Relation of pulse pressure and blood pressure reduction to the incidence of myocardial infarction

Systolic blood pressure revisited

The clinical importance of systolic blood pressure (SBP) needs no emphasis. Its determinants are well known, but recent studies of one of these determinants, arterial distensibility, have led to results that now have clinical relevance. This review summarizes the role of arterial stiffness in ventricular-vascular coupling in the normal circulation and that disordered by aging and hypertension. The discussion defines the unfamiliar terms of compliance, distensibility and modulus and indicates how they are measured. Such measurements have increased our understanding of the parts played by the inhomogeneity of the arterial tree and reflected pressure waves in governing SBP. Elevated SBP is a recognized risk factor for cardiovascular complications among older patients, but when this elevation is due to a stiffened arterial tree, diastolic blood pressure (DBP) is necessarily reduced. Early epidemiologic studies in hypertension required a DBP > or = 90 mm Hg for hospital admission. They therefore excluded persons with high SBP, low DBP and very wide pulse pressure (PP). More recent inclusion of such patients has shown that elevation of SBP and PP is a strong predictor of cardiovascular risk. These considerations point to a possible redefinition of hypertension to include patients with lower DBP and to the inaccuracy but indispensability of the brachial artery pressure as a surrogate for aortic pressure--the pressure the heart sees. Finally, we review the known effects of available antihypertensive drugs on the arterial wall and indicate possible future directions of research stemming from wider understanding of the role of arterial distensibility in hypertension.

Influence of nycthemeral blood pressure pattern in treated hypertensive patients on hemodialysis

Arterial hypertension in end-stage renal disease (ESRD) patients is characterized by an altered nycthemeral blood pressure (BP) rhythm and an increased pulse pressure, and it could be suggested that this association of risk factors plays a major role in the cardiovascular prognosis of this population. The aim of this study was to determine the influence of nycthemeral BP pattern on arterial distensibility and pulsatile components of BP in treated hypertensive patients on regular hemodialysis. Forty-two hypertensive patients were included, and all underwent ambulatory BP and pulse wave velocity (PWV) measurements between the femoral and carotid arteries. The patients were divided into two groups according to the magnitude of the nocturnal fall in BP: dippers and non-dippers. The groups were similar in gender, age, duration of hemodialysis, body mass index, body size, history of cardiovascular complications, class and number of antihypertensive drugs used per patient. PWV was significantly higher in non-dippers. For the whole population, a stepwise regression analysis showed that PWV and erythropoietin therapy were independently related to the impaired nycthemeral BP pattern. In addition to its pressor effect, erythropoietin could have a deleterious influence on the ambulatory BP profile of treated hypertensive patients in ESRD. Arterial distensibility and nycthemeral BP impairment are linked, and these cardiovascular risk factors should be taken into account together for the management of hypertensive hemodialysis patients.

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.

Large artery stiffness in hypertension

EFFECTS OF HYPERTENSION ON LARGE ARTERIES: The mechanical properties of large arteries make a major contribution to cardiovascular haemodynamics through the buffering of stroke volume and by propagation of the pressure pulse. A sustained increase in blood pressure often leads to stiffness of the large arteries, especially when other risk factors are present. The increased stiffness, in turn, aggravates hypertension by increasing systolic blood pressure and can induce cardiac hypertrophy and arterial lesions. Epidemiological studies strongly suggest that subjects with stiffer arteries have a high pulse pressure, and that stiffening of large arteries is associated with excess morbidity and mortality independently of other cardiovascular risk factors. ENVIRONMENTAL AND GENETIC FACTORS: Apart from high blood pressure and ageing, various environmental and genetic factors that influence the composition of the extracellular matrix of the arterial wall can increase arterial stiffness. Clinical studies suggest that the presence of some genotypes may be a particularly important risk marker for arterial stiffness, and may modulate the effects of hypertension, ageing and lipids on large arteries. EFFECTS OF ANTIHYPERTENSIVE DRUGS: The development of accurate, non-invasive methods has now made it possible to detect alterations of the large arteries. Among antihypertensive drugs, angiotensin converting enzyme inhibitors and calcium channel blockers have proved to be highly effective in improving large artery compliance, and have shown no adverse effects on metabolic factors that can alter arterial structure and function such as lipids, plasma glucose and insulin tolerance. Therefore these drugs may be particularly suitable for treating patients with increased arterial stiffness. Finally, a determination of genotypes may be helpful in the future in choosing antihypertensive therapy.

