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

Hemodynamic profiles of arterial hypertension with ambulatory blood pressure monitoring

Blood pressure (BP) measurements obtained during a twenty-four-hour ambulatory blood pressure monitoring (24 h ABPM) have not been reliably applied to extract arterial hemodynamics. We aimed to describe the hemodynamic profiles of different hypertension (HT) subtypes derived from a new method for total arterial compliance (C_t) estimation in a large group of individuals undergoing 24 h ABPM. A cross-sectional study was conducted, which included patients with suspected HT. Cardiac output, C_t, and total peripheral resistance (TPR) were derived through a two-element Windkessel model without having a pressure waveform. Arterial hemodynamics were analyzed according to HT subtypes in 7434 individuals (5523 untreated HT and 1950 normotensive controls [N]). The individuals mean age was 46.2 ± 13.0 years; 54.8% were male, and 22.1% were obese. In isolated diastolic hypertension (IDH), the cardiac index (CI) was greater than that in normotensive (N) controls (CI: IDH vs. N mean difference 0.10 L/m/m²; CI 95% 0.08 to 0.12; p value <0.001), with no significant clinical difference in C_t. Isolated systolic hypertension (ISH) and divergent systolic-diastolic hypertension (D-SDH) had lower C_t values than nondivergent HT subtype (C_t: divergent vs. nondivergent mean difference -0.20 mL/mmHg; CI 95% -0.21 to -0.19 mL/mmHg; p value <0.001). Additionally, D-SDH displayed the highest TPR (TPR: D-SDH vs. N mean difference 169.8 dyn*s/cm^-5; CI 95% 149.3 to 190.3 dyn*s/cm^-5; p value <0.001). A new method is provided for the simultaneous assessment of arterial hemodynamics with 24 h ABPM as a single diagnostic tool, which allows a comprehensive assessment of arterial function for hypertension subtypes. Main hemodynamic findings in arterial HT subtypes with regard to C_t and TPR. The 24 h ABPM profile reflects the state of C_t and TPR. Younger individuals with IDH present with a normal C_t and frequently increased CO. Patients with ND-SDH maintain an adequate C_t with a higher TPR, while subjects with D-SDH present with a reduced C_t, high PP and high TPR. Finally, the ISH subtype occurs in older individuals with significantly reduced C_t, high PP and a variable TPR proportional to the degree of arterial stiffness and MAP values. There was an observed increase in PP with age in relation to the changes in C_t (see also text). SBP: systolic blood pressure; DBP: diastolic blood pressure; MAP: mean arterial pressure; PP: pulse pressure; N: normotension; HT: hypertension; IDH: isolated diastolic hypertension; ND-SDH: nondivergent systole-diastolic hypertension; D-SDH: divergent systolic-diastolic hypertension; ISH: isolated systolic hypertension; C_t: total arterial compliance; TPR: total peripheral resistance; CO: cardiac output; 24 h ABPM: 24 h ambulatory blood pressure monitoring.

Loneliness and cardiovascular reactivity to acute stress in older adults

Loneliness has been linked to cardiovascular health outcomes in older adulthood. One proposed mechanism by which loneliness influences cardiovascular health is through atypical cardiovascular reactivity (CVR) to stress. This study is an examination of loneliness and CVR in older adults, comparing associations across two stressors and two commonly used measures of loneliness, with a particular focus on underlying hemodynamic variables including cardiac output, total peripheral resistance, and ejection time (EJT). Eighty older adults, ranging in age from 55 to 88 years (M = 68.93, SD = 8.28), completed two versions of the UCLA loneliness scale (a 20‐item and a briefer, three‐item) and took part in a laboratory stress‐testing procedure which included a mental arithmetic challenge and a public speaking task. Cardiovascular activity was monitored continuously throughout. For the 20‐item version of the UCLA loneliness scale, loneliness was not significantly related to CVR, and was only significantly associated with lower levels of overall EJT. For the three‐item version of the UCLA, no associations withstood adjustment for multiple testing. Loneliness was not reliably associated with CVR. Further, although greater loneliness was related to lower levels of overall EJT, this was only observed for the 20‐item scale. The findings do not strongly provide support for reactivity to acute stress as a pathway linking loneliness to disease outcomes, and highlight key methodological issues related to the assessment of loneliness‐reactivity associations for future.

This article provides an examination of associations between loneliness and cardiovascular reactivity (CVR) to acute stress in a sample of older adults. The findings do not provide support for a reliable association between loneliness and CVR in older adults. This article highlights methodological issues that are important to consider for future in this research area.

Inadequacy of Augmentation Index for Monitoring Arterial Stiffness: Comparison with Arterial Compliance and Other Hemodynamic Variables

PURPOSE

Augmentation Index (AI_x) is used clinically for monitoring both wave reflections and arterial stiffness, which when increased is a risk factor of cardiovascular mortality and morbidity. We hypothesize that AI_x is not solely related to vascular stiffness as described by arterial compliance and other hemodynamic parameters since AI_x underestimates wave reflections.

