Systolic hypertension: nonhomogeneous diseases

Blood Pressure Behaviour in Hemodialysis Patients Treated for 10 Years

A longitudinal analysis of blood pressure was performed in 30 patients on hemodialysis for at least 10 years, in order to clarify the long-term outcome of hypertension in dialysis patients. Before the start of the dialysis treatment 22 (73.3%) patients were hypertensive, while, after 10 years, only 5 (16.6%) were still hypertensive. Body weight tended to decrease progressively thoughout the period of observation. Hypertension disappeared in the younger patients while it remained/appeared in those who were order showing the characteristics of systolic hypertension. Except for hematocrit no significant differences in metabolic findings were found between normotensive and hypertensive patients. ECG abnormalities were found to be more frequent after 10 years of dialysis than before the start of treatment. High blood pressure tends to disappear progressively in hemodialysis patients and to be no longer a problem in long-term survivors.

Cross-talk between macro- and microcirculation

Physiologically, macro- and microcirculation differ markedly as macrocirculation deals with pulsatile pressure and flow and microcirculation with steady pressure and flow. Various such haemodynamic aspects correspond to a large heterogeneity in the structure and function of the vascular tree. In the past, diseases such as hypertension and diabetes mellitus were classified on the basis of the structure and function of small and large arteries. The purpose of this paper is to review the cross-talk between the micro- and macrocirculation. We shall discuss this cross-talk from the perspective of the development, physiology and pathology of the entire arterial tree.

Allometric hemodynamic analysis of isolated systolic hypertension and aging

Isolated systolic hypertension (ISH) is prevalent in the elderly and the contributing factors are predominantly vascular in origin. We previously showed that the hemodynamic manifestation of ISH is the result of a concurrently mild increase in peripheral resistance with a large reduction in arterial compliance or greatly increased vascular stiffness. Such elastic mismatching can lead to increased wave reflections. Therefore, we hypothesize that significantly increased pulse wave reflections associated with a drastically reduced arterial compliance beyond normal aging is a principle contributing factor to the production of ISH. To investigate this, we developed a new allometric hemodynamic model that can account for the arterial compliance and peripheral resistance changes during the progression of aging. This model also affords the time domain analysis of forward and reflected waves during aging and ISH. Results show that a further and much greater reduction in arterial compliance beyond normal aging is necessary to produce ISH. Comparison of ISH with normal aging at 60-year old showed that in ISH the amount of wave reflections is much more pronounced, with a greater amplitude and earlier arrival in systole. The increased wave reflections in ISH further amplify the cyclic stress on the already stiffened blood vessels. Therefore, therapies to treat ISH patients need to focus on reducing pulse wave reflections as well as on improving large vessel compliance.

Isolated systolic hypertension in elderly WKY is reversed with L-arginine and ACE inhibition

This study was designed to examine the preventability of progressive deterioration of cardiovascular structure and function in very old Wistar-Kyoto (WKY) rats with isolated systolic hypertension (ISH). To this end, male 18-month-old normotensive WKY rats were given either placebo or L-arginine (70 mg. kg(-1). d(-1)) and an ACE inhibitor (enalapril, 30 mg. kg(-1). d(-1)) for 6 months. These control and treated rats were studied at the age of 2 years by examining: cardiovascular mass and collagen content, cardiac function, and systemic and regional (including coronary) hemodynamics. Additional data obtained in adult, 35-week-old WKY are included for comparison. ISH associated with increased total peripheral resistance was found in the old, untreated WKY, and this was prevented by the combined treatment. The untreated rats also exhibited impaired left ventricular function, as denoted by increased left ventricular end-diastolic pressure and reduced maximal rates of rise and fall of left ventricular pressure. These functional changes were also ameliorated with the combined treatment. Coronary hemodynamics were also compromised in the untreated WKY; and therapy improved coronary flow reserve and minimal coronary vascular resistance in both ventricles of the old WKY in parallel with reduction of arterial pressure. Blood flow to various other organs was uncompromised in the old rats, although increased vascular resistances were observed in untreated old WKY with ISH. These changes were also improved by the combined therapy. Finally, therapy diminished left ventricular mass and collagen concentration in old WKY compared with the untreated WKY. However, when compared with the 35-week-old WKY, both groups of old WKY (untreated and treated) demonstrated myocardial fibrosis, depressed ventricular function, and compromised coronary hemodynamics. Therefore, L-arginine and ACE inhibitory therapy ameliorated the hypertensive and associated adverse cardiovascular changes in old WKY, although it failed to improve totally the progressive deterioration of cardiovascular structure and function that occurred with aging. The results suggest that different mechanisms may be responsible for the hypertension- and age-related cardiovascular changes, although they may appear to be similar.

The diastolic blood pressure in systolic hypertension

Because antihypertensive therapy is effective in elderly patients with isolated systolic hypertension, attention has been focused on the systolic blood pressure as a predictor of cardiovascular risk. However, it is a normal diastolic pressure that separates patients with isolated systolic hypertension from those with essential hypertension. The normal diastolic and elevated systolic pressures are largely due to age-related stiffening of the aorta. An indistensible aorta causes the pressure pulse to travel faster than normal, where it is quickly reflected off the peripheral resistance. The reflected wave then returns to the central aorta in systole rather than diastole. This augments the systolic pressure further, increasing cardiac work while reducing the diastolic pressure, on which coronary flow is dependent. The potential harm of further reducing the diastolic pressure with antihypertensive therapy, especially in patients with coronary heart disease, underlies the controversial "J curve." By decreasing the blood pressure, all antihypertensive agents improve aortic distensibility, but no agents do so directly; the nitrates come the closest. Such an agent would be useful because any therapeutic increase in aortic distensibility would decrease systolic pressure without greatly reducing diastolic pressure. The problem is complicated by the suspected inaccuracy of the cuff technique in predicting the aortic diastolic pressure. New noninvasive methods to predict the aortic diastolic pressure may help in the future. At present, the combination of a high systolic and normal diastolic pressure-a widened pulse pressure-seems to be the best predictor of cardiovascular risk in patients with hypertension or heart disease. Patients with isolated systolic hypertension should be treated, but marked diastolic hypotension should be avoided.