Influence of the angiotensin II type 1 receptor gene polymorphism on the effects of perindopril and nitrendipine on arterial stiffness in hypertensive individuals

Angiotensin-converting enzyme inhibitors improve arterial stiffness independently of blood pressure reduction. Since we have recently shown that in hypertensive individuals the A1166C polymorphism of the angiotensin II type 1 receptor (AT1-R) is an independent determinant of aortic stiffness, we designed the present study to assess the influence of this polymorphism on the changes of aortic stiffness after chronic treatment with the angiotensin-converting enzyme inhibitor perindopril and the calcium channel blocker nitrendipine. Forty perindopril- and 42 nitrendipine-treated hypertensive individuals were studied. We evaluated aortic stiffness by measuring the carotid-femoral pulse wave velocity. Carriers of the AT1-RC allele showed higher baseline values of pulse wave velocity than AA homozygotes (P < .05). In the perindopril group, a threefold greater reduction in pulse wave velocity was observed in carriers of the C allele than in AA homozygotes (-2.85 +/- 0.62 versus -0.94 +/- 0.32 m/s, respectively; P < .001), whereas in the nitrendipine group, pulse wave velocity decreased only in AA homozygotes and not in AT1-R C carriers (-1.38 +/- 0.35 versus +0.04 +/- 0.60 m/s, respectively; P < .01). These results indicate that according to the AT1-R A1166C genotype, an angiotensin-converting enzyme inhibitor and a calcium channel blocker affect pulse wave velocity in opposite ways. Since some evidence shows that increased pulse wave velocity may enhance cardiovascular risk, it might be useful for physicians to consider the AT1-R genotype when prescribing an angiotensin-converting enzyme inhibitor or calcium channel blocker to a hypertensive individual.

A new classification scheme for hypertension based on relative and absolute risk with implications for treatment and reimbursement

Classification schemes for hypertension are necessary. They provide us with definitions for when hypertension begins and help us to assess risk, determine prognosis, and guide management. Systems in current use rely on either the level of blood pressure (diastolic, systolic, or both) and classify patients based on the level of relative risk (the proportional likelihood of cardiovascular events occurring as blood pressure rises), absolute risk (the actual odds that a patient or a population will develop an event), or both. Absolute risk reflects the sum of all the factors that contribute to the likelihood that a patient will experience cardiovascular disease. The system we propose stages hypertensive individuals on the basis of blood pressure level (as does the Fifth Joint National Committee report on the detection, evaluation, and treatment of high blood pressure [JNC-V] and the World Health Organization/International Society of Hypertension guidelines) but uses different levels for each stage than do the previous systems and then modifies the numerical stage with the subscript "c" for complicated (when target-organ damage and/or other cardiovascular risk factors are present) or "u" for uncomplicated (when they are absent). The data obtained from a complete medical history and physical examination and a few inexpensive laboratory tests provide the information a provider needs to classify an individual as being complicated or uncomplicated. This system also provides a guide to treatment, as drug therapy would be used sooner in individuals with complicated hypertension, and we propose that compensation for providers be higher when they are caring for a patient with complicated rather than uncomplicated hypertension.

Isolated diastolic hypertension. A favorable finding among young and middle-aged hypertensive subjects

To identify pretreatment characteristics associated with subsequent myocardial infarction in young and middle-aged previously untreated hypertensive individuals, we examined the experience of 1560 participants in a work-site hypertension control program who were younger than 60 years. Subjects were categorized by initial blood pressure as having isolated diastolic hypertension (< 160/> or = 90 mm Hg, n = 965) or combined systolic and diastolic hypertension (> or = 160/> or = 90 mm Hg, n = 595). During 4.5 years of follow-up, there were 24 myocardial infarctions, yielding an overall incidence of 3.89 per 1000 person-years. Subjects with systolic/diastolic hypertension were older, had higher cholesterol and blood sugar levels, and included more smokers and people with left ventricular hypertrophy on electrocardiogram than those with isolated diastolic hypertension. Age-adjusted incidence rates for myocardial infarction were 5.20 and 2.21 per 1000 person-years in systolic/diastolic hypertension and isolated diastolic hypertension, respectively, and the relative risk of systolic/diastolic hypertension was 2.31 (95% confidence interval, 1.29-4.15). Among subjects with isolated diastolic hypertension, no myocardial infarction occurred in those with systolic pressure less than 140 mm Hg. Cox regression analysis including other known risk factors showed that pulse pressure, as a continuous variable (hazards ratio, 1.54; 95% confidence interval, 1.08-2.20), and type of hypertension, ie, systolic/diastolic hypertension versus isolated diastolic hypertension (hazards ratio, 2.11; 95% confidence interval, 1.08-4.13), were independently associated with myocardial infarction. These results suggest that young and middle-aged treated hypertensive individuals with normal pretreatment systolic pressure enjoy a more favorable prognosis than do those with systolic elevation.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolated elevation of diastolic blood pressure. Real or artifactual?