METHODS

Aortic pressure and flow datasets (n = 42) from mongrel dogs were obtained from our experiments and Mendeley Data under various conditions. Arterial compliances based on the Windkessel model (C_t), the stroke volume (SV) to pulse pressure (PP) ratio (C_v = SV/PP), and at inflection pressure point (C_Pi) were computed. Other relevant hemodynamic factors are also computed.

RESULTS

AI_x was poorly associated with arterial stiffness calculated from C_t (r = 0.299, p = 0.058) or C_Pi (r = 0.203, p = 0.203), even when adjusted for heart rates. C_t and C_v were monotonically associated. Alterations in inflection pressure (P_i) did not follow the changes in pulse pressure (PP) (r = 0.475, p = 0.002), and P_i was quantitatively similar to systolic pressure (r = 0.940, p < 0.001).

CONCLUSION

AI_x is neither linearly correlated with arterial stiffness, nor with arterial compliance and several cardiac and arterial parameters have to be considered when AI_x is calculated.

Arterial Flow, Pulse Pressure and Pulse Wave Velocity in Men and Women at Various Ages

The increase in pulse pressure (PP) that occurs with advancing age is predominantly due to reduced arterial distensibility leading to decreased aortic compliance, particularly in the elderly, in whom high blood pressure mainly manifests as isolated systolic hypertension. Since age-related changes in stroke volume are minimal compared with changes in PP, PP is often considered a surrogate measure of arterial stiffness. However, since PP is determined by both cardiac and arterial function, a more precise and reliable means of assessment of arterial stiffness is arterial pulse wave velocity (PWV), a parameter that is only dependent on arterial properties. Arterial stiffness as measured by PWV has been found to be a powerful pressure-related indicator for cardiovascular morbidity and mortality. We analyzed PP and PWV in men and women of various age groups in healthy volunteers as well as cardiac patients with different types of diseases. The findings identified several striking sex-specific differences which demand consideration in guidelines for diagnostic procedures, for epidemiological analysis, and in evaluation of therapeutic interventions.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

Increasing pulse wave velocity in a realistic cardiovascular model does not increase pulse pressure with age

The mechanism of the well-documented increase in aortic pulse pressure (PP) with age is disputed. Investigators assuming a classical windkessel model believe that increases in PP arise from decreases in total arterial compliance (C(tot)) and increases in total peripheral resistance (R(tot)) with age. Investigators assuming a more sophisticated pulse transmission model believe PP rises because increases in pulse wave velocity (c(ph)) make the reflected pressure wave arrive earlier, augmenting systolic pressure. It has recently been shown, however, that increases in c(ph) do not have a commensurate effect on the timing of the reflected wave. We therefore used a validated, large-scale, human arterial system model that includes realistic pulse wave transmission to determine whether increases in c(ph) cause increased PP with age. First, we made the realistic arterial system model age dependent by altering cardiac output (CO), R(tot), C(tot), and c(ph) to mimic the reported changes in these parameters from age 30 to 70. Then, c(ph) was theoretically maintained constant, while C(tot), R(tot), and CO were altered. The predicted increase in PP with age was similar to the observed increase in PP. In a complementary approach, C(tot), R(tot), and CO were theoretically maintained constant, and c(ph) was increased. The predicted increase in PP was negligible. We found that increases in c(ph) have a limited effect on the timing of the reflected wave but cause the system to degenerate into a windkessel. Changes in PP can therefore be attributed to a decrease in C(tot).

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.

Analysis of the effect of ageing on rising edge characteristics of the photoplethysmogram using a modified Windkessel model

Ageing is one of the main contributing factors towards increasing arterial stiffness, leading to changes in peripheral pulses propagation. Therefore the characteristics of the photoplethysmogram (PPG) pulse, especially the rising edge and peak position, are greatly affected. In this study, the PPG pulse rising edge and corresponding peak position have been investigated non-invasively in human subjects as a function of age. Fifteen healthy subjects were selected and grouped in five age intervals, from 20 to 59 years, based on their comparable systolic-diastolic blood pressure and PPG amplitude. As expected, the peripheral pulse shows a steep rise and early peak in younger subjects. With age, the slope becomes blunted and in older subjects, the rise is very gradual and the pulse peak appears much later. Qualitative results were further verified by a modified 10-element Windkessel model to quantify the lumped parameter changes with ageing. This verification highlighted some specific changes in vascular parameters with aging. The rising edge could be considered as one parameter in determining the age-dependent vascular state.

