Diastolic pressure underestimates age-related hemodynamic impairment

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.

Does body position, age, and heart rate induce IOP's changes?

OBJECTIVES

The main goal of this research was to determine the differences between the values of intraocular pressure (IOP) in the supine and sitting positions, and to assess the effect of age and cardiovascular parameters.

METHODS

Seventy-two healthy adults were enrolled and classified into age groups: 20-30 years (group A), 31-40 years (group B), and 41-71 years (group C). Corneal biometry and cardiovascular parameters, such as heart rate (HR), were measured. IOP measurements were taken in the sitting position (IOP_S) and in the supine position (IOP_L) using the iCare^® Pro tonometer.

RESULTS

A significant difference between the IOP_S and IOP_L in the entire cohort was found (p < 0.001). Regarding the age subgroups, a significant difference (p < 0.001) between the IOP_S and IOP_L was obtained in group A (2.6 ± 1.6 mmHg) and group C (1.5 ± 1.3 mmHg). There were no significant differences in the IOP_S between groups. The highest IOP values were obtained for group A. The correlations between HR and IOP_S are statistically significant for group A and group B, and for HR and IOP_L-S for group B only. Multivariate analysis showed that HR has a significant influence on the difference in IOP in the two body positions.

CONCLUSION

A statistically significant difference between the effect of age and the values of IOP_S and IOP_L was shown. Cardiovascular parameters showed some relevant statistical dependencies, but with a rather marginal significance in young people. The influence of body position for the measurement of IOP for healthy subjects does not seem to matter, despite the fact that there are some dependencies that are statistically significant.

Update on Hypertension and Adaptations for Treatment

Hypertension (HTN) affects 46% of the US adult population and plays a major role in cardiovascular disease (CVD). Approximately, there were 90,098 deaths in 2017 primarily attributed to high blood pressure (BP). Recent guidelines recommend screening all adults for HTN. Management of elevated BP substantially reduces the risk of heart failure, stroke, and myocardial infarction. Recommended lifestyle modifications include weight loss for overweight or obese patients, regular exercise, the dietary approached to stop hypertension (DASH) diet, reduced dietary sodium intake, and reduced alcohol intake. Most HTN patients will need at least 2 drugs to control BP. Current guidelines from the ACC and AHA state that a BP level goal of < 130/80mmHg for adults with confirmed HTN and without additional markers of increased atherosclerotic cardiovascular disease (ASCVD) risk may be acceptable.

[Current status of noninvasive hemodynamics in hypertension]

Hypertension is a haemodynamic disorder resulting from a persistent mismatch between cardiac output and peripheral resistance. Hypertension undergoes haemodynamic progression during its natural history. Impedance cardiography is a method of evaluating the cardiovascular system that obtains haemodynamic information from beat to beat through the analysis of variations in the impedance of the thorax on the passage of an electric current. Impedance cardiography unmasks the haemodynamic deterioration underlying the increase in blood pressure as age and systolic blood pressure increases. This method may help to improve blood pressure control through individualized treatment with reduction of peripheral resistance, maintenance of cardiac output or its increase, improvement of arterial compliance and preservation of organ-tissue perfusion. It is useful in the management of patients with resistant hypertension, since a greater percentage of patients controlled with changes in the treatment in relation to the haemodynamic measurements are obtained. Impedance cardiography is important and has prognostic utility in relation to a haemodynamic deterioration pattern and increased cardiovascular events.

Review: The role of noninvasive hemodynamic monitoring in the evaluation and treatment of hypertension

Advances in the understanding of the mechanisms accounting for the elevation of arterial pressure in essential hypertension suggest that there is value in assessing the relative contribution of hemodynamic factors in tailoring specific therapies to control arterial pressure. The non-invasive method of impedance cardiography (ICG) to measure hemodynamic abnormalities in hypertensive patients has emerged as a valuable adjuvant in the decision-making process of selecting antihypertensive agents. The technique is both accurate and reproducible in delineating the hemodynamic mechanisms of hypertension, comparing age-and gender-related changes in hemodynamics, detecting the presence of left ventricular dysfunction, and demonstrating clinically significant improvement in blood pressure control using ICG-guided therapy.

