[Antihypertensive therapy: why and how?]

Many clinical trials have shown that lowering increased blood pressure by an antihypertensive agent reduces the risk of morbidity and mortality due to hypertension. Despite these beneficial effects, several questions remain largely unanswered, particularly with respect to the degree of cardiovascular protection conferred by the antihypertensive complications. This article addresses some of these questions by reviewing the recommended means of lowering the blood pressure in hypertensive patients. The clinical value of effective blood pressure control throughout the 24 hour period is discussed together with the therapeutic strategies available to obtain this objective.

Smoking impairs baroreflex sensitivity in humans

In 10 healthy smokers, finger blood pressure was recorded continuously for 1 h in a supine control condition and for 1 h while smoking four cigarettes, one every 15 min. Smoking increased average systolic blood pressure (+19%, P < 0.01) and its variability and reduced pulse interval (reciprocal of heart rate, -22%, P < 0.01) and its variability. Baroreflex sensitivity, as assessed by the slope of spontaneous hypertension/bradycardia or hypotension/tachycardia sequences and by the alpha-coefficient (squared ratio between pulse interval and systolic blood pressure spectral powers at 0.1 Hz) was significantly decreased (P < 0.01) during smoking, whereas there were no effects of smoking on the reflex changes in pulse interval induced by carotid baroreceptor stimulation through a neck suction device. Sham smoking by a drinking straw had no effects on any of the above parameters. Thus, when assessed in the absence of laboratory maneuvers in daily life conditions, baroreflex sensitivity is markedly impaired by smoking. This impairment may contribute to the smoking-induced increase in blood pressure and heart rate as well as to the concomitant alterations in their variability.

Large and medium sized artery abnormalities in untreated and treated hypothyroidism

BACKGROUND

Hypothyroidism is frequently accompanied by cardiac dysfunction, increased vascular resistance and a greater prevalence of hypertension. Whether this condition is also accompanied by alterations of large artery function and structure is not known, however.

PATIENTS AND METHODS

We investigated radial artery compliance and wall thickness as well as carotid artery compliance in 11 normotensive recently diagnosed and never treated hypothyroid patients. Fifteen euthyroid healthy age- and sex-matched subjects served as controls. No subject had evidence of large artery atherosclerotic lesions. Carotid artery diameter was evaluated continuously by a B-M mode device and carotid compliance obtained by the Reneman formula. Radial artery diameter and wall thickness were continuously acquired over the systodiastolic blood pressure range (beat-to-beat finger measurement) by an echo-tracking device, and compliance (Langewouters formula) was expressed as the integral of the area under the compliance/blood pressure curve normalized for pulse pressure.

RESULTS

Patients with hypothyroidism showed greater radial wall thickness (+109%, P < 0.01) and compliance (+58%, P < 0.03) than controls. Carotid artery compliance was not different in the two groups. In 10 hypothyroid patients L- tiroxine therapy for 9.0 +/- 2.3 months did not change carotid artery function but markedly reduced radial artery wall thickness (-36%, P < 0.05) and compliance (-20%, P < 0.05).

CONCLUSIONS

Hypothyroidism is associated with early arterial structural and functional alterations, which involve more muscular than elastic arteries. These alterations, however, are reversible by hormonal replacement therapy.

Effects of chronic ACE inhibition on sympathetic nerve traffic and baroreflex control of circulation in heart failure

BACKGROUND

In congestive heart failure ACE inhibitors chronically reduce plasma norepinephrine. No information exists, however, on whether and to what extent this reduction reflects a true chronic inhibition of sympathetic outflow and which mechanisms may be responsible.