Increase in pulse wavelength causes the systemic arterial tree to degenerate into a classical windkessel

Two competing schools of thought ascribe vascular disease states such as isolated systolic hypertension to fundamentally different arterial system properties. The "windkessel school" describes the arterial system as a compliant chamber that distends and stores blood and relates pulse pressure to total peripheral resistance (R(tot)) and total arterial compliance (C(tot)). Inherent in this description is the assumption that arterial pulse wavelengths are infinite. The "transmission school," assuming a finite pulse wavelength, describes the arterial system as a network of vessels that transmits pulses and relates pulse pressure to the magnitude, timing, and sites of pulse-wave reflection. We hypothesized that the systemic arterial system, described by the transmission school, degenerates into a windkessel when pulse wavelengths increase sufficiently. Parameters affecting pulse wavelength (i.e., heart rate, arterial compliances, and radii) were systematically altered in a realistic, large-scale, human arterial system model, and the resulting pressures were compared with those assuming a classical (2-element) windkessel with the same R(tot) and C(tot). Increasing pulse wavelength as little as 50% (by changing heart rate -33.3%, compliances -55.5%, or radii +50%) caused the distributed arterial system model to degenerate into a classical windkessel (r(2) = 0.99). Model results were validated with analysis of representative human aortic pressure and flow waveforms. Because reported changes in arterial properties with age can markedly increase pulse wavelength, results suggest that isolated systolic hypertension is a manifestation of an arterial system that has degenerated into a windkessel, and thus arterial pressure is a function only of aortic flow, R(tot), and C(tot).

Effects of Aging on the Diagnostic Assessment of Valvular Heart Disease

The diagnostic assessment of the severity of valvular heart disease in the older population is impacted by the anatomic and physiologic changes that accompany normal aging and by the interposition of diseases prevalent in the elderly. In this paper, the impact of those changes on the assessment of valvular heart disease will be reviewed. Special attention will be paid to the effects of age and disease on the measurement of the pressure drop and orifice area.

Age-related changes in hemodynamics affecting valve performance

Degenerative processes result in changes in both the aortic and mitral valves. For example, degenerative changes may lead to significant aortic stenosis or myxomatous mitral valves. Flows through each valve are determined not only by the properties of the valve itself, but also by the properties of proximal and distal chambers, which also undergo changes with age and diseases associated with the elderly, such as hypertension and coronary artery disease. Assessment of valvular performance should consider the effects of atrial-ventricular coupling (for the mitral valve) or ventricular-arterial coupling (for the aortic valve). Design of therapy or intervention should accordingly consider effects on the system as a whole.

Resolving the hemodynamic inverse problem

The "hemodynamic inverse problem" is the determination of arterial system properties from pressures and flows measured at the entrance of an arterial system. Conventionally, investigators fit reduced arterial system models to data, and the resulting model parameters represent putative arterial properties. However, no unique solution to the inverse problem exists-an infinite number of arterial system topologies result in the same input impedance (Zin) and, therefore, the same pressure and flow. Nevertheless, there are exceptions to this theoretical limitation; total peripheral resistance (Rtot), total arterial compliance (Ctot), and characteristic impedance (ZO) can be uniquely determined from input pressure and flow. Zin is determined completely by Ctot and Rtot at low frequencies, Zo at high frequencies, and arterial topology and reflection effects at intermediate frequencies. We present a novel method to determine the relative contribution of Zo, Ctot, Rtot and arterial topology/reflection to Zin without assuming a particular reduced model. This method is tested with a large-scale distributed model of the arterial system, and is applied to illustrative cases of measured pressure and flow. This work, thus, lays the theoretical foundation for determining the arterial properties responsible for increased pulse pressure with age and various arterial system pathologies.

Constructive and destructive addition of forward and reflected arterial pulse waves

Although the physics of arterial pulse wave propagation and reflection is well understood, there is considerable debate as to the effect of reflection on vascular input impedance (Z(in)), pulsatile pressure, and stroke work (SW). This may be related to how reflection is studied. Conventionally, reflection is experimentally abolished (thus radically changing unrelated parameters), or a specific model is assumed from which reflection can be removed (yielding model-dependent results). The present work proposes a simple, model-independent method to evaluate the effect of reflection directly from measured pulsatile pressure (P) and flow (Q). Because characteristic impedance (Z(0)) is Z(in) in the absence of reflection, the P with reflection theoretically removed can be calculated from Q x Z(0). Applying this insight to an illustrative case indicates that reflection has the least effect on P and SW at normal pressure but a greater effect with vasodilation and vasoconstriction. Z(in), P, and SW are increased or decreased depending on the relative amount of constructive and destructive addition of forward and reflected arterial pulse waves.

Sotalol in the treatment of fetal dysrhythmias

BACKGROUND

Fetal tachycardia may cause hydrops fetalis and lead to fetal death. No unanimity of opinion exists regarding the optimum treatment. This study evaluates our experience with transplacental sotalol therapy to treat fetal tachycardias in terms of safety and efficacy.

METHODS AND RESULTS

The charts of 21 patients who were treated with sotalol for fetal tachycardia were reviewed. Ten fetuses had atrial flutter (AF), 10 had supraventricular tachycardia (SVT), and 1 had VT. Hydrops fetalis was present in 9 fetuses. Drug treatment was successful in establishing sinus rhythm in 8 of 10 fetuses with AF and in 6 of 10 fetuses with SVT. The mortality rate in this study was 19% (4 of 21 fetuses; 3 had SVT and 1 had AF); 3 deaths occurred just days after the initiation of sotalol therapy, and 1 occurred after a dosage increase. At birth, tachycardia was present in 6 infants. Two patients who converted to sinus rhythm in utero suffered from neurologic pathology postnatally.