Contribution of stroke volume to the change in pulse pressure pattern with age

This study investigated the effect of age on pulse pressure and its underlying mechanisms in unmedicated hypertensive men with the same level of mean arterial pressure. We included 77 men 17 to 76 years old with daytime mean arterial pressure between 95 and 114 mm Hg. In the supine position, pulse pressure showed a significant widening in young (<30 years) and older (>/=60 years) patients. Pulse pressure decreased in parallel with stroke index from age >30 to 40 to 49 years. Upright posture, however, eliminated this difference through a larger orthostatic fall in stroke index and pulse pressure in the youngest patients. After age 50 years, pulse pressure exhibited a progressive widening despite the further age-related decrease in stroke index. Supine, upright, and 24-hour pulse pressure fitted a curvilinear correlation with age (r=0.55, 0.56, and 0.68, respectively, P<0.001), with a transition at age 50 years. Before age 50 years, 24-hour pulse pressure correlated positively with stroke volume (r=0.5, P<0.001) and negatively with arterial compliance (SV/PP ratio, r=-0.37, P<0.01). In contrast, in men >/=50 years old, 24-hour pulse pressure correlated negatively with the SV/PP ratio (r=-0.5; P<0.01), without significant influence of stroke volume. Thus, in hypertensive men, the age-related change in stroke volume significantly accounted for the change in clinic and ambulatory pulse pressure during young adulthood, but its contribution decreased after the fifth decade.

Recent advances on large arteries in hypertension

The most classic hemodynamic concept explaining the increased mean arterial pressure in hypertension reflects an increased total peripheral resistance dynamically and an increased wall-to-lumen ratio to suppress smaller arteries. However, a more current consideration takes into account not only that steady component but also the pulsatile component of blood pressure, a point that importantly modifies the traditional hemodynamic definition. Whereas mean arterial pressure is almost constant along the arterial tree, the pulse pressure increases markedly from the more central to the peripheral arteries, indicating that in vivo each artery should be characterized according to its own blood pressure curve. This important concept implies major modifications in the methods used to investigate the relationships between mechanical factors and large artery structure and function. It therefore seems reasonable that in hypertension the large arteries should no longer be considered as passive conduits but rather in terms of their active behavioral response to the mechanical forces to which they are subjected. New investigational aspects in hypertension therefore now involve not only genetic, cellular, and molecular mechanisms but also transductional hemodynamic mechanisms reflecting changing patterns in the extracellular matrix that influence structural remodeling of the vessels.

Vascular remodeling: the role of angiotensin-converting enzyme inhibitors

Chronic sustained hypertension leads to structural changes of the small and large arteries. These alterations consist of smooth-muscle hypertrophy, increased deposition of collagen, and "dilution" or destruction of elastin fibers. In addition, there may be no growth at all, but a "rearrangement" of vascular wall material termed "remodeling." These changes serve to increase wall thickness and the media-to-lumen ratio and to decrease the external and internal diameter of the vessel--all of which contribute to increased systemic vascular resistance by the small arteries and increased impedance by the larger arteries. It has been suggested that these structural changes are an adaptive effort by the vessel to maintain a constancy of wall tension, but the end result is detrimental in that the effect is a further increase in systemic vascular resistance and blood-flow impedance, which lead to left ventricular hypertrophy and its consequences. The stimuli for these changes are stretch stimuli, mediated through stretch receptors on the arterial wall, and trophic stimuli mediated at the tissue level through the action of angiotensin II, aldosterone, and catecholamines. Angiotensin-converting enzyme inhibitors, especially those with effective tissue penetration, are ideal drugs to reverse these structural changes ("reverse remodeling"), decrease the systemic vascular resistance, and increase the vascular compliance. These agents exert their effects through suppression, at the tissue level, of angiotensin II, aldosterone, catecholamines, endothelins (ET1, ET3), and transforming growth factor-beta1 (TGF-beta1) and through an increase in local levels of kinins, prostaglandins, and nitric oxide, which have antigrowth effects. Although this is a class effect, it appears to be stronger with those angiotensin-converting enzyme inhibitors providing the greatest tissue penetration.

Diastolic pressure underestimates age-related hemodynamic impairment

It has been hypothesized that as large arteries become more rigid with age, the pattern of hypertension changes from diastolic to systolic. Thus, diastolic blood pressure (DBP) may lose its ability to reflect the increase in vascular resistance with age. To assess this, we studied the age-related changes in blood pressure pattern and its steady-state and pulsatile determinants. We performed an epidemiological analysis based on a national survey of 10,462 subjects from Argentina. A hemodynamic analysis (impedance cardiography) was then carried out in 636 consecutive hypertensive patients (age, 25 to 74 years). Whereas the rate of increment in the prevalence of mild to moderate hypertension (MMH) reached a plateau after the sixth decade, isolated and borderline systolic forms of hypertension began a steep and sustained rise. Among patients with MMH, DBP remained stable from the third to the seventh decade, whereas SBP maintained a sustained increase. Despite similar DBP, the systemic vascular resistance index increased 47% (P<.01) and the cardiac index decreased 27% (P<.01), whereas the ratio of stroke volume to pulse pressure, an index of arterial compliance, decreased 45% (P<.01). However, there were no significant differences between older patients with MMH and those with isolated systolic hypertension in the level of SBP, vascular resistance, stroke volume, and cardiac index. Compared with age-matched normotensive control subjects, the ratio of stroke volume to pulse pressure was much more reduced in isolated systolic hypertension (48%) than in MMH (30%). In summary, the present study, carried out in a large sample of hypertensive subjects with a wide age range, showed a simultaneous impairment in vascular resistance and arterial compliance associated with aging in different patterns of hypertension. The magnitude of these changes, with opposite effects on DBP but additive effects on SBP, suggests that a hemodynamic mechanism could determine the transition in the prevalence of diastolic hypertension toward a systolic pattern of hypertension with aging. Also, the results suggest that SBP, but not DBP, is a reliable indicator of the underlying hemodynamic abnormalities (high resistance and low arterial compliance) in the elderly.