METHODS AND RESULTS

In 24 patients aged 60.3+/-2.0 years (mean+/-SEM) affected by congestive heart failure (New York Heart Association class II) and treated with diuretics and digitalis, we measured mean arterial pressure (Finapres), plasma renin activity and angiotensin II levels (radioimmunoassay), plasma norepinephrine (high-performance liquid chromatography), and muscle sympathetic nerve activity (microneurography at a peroneal nerve) at rest and during baroreceptor stimulation and deactivation caused by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively. In 12 patients measurements were repeated after a 2-month addition of the ACE inhibitor benazepril (10 mg/d P.O.), while in the remaining 12 patients they were performed again after 2 months without any treatment modifications. Benazepril did not alter mean arterial pressure, markedly increased plasma renin activity, reduced plasma angiotensin II, and caused a nonsignificant reduction in plasma norepinephrine. In contrast, muscle sympathetic nerve traffic was significantly reduced (-30.5+/-5.3%, P<.01). This reduction was accompanied by no change in the sympathoexcitatory responses to baroreceptor deactivation but by a marked enhancement of the sympathoinhibitory responses to baroreceptor stimulation (103.5+/-3.4%).

CONCLUSIONS

These results provide the first direct evidence that in congestive heart failure chronic ACE inhibitor treatment is accompanied by a marked reduction in central sympathetic outflow. This reduction may depend on a persistent restoration of baroreflex restraint on the sympathetic neural drive.

Sympathetic activity, blood pressure variability and end organ damage in hypertension

Animal studies have provided clearcut evidence that sympathetic factors are involved in the development and maintenance of high blood pressure (BP). This also appears to be the case in humans, in which sympathetic activation, detected through plasma noradrenaline measurement, noradrenaline spillover technique and direct recording of muscle sympathetic nerve activity, has been shown to characterize the early phases of the hypertensive state and parallel its severity. Sympathetic factors also play in a variety of pathophysiological states frequently associated with hypertension, such as obesity, insulin resistance and atherosclerosis. In addition evidence has been collected that adrenergic factors represent one of the mechanisms involved in determining BP variability, which is strictly associated with end organ damage. Taken together these findings underline the importance that the therapeutical approach to hypertension is aimed not only at lowering BP but also at reducing sympathetic activity.

[Secondary prevention of stroke through arterial blood pressure reduction]

Large scale observational studies have conclusively demonstrated that systolic and diastolic blood pressure values are linearly related to the incidence of cerebrovascular diseases and that high blood pressure is an important risk factor for both primary and secondary development of stroke. Interventional studies have shown that blood pressure lowering by antihypertensive treatment reduces the incidence of stroke in hypertensive patients without a history of previous stroke. Whether this is the case also for the secondary prevention of cerebral ischemic attacks has not been unequivocally shown, however. The PROGRESS ("Perindopril Protection Against Recurrent Stroke Study") study has been designed and is under way to collect information on this important issue of the antihypertensive treatment, its purpose being to evaluate the blood pressure lowering effects with an ACE-inhibitor on recurrent stroke in an overall population of 6000 patients with a positive history of previous cerebral ischemic attacks or stroke.

Ambulatory and home blood pressure normality in the elderly: data from the PAMELA population

To determine ambulatory blood pressure (BP) means and distributions in an elderly population, we studied a random sample of 800 subjects stratified by sex and representative of residents aged 65 to 74 years of the city of Monza. Participation was 50%. Measurements consisted of clinic BP (average of three measurements with mercury sphygmomanometry), home BP (average of morning and evening measurements with a semiautomatic device), and ambulatory BP (SpaceLabs 90207). Clinic BP was obtained before and after home and ambulatory BP measurements. In normotensive and untreated hypertensive subjects (n=248), clinic, home, and ambulatory BPs were significantly related (P<.001). The means of the clinic BPs obtained on consecutive days were very similar and markedly higher than 24-hour average BP (+25 mm Hg systolic and + 10 mm Hg diastolic, P<.001). Nighttime BP was markedly less than daytime BP (-14 and -13 mm Hg, P<.001), whereas home BP values occurred approximately midway between clinic and 24-hour average BP values. Only minor differences existed between data in men and women, and the differences in clinic, home, and ambulatory BP values occurred in both normotensive and untreated hypertensive subjects. All BPs were similar in the untreated and treated hypertensive groups. Thus, as previously reported in subjects younger than 65 years, in the elderly fraction of the population, 24-hour average BP is much lower than clinic BP. The upper limit of normality for 24-hour average BP (calculated as the value corresponding to 140/90 mm Hg clinic BP) is about 120 mm Hg systolic and 76 mm Hg diastolic. At variance with data from younger subjects, home BP in the elderly is higher than 24-hour average BP. However, similar to data from younger subjects, clinic, home, and ambulatory BPs are higher in treated hypertensive than normotensive elderly subjects, indicating that in hypertensive elderly subjects, antihypertensive treatment does not commonly achieve full BP control both inside and outside the clinic environment.