CONCLUSIONS

Fetal tachycardia is a serious condition in which treatment should be initiated, especially in the presence of hydrops fetalis. The high success rate in fetuses with AF suggests that sotalol should be considered a drug of first choice to treat fetal AF. The low conversion rate and the fact that 3 of the 4 deaths in this study occurred in fetuses with SVT indicate that the risks of sotalol therapy outweigh the benefits in this group and that sotalol should, therefore, be limited in the treatment of fetal SVT.

Pathophysiology of Hypertension in the Elderly

The onset and progression of hypertension is associated with alterations in structure, function, and hemodynamics of the heart, vascular system, and other major organs. An understanding of the structural and functional changes in the cardiovascular system associated with this process would allow for early detection and the development of treatment strategies. In this paper, we focus on the anatomic alterations that accompany vascular aging and the resulting cardiovascular dynamics. Techniques to measure changes in cardiovascular dynamics and left ventricular performance are reviewed. The impact of therapeutic strategies on cardiovascular dynamics and left ventricular function are also discussed. (c)2000 by CVRR, Inc.

Echocardiographic features and QT dispersion in borderline isolated systolic hypertension in the elderly

The aim of our study was to examine the structure of left ventricle, diastolic filling indexes and QT dispersion in elderly patients (aged 60 years and over) with borderline isolated systolic hypertension in a population screening program and to compare them with age matched controls. One hundred and four subjects (66 female, 38 male, mean age 66+/-5) and 110 normotensive age and sex matched controls (64 female, 46 male, mean age 66+/-5) were included in the study. Echocardiographic features of left ventricle, left atrium and cardiac valves, diastolic filling indexes and QT dispersion in 12 lead electrocardiographic examination were studied. In borderline hypertensive elderly, left ventricular hypertrophy was a more frequent finding compared with the controls (33% versus 15% respectively). Diastolic filling indexes were impaired, presence of left atrial enlargement and cardiac valve calcification were also more frequent in the patients group. In the electrocardiographic examination, the duration of QT and corrected QT interval and dispersion of QT and QTc were significantly prolonged compared with the controls. It is concluded that patients with borderline isolated systolic hypertension have more unfavourable echocardiographic and electrocardiographic findings compared with the normotensive elderly and especially those with end organ damage should be treated as defined for isolated systolic hypertension.

Ambulatory pulse pressure: a potent predictor of total cardiovascular risk in hypertension

A wide pulse pressure (PP) is a marker of increased artery stiffness and high cardiovascular (CV) risk. To investigate the prognostic value of ambulatory PP, which is currently unknown, we studied 2010 initially untreated subjects with uncomplicated essential hypertension (mean age, 51.7 years; 52% men). All subjects underwent baseline procedures including 24-hour noninvasive ambulatory blood pressure (BP) monitoring. The mean duration of follow-up was 3.8 years (range, 0 to 11 years), and CV morbidity and mortality were the outcome measures. There were 200 major CV events (2.61 per 100 person-years), 36 of which were fatal (0.47 per 100 person-years). In the 3 tertiles of the distribution of office PP, the rate of total CV events (per 100 persons per year) was 1.38, 2. 12, and 4.34, respectively, and that of fatal events was 0.12, 0.30, and 1.07 (log-rank test, both P<0.01). In the 3 tertiles of the distribution of average 24-hour PP, the rate of total CV events was 1.19, 1.81, and 4.92, and that of fatal events was 0.11, 0.17, and 1. 23 (log-rank test, both P<0.01). After controlling for several independent risk markers including white coat hypertension and nondipper status, we found that ambulatory PP was associated with the biggest reduction in the -2 log likelihood statistics for CV morbidity (P<0.05 versus office PP). In each of the 3 tertiles of office PP, CV morbidity and mortality increased from the first to the third tertile of average 24-hour ambulatory PP (log-rank test, all P<0.01). Age, left ventricular hypertrophy, and nondipper status were independent predictors of CV mortality, and the further predictive effect of ambulatory PP (P<0.001) was marginally but not significantly superior to that of office PP and average 24-hour systolic BP. We conclude that ambulatory PP is a potent risk marker in essential hypertension. CV morbidity is more closely predicted by ambulatory than by office PP even after control for multiple risk factors.

A new description of arterial function: the compliance-pressure loop

Hypertension and atherosclerosis are associated with reduced arterial compliance, which is the principal component that reflects the dynamic behavior of the arterial system. Hence, change in arterial compliance has been used as a compass of arterial wall properties, as well as an effective parameter for assessing therapeutic treatment efficacy. The arterial compliance-blood pressure loop concept is introduced here for assessment of arterial function. Aortic pressure and flow were measured in experimental dogs during normal and acute hypertension. The compliance-pressure loops were constructed from pulsatile blood pressure waveforms and the corresponding compliances. The features of the loop are that, for any given heart beat, arterial compliance is seen to be maximal in early systole to facilitate ventricular ejection, compliance decreasing during the remainder of systole owing to increased blood pressure and reduced aortic flow, compliance in diastole increasing as pressure declines. The arteries are stiffer with reduced compliance in hypertension. Thus, the compliance-pressure loop can provide an effective characterization of the dynamic behavior of the arterial system in terms of pressure-flow relation and blood vessel properties.