Hemodynamic patterns of age-related changes in blood pressure. The Framingham Heart Study

BACKGROUND

We attempted to characterize age-related changes in blood pressure in both normotensive and untreated hypertensive subjects in a population-based cohort from the original Framingham Heart Study and to infer underlying hemodynamic mechanisms.

METHODS AND RESULTS

A total of 2036 participants were divided into four groups according to their systolic blood pressure (SBP) at biennial examination 10, 11, or 12. After excluding subjects receiving antihypertensive drug therapy, up to 30 years of data on normotensive and untreated hypertensive subjects from biennial examinations 2 through 16 were used. Regressions of blood pressure versus age within individual subjects produced slope and curvature estimates that were compared with the use of ANOVA among the four SBP groups. There was a linear rise in SBP from age 30 through 84 years and concurrent increases in diastolic blood pressure (DBP) and mean arterial pressure (MAP); after age 50 to 60 years, DBP declined, pulse pressure (PP) rose steeply, and MAP reached an asymptote. Neither the fall in DBP nor the rise in PP was influenced significantly by removal of subsequent deaths and subjects with nonfatal myocardial infarction or heart failure. Age-related linear increases in SBP, PP, and MAP, as well as the early rise and late fall in DBP, were greatest for subjects with the highest baseline SBP; this represents a divergent rather than parallel tracking pattern.

CONCLUSIONS

The late fall in DBP after age 60 years, associated with a continual rise in SBP, cannot be explained by "burned out" diastolic hypertension or by "selective survivorship" but is consistent with increased large artery stiffness. Higher SBP, left untreated, may accelerate large artery stiffness and thus perpetuate a vicious cycle.

Advances in management of hypertension in older persons

Recent studies have now demonstrated that it is more important to focus on the SBP level than the DBP level in older persons. In addition, recent studies indicate that persons over age 80 still derive substantial benefit from treating ISH or DH. Also, studies now show that low-dose diuretics have a more favorable impact on subsequent coronary heart disease rates than was previously demonstrated. Finally, although caution is urged, it is unlikely the J-shaped relationship between treated DBP or SBP and subsequent mortality is due to overly aggressive treatment of high blood pressure. Table 4 provides the authors' guidelines for treating older persons with high blood pressure.

Pathophysiology of isolated systolic hypertension in elderly patients: Doppler echocardiographic insights

Systemic hemodynamics were evaluated with aortic pulsed wave Doppler echocardiography in 79 elderly subjects with isolated systolic hypertension participating in the Systolic Hypertension in the Elderly Program (SHEP) and were compared with the values in 39 normal age-matched subjects. Cardiac output was elevated (4.50 +/- 1.13 L/min versus 3.94 +/- 1.12 L/min, p less than 0.05) in patients with isolated systolic hypertension in comparison with values in normal elderly subjects. Systemic vascular resistance did not differ between both groups (2140 +/- 536 dyn.sec/cm-5 versus 2011 +/- 553 dyn.sec/cm-5, p = NS). The mean acceleration of blood during left ventricular ejection was similar in patients with isolated systolic hypertension in comparison with normals (12.6 +/- 5.6 m/sec2 versus 11.5 +/- 3.5 m/sec2, p = NS). Patients with isolated systolic hypertension had significantly decreased arterial compliance, as measured by the stroke volume-to-pulse pressure ratio (0.77 +/- 0.26 cm3/mm Hg versus 1.11 +/- 0.30 cm3/mm Hg, p less than 0.0001). The prevalence of aortic and mitral regurgitation as well as valvular and annular calcification did not differ between analyzed groups. Isolated systolic hypertension in elderly patients appears to be multifactorial, with reduced arterial compliance and increased cardiac output both playing a role.

Systolic hypertension in the elderly

Historically diastolic blood pressure (BP) rather than systolic BP has been regarded clinically as the more important component related to subsequent hypertensive morbidity and mortality, and treatment has thus been directed towards lowering the diastolic BP. Observational studies across many different populations have related cerebrovascular disease and death more to the systolic BP, which appears selectively to increase as the population ages. Isolated systolic hypertension (ISH), therefore, may be more prevalent as westernized societies become older. Those affected with ISH suffer a two- to fivefold increase in rates of stroke and ischemic heart disease compared to normotensives. Currently no clinical trials data exist for ISH showing the efficacy of antihypertensive therapy upon final morbidity and mortality, but a large-scale multicenter clinical trial, the Systolic Hypertension in the Elderly Program (SHEP), is currently underway in the United States. Results are expected in the early 1990s. If the results of this trial confirm the efficacy of treating ISH, the therapeutic challenge of ISH will be to selectively decrease systolic BP without undue side effects.

Blood pressure levels and variance assessed by ambulatory monitoring: optimal parameters

We obtained multiple ambulatory blood pressure monitoring (ABPM) records over five years from two trained, normotensive subjects experienced in wearing the apparatus. The resulting time series data on systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were used to suggest optimal parameters for monitoring by two instruments (Colin Medical Instruments ABPM-630 and Del Mar Avionics Pressurometer) and to compare two indirect methods (auscultatory and oscillometric). A 10-min sampling interval day and night provided sufficient density of data to support spectral analysis for ultradian rhythms in the frequency range of one cycle per hour to one cycle per 9 h on a 24-h record. Rhythms with major periods of approximately 3, 6, and 9 h were variously found in 94 normotensive subjects, aged 20 to 95 years, including the two trained subjects. When the monitoring period was extended to 72 h, the circadian (approximately 24 h) rhythm could be more sharply defined, as well as a 12-h harmonic. In some studies the two trained subjects wore two monitors, one on each arm, set to read simultaneously. From the simultaneous measurements on both arms, it was shown that averaging across three points (30 min of record) reduced the coefficient of variation between the two simultaneous records to 6% or less. Auscultatory and oscillometric methods were equally reliable. Echocardiographic data were obtained in five normotensive subjects and compared to their ABPM data. The ABPM records provided additional information about cardiovascular function not merely duplicating that obtained by acute stress tests, such as exercise or cold pressor responses, or echocardiography. Standards for ABPM are suggested.