Ambulatory blood pressure in hypertension with particular reference to the kidney

Ambulatory blood pressure is more closely related to the end organ damage of hypertension than clinic blood pressure is. This is the case not only for left ventricular hypertrophy, but also for an index of renal involvement such as microalbuminuria. The closer correlation of ambulatory blood pressure with end organ damage characterises not only the 24 hour average value but also, to a similar extent, day-time and night-time average blood pressure, while the clinical importance of the difference between day and night blood pressure is still a matter of controversy. A more promising index derived from ambulatory blood pressure recordings seems to be blood pressure variability, which in preliminary studies has been shown to display an independent correlation with the end organ damage of hypertension.

Combination treatment in hypertension: the VeraTran Study

In the past few years, the combination of two antihypertensive drugs has become a popular approach to hypertension treatment, because this procedure allows one to obtain satisfactory blood pressure control when monotherapy is partially ineffective and also to improve a patient's adherence to the therapeutic regimen, thereby enhancing the tolerance/effectiveness ratio of the treatment. This paper will briefly review the theoretical background and the requirements for an effective combination treatment. It will also discuss the results of the VeraTran Study, a multicenter study performed according to a double-blind parallel group design and aimed at assessing the antihypertensive efficacy of the fixed combination verapamil slow release (SR) and trandolapril, administered for 8 weeks, on clinic and 24-h ambulatory blood pressure. The results of the study demonstrate that the fixed combination of a calcium antagonist and an angiotensin converting enzyme (ACE) inhibitor allows one to obtain an effective and balanced blood pressure control throughout the 24 h.

Intracoronary angiotensin II potentiates coronary sympathetic vasoconstriction in humans

BACKGROUND

In humans with coronary artery disease, ACE inhibition attenuates coronary sympathetic vasoconstriction. Whether this is due to removal of angiotensin (Ang) II production or to a reduced bradykinin breakdown, however, is unknown.

METHODS AND RESULTS

In eight normotensive patients with angiographic evidence of mild left coronary artery lesions (< or = 50%), mean arterial pressure (MAP, intra-arterial catheter), heart rate (HR, ECG lead), coronary sinus blood flow (CBF, thermodilution method), and coronary vascular resistance (CVR, ratio between MAP and CBF) were measured before and during a 15-minute left intracoronary infusion of Ang II at a dose that had no direct coronary or systemic vasomotor effects. The same measurements were made before and during a 15-minute infusion of saline. A 2-minute cold pressor test (CPT) and a 45-second diving were performed at the end of either infusion period. These maneuvers were used because their coronary vasomotor effects are abolished by phentolamine and thus depend on sympathetic activation. During saline infusion, both CPT and diving caused a marked increase in MAP. HR increased with CPT and fell with diving. CBF increased in parallel to the MAP increase, with little change in CVR. The MAP and HR responses were similar during Ang II infusion, which, however, caused either no change or a reduction in CBF with a consequent marked increase in CVR with both CPT and diving. In four additional patients, the diameter of the stenotic vessels remained unchanged during the CPT performed under saline and Ang II infusion.

CONCLUSIONS

Ang II markedly enhances sympathetic influences on coronary circulation in humans, presumably by acting at the arteriolar level. This may explain the blunting effect of ACE inhibition on sympathetic coronary vasoconstriction in patients with coronary artery disease.

Randomised study of effect of ibopamine on survival in patients with advanced severe heart failure. Second Prospective Randomised Study of Ibopamine on Mortality and Efficacy (PRIME II) Investigators

BACKGROUND

Drugs that improve symptoms in patients with heart failure must also be assessed for their effects on survival. Ibopamine stimulates DA-1 and DA-2 receptors and causes peripheral and renal vasodilatation; the drug improves symptoms of heart failure. We assessed the effect of ibopamine on survival in patients with advanced heart failure in a multicentre, randomised placebo-controlled study.