Combretastatin A4 disodium phosphate-induced myocardial injury

Histopathological and electrocardiographic features of myocardial lesions induced by combretastatin A4 disodium phosphate (CA4DP) were evaluated, and the relation between myocardial lesions and vascular changes and the direct toxic effect of CA4DP on cardiomyocytes were discussed. We induced myocardial lesions by administration of CA4DP to rats and evaluated myocardial damage by histopathologic examination and electrocardiography. We evaluated blood pressure (BP) of CA4DP-treated rats and effects of CA4DP on cellular impedance-based contractility of human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs). The results revealed multifocal myocardial necrosis with a predilection for the interventricular septum and subendocardial regions of the apex of the left ventricular wall, injury of capillaries, morphological change of the ST junction, and QT interval prolongation. The histopathological profile of myocardial lesions suggested that CA4DP induced a lack of myocardial blood flow. CA4DP increased the diastolic BP and showed direct effects on hiPS-CMs. These results suggest that CA4DP induces dysfunction of small arteries and capillaries and has direct toxicity in cardiomyocytes. Therefore, it is thought that CA4DP induced capillary and myocardial injury due to collapse of the microcirculation in the myocardium. Moreover, the direct toxic effect of CA4DP on cardiomyocytes induced myocardial lesions in a coordinated manner.

Hemodynamic circulatory patterns in young patients with predominantly diastolic hypertension

To evaluate the spectrum of hemodynamic patterns in patients with isolated diastolic hypertension-predominantly diastolic hypertension, we re-analyzed a previously reported cohort of 189 non-medicated hypertensive individuals that were assessed by impedance cardiography. We selected 46 patients who were less than 50 years old and had pulse pressure less or equal than 45 mm Hg confirmed by ambulatory blood pressure monitoring. The selected cohort had a mean age of 39.7 years and was 47% men. Three distinct groups were identified: a high cardiac index (CI) "hyperdynamic" group, with normal to near normal systemic vascular resistance (SVR); an intermediate CI and SVR group; and a "vasotonic" group, with low CI and high SVR. Heart rate was similar among the three groups. Stroke volume index (SVI) was significantly higher in the hyperdynamic group (61.8, 49.7, and 39.7 mL/m(2) in the high, intermediate, and low CI groups, respectively). The hyperdynamic group had greater total arterial compliance index than the vasotonic group (1.3 ± 0.3 vs 0.92 ± 0.2 mL/m(2) mm Hg for high vs low CI, respectively; P < .001). In conclusion, isolated diastolic hypertension-predominantly diastolic hypertension patients can have diverse hemodynamic patterns that cannot be predicted based on peripherally measured blood pressure and heart rate alone. This hemodynamic complexity must be taken into account when considering the genetic and pathophysiologic mechanisms of hypertension.

Hypothesis: it is time to reconsider phenotypes in hypertension

The study of genes and mechanisms associated with hypertension is hampered by the heterogeneity of hypertensive patients. Refining the definition of hypertension is a potential means of improving the clarity of mechanistic studies, but the lack of intermediate phenotypes hinders the assessment of causal relationships. Looking at younger individuals and hemodynamic subsets of hypertension is one such refinement. The authors argue that the separate analysis of patients with isolated diastolic hypertension, predominantly diastolic hypertension, and isolated systolic hypertension in the young in combination with common biomarkers may be an initial step to decrease heterogeneity within patient subsets, thus providing new avenues for genetic and pathophysiological studies.

Association of ACE genotype and predominantly diastolic hypertension: a preliminary study

BACKGROUND

The insertion/deletion (I/D) angiotensin-converting enzyme (ACE) polymorphism has been established as a cardiovascular risk factor in some populations, but the association with essential hypertension is controversial. Predominantly diastolic hypertension (PDH), or narrow pulse pressure hypertension, has been shown to have increased peripheral resistance. Because a DD genotype has been associated with higher plasma ACE levels and angiotensin II activity, we genotyped PDH patients for ACE I/D polymorphism.

METHODS

Ninety-three patients with systolic blood pressure (BP)<140 mmHg systolic and diastolic BP>90 mmHg, or BP>140/90 mmHg with a pulse pressure<45 mmHg, were defined as PDH. The II, ID and DD genotype variants of ACE were characterised by the triple primer nested-PCR method. Results were compared to 75 normotensive control individuals. Statistical significance was assessed by the Chi square test.