Aortic and large artery stiffness: current methodology and clinical correlations

Current methodology for the in vitro determination of aortic and large artery stiffness is reviewed and involves three approaches: (1) the estimation of distensibility by pulse wave velocity measurement; (2) the estimation of distensibility from the fractional diameter change of a given arterial segment by imaging techniques (e.g., angiography, Doppler ultrasound) against pressure change; (3) the estimation of compliance by determining volume change against pressure change in the arterial system during diastolic runoff from the Windkessel model of the circulation. Clinical correlations may be summarized as follows: (1) age: a progressive stiffening on aging due to structural changes up to the seventh decade; (2) sex: a lower degree of stiffness in women until menopause, after which they show an accelerated stiffening, catching up with men by the seventh decade; (3) atherosclerosis: a dissociation between degree of stiffness and extent of atherosclerosis, with a suggestion that in advanced atherosclerosis the extensive calcification may lead to increased stiffness; (4) coronary disease: an inconsistent correlation by pulse wave velocity studies, but a strongly positive correlation by angiographic study of the aortic root; (5) diabetes mellitus: a significant correlation by pulse wave velocity study, particularly in the presence of advanced peripheral vascular disease; (6) hypertension (both essential and elderly patients with systolic): positive correlation but only referable to the stiffening effect of a higher mean arterial pressure (i.e., unrelated to structural changes), although an experimental study did show a loss of compliance unrelated to the mean arterial pressure level in baboons with chronic renovascular hypertension.

Concurrent compliance reduction and increased peripheral resistance in the manifestation of isolated systolic hypertension

The hemodynamic mechanisms responsible for producing isolated systolic hypertension (ISH) in the elderly are generally attributed to a decrease in arterial compliance. However, no consistent theoretical or experimental model has been proposed for the production of ISH. This problem was investigated with the use of computer simulation of the modified Windkessel model, an often-used tool in the study of arterioventricular function. Aortic pressure (Pa(t] and aortic flow (Qa(t] data were used to obtain the model parameters: peripheral resistance (Rs), arterial compliance (C) and characteristic impedance of the proximal aorta (Zo). Using Qa(t) as the input to the model, the effects of altered vascular properties on Pa(t) were studied by changing these model parameters. Graded reductions of C (25, 50 and 75%) alone increased systolic pressure (Ps), but also decreased diastolic pressure (Pd) to values below those found in ISH. On the other hand, an increase in Rs of 25% along with a 50 to 75% increase in C resulted in percent changes in Ps and Pd that would result in ISH from a normal pressure level. These results were consistent for a wide range of pressures. Decreased arterial compliance alone is not always responsible for the production of ISH. Rather, isolated systolic hypertension is usually the result of greatly reduced arterial compliance along with a smaller but significant increase in peripheral resistance.

Blood pressure changes with aging: evidence for a cohort effect

Data from cross-sectional surveys show an increase in systolic blood pressure with increasing age. However, cross-sectional data can be misleading. Our purpose in this study is to prospectively describe changes in systolic and diastolic blood pressure levels over time in community-dwelling elderly persons. The participants were 1,917 men and women aged 65 to 98 yr who had participated at least seven years in the Florida Geriatric Research Program, a community-based, multi-phasic health screening program located in Dunedin, Florida (USA). Our results show that contrary to the cross-sectional data, systolic and diastolic blood pressure levels tend to decrease with increasing age. Mean systolic blood pressure in women at the baseline visit (Visit 2) was 143 mmHg and three years later (Visit 5) it had dropped to 140 mmHg. This downward trend was consistent at all ages and for both men and women. Stratification by use of antihypertensive medication, weight change, and survivorship did not alter this association. Further follow-up of this cohort to Visit 7 revealed a U-shaped trend of blood pressure with aging. There was also clear evidence of a cohort effect, as the age-specific mean systolic blood pressure was consistently lower in each younger 5 yr birth cohort. Our results suggest that in a healthy elderly population, systolic and/or diastolic blood pressure levels do not increase with aging; this finding may have implications for the diagnosis and treatment of hypertension in the elderly.

Epidemiologic considerations in defining hypertension

Definitions of hypertension have historically been based on at least one of three concepts. The first approach identifies thresholds of hypertension based on the frequency of occurrence in the population. The statistical approach designates a point in the distribution (e.g., the 95th percentile), as the threshold for hypertension. This distribution method identifies different limits for hypertension depending on the age, sex, and race, of the population, all of which affect the average pressure. Although distribution curves do not by themselves identify thresholds for intervention, they are useful for examining changes in population groups over time. The second approach to defining hypertension relates pressures to the risk of morbidity and mortality and is characterized by a continuously graded curve with no clear categorical thresholds. Studies correlating both diastolic and systolic pressures with cardiovascular complications demonstrate continuous risks from lowest to highest values for both sexes, all ages, and both blacks and whites in the United States. The blood pressure-risk relationship provides a compelling rationale for treatment but does not by itself define thresholds for the initiation of therapy. The third approach uses data from clinical intervention trials to identify thresholds where the benefits of therapy outweigh the costs and side effects of long-term treatment. Although results of large randomized trials have clearly demonstrated reductions in morbidity and mortality by lowering blood pressures, consensus on the lowest threshold within the mild range for which antihypertensive drug treatment is recommended has not been reached. Because an optimal definition of hypertension must encompass all three approaches and the resultant classification scheme must be sufficient for all purposes, attempts to refine and improve upon the presently recommended thresholds will undoubtedly continue.