Not infrequently, blood pressure measurement by the standard auscultatory technique yields a normal systolic pressure with an elevated diastolic pressure. The relatively narrow pulse pressure of such a measurement raises concern about the accuracy of the blood pressure measurement. The purpose of this study was to assess the accuracy of auscultatory blood pressure measurements in patients with an uncommonly narrow pulse pressure, particularly patients with an elevated diastolic but normal systolic pressure. Auscultatory blood pressure measurements were compared with an objective noninvasive standard, called K2 analysis, which has been shown to be more accurate than the auscultatory technique. Blood pressure was measured simultaneously by auscultatory and K2 techniques in 175 subjects. Comparisons were performed (1) in the group as a whole, (2) in four clinical subgroups (normotensive [< 140/< 90 mm Hg, n = 69], hypertensive [> or = 140/> or = 90 mm Hg, n = 53], isolated systolic hypertensive [> or = 140/< 90 mm Hg, n = 38], and isolated diastolic hypertensive [< 140/> or = 90 mm Hg, n = 15]), and (3) in two subgroups whose ratio of pulse pressure to diastolic pressure was greater than or equal to 0.45 (n = 151) or less than 0.45 (n = 24). Subjects in the isolated diastolic hypertensive group and in the group with a pulse pressure ratio less than 0.45 were considered to have a narrow pulse pressure. In the group as a whole, consistent with previous auscultatory-K2 comparisons, systolic pressure was slightly higher and diastolic pressure slightly lower when measured by K2 versus the auscultatory technique (auscultatory, 145/85 mm Hg; K2, 147/83 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)

Pulse pressure and resistance artery structure in the elderly

There has been recent interest in the possibility that resistance vessel structural adaptation in hypertension may be more closely related to pulse pressure than to other blood pressure parameters. We investigated the relation between blood pressure and resistance vessel structure in a group of subjects from an age group (older than 60 years) in which a widening of pulse pressure is a typical finding and characterized blood pressure parameters using 24-hour ambulatory blood pressure monitoring. We studied resistance vessels retrieved from biopsies of skin and subcutaneous fat taken from the gluteal region of 32 subjects under local anesthesia (age, 70 +/- 1 years [mean +/- SEM], 21 of whom were hypertensive and 11 normotensive. Media-lumen ratio was higher in the hypertensive than the normotensive subjects (18.6 +/- 1.6% versus 12.8 +/- 1.2%, P < .01) and correlated with age (r = .44, P < .05), clinic systolic pressure (r = .35, P < .05), 24-hour systolic pressure (r = .40, P < .05), and 24-hour pulse pressure (r = .56, P < .001). Stepwise multivariate regression analysis identified clinic and 24-hour pulse pressure as the only significant predictors of media-lumen ratio independent of age, other parameters of clinic blood pressure, and blood pressure variability (R2 = 41%, P < .05). These findings confirm those from animal models of hypertension in demonstrating the importance of pulse pressure in relation to cardiovascular structural adaptation and have important implications for the goals of treatment of hypertension in the elderly.

The arterial system in hypertension. A prospective view

Hypertension has long been considered a hemodynamic disorder, the hallmark of which is an increased total peripheral resistance that is more or less uniformly distributed in the arterioles of the component organ circulations. In recent years, because of the introduction of innovative technologies and methods, it is now possible to obtain a meaningful assessment of the physiological role of the larger arteries, thereby providing an index of arterial distensibility and compliance and a new means to assess the role of pulsatile pressure and arterial stiffening in hypertension and its comorbid diseases (eg, arteriosclerosis, diabetes mellitus). This discussion addresses these newer methodological aspects in assessing arterial stiffening in systemic hypertension and other cardiovascular disorders. In addition, the epidemiological, the molecular biological, and genetic, as well as certain therapeutic, aspects of pulse pressure in these circumstances are discussed.