Superiority of ibutilide (a new class III agent) over DL-sotalol in converting atrial flutter and atrial fibrillation. The Ibutilide/Sotalol Comparator Study Group

OBJECTIVE

To compare the efficacy and safety of a single dose of ibutilide, a new class III antiarrhythmic drug, with that of DL-sotalol in terminating chronic atrial fibrillation or flutter in haemodynamically stable patients.

DESIGN

Double blind, randomised study.

SETTING

43 European hospitals.

PATIENTS

308 patients (mean age 60 years, 70% men, 48% with heart disease) with sustained atrial fibrillation (n = 251) or atrial flutter (n = 57) (duration three hours to 45 days) were randomised to three groups to receive a 10 minute infusion of 1 mg ibutilide (n = 99), 2 mg ibutilide (n = 106), or 1.5 mg/kg DL-sotalol (n = 103). Infusion was discontinued at termination of the arrhythmia.

MAIN OUTCOME MEASURE

Successful conversion of atrial fibrillation or flutter, defined as termination of arrhythmia within one hour of treatment.

RESULTS

Both drugs were more effective against atrial flutter than against atrial fibrillation. Ibutilide was superior to DL-sotalol for treating atrial flutter (70% and 56% v 19%), while the high dose of ibutilide was more effective for treating atrial fibrillation than DL-sotalol (44% v 11%) and the lower dose of ibutilide (44% v 20%, p < 0.01). The mean (SD) time to arrhythmia termination was 13 (7) minutes with 2 mg ibutilide, 19 (15) minutes with 1 mg ibutilide, and 25 (17) minutes with DL-sotalol. In all patients, the duration of arrhythmia before treatment was a predictor of arrhythmia termination, although this was less obvious in the group that received 2 mg ibutilide. This dose converted almost 48% of atrial fibrillation that was present for more than 30 days. Concomitant use of digitalis or nifedipine and prolongation of the QTc interval were not predictive of arrhythmia termination. Bradycardia (6.5%) and hypotension (3.7%) were more common side effects with DL-sotalol. Of 211 patients given ibutilide, two (0.9%) who received the higher dose developed polymorphic ventricular tachycardia, one of whom required direct current cardioversion.

CONCLUSION

Ibutilide (given in 1 or 2 mg doses over 10 minutes) is highly effective for rapidly terminating persistent atrial fibrillation or atrial flutter. This new class III drug, under monitored conditions, is a potential alternative to currently available cardioversion options.

Lacidipine, hydrochlorothiazide and their combination in systolic hypertension in the elderly

OBJECTIVE

To compare with placebo the efficacies of once-daily administrations of lacidipine and hydrochlorothiazide separately and in combination to elderly patients with systolic hypertension.

DESIGN AND METHODS

Nineteen elderly subjects (five men and 14 women, median age 71 years, range 62-79 years) participated in the study, which had a randomized double-blind crossover design. For each subject there were four treatment phases, each of duration 4 weeks. The initial treatments in each phase were 2 mg lacidipine once a day and 25 mg hydrochlorothiazide once a day, separately and in combination, and placebo. Doses of each agent could be doubled after 2 weeks in each phase if the patient's goal systolic blood pressure had not been achieved. The numbers of subjects administered the higher dose of each treatment were 13 for placebo, 14 for lacidipine, 11 for hydrochlorothiazide and eight for lacidipine plus hydrochlorothiazide.

RESULTS

End-of-phase mean clinic blood pressures were 164/85 mmHg with placebo, 159/82 mmHg with lacidipine, 157/84 mmHg with hydrochlorothiazide and 152/82 mmHg with lacidipine plus hydrochlorothiazide. Systolic blood pressure was significantly reduced during all active treatment phases compared with placebo and that for the lacidipine plus hydrochlorothiazide phase was also significantly less than those for both of the other active treatment phases. There was no difference between sitting and standing blood pressure for any phase. Factorial analysis of the main effects of treatment indicated that the effects of lacidipine and hydrochlorothiazide on clinic blood pressure were additive and also that heart rate was higher when hydrochlorothiazide had been administered. Ambulatory blood pressure monitoring confirmed the pattern of the responses of blood pressure and showed that administration of hydrochlorothiazide had a significantly greater effect on systolic blood pressure and a longer duration of action than did administration of lacidipine. There was no difference in the frequency of adverse effects among any of the phases.

CONCLUSIONS

In treating elderly systolic hypertensives the diuretic hydrochlorothiazide is a more effective antihypertensive agent with a longer duration of action than is the calcium channel antagonist lacidipine. In combination the effects of these two drugs on blood pressure are additive.

Vessel growth and collapsible pressure-area relationship

The role that the pattern of vessel wall growth plays in determining pressure-lumen area (P-A) and pressure-compliance curves was examined. A P-A vessel model was developed that encompasses the complete range of pressure, including negative values, and accounts for size given the fixed length, nonlinear elastic wall properties, constant wall area, and collapse. Data were obtained from excised canine carotid and femoral arteries, jugular veins, and elastic tubing. The mean error of estimate was 8 mmHg for all vessels studied and 2 mmHg for blood vessels. The P-A model was employed to examine two patterns of arterial wall thickening, outward growth and remodeling (constant wall area), under the assumption of constant wall properties. The model predicted that only outward wall growth resets compliance such that it increases at a given arterial pressure, explaining previously contradictory data. In addition, it was found that outward wall growth increases the lumen area between normal and high pressures. Remodeling resulted in lumen narrowing and a decrease in compliance for positive pressures.