Effect of advancing age on cardiopulmonary baroreceptor function in hypertensive men

Blood pressure, heart rate, forearm vascular resistance, and hormonal responses to graded lower body negative pressure were investigated in 15 hypertensive men younger than 55 years of age (mean age, 44 +/- 2 years) and 13 comparably hypertensive men older than 55 years of age (mean age, 63 +/- 2 years). Baseline forearm vascular resistance was greater in the elderly group compared with the younger hypertensive men. However, forearm vascular resistance responses to selective unloading of low pressure cardiopulmonary baroreceptors were similar in the two groups. This finding suggests that normal vascular responses to the unloading of cardiopulmonary baroreceptors are preserved in subjects with advancing age and mild to moderate hypertension. Baseline plasma norepinephrine levels, as well as norepinephrine responses to lower body negative pressure, were comparable in the two groups. This finding suggests that, unlike normotensive subjects, essential hypertensive subjects do not have an age-related increase in sympathetic nervous system activity.

Systemic systolic hypertension in the elderly: correlation of hemodynamics, plasma volume, renin, aldosterone, urinary metanephrines and response to thiazide therapy

Twenty-four men, mean age 63 +/- 1.7 years, with systemic systolic hypertension were studied before and after 1 month of therapy with oral hydrochlorothiazide, 50 mg/day. The control mean plasma volume was 2,664 +/- 96 ml, cardiac index 3.9 +/- 0.2 liters/min/m2, stroke volume index 52 +/- 2 ml/beat/m2, systemic vascular resistance 1,351 +/- 80 dynes s cm-5, plasma aldosterone 8.6 +/- 1.0 ng/dl and 24-hour urinary excretion of metanephrines 0.371 +/- 0.044 mg. On renin-sodium profiling in 23 patients, 12 were classified into a normal group and 11 into a low-renin group; none had high renin values. Based on multiple regression analysis, the 24-hour urinary excretion of total metanephrines appeared to be the single most important factor explaining 28% of the variability in systolic blood pressure (BP). After therapy with oral hydrochlorothiazide, the elevated systolic BP decreased (p less than 0.0001) and diastolic BP decreased (p less than 0.005), with concomitant reduction in systemic vascular resistance (p less than 0.03). Patients in both the normal- and low-renin groups had normal plasma volume and responded similarly to thiazide diuretic therapy, without symptomatic side effects.

Management of isolated systolic hypertension in the elderly

Now that the benefits of treating diastolic hypertension in the elderly have been convincingly proved, attention is turning to the need for, and the choice of, treatment of isolated systolic hypertension in this age group. The hemodynamic mechanism differs in the elderly, whose isolated systolic hypertension is likely to be accompanied by reduced cardiac output, high peripheral resistance, and reduced plasma volume, whereas young people with similar blood pressure may have high cardiac output, normal peripheral resistance, and normal plasma volume. Increased risk of cardiovascular morbidity and mortality and the importance of reducing cardiac workload in older persons, are significant factors in the need for reduction of systolic pressure. After a good history and physical examination, and a careful check to ascertain that the elevated pressure is measured accurately, elderly patients can begin stepped-care therapy with a diuretic such as hydrochlorothiazide or chlorthalidone. The considerable dangers of a sudden drop in blood pressure can be avoided by giving small initial doses. Methyldopa or clonidine is recommended for step two; the third step can be hydralazine. Side effects, especially in the elderly, should be monitored carefully.

Comparison of the effects of diuretic therapy and low sodium intake in isolated systolic hypertension

Of 103 patients with isolated systolic hypertension, 71 were treated with diuretics and another 32 with low-sodium diet. In the 71 who were treated with diuretics, body weight decreased from 69.48 +/- 1.47 to 68.60 +/- 1.45 kg (p less than 0.0005) and systolic blood pressure from 178 +/- to 152 +/- 2 mm Hg (p less than 0.0005). Plasma renin activity increased from 1.78 +/- 0.30 to 7.32 +/- 1.78 ng/ml per hour (p less than 0.005) and urinary aldosterone from 10 +/- 1 to 23 +/- 4 micrograms per 24 hours (p less than 0.005). The greatest decrease in systolic blood pressure occurred in patients in the low-renin group (-32 +/- 2 mm Hg), whereas it decreased by 24 +/- 2 mm Hg (p less than 0.04) in the normal-renin group; however, blood pressure did not change significantly in the high-renin group. In the 32 patients who were treated with low-sodium diet, the 24-hour urinary sodium excretion decreased from 143 +/- 10 to 48 +/- 5 meq (p less than 0.005), body weight decreased from 71.18 +/- 2.50 to 70.17 +/- 2.47 kg (p less than 0.005), systolic blood pressure decreased from 174 +/- 2 to 156 +/- 3 mm Hg (p less than 0.0005), and diastolic blood pressure decreased from 90 +/- 1 to 87 +/- 1 mm Hg (p less than 0.01). Plasma renin activity increased from 2.25 +/- 0.33 to 4.27 +/- 0.43 ng/ml per hour (p less than 0.005) and urinary aldosterone from 9 +/- 1 to 15 +/- 2 micrograms per 24 hours (p less than 0.005). The decrease in the systolic blood pressure was related to the pretreatment 24-hour urinary sodium excretion (r = 0.40, p less than 0.05). The smallest decrease in systolic blood pressure occurred in the patients with high renin values (-1 +/- 9 mm Hg, n = 5), whereas the decrease in systolic blood pressure in the low-renin (n = 12) and normal-renin groups (n = 15) was similar, -22 +/- 2 mm Hg and -21 +/- 3 mm Hg, respectively (p less than 0.005 compared with the high-renin group). These results indicate that both diuretic therapy and low-sodium diet are effective antihypertensive means in most patients with isolated systolic hypertension and low or normal plasma renin activity.