METHODS

Patients with advanced severe heart failure (New York Heart Association classes III and IV) and evidence of severe left-ventricular disease, who were already receiving optimum treatment for heart failure, were randomly allocated oral ibopamine 100 mg three times daily or placebo. The primary endpoint was all-cause mortality. The study was designed to recruit 2200 patients, and the minimum duration of treatment would be 6 months. We did intention-to-treat and on-treatment analyses; a post-hoc subgroup analysis was also done.

FINDINGS

After we had recruited 1906 patients the trial was stopped early, because of an excess of deaths among patients in the ibopamine group. 232 (25%) of 953 patients in the ibopamine group died, compared with 193 (20%) of 953 patients in the placebo group (relative risk 1.26 [95% CI 1.04-1.53], p = 0.017). The average length of follow-up was 347 days in the ibopamine group and 363 days in the placebo group. In multivariate analysis, only the use of antiarrhythmic drugs at baseline was a significant independent predictor of increased fatality in ibopamine-treated patients.

INTERPRETATION

Ibopamine seems to increase the risk of death among patients with advanced heart failure who are already receiving optimum therapy, but the reasons for this increase are not clear. Our finding that antiarrhythmic treatment was a significant predictor of increased mortality in ibopamine-treated patients may be important, but exploratory analyses must be interpreted with caution.

Ambulatory blood pressure is superior to clinic blood pressure in predicting treatment-induced regression of left ventricular hypertrophy. SAMPLE Study Group. Study on Ambulatory Monitoring of Blood Pressure and Lisinopril Evaluation

BACKGROUND

In cross-sectional studies, ambulatory blood pressure (ABP) correlates more closely than clinic BP with the organ damage of hypertension. Whether ABP predicts development or regression of organ damage over time better than clinic BP, however, is unknown.

METHODS AND RESULTS

In 206 essential hypertensive subjects with left ventricular hypertrophy (LVH), we measured clinic supine BP, 24-hour ABP, and left ventricular mass index (LVMI, echocardiography) before and after 12 months of treatment with lisinopril (20 mg UID) without or with hydrochlorothiazide (12.5 or 25 mg UID). Measurements included random-zero, clinic orthostatic, and home BP. In all, 184 subjects completed the 12-month treatment period. Before treatment, clinic supine BP was 165 +/- 15/105 +/- 5 mm Hg (systolic/diastolic), 24-hour average BP was 149 +/- 16/95 +/- 11 mm Hg, and LVMI was 158 +/- 32 g/m2. At the end of treatment, they were 139 +/- 12/87 +/- 7 mm Hg, 131 +/- 12/83 +/- 10 mm Hg, and 133 +/- 26 g/m2, respectively (P < .01 for all). Before treatment, LVMI did not correlate with clinic BP, but it showed a correlation with systolic and diastolic 24-hour average BP (r = .34/.27, P < .01). The LVMI reduction was not related to the reduction in clinic BP, but it was related to the reduction in 24-hour average BP (r = .42/.38, P < .01). Treatment-induced changes in average daytime and nighttime BPs correlated with LVMI changes as strongly as 24-hour BP changes. No substantial advantage over clinic supine BP was shown by clinic orthostatic, random-zero, and home BP.

CONCLUSIONS

In hypertensive subjects with LVH, regression of LVH was predicted much more closely by treatment-induced changes in ABP than in the clinic BP. This provides the first longitudinally controlled evidence that ABP may be clinically superior to traditional BP measurements.

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.