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.

Hypertension and peripheral arterial disease: a plethysmographic study

Sixty patients suffering from arterial hypertension and/or obliterative arteriopathy of the lower limbs (20 hypertensive uncomplicated [H group], 20 normotensive affected by obliterative arteriopathy [A group], 20 suffering from both hypertension and peripheral arterial disease [HA group]) were studied, by strain gauge plethysmography, in comparison with 20 healthy subjects (N group). The aims were to evaluate the arterial and venous hemodynamics of the lower limbs in such conditions and also to determine whether the vascular damage is primary or represents a consequence of the hypertensive pathology in the patients affected by both hypertension and peripheral arterial disease. The resting blood flow did not show significant differences in the mean values, even if lightly decreased in hypertensive patients (with or without peripheral arteriopathy). The peak flow was reduced significantly both in the H group and in the A and HA groups. The half-time (t1/2) and total time (tT), which indicate vascular reactivity, were significantly decreased in the H group, but they were increased in the A and HA groups. Finally, the venous compliance was decreased in the H group, did not vary significantly in the A group, and showed an intermediate behavior in the HA group. These results suggest that hypertensive and arteriopathic patients develop similar arterial structural changes. However, they show a different behavior with regard to vascular reactivity and venous hemodynamics, as demonstrated by venous plethysmography.

Sex difference in risk of torsade de pointes with d,l-sotalol

BACKGROUND

The present study was undertaken to test the hypothesis that women are more prone than men to develop torsade de pointes (TdP) in a defined cohort of patients exposed to the QT-prolonging antiarrhythmic drug d,l-sotalol.

METHODS AND RESULTS

In a database derived from 22 clinical trials involving 3135 adult patients who received oral d,l-sotalol (median follow-up, 164 days), TdP developed in 44 (1.9%) of 2336 men and in 33 (4.1%) of 799 women (P < .001). Logistic regression analysis identified female sex (P < .0001), presenting arrhythmia of sustained ventricular tachycardia or fibrillation (P < .0001), history of congestive heart failure (P < .001), and d,l-sotalol dose > 320 mg/d (P < .001) as factors most predictive of TdP; in addition to these, a serum creatinine > 1.4 mg/dL in women and > 1.6 mg/dL in men was weakly predictive (P < .05). After adjustment for these risk factors, women had threefold greater odds of developing TdP than men. The sex difference in TdP risk was age independent and could not be explained by differential dose-related bradycardic responses in women versus men.

CONCLUSIONS

Women are at increased risk of developing TdP during-administration of d,l-sotalol. This finding needs to be taken into account, together with other TdP risk factors, when patients are treated with this antiarrhythmic agent. Given the consistency between the present and other recent observations, greater caution in women regarding use of QT-prolonging drugs, in general, is advisable.

Vascular dynamics in isolated systolic arterial hypertension

With a growing elderly population, the incidence of isolated systolic hypertension (ISH) has increased. This study characterizes dynamic vascular changes that occur with advanced age and with ISH. Fifty-five healthy individuals and seven with ISH were distributed in seven age groups from the second to the seventh decade. An index of aortic stiffness (delta P/delta V) was derived using a mercury sphygmomanometer to obtain pulse pressure, and ultrasonographic measurements were used to estimate aortic volumes applying the "cylinder formula." The mathematic derivation of this formula is explained in detail. Pulse pressure showed no significant change with age, but showed a significant increase with ISH. A decrease in volume change from systole to diastole was found with advanced age. Normotensive subjects aged 65 +/- 2 years had a 2.6-fold increase in aortic stiffness compared with young individuals. Elderly patients with ISH had a 7-fold increase in aortic stiffness compared with Group 1 (15 +/- 2 years) (p < 0.001) and a 2.7-fold increase compared with Group 6 (normotensive subjects aged 65 +/- 2 years). A strong correlation between systolic pressure and arterial stiffness was observed (r = 0.953) (p < 0.001). The proposed stiffness index was compared with the one described by Hirai, obtaining a high correlation, that is, r = 0.989 (p < 0.001). When compared with Stefanadis' index of distensibility, our index showed a correlation of r = 0.932 (p < 0.003). It is concluded that while systolic pressure is a main determinant of arterial stiffness, the delta P/delta V is a more sensitive method to estimate dynamic changes in elastic arteries such as the aorta.

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.