Renin dependency of blood pressure in isolated systolic hypertension

The role of the renin system in the maintenance of the elevated systolic blood pressure in isolated systolic hypertension was investigated in 31 patients who received long-term treatment with propranolol (120 mg daily) and in another group of 22 patients with isolated systolic hypertension who received a test dose of captopril (25 or 50 mg). The greatest systolic blood pressure decrease (35 +/- 5 mm Hg) by propranolol occurred in the high-renin group (n = 9), and the smallest decrease (3 +/- 2 mm Hg) in the low-renin group (n = 9), whereas in the normal-renin group (n = 13), systolic blood pressure was decreased by propranolol by 22 +/- 5 mm Hg. For all the propranolol-treated patients, the decrement in the systolic blood pressure by propranolol was related to the control plasma renin activity (r = 0.63, p less than 0.01) and to the concurrent change in plasma renin activity (r = 0.70, p less than 0.001). Captopril decreased the systolic blood pressure by 55 +/- 10 mm Hg in the high-renin group (n = 11) and by 17 +/- 5 mm Hg in the normal-renin group (n = 6), whereas the smallest decrease (12 +/- 5 mm Hg) in systolic blood pressure occurred in the low-renin group (n = 5). In all the captopril-tested patients (n = 22), the decrease in systolic blood pressure by captopril was related to the control plasma renin activity (r = 0.75, p less than 0.001). These results indicate that the plasma renin activity value indicates the participation of the renin-angiotensin system in the maintenance of the elevated systolic blood pressure in patients with isolated systolic hypertension.

Impaired systemic arterial compliance in borderline hypertension

Arterial compliance was evaluated by pulse wave velocity, pulse pressure/stroke volume, and by an exponential analysis of the diastolic blood pressure decay curve in three groups of normotensive, borderline hypertensive, and established essential hypertensive patients. Two of the above three indices reflected significantly impaired arterial compliance in borderline hypertension, and all three indices were distinctly abnormal in patients with established hypertension. A close correlation among the three indices was observed in the entire study population. Multiple regression analysis indicated that age (p less than 0.005), systolic (p less than 0.005) and diastolic (p less than 0.025) pressure were independent determinants of pulse wave velocity; other factors such as total peripheral resistance, pulse pressure, and stroke volume were not. We conclude that arterial compliance becomes impaired early in hypertensive cardiovascular disease at the time when arterial pressure may be only slightly elevated. Thus structural alteration of the arterial wall can be demonstrated in borderline hypertension. Age, systolic and, to a lesser degree, diastolic pressures are the best determinants of arterial compliance in large vessels and are therefore important risk factors for evolving systemic arterial disease in essential hypertension.

Effects of diuretic therapy in low-, normal- and high-renin isolated systolic systemic hypertension

In 30 patients with isolated systolic systemic hypertension, diuretic therapy decreased body weight from 71.33 +/- 2.67 to 70.37 +/- 2.65 kg (p less than 0.0005) and the systolic blood pressure from 174 +/- 3 to 156 +/- 3 mm Hg (p less than 0.0005). Diastolic blood pressure and heart rate did not change significantly. Plasma renin activity increased from 2.25 +/- 0.33 to 4.27 +/- 0.43 ng/ml/hour (p less than 0.0005) and urinary aldosterone from 9 +/- 1 to 16 +/- 2 micrograms/24 hours (p less than 0.005). The antihypertensive effect of diuretics was significantly related only to the pretreatment plasma renin activity (r = -0.50, n = 30, p less than 0.05), and therefore the greatest decrease in systolic blood pressure occurred in the low-renin group, whereas the smallest occurred in the high-renin group (-22 +/- 2 vs -3 +/- 9 mm Hg, p less than 0.005). The diastolic blood pressure was significantly decreased only in the low-renin group (-7 +/- 2 mm Hg, p less than 0.005). There were no significant changes in blood pressure in 11 untreated control patients. These results indicate that diuretics are effective antihypertensive agents in most patients with low- and normal-renin isolated systolic systemic hypertension.

Forearm arterial distensibility in systolic hypertension

It is unclear whether the stiffened arterial tree in systolic hypertension is the cause or the effect of the disease. In this study, brachial and radial arterial pulses were sensed by external Pixie transducers and measurements of pulse wave velocity converted to volume distensibility using the Bramwell-Hill equation. Blood pressure was controlled as a variable by repeating the measurements at a variety of transmural arterial pressures. This was accomplished by encasing the forearm in a rigid plastic cylinder within which pressures were varied. Twenty-nine patients with systolic hypertension were compared with 22 age-matched control subjects. At ambient pressures the volume distensibility of patients was lower than that of control subjects (0.10 versus 0.18% delta volume/mm Hg, p less than 0.001) but there was no difference in volume distensibility between the two groups at any comparable transmural pressure. Nineteen patients were treated for 1 month with a thiazide diuretic agent and the studies were then repeated. Systolic and diastolic blood pressure decreased significantly and volume distensibility increased (0.10 to 0.15% delta volume/mm Hg, p less than 0.001) at ambient pressures. But at comparable transmural pressures, volume distensibility was unchanged. It is concluded that, in the forearm, increased arterial stiffness is the result and not the cause of systolic hypertension, but these data cannot exclude increased aortic stiffness as a significant factor. Thiazide diuretic drugs increase forearm arterial compliance by lowering blood pressure without a demonstrable drug effect on this arterial wall.

Geriatric hypertension

Hypertension in the elderly is a frequent occurrence and is associated with an increase in cardiovascular complications. Therapeutic drug intervention in diastolic-systolic hypertension is both safe and effective in decreasing cardiovascular morbidity and mortality. Convincing evidence supporting the value of therapeutic intervention in isolated systolic hypertension is not yet available. At present, selection of specific antihypertensive drugs remains empirical because of insufficient controlled trials in elderly hypertensives. Antihypertensive agents should be initiated in smaller dosages and titrated upward slowly with particular care in avoiding orthostatic hypotension. Above all, lifestyle modification should be kept to a minimum and special attention should be given to the patient's quality of life while on drug treatment.

