Prognostic value of ambulatory blood pressure : current evidence and clinical implications

Genetic influence on blood pressure measured in the office, under laboratory stress and during real life

To determine to what extent the genetic influences on blood pressure (BP) measured in the office, under psychologically stressful conditions in the laboratory and during real life are different from each other. Office BP, BP during a video game challenge and a social stressor interview, and 24-h ambulatory BP were measured in 238 European American and 186 African American twins. BP values across the two tasks were averaged to represent stress levels. Genetic model fitting showed no ethnic or gender differences for any of the measures. The model fitting resulted in heritability estimates of 63, 75 and 71% for office, stress and 24-h systolic BP (SBP) and 59, 67 and 69% for diastolic BP (DBP), respectively. Up to 81% of the heritability of office SBP and 71% of office DBP were attributed to genes that also influenced stress BP. However, only 45% of the heritability of 24-h SBP and 49% of 24-h DBP were attributed to genes that also influence office BP. Similarly, about 39% of the heritability of 24-h SBP and 42% of 24-h DBP were attributed to genes that also influence stress BP. Substantial overlap exists between genes that influence BP measured in the office, under laboratory stress and during real life. However, significant genetic components specific to each BP measurement also exist. These findings suggest that partly different genes or sets of genes contribute to BP regulation in different conditions.

Clinical implications of ambulatory and home blood pressure monitoring

Because blood pressure (BP) is an ever changing hemodynamic phenomenon, a BP value, once measured at a physician's office (Office BP), is often unrepresentative of an individual's true BP status. Both ambulatory blood pressure monitoring (ABPM) and home blood pressure monitoring (HBPM) provide more accurate and reproducible estimate of BP, and produce stronger predictive ability for cardiovascular outcome than conventional office BP. Two BP measuring techniques, ABPM and HBPM have been widely in clinical use for the detection and management of hypertension. However, they have different advantages and limitations in practice. At present, it has become crucial to understand the characteristics and clinical implications of these BP measuring techniques for those responsible for the care of hypertensive patients.

Effects of high- and low-sodium diets on ambulatory blood pressure in patients with hypertension receiving aliskiren

Dietary sodium reduction and, as necessary, pharmacologic treatment are recommended for hypertension management. This prospective, randomized, open-label, blinded-end point, multicenter, crossover study investigated the effect of dietary sodium intake on mean ambulatory systolic blood pressure (maSBP) in patients with hypertension receiving aliskiren 300 mg once daily. Following a 2- to 4-week washout period, patients were randomized to a high- (≥ 200 mmol/d) or low- (≤ 100 mmol/d) sodium diet and were started on aliskiren, 300 mg/d. After 4 weeks, patients were crossed over to the alternate diet for an additional 4 weeks. The primary efficacy variable was change in maSBP between diets. During treatment with aliskiren, maSBP was significantly lower with the low-sodium diet compared with the high-sodium diet (least squares mean difference, 9.4 mm Hg; 95% CI, 7.5-11.4; P < .0001). The percentage of patients achieving a maSBP response to aliskiren (<130 mm Hg or a ≥ 20-mm Hg reduction from baseline) was greater with the low- (76.5%) versus the high-sodium diet (42.6%; P < .0001). Overall, 40.9% patients had ≥ 1 adverse event and the rates were similar between groups. In this study, aliskiren was well tolerated and a low-sodium diet accentuated its antihypertensive effect.

Wistar-Kyoto and spontaneously hypertensive rat blood pressure after embryo transfer into different wombs and cross-suckling

Blood pressure (BP) varies based on genetic and environmental factors. To test genetic and environmental influences on body weight (BW) and BP, one-cell homozygous embryos were transferred into spontaneously hypertensive (SHR, pup:shr) or (Wistar-Kyoto normotensive [WKY], pup:wky) normotensive rats' oviducts (embryos: s,w; oviduct-uterine: S,W), cross-suckled at birth (nurses S,W) and weaned to normal diets at day-21. BP at day-120 was measured by radiotelemetry and analyzed by methods of linear least square rhythmometry and analysis of variance. Genetics dominantly affected shr BP, causing it to be significantly higher at birth (24.6 ± 1.8 in sS versus 21.8 ± 1.7 mmHg in wW, P < 0.005), and at day-120 (198 ± 0.5 in sSS versus 127 ± 0.2 mmHg in wWW, P < 0.001), with lower BW than those of wky (5.3 ± 0.2 versus 5.7 ± 0.2 g at birth, 332 ± 5 versus 404 ± 6 g at day-120, both P < 0.001). Surprisingly, uterine-suckling milieus lowered shr BP significantly at day-120 (198 ± 0.5 in sSS versus 178 ± 0.5, 147 ± 0.6, 179 ± 0.5 mmHg in sSW, sWS, sWW, respectively, all P < 0.01). BP was slightly elevated when wky-genetics were implanted into the S-uterine by 4 mmHg (wSW, P < 0.05), whereas implanting shr embryos into the W-uterine environment (sWS) lowered BP by 51 mmHg (P < 0.001). In summary, the hypertensive shr-strain showed significantly lower BP when provided with an WKY-uterine environment and/or by WKY-nursing mothers, indicating that environment can modify genetic influences; yet the shr MESORs (rhythm-adjusted 24-h mean: midline estimating statistic of rhythm) lowered by WKY environments remained above MESORs encountered in wky-donors.

Masked hypertension: evaluation, prognosis, and treatment

Blood pressure (BP) may be high during usual daily life in one out of 7-8 individuals with normal BP in the clinic or doctor's office. This condition is usually defined as masked hypertension (MH). Prevalence of MH varied across different studies depending on patient characteristics, populations