Comparison between reproducibility and sensitivity of muscle sympathetic nerve traffic and plasma noradrenaline in man

1. Although plasma noradrenaline and muscle sympathetic nerve traffic have been shown to be suitable markers of sympathetic activity in man, no study has systematically compared the reproducibility and sensitivity of these two indices of adrenergic tone. 2. Reproducibility data were collected in 10 subjects, in whom plasma noradrenaline was assessed by HPLC on blood samples withdrawn from an antecubital vein and efferent postganglionic muscle sympathetic nerve activity was measured by microneurography from a peroneal nerve, together with arterial blood pressure (Finapres technique). Measurements were obtained in a first session (session 1), 60 min later (session 2) and after 14 days (session 3). While muscle sympathetic nerve activity values recorded in the three different experimental sessions were closely and significantly correlated with each other (r always > 0.90, P < 0.001), noradrenaline showed a less significant correlation between sessions 1 and 2 (r = 0.71, P < 0.05) or no correlation between sessions 1 and 3 (r = 0.45, P not significant). 3. Sensitivity data were collected by evaluating muscle sympathetic nerve activity and noradrenaline values in three different age groups (young, middle-age and old subjects, n = 18), in three groups with different blood pressures (normotensive, mild and severe hypertensive subjects, n = 30) and in a group of eight subjects before and after a physical training programme, i.e. conditions known to increase or reduce sympathetic cardiovascular drive. Muscle sympathetic nerve activity was significantly increased by aging and hypertension, and reduced by physical training. The noradrenaline changes were much less marked and consistent. 4. These data suggest that muscle sympathetic nerve activity has a greater short- and medium-term reproducibility than noradrenaline. In several conditions known to modify sympathetic cardiovascular drive muscle sympathetic nerve activity also appears to change more clearly than noradrenaline.

Baroreflex impairment by low sodium diet in mild or moderate essential hypertension

Low sodium intake is the most widely used nonpharmacological approach to the treatment of hypertension. Although nonpharmacological treatment is by definition regarded as safe, the suggestion has been made that low sodium intake is not totally devoid of inconveniences, and animal data have shown it to be accompanied by an impairment of reflex blood pressure control and homeostasis. However, no data exist on this issue in humans. In mild essential hypertensive patients (age, 34.1+/-3.3 years [mean+/-SEM]), we measured beat-to-beat arterial blood pressure (finger photoplethysmographic device), heart rate (electrocardiogram), and efferent postganglionic muscle sympathetic nerve activity (microneurography) at rest and during baroreceptor stimulation and deactivation, induced by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively. Measurements were performed at the end of three dietary periods, ie, after 8 days of regular sodium intake (210 mmol NaCl/d), low sodium intake (20 mmol NaCl/d) with unchanged potassium intake, and again regular sodium intake. Compared with the initial regular sodium diet, low sodium intake reduced urinary sodium excretion, whereas urinary potassium excretion was unchanged. Systolic blood pressure was significantly (P<.05), although slightly, reduced, whereas diastolic blood pressure was unaffected. Muscle sympathetic nerve activity was increased by 23.1+/-5.2% (P<.05). The increase was accompanied by a clear-cut impairment of the baroreceptor ability to modulate muscle sympathetic nerve activity, ie, by a 43.9+/-5.7% (P<.01) reduction in the sensitivity of the baroreceptor-muscle sympathetic nerve activity reflex compared with the control condition. Baroreceptor modulation of heart rate was also impaired, although to a smaller and less consistent extent. When regular sodium intake was restored, all the above-mentioned parameters and baroreflex responses returned to the values observed at the initial regular sodium diet. These data raise evidence that in humans sodium restriction may impair the arterial baroreflex. This may be responsible for the sympathetic activation occurring in this condition and for the impairment of blood pressure homeostasis.

Blood-pressure control in the hypertensive population

BACKGROUND

In large-scale surveys of individuals with hypertension those whose clinic blood pressure is reduced to 140/90 mm Hg or less have been found to represent only a small fraction of the hypertensive population. We assessed whether these results arise because of a white-coat effect elevating clinic blood pressure.

METHODS

We randomly selected 2400 individuals from the town of Monza, Italy, and invited them to take part in our study. We measured clinic blood pressure as well as home (morning and evening measurements), and 24 h ambulatory blood pressure-ie, blood pressures largely devoid of a white-coat effect. Based on clinic blood pressure participants were then classified as normotensive, untreated hypertensive (clinic blood pressure > 140 mm Hg systolic and/or > 90 mm Hg diastolic), or treated hypertensive (having antihypertensive treatment). The mean blood pressures for each group were calculated.