Effect of arterial compliance on systolic blood pressure and cardiac function

To study the effects of arterial compliance on blood pressure and ventricular performance, 33 patients undergoing diagnostic cardiac catheterization who were found to be free of significant cardiac disease were selected. Since blood pressure is a continuous variable, a specific cutting point was not used as a criterion for selection, although 12 patients were classified as hypertensive. The interrelationships between blood pressure, peripheral resistance, arterial compliance, and stroke volume index were investigated by determining the linear correlation between any two desired variables; and by employing partial correlative analysis to determine whether an observed relationship was dependent upon or independent of the influence of a third variable. Peripheral resistance was observed to be independently related to diastolic pressure (r = 0.59, p less than 0.01); while arterial compliance was not only related to stroke volume index (r = 0.67, p less than 0.01) but was also independently related to systolic pressure (r = -0.63, p less than 0.01). Thus, these observations suggest that arterial compliance is a common hemodynamic variable related to both the level of systolic pressure and ventricular performance.

Aortic rigidity and plasma catecholamines in essential hypertensive patients

Aortic rigidity, plasma noradrenaline and adrenaline, and hemodynamic parameters were measured in 48 essential hypertensive patients, 25 younger than 45 (Group I) and 23 of 45 years and over (Group II). Aortic rigidity was determined by the ratio of pulse pressure over stroke volume. Aortic rigidity and hemodynamic parameters were also determined after combined alpha-beta receptor blockade induced by Labetalol (mg 100 IV) or by Propranolol (mg 10 IV) plus Phentolamine (mg 10 IV). The aortic rigidity index was significantly higher in Group II, systolic arterial pressure being significantly higher. All other data, including plasma noradrenaline and adrenaline, were not significantly different in the two groups. In Group II a significant correlation (r = 0.62) was noted between aortic rigidity indexes and plasma noradrenaline values. The alpha-beta receptor blockade induced a decrease of aortic rigidity particularly in Group II, owing to a more marked decrease of systolic arterial pressure. A highly significant correlation was noted in Group II between the changes in aortic rigidity index and the basal plasma noradrenaline levels (r = 0.81). Therefore, the aortic rigidity in essential hypertensive patients older than 45 is influenced by the sympathetic nervous system activity, as judged by plasma noradrenaline levels. This influence seems related to an increase with age of aortic responsiveness to sympathetic stimulation.

Arterial compliance in systolic hypertension

Arterial compliance as estimated by pulse wave velocity and the pulse pressure/stroke volume index was evaluated in 27 normotensive subjects, 21 patients with established, and 18 patients with systolic essential hypertension. Pulse wave velocity was elevated to the same degree in both hypertensive groups when compared to the normotensive controls. The pulse pressure/stroke volume index was higher in essential hypertension than in normotensive subjects and even higher in patients with systolic hypertension. It is concluded that both indices are useful clinical tools to determine arterial compliance. Systolic hypertension does not always indicate stiffening of the arterial tree, but may result from a high stroke volume in the presence of a normal arterial compliance.

Isolated systolic hypertension in Evans county--I. Prevalence and screening considerations

Studies suggest that isolated hypertension involves pathophysiological change different from essential hypertension; while clinical trials of drug treatment of isolated systolic hypertension are underway, little is known of its descriptive epidemiology. This paper reports characteristics of isolated systolic hypertension in biracial Evans County, Georgia, 1967-69. Isolated systolic hypertension was rare below age 40, but the percent prevalence increased greatly at older ages. Defining isolated systolic hypertension as diastole blood pressure (DBP) less than 95 and systolic blood pressure (SBP) greater than 160, age-adjusted percent prevalence at ages 40 and above were 9.6, 10.6, 15.1, and 18.3 for white males, black males, white females, and black females respectively. Percent prevalence declined to 4.8, 6.3, 9.7, and 12.7 in the four race/sex groups when a DBP cutoff of 90 was used. Unlike essential hypertension, percent prevalence of isolated systolic hypertension varied more by sex than by race: it was 60-100% higher in females than in males and only 10--30% higher in blacks than in whites. Percent prevalence of isolated systolic hypertension for the second and third of three BP readings (one clinic visit) increased compared to the first reading, the reverse of what is usually found for essential hypertension. DBP variability was relatively greater than SBP variability and probably accounted for the changes in percent prevalence. These data support clinical studies indicating isolated systolic hypertension is a distinct syndrome. This condition, shown to be a risk factor for death and disease in other studies, was common at older ages and may increasingly become health problem as the population ages.

Pulse pressure-I. Level and associated factors in four Chicago epidemiologic studies

Because systolic blood pressure rises more sharply than diastolic blood pressure for those middle aged and beyond, leading to an increasing prevalence with advancing age of elevated systolic blood pressure without elevated diastolic pressure, i.e. so-called pure systolic hypertension, the question arises as to whether or not factors that have been shown to be related to blood pressure and hypertension are related to pure systolic hypertension or to 'classical' hypertension, i.e. hypertension defined solely by the level of the diastolic pressure. This question was examined in four Chicago epidemiologic studies by examining the associations between several variables and pulse pressure, with pulse pressure redefined so that the association between a variable and pulse pressure indicated whether the variable was more strongly related to systolic or diastolic blood pressure. In these four studies, glucose, heart rate and cigarette use tended to show a stronger association with systolic pressure, suggesting a possible association with pure systolic hypertension, while hematocrit, serum cholesterol, and uric acid tended to be more strongly associated with diastolic pressure, or equally associated with systolic and diastolic pressure, suggesting an association with 'classical' hypertension. Relative weight tended to be more strongly associated with systolic pressure under the age of 35 and more strongly associated with diastolic pressure after age 45.