RESULTS

The genotype distribution among PDH patients was II=20 (21.5%), ID=34 (36.5%), DD=39 (42%), while the distribution among normotensive controls was II=16 (21.4%), ID=42 (56%), DD=17 (22.6%). The difference in genotype distribution between PDH patients and controls was significant (p<0.02). ACE allele frequencies in PDH patients and controls were D=0.60, I=0.40 and D=0.51, I=0.49, respectively, statistically non-significant (ns).

CONCLUSION

These results suggest an association between ACE genotype DD and predominantly diastolic hypertension.

Hypertension in special populations

Hypertension is a multifaceted disease that may present somewhat differently in various populations. It is clear that hypertensive treatment reduces cardiovascular, renal, and cerebrovascular outcomes for all patients, yet recent clinical trial data suggest that some groups may benefit more than others from specific drug intervention. Furthermore, these data justify specific approaches for some special populations. This article reviews important features of the presentation, rationale for treatment, and treatment recommendations for the treatment of hypertension in special populations. The special populations addressed include diabetic patients, the elderly, and women.

Hypertension: a review for clinicians

Despite the existence of a variety of consistent hypertension guidelines,the issue of inadequate management of the condition persists. The challenge for health care professionals is not only to understand and adopt the guidelines but also to take a holistic approach to patient care. In addition, clinicians need to encourage adherence to medication protocols, which will hopefully lead to an overall reduction in morbidity and mortality associated with hypertension. It is the clinician's professional responsibility to be cognizant of the emerging research on vasoactive substances as new drugs are being developed that will effect endothelial receptors. It is important that clinicians are trained appropriately in blood pressure measurement and risk factor identification and intervention.

Narrowing the Gap in Hypertension: Effectiveness of a Complex Antihypertensive Program in the Elderly

Hypertension control is a difficult goal to achieve in common practice even when its benefits have been widely proved. We assessed the effectiveness of a Complex Antihypertensive Intervention Program in the Elderly (CAPE). A program trial of 500 elderly hypertensive patients was conducted. 250 were followed by primary care physicians and intervened by the CAPE and 250 received usual care. The program included an organizational change with the addition of an office where patients had their blood pressure measured, were appointed to join educational sessions and received verbal and printed advice before medical attendance. Data was systematically recorded in the electronic medical record which functioned as a physician reminder during the visit. Differences in systolic blood pressure level and in percentage of well-controlled (<140/90 mm Hg) patients between groups were measured after 12 months of follow-up. The difference of mean change in systolic blood pressure between groups was 7.1 mm Hg (95% confidence interval, 4-10 mm Hg). Sixty-seven percent of patients in the intervention group were well-controlled, as were 51% of patients in the control group (p < 0.001). Patients who attended educational sessions showed the lowest odd ratio (0.25; 95% confidence interval, 0.11-0.54) for blood pressure above 140/90 mm Hg in multivariate analysis after adjusting for age, sex, initial systolic blood pressure level, and changes in antihypertensive treatment. These results support the effectiveness of our complex intervention program. Routine clinical care of hypertension can be improved with simple strategies that go beyond pharmacotherapy, tending to overcome clinical inertia.

Lipoprotein Levels Are Associated with Incident Hypertension in Older Adults

OBJECTIVES

To determine the relationship between baseline measures of serum lipoproteins and incident hypertension in older adults.

DESIGN

Prospective cohort study.

SETTING

Pittsburgh, Pennsylvania, site of Systolic Hypertension in the Elderly Program (SHEP).

PARTICIPANTS

One hundred eighty-seven men and women (mean age 71.3), normotensive (systolic blood pressure (SBP) <160 mmHg, diastolic blood pressure (DBP) <90 mmHg) at baseline, were followed annually over 8 years as an ancillary study to the SHEP.

MEASUREMENTS

Hypertension development, defined as initiation of antihypertensive therapy or SBP greater than 160 mmHg or DBP greater than 90 mmHg. Lipoprotein measures included total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), HDL(2)-C, HDL(3)-C, triglycerides, and apolipoproteins 1, 2, and B.

