardiovascular diseases. We undertook this cross-sectional observational study to test the hypothesis that regular garlic intake would delay the stiffening of the aorta relating to aging.

METHODS AND RESULTS

We studied healthy adults (n=101; age, 50 to 80 years) who were taking > or = 300 mg/d of standardized garlic powder for > or = 2 years and 101 age- and sex-matched control subjects. Pulse wave velocity (PWV) and pressure-standardized elastic vascular resistance (EVR) were used to measure the elastic properties of the aorta. Blood pressures, heart rate, and plasma lipid levels were similar in the two groups. PWV (8.3+/-1.46 versus 9.8+/-2.45 m/s; P<.0001) and EVR (0.63+/-0.21 versus 0.9+/-0.44 m2 x s(-2) x mm Hg(-1); P<.0001) were lower in the garlic group than in the control group. PWV showed significant positive correlation with age (garlic group, r=.44; control group, r=.52) and systolic blood pressure (SBP) (garlic group, r=.48; control group, r=.54). With any degree of increase in age or SBP, PWV increased less in the garlic group than in the control group (P<.0001). ANCOVA and multiple regression analyses demonstrated that age and SBP were the most important determinants of PWV and that the effect of garlic on PWV was independent of confounding factors.

CONCLUSIONS

Chronic garlic powder intake attenuated age-related increases in aortic stiffness. These data strongly support the hypothesis that garlic intake had a protective effect on the elastic properties of the aorta related to aging in humans.