Low urinary sodium is associated with greater risk of myocardial infarction among treated hypertensive men

A sodium-reduced diet is frequently recommended for hypertensive individuals. To determine the relationship of sodium intake to subsequent cardiovascular disease, we assessed the experience of participants in a worksite-based cohort of hypertensive subjects. The 24-hour urinary excretion of sodium (UNaV), potassium, creatinine, and plasma renin activity was measured in 2937 mildly and moderately hypertensive subjects who were unmedicated for at least 3-4 weeks. Morbidity and mortality in these systematically treated subjects were ascertained. Men and women were stratified according to sex-specific quartiles of UNaV. Subjects in these strata were similar in race, cardiovascular status, and pretreatment and intreatment blood pressure. Subjects with lower UNaV were thinner, excreted less potassium, and had higher plasma renin activity. During an average 3.8 years of follow-up, a total of 55 myocardial infarctions occurred. Myocardial infarction and UNaV were inversely associated in the total population and in men but not in women, who sustained only nine events. In men, age- and race-adjusted myocardial infarction incidence in the lowest versus highest UNaV quartile was 11.5 versus 2.5 (relative risk, 4.3, 95% confidence interval, 1.7-10.6). No association was observed between non-cardiovascular disease mortality (n = 11) and UNaV. There was a significant linear trend in proportions of myocardial infarction by UNaV quartile, with a break point after the lowest UNaV quartile.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal function during antihypertensive treatment

To determine the association of renal function and the course of blood pressure in antihypertensive therapy, we studied the changes in serum creatinine as a measure of renal function and in-treatment blood pressure in black and white hypertensive patients. We measured serum creatinine in 2125 mild and moderately hypertensive men during treatment over an average of 5 years. Both unadjusted mean initial and final serum creatinine of 758 blacks (113 and 117 mumol/L respectively) were significantly higher than those of 1367 whites (108 and 107 mumol/L), with a small increase of 4 mumol/L (p < 0.01) for blacks and a fall of 0.9 mumol/L (p > 0.05) for whites. Less than 2% of all patients attained or remained at a final serum creatinine of 177 mumol/L or more. Of this small group (3% blacks, 1.4% whites), 31% had proteinuria at entry. After stratification by in-treatment diastolic blood pressure (< 95 and > or = 95 mm Hg) in each race, mean slopes of reciprocal serum creatinine were estimated, adjusting for age at entry, initial serum creatinine, diastolic pressure, and body-mass index by analysis of covariance. The two adjusted mean slopes did not differ significantly within each race. Multiple regression analysis confirmed that in-treatment diastolic pressure was not independently associated with final serum creatinine. The change in renal function was most likely a reflection of regression towards the mean, and does not support the view that antihypertensive treatment is an important determinant of renal function in mild-to-moderate hypertensive patients. Patients with substantial renal insufficiency may have pre-existing intrinsic renal disease.

Hypertension in the elderly

Elderly people have a very high prevalence of hypertension, which markedly increases their risk for cardiovascular morbidity and mortality. Convincing evidence demonstrates the effectiveness of antihypertensive therapy in reducing these risks significantly. With appropriate caution, most elderly hypertensives can be treated and thereby protected from many of the debilities of old age.

Ambulatory blood pressure. An independent predictor of prognosis in essential hypertension

To determine the prognostic significance of ambulatory blood pressure, we prospectively followed for up to 7.5 years (mean, 3.2) 1187 subjects with essential hypertension and 205 healthy normotensive control subjects who had baseline off-therapy 24-hour noninvasive ambulatory blood pressure monitoring. Prevalence of white coat hypertension, defined by an average daytime ambulatory blood pressure lower than 131/86 mm Hg in women and 136/87 mm Hg in men in clinically hypertensive subjects, was 19.2%. Cardiovascular morbidity, expressed as the number of combined fatal and nonfatal cardiovascular events per 100 patient-years, was 0.47 in the normotensive group, 0.49 in the white coat hypertension group, 1.79 in dippers with ambulatory hypertension, and 4.99 in nondippers with ambulatory hypertension. After adjustment for traditional risk markers for cardiovascular disease, morbidity did not differ between the normotensive and white coat hypertension groups (P = .83). Compared with the white coat hypertension group, cardiovascular morbidity increased in ambulatory hypertension in dippers (relative risk, 3.70; 95% confidence interval, 1.13 to 12.5), with a further increase of morbidity in nondippers (relative risk, 6.26; 95% confidence interval, 1.92 to 20.32). After adjustment for age, sex, diabetes, and echocardiographic left ventricular hypertrophy (relative risk versus subjects with normal left ventricular mass, 1.82; 95% confidence interval, 1.02 to 3.22), cardiovascular morbidity in ambulatory hypertension was higher (P = .0002) in nondippers than in dippers in women (relative risk, 6.79; 95% confidence interval, 2.45 to 18.82) but not in men (P = .91). Our findings suggest that ambulatory blood pressures stratifies cardiovascular risk in essential hypertension independent of clinic blood pressure and other traditional risk markers including echocardiographic left ventricular hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)