RESULTS

Over 8 years, 44 participants developed hypertension, for a Kaplan-Meier cumulative incidence rate of 31% (95% confidence interval (CI)=23-39%). Cumulative incidence rates were highly associated with baseline SBP, ranging from 8% in those with baseline SBP less than 120 mmHg to 70% in those with SBP of 140 to 159 mmHg. Other univariate associations included higher DBP, pulse pressure (P <.01 for both), triglycerides (P=.03), apolipoprotein B (P=.03), and lower HDL-C (P=.04) and HDL(3)-C (P=.02). In multivariate Cox regression analysis, higher baseline SBP (relative risk (RR)=1.8 per 10 mmHg, 95% CI=1.5-2.3) and lower HDL(3)-C (RR=0.8 per 5 mg/dL, 95% CI=0.42-1.0) remained significant independent predictors of time to hypertension.

CONCLUSION

Older adults with abnormal serum lipoproteins are at increased risk of developing hypertension. Clinical trials exploring the effects of the modification of lipoprotein levels on hypertension incidence rates are needed.

Effects of central hypocretin-1 administration on hemodynamic responses in young-adult and middle-aged rats

The prevalence of hypertension in middle age correlates with impaired autonomic regulation and as norepinephrinergic neurons decline with increasing age, and this reduction may contribute to this impairment. Central hypocretin-activated norepinephrinergic neurons contribute to sympathetic regulation. In the present study we compared sympathoadrenal effects of intracerebroventricular (i.c.v.) hypocretin-1(5 nmol) between young-adult (12-14 weeks) and middle-aged (12-14 months) rats. Arterial blood pressure, heart rate and plasma catecholamines were assessed under pentobarbital anesthesia. In addition, we compared hypocretin-1 and K(+)-evoked norepinephrine release from the cerebrocortical slices prepared from young-adult and middle-aged rats. We also examined whether the novel hypocretin receptor-1 antagonist (SB-334867) could reverse these hypocretin-1 effects both in vivo and in vitro. I.c.v. hypocretin-1 significantly increased blood pressure by some 7%, heart rate by 9% and plasma norepinephrine concentrations by 100% in young-adult rats. In middle-aged rats these parameters did not change. Plasma epinephrine did not increase in either group. There was a significant correlation between changes in mean arterial pressure and plasma norepinephrine. Similarly, hypocretin-1 evoked norepinephrine release from cerebrocortical slices prepared from young-adult rats was significantly higher than that of middle-aged rats whilst K(+)-evoked release did not differ between the groups. SB-334867 significantly attenuated hypocretin-1-increased blood pressure and both in vivo and in vitro norepinephrine release. The present data suggest that hypocretinergic neurons may contribute to the regulation of central but not adrenal sympathetic activity. Moreover, sympathetic regulation by hypocretinergic neurones may disappear in middle-age in rats.

Mean arterial pressure and pulse pressure are associated with different clinical parameters in chronic haemodialysis patients

The mean arterial pressure (MAP) usually serves as an expression of blood pressure in patients on chronic haemodialysis (PCHD), instead of using solely systolic or diastolic pressure. Pulse pressure (PP) has been recognized as an important correlate of mortality in PCHD. We conducted this study in order to demonstrate clinical and biochemical determinants and variability of predialysis and postdialysis MAP and PP values. A total of 136 single haemodialysis (HD) treatments in 23 subjects (PCHD, 11 male and 12 female patients) were processed during 15 months. MAP before HD was in negative correlation with haemoglobin (P<0.001) and body mass index (BMI) (P<0.001), and in positive correlation with weekly erythropoietin dosage (P=0.017). MAP after HD was in negative correlation with haemoglobin (P<0.001), ultrafiltration per HD (P=0.015), and BMI (P=0.001), and in positive correlation with weekly erythropoietin dosage (P=0.003). PP before HD was in negative correlation with parathyroid hormone (PTH) level (P=0.020), haemoglobin (P<0.001), ultrafiltration per HD (P=0.001), and years on the chronic HD treatment (P=0.001), and in positive correlation with weekly erythropoietin dosage (P<0.001) and age (P<0.001). PP after HD was in significant negative correlation with PTH (P=0.015), haemoglobin (P=0.005), ultrafiltration per HD (P<0.001), BMI (P=0.003), and in positive correlation with weekly erythropoietin dosage (P<0.001) and age (P=0.004). Multiple regression analyses unveiled the strongest and negative correlations between MAP before HD and BMI (beta=-0.37, P=0.01); MAP after HD and haemoglobin (beta=-0.36, P=0.01); PP after HD and ultrafiltration/body weight ratio (beta=-0.41, P<0.001). The strongest and positive correlation was found between PP before HD and erythropoietin dosage per week (beta=0.51, P&<0.001). In conclusion, our findings support the assumption that PP and MAP are associated with different clinical parameters. PP values have advantages as the method of blood pressure expression.