FINDINGS

1651 people took part in the study. The clinic blood pressure of treated hypertensives (n = 207; 146.9 [SD 18] mm Hg/90.2 [8.6] mm Hg) was only slightly less than in untreated hypertensives (n = 402; 148 [15.2] mm Hg/93.3 [8] mm Hg) and in both groups the blood pressure values were much greater than those of normotensive individuals (n = 1042; 119.5 [10.3] mm Hg/78.1 [6.6] mm Hg) p < 0.001. Averaged home and 24 h blood pressures were lower than clinic blood pressures but similarly higher in untreated and treated hypertensive individuals when compared with normotensive individuals. This was also the case for day and night average blood pressures. The number of treated hypertensive patients found to have blood pressures within the normal limits was small not only when based on clinic blood pressure values but also when based on ambulatory blood-pressure values.

INTERPRETATION

In the hypertensive population the number of patients with inadequate blood-pressure control is high not only when assessed in the clinic but also when assessed by ambulatory-blood-pressure monitoring or at home. The high blood-pressure values commonly found in treated hypertensive individuals cannot be accounted for by a white-coat effect but by a true lack of daily-life blood-pressure control.

Performance of the AM-5600 blood pressure monitor: comparison with ambulatory intra-arterial pressure

The AM-5600 is a new device that simultaneously monitors electrocardiogram (ECG) and noninvasive blood pressure (BP) over a 24-h period. BP readings (Korotkoff sounds and cuff air pressure) are stored into the recorder, allowing the removal of BP artifacts after a visual check. In 12 subjects with essential hypertension, we compared BP values simultaneously provided by the AM-5600 and intra-arterial recordings. At rest, noninvasive systolic BP (SBP) values were lower (5.4 +/- 4.9 mmHg) and diastolic BP (DBP) values were higher (7.3 +/- 7.3 mmHg) than were intra-arterial values. In ambulatory conditions (9 subjects), between-method discrepancies were +0.8 +/- 6.1 and +12.2 +/- 7.4 mmHg for 24-h SBP and DBP, respectively. AM-5600 underestimated 24-h intra-arterial SBP and DBP SD, but it accurately tracked intra-arterial SBP and DBP changes. Editing removed 22.1% of total readings, slightly reducing between-method discrepancies. Thus the AM-5600 provides an accurate average estimate of resting and ambulatory SBP and, for DBP, a less accurate estimate that is slightly improved by editing. The AM-5600 allows accurate description of SBP and DBP profiles and thus may be suitable to describe the abrupt BP changes accompanying a number of clinical events.

Combined effects of hypertension and hypercholesterolemia on radial artery function

Compliance and distensibility of middle-sized conduit arteries are increased in hypertension and reduced in hypercholesterolemia. Despite their frequent association in the same individual, the combined effect of these two conditions on arterial mechanical properties is unknown. We studied four groups of age- and sex-matched subjects: 10 normotensive normocholesterolemic subjects, 10 mild hypertensive normocholesterolemic subjects, 10 mild hypercholesterolemic normotensive subjects, and 10 mild hypertensive and mild hypercholesterolemic subjects. We measured radial artery diameter by an echotracking device and beat-to-beat blood pressure from an ipsilateral finger. Compliance-pressure and distensibility-pressure curves were derived by Langewouters' formula. Between-group comparisons were made by calculating for both compliance and distensibility the integral of the area under the portion of the curve common to the four groups ("isobaric" compliance and distensibility). Blood pressure was similarly elevated in the two hypertensive groups, and serum cholesterol was similarly elevated in the two hypercholesterolemic groups. Compared with values in normotensive normocholesterolemic subjects, isobaric compliance and distensibility were greater in hypertensive normocholesteroclemic (+38% and 47%, respectively) and smaller in normotensive hypercholesterolemic (-6% and -23%) subjects. However, when both hypertension and hypercholesterolemia were present, isobaric compliance and isobaric distensibility were significantly reduced (-26% and -18%, P < .05). Therefore, hypercholesterolemia reverses the effect of hypertension on arterial compliance and causes arterial stiffening, as when present alone.