Hypertension in the elderly: the time has come to treat

Both pure systolic, and systolic plus diastolic hypertension are risk factors for cerebrovascular and cardiovascular disease in patients over 65 years old, but the efficacy of antihypertensive therapy in preventing the complications of hypertension in the elderly has been questioned. The risks associated with such therapy seem to have been overemphasized. Although the evidence is incomplete, elderly patients should be treated when the systolic blood pressure exceeds 160 mm Hg or the diastolic pressure exceeds 95 mm Hg, or both. A revised stepped-care approach, with use of vasodilating agents as the Step-2 drugs, is proposed.

Systolic hypertension: hemodynamic mechanism and choice of antihypertensive treatment

Arterial compliance and indexes of ventricular ejection were measured in 27 men with systolic hypertension. The patients were separated into two age groups, younger or older than age 35 years, and matched with normotensive control subjects. Arterial compliance was estimated from analysis of the monoexponential blood pressure-time curve during diastole, according to a simple viscoelastic model. In the younger patients, arterial compliance and stroke volume were within normal ranges. Rapid ejection time was significantly reduced (P less than 0.001), indicating an increased venlocity in the first part of ventricular ejection. Systolic pressure decreased significantly after administration of propranolol, which also caused prolongation of rapid ejection time. In the older patients, indexes of ventricular ejection were within normal limits. arterial compliance was significantly reduced (P less than 0.01) and was negatively correlated with the level of systolic pressure (P less than 0.001). Systolic pressure decreased significantly after administration of sodium nitroprusside, which caused an increase in arterial compliance. These findings provide evidence that: (1) the hemodynamic mechanisms of systolic hypertension differ in younger and older patients, and (2) these hemodynamic differences should be taken into account when choosing drugs to decrease systolic pressure.

Systolic hypertension: occurrence and treatment in a defined community

Systolic hypertension, a disorder occurring predominantly in the elderly, is associated with an increased incidence of stroke and coronary artery disease. Based on the supposition that it is a risk factor, many authorities have urged that it be treated. This report concerns an experience in treating systolic hypertension in a defined ambulatory population of 898 hypertensive subjects in a work-site program. The systolic hypertension group (N = 39) was compared with a matched diastolic hypertension group and with a matched systolic/diastolic hypertension group (N = 39 each). The patients with systolic hypertension responded to standard treatment (chiefly with diuretics), but less satisfactorily than did the patients with diastolic hypertension. Side effects or toxicity were uncommon and did not interfere with the therapeutic regimen. However, the ultimate value of such therapy in the prevention of vascular complications remains to be determined.

Hazards in treatment of systolic hypertension

Eight patients with arteriosclerotic systolic hypertension whose blood pressure had been nonresponsive to conventional antihypertensive therapy, were given minoxidil in daily doses of 4 to 15 mg. Within 2 to 5 days the blood pressure of seven patients was brought to more "normal" levels. After 10 to 20 days of treatment, a significant weight increase was observed with a concomitant rise of blood pressure, which could be overcome by more vigorous diuretic therapy. However, six of the seven blood pressure responders and the one nonresponder complained of severe adverse effects curtailing further use of the drug. It is concluded that despite the effectiveness of arteriolar vasodilation in the reduction of elevated systolic blood pressure, such lowering may be deleterious in patients with atherosclerotic involvement of vital organs.

Hemodynamics of essential hypertension in young subjects

Cardiac output was determined in 42 young essential hypertensives (15 to 25 yrs); values ranged from 3.86 to 10.30 L./minute. These differences were not related to magnitude of volemia. Correlation of output to weekly blood pressure average (BPav) was not significant; its relationship to intraarterial pressure (BPia) was not significant in 21 patients aged 20 to 25 and of borderline significance in 13 aged 15 to 19. Blood pressure changes associated with the study (BPia--BPav) were also not consistently related to cardiac output. Six patients had systolic hypertension; only one had elevated stroke volume. These results outline as complex a picture in young essential hypertensives as in older subjects.

Role of hypertension in atherosclerosis and cardiovascular disease

Clinical, experimental and pathologic studies strongly indicate that hypertension is a major factor in coronary heart disease, sudden death, stroke congestive heart failure and renal insufficiency. The deleterious effect of the elevated blood pressure on the cardiovascular system appears to be due mainly to the mechanical stress placed on the heart and blood vessels. Humoral factors and vasoactive hormones such as angiotensin, catecholamines and prostaglandins may play a role in the pathogenesis of hypertensive cardiovascular disease but this role has not yet been defined and is probably secondary. Hypertension and the resulting increase in tangential tension on the myocardial and arterial walls, leads to the development of hypertensive heart disease and congestive heart failure as well as hypertensive vascular disease that affects not only the kidneys but also the heart and brain. Hypertensive vascular disease involves both large and small arteries as well as arterioles and is characterized by fibromuscular thickening of the intima and media with luminal narrowing of the small arteries and arterioles. The physical stress of hypertension on the arterial wall also results in the aggravation and acceleration of atherosclerosis, particularly of the coronary and cerebral vessels. Moreover, hypertension appears to increase the susceptibility of the small and large arteries to atherosclerosis. Thus the patient with hypertension is a candidate for both hypertensive and atherosclerotic vascular disease of the coronary and cerebral vessels leading to occlusive disease of both the large and small arteries and resulting in myocardial infarction and stroke. Other major complications of hypertensive vascular disease include rupture and thrombotic occlusion of blood vessels, especially in the brain. Disease of the arterial media, which begins in childhood with the deposition of calcium in the vessels, may be an important cause of arterial hypertension. This form of hypertension may manifest itself in adults as arteriosclerotic hypertension and lead to cardiovascular complications very similar to those of essential hypertension. The relation of arteriosclerotic hypertension to nutritional factors, including dietary salt intake, deserves study.

High cardiac output hypertensions

Hyperkinetic circulation, as it is related to the clinical hypertensive diseases, is defined and its implications interpreted. These pathophysiological considerations have an important bearing in understanding the pressor mechanisms underlying hypertension and the application of therapy. Another very important consideration is the value of elucidating the mechanisms for the hyperdynamic circulation, for with a clearer understanding of these, we shall come closer to an explanation of the pathogenesis of hypertension.