Measuring hypertensive cardiovascular risk: the vascular overload concept

Hypertensive cardiovascular risk may be related primarily to vascular overload, the sum of three vascular abnormalities: increased arteriolar resistance, increased large-artery stiffness, and the effect of increased early pulse-wave reflection. A method for quantifying vascular overload as an index can be derived from measurements of mean arterial pressure and pulse pressure. Several lines of evidence support the hypothesis that abnormal artery stiffness and early pulse-wave reflection become larger components of vascular overload as the duration and severity of hypertension increase. Moreover, these studies suggest that vascular overload is a true indicator of hypertensive cardiovascular risk. Increased systolic blood pressure is a surrogate for vascular overload in young and middle-aged hypertensive subjects. Increased pulse pressure and decreased diastolic pressure are superior to increased systolic pressure as surrogates for vascular overload in geriatric isolated systolic hypertension. By itself, diastolic blood pressure is difficult to interpret and may be an epiphenomenon. Therefore new therapeutic goals, are control of systolic pressure in the young and of pulse pressure in the elderly.

Felodipine, metoprolol and their combination compared with placebo in isolated systolic hypertension in the elderly

This study compared with placebo the efficacy and tolerability of optimised doses of felodipine 5-20 mg daily, metoprolol 50-200 mg daily and their combination in subjects 60 years or over with isolated systolic hypertension. The study employed a randomised double-blind crossover design with allocation of treatment order within subjects by Latin squares. For each subject, after a single-blind run-in placebo phase, there were four randomised treatment phases each of six weeks duration, with a dose titration step at three weeks if necessary. Twenty-eight subjects entered the randomised phases of the study and twenty-one completed all four phases--13 male, 8 female (ages: median 71, range 59-85 years). At the end of both the felodipine and metoprolol phases systolic and diastolic pressure were reduced at 2 hours postdose compared with the placebo phase (p < 0.001), the blood pressure reduction with felodipine (-40/-20 mmHg) being greater than that with metoprolol (-15/-9 mmHg) (p < 0.01). Immediately predose (12 hours postdose) there was a persisting reduction of supine systolic blood pressure (-17 mmHg) with felodipine (p < 0.001), but there was no significant effect of metoprolol. At both measurement times the two drugs when in combination had an additive effect on blood pressure. There was a 20% increase in reported symptoms during each of the active treatment phases. Four subjects withdrew during the randomised phases because of probable drug-related adverse events and six subjects required dosage reductions during the felodipine or combination phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Mono- and combination therapy with felodipine or enalapril in elderly patients with systolic hypertension

Using a randomised double-blind crossover design with Latin square allocation of treatments in 20 subjects (7 male, 13 female-ages: 61-87 years) with systolic hypertension, we investigated the efficacy and tolerability of once daily felodipine (extended release) 5-20 mg, enalapril 5-20 mg and their combination compared with placebo in four treatment phases each of 6 weeks duration. During each phase, doses were titrated to achieve a predose clinic supine systolic blood pressure of 140 mmHg or to a predetermined maximum dose. In both the felodipine and combination phases, predose supine and standing systolic and diastolic pressures were significantly reduced compared with the placebo phase (decrease in supine pressure: -13/-5 and -18/-7, respectively). Only predose supine diastolic pressure was significantly reduced (-3 mmHg) compared to placebo in the enalapril phase. In combination the effects of the two drugs on predose blood pressure were additive. There was a 40-60% increase in reported symptoms in the felodipine and combination phases compared with the placebo and enalapril phases. Thus, in elderly subjects with systolic hypertension, felodipine effectively reduces blood pressure throughout the dose interval but with vasodilator adverse effects. In contrast, enalapril is well tolerated but is less effective in reducing blood pressure throughout the whole dose interval.

Arterial compliance and its pressure dependence in hypertension and vasodilation

Arterial compliance has been recognized to be pressure-dependent. Its variation due to changing systolic and diastolic blood pressures in hypertension and subsequent vasodilation has not been investigated. The authors examined this aspect by combining an animal experiment and a recently established nonlinear windkessel model of the arterial system that incorporates a pressure-dependent arterial compliance, C(P). Aortic pressure and flow were simultaneously measured in experimental dogs during control and during methoxamine-induced hypertension and nitroprusside-induced vasodilation. A numerical procedure was implemented to compute the nonlinear compliance and account for the pressure dependence. Results show that within the cardiac cycle, C(P) reached its maximum at end-systole and increased in diastole when diastolic aortic pressure decayed. The magnitude of C(P) and its variation within the cardiac cycle was larger at low pressures, while the reverse was found when blood pressure was high. C(P) decreased significantly in hypertension and increased during subsequent vasodilation.

Predictors of carotid stenosis in older adults with and without isolated systolic hypertension

BACKGROUND AND PURPOSE

This study was designed to determine the prevalence of carotid stenosis and atherosclerosis in older adults with and without isolated systolic hypertension and to determine risk factors for carotid artery disease in these two groups.

METHODS

Duplex scans were performed on 187 participants of the Systolic Hypertension in the Elderly Program and on 187 normotensive control subjects. Doppler measures of blood flow velocity were used to determine the prevalence of internal carotid artery stenosis.