Randomized, comparative, double-blind study of amlodipine vs. nicardipine as a treatment of isolated systolic hypertension in the elderly

A 90-day, multicenter, randomized, double-blind, parallel-group study was conducted to compare the efficacy of amlodipine (once a day) with nicardipine (two to three times a day), in the treatment of isolated systolic hypertension (ISH) in the elderly. Patients (n = 133) aged > or = 60 years, with ISH were randomized to receive either amlodipine 5 mg/day, or nicardipine 60 mg/day (titrated if necessary to 10 mg/day and 100 mg/day, respectively) for 90 days. Efficacy was assessed by measuring office blood pressure (BP), and 24-h ambulatory blood pressure monitoring (ABPM). The two treatments substantially and comparably reduced office systolic blood pressure (SBP) and pulse pressure (PP), and also produced a slight decrease in diastolic blood pressure (DBP). Amlodipine reduced SBP, as assessed by ABPM, to a significantly greater extent than nicardipine. Both treatments were well-tolerated. The sustained effect of amlodipine, compared with nicardipine, was reflected in its significantly greater antihypertensive activity, particularly during the nocturnal period, as assessed by ABPM. The study demonstrates that once a day dose of amlodipine is an effective antihypertensive treatment for elderly ISH patients.

Cardiovascular reactivity patterns elicited by the cold pressor test as a function of aging

BACKGROUND AND AIMS

The cold pressor test has been widely used in previous cardiovascular reactivity studies as a predictor of hypertension. However, the influence of the physical adaptations of the arterial wall with increasing age on reactivity has not been delineated.

METHODS

64 men divided into 5 different age groups participated in a laboratory protocol consisting of submerging one hand in ice water for one minute while changes in blood pressure were continuously measured.

RESULTS

The results indicated that with increasing age, the systolic blood pressure change, especially the rate of change (slope) is more pronounced than changes in diastolic blood pressure.

CONCLUSIONS

With increasing age, there is a shift from a diastolic blood pressure reactivity pattern to a more systolic blood pressure reactivity pattern during application of the cold pressor test. This could be ascribed to a decrease in arterial compliance.

Relation of effective arterial elastance to arterial system properties

Effective arterial elastance (E(a)), defined as the ratio of left ventricular (LV) end-systolic pressure and stroke volume, lumps the steady and pulsatile components of the arterial load in a concise way. Combined with E(max), the slope of the LV end-systolic pressure-volume relation, E(a)/E(max) has been used to assess heart-arterial coupling. A mathematical heart-arterial interaction model was used to study the effects of changes in peripheral resistance (R; 0.6-1.8 mmHg x ml(-1) x s) and total arterial compliance (C; 0.5-2.0 ml/mmHg) covering the human pathophysiological range. E(a), E(a)/E(max,) LV stroke work, and hydraulic power were calculated for all conditions. Multiple-linear regression analysis revealed a linear relation between E(a), R/T (where T is cycle length), and 1/C: E(a) = -0.13 + 1.02R/T + 0.31/C, indicating that R/T contributes about three times more to E(a) than arterial stiffness (1/C). It is demonstrated that different pathophysiological combinations of R and C may lead to the same E(a) and E(a)/E(max) but can result in differences of 10% in stroke work and 50% in maximal power.

Similar effects of isolated systolic and combined hypertension on left ventricular geometry and function: the LIFE Study

Echocardiograms of 143 patients with isolated systolic hypertension were compared to 808 patients with combined (systolic and diastolic) hypertension. All patients met electrocardiographic criteria for left ventricular hypertrophy and were evaluated off medication. Patients with isolated systolic hypertension were older, shorter, weighed less, and were mostly women, but body mass index (BMI) was similar in both groups. Systolic blood pressure (SBP) was 172 mm Hg in isolated systolic hypertension, 174 mm Hg in combined (P = not significant). Diastolic blood pressure was 83 and 101 mm Hg, respectively (P < .001). Despite having mean arterial pressure 12 mm Hg lower than patients with combined hypertension, the group with isolated systolic hypertension had equally severe abnormalities of left ventricular mass, left ventricular geometric patterns, and measures of systolic and diastolic function. Peripheral resistance was lower and pulse pressure/stroke volume ratio (arterial stiffness index) was higher and the isovolumic relaxation time shorter in isolated systolic hypertension. Multiple regression analyses identified age, height, BMI, stress-corrected mid wall shortening, stroke volume, male gender, and systolic or mean blood pressure (but not isolated systolic hypertension) as independent correlates of left ventricular mass. Relative wall thickness was independently associated with isolated systolic hypertension (P = .001) in addition to mean pressure and other covariates. The present results add support to the concept that systolic blood pressure (SBP) is a stronger determinant than diastolic pressure of cardiac target organ damage in hypertension.