RESULTS

Carotid stenosis was found in 25% of hypertensive participants but in only 7% of normotensive participants (p < 0.001). Among hypertensive participants, carotid stenosis was correlated with lower diastolic blood pressure (p = 0.022). In multivariate analysis, systolic blood pressure of > or = 160 mm Hg was the strongest predictor of carotid stenosis. Other variables independently related to stenosis were diastolic blood pressure of < 75 mm Hg (p = 0.001), alcohol use (p = 0.005), heart rate of > or = 80 beats per minute (p = 0.013), smoking (p = 0.034), high concentration of apoprotein B (p = 0.001), and low concentration of high density lipoprotein cholesterol (borderline significant, p = 0.069). Among hypertensive participants, the strongest predictor of carotid stenosis was low diastolic blood pressure. This relation persisted even after taking into account differences in pulse pressure.

CONCLUSIONS

Isolated systolic hypertension is strongly correlated with carotid stenosis, and among those with isolated systolic hypertension low diastolic blood pressure is a marker for carotid stenosis.

Epidemiology of isolated systolic hypertension in Pu-Li, Taiwan

The clinical significance of isolated systolic hypertension (systolic blood pressure greater than or equal to 160 mmHg and diastolic blood pressure less than 90 mmHg) has long been recognized, but its prevalence and correlates have not been well characterized. A community-based study was carried out by the Yang-Ming Crusade in 1987-1988 in Pu-Li Town, Taiwan. Of the 2573 registered residents over 30 years old, 1738 were interviewed, and their fasting blood samples were drawn and tested. The prevalence of isolated systolic hypertension was 2.1%. Age-specific prevalence increased with age. No significant difference was found between men and women. No trend was found at the urbanizational level. To study the significant correlates of isolated systolic hypertension, univariate analyses were applied first. Stratified analyses by age and by sex were used for interaction assessment. Based on the above findings as well as from the clinical point of view, logistic regression was used for multivariate analyses. Logistic regression analysis showed that after controlling the covariates simultaneously, four variables were significantly correlated with isolated systolic hypertension: age (greater than or equal to 50 vs. less than 50 years, OR = 3.4, 95% CI = 1.6-7.2); diabetes (yes vs. no, OR = 2.4, 95% CI = 1.2-4.7); blood urea nitrogen (greater than or equal to 25 vs. less than 25 mg/dl, OR = 2.1, 95% CI = 1.2-3.9); and physical activity (frequent vs. infrequent, OR = 1.8, 95% CI = 1.0-3.1). In comparison with definite (greater than or equal than 160/95 mmHg) and borderline (140/90-160/95 mmHg) hypertension as defined by WHO, the different sets of predictors and the possible adverse effect of frequent physical activity on isolated systolic hypertension were found and discussed.

Temporal relationship between left ventricular and arterial system elastances

Arterial compliance is an important component of ventricular afterload. Although its pressure dependence has been recognized, its temporal relationship to ventricular elastance (Elv(t)) has not been established. We investigated this in five open chest anesthetized dogs where simultaneous aortic pressure and flow and left ventricular pressure were measured. Elv(t) was derived using an elastance-resistance model of the left ventricle assuming an ejection fraction of 0.50 and a dead volume (Vd) of 3.0 mL. The nonlinear pressure-dependent compliance (C(P)) of the arterial system was incorporated in a three-element Windkessel model and determined by accurate prediction of aortic pressure from aortic flow. The resulting arterial elastance (Eas(t)) was computed as Eas(t) = 1/C(P). Results show that Eas(t) reaches a minimum value at or near the start of ventricular ejection and attains its peak value at or near the same time maximum LV elastance (Emax) is reached, at end-systole. Finally, numerical simulation of the model demonstrates its ability to adequately reproduce measured pressure and flow. Thus, the arterial system, in terms of elastance, is dynamically and temporally coupled to the left-ventricle during ejection.

Epidemiology, pathophysiology, and management of isolated systolic hypertension in the elderly

Isolated systolic hypertension (ISH) is a common disorder in the elderly, carrying with it a high risk of cardiovascular morbidity and mortality. Environmental and age-related factors believed to contribute to ISH include obesity, declining physical activity, stress, and such dietary changes as increased salt intake and decreased intake of calcium and potassium. Increased rigidity of the aorta resulting in reduced compliance is an important hemodynamic feature, but factors that increase peripheral resistance also appear to play a role. Antihypertensive drugs have been shown to effectively and safely lower the systolic blood pressure elevations characteristic of ISH. To date, use of low drug doses and careful titration of dosage have avoided significant orthostatic hypotension and undue lowering of the diastolic pressure. Studies of relatively small groups of patients suggest that antihypertensive drugs can lower the risk of cardiovascular morbidity/mortality associated with ISH but the definitive answer awaits results of the ongoing large-scale Systolic Hypertension in the Elderly Program trial. In the interim, management should begin with conservative measures such as weight loss, salt restriction and, possibly, calcium supplementation. If this fails, drug therapy should be considered in patients with systolic blood pressures above 180 mm Hg and in those with systolic readings between 160 and 180 mm Hg who have concomitant cardiovascular risk factors. To date, no controlled trials of sufficient size have demonstrated that one drug class is more effective than another in treating ISH. Drug therapy should be tailored to the individual patient, starting with a low dose of a single drug and, if necessary, slowly increasing dosage until a systolic blood pressure under 160 mm Hg is attained.