Pulse pressure, arterial compliance and cardiovascular morbidity and mortality

Pulse pressure, an indicator of conduit vessel stiffness, has recently emerged as an important predictor of adverse cardiovascular events. The normally compliant conduit vessels provide an essential buffering role that minimizes potentially harmful pressure swings associated with intermittent pumping by the heart. A number of common conditions and acknowledged cardiac risk factors stiffen the conduit vessels, resulting in a vicious cycle of progressive vessel stiffening, increasing pulsatile load, pressure-related end-organ damage and clinical events. An emerging awareness of the central role of conduit vessel stiffness in cardiovascular pathophysiology has important implications for the classification and treatment of hypertension and other disorders that affect conduit vessel function and pulsatile hemodynamics.

Effects of heart rate on arterial compliance in men

1. Arterial compliance is a major determinant of left ventricular afterload. In keeping with earlier experimental data obtained in isolated arterial segments, it has recently been shown in the rat that arterial compliance decreases with an increase in heart rate (HR) induced by atrial pacing. 2. To elucidate the potential relevance of this effect in humans, we investigated nine male volunteers (age 20-30 years; mean 26 years). Systemic arterial compliance (SAC) was measured with the diastolic area method and carotid-to-femoral and femoral-to-dorsalis pedis pulse wave velocities (PWV) were measured to determine regional changes in compliance. Heart rate was first lowered with intravenous metoprolol to 56 +/- 2 b.p.m. and then increased by transoesophageal atrial pacing to 80 and 100 b.p.m. 3. Increasing HR from 56 +/- 2 to 80 b.p.m. by pacing increased mean arterial pressure (MAP) from 78 +/- 2 to 98 +/- 1 mmHg (P < 0.001) and then to 102 +/- 2 mmHg (P = NS). Systemic arterial compliance fell from 0.48 +/- 0.06 to 0.33 +/- 0.04 arbitrary compliance units (ACU; P < 0.01), carotid-to-femoral PWV increased from 6.1 +/- 0.3 to 6.8 +/- 0.4 m/s (P < 0.001) and femoral-to-dorsalis pedis PWV increased from 8.9 +/- 0.4 to 10.1 +/- 0.5 m/s (P < 0.001). Pacing at 100 b.p.m did not change MAP, but did lead to a further decrease in SAC (to 0.24 +/- 0.03 ACU; P < 0.05) and further increases in carotid-to-femoral (7.3 +/- 0.4 m/s; P = NS) and femoral-to-dorsalis pedis PWV (11.3 +/- 0.4 m/s; P < 0.001). 4. We conclude that systemic, central and peripheral compliances decrease in vivo with an increase in HR induced by atrial pacing.

Isolated systolic hypertension: an important cardiovascular risk factor

Hypertension is an established risk factor for cardiovascular disease morbidity and mortality. Randomized trials of antihypertensive therapy have demonstrated the benefits of treating diastolic blood pressure, and recently the value of treating isolated systolic blood pressure has also been established. There is an excess risk of cardiovascular disease in subjects with borderline isolated systolic hypertension. In fact, data from men screened for the Multiple Risk Factor Intervention Trial show that the great majority of excess deaths are in those with high-normal systolic blood pressure or with stage 1 hypertension, i.e., systolic blood pressure 130 to 159 mmHg. Similarly, data from the Framingham Heart Study and the Physicians' Health Study emphasize the importance of mild elevations of systolic blood pressure. As age increases the hemodynamic patterns of blood pressure change due to an increase in large artery stiffness, and borderline isolated systolic hypertension becomes the dominant form of hypertension. These facts make the prevention and control of borderline isolated systolic hypertension a key strategic challenge in the effort to prevent excess mortality attributable to blood pressure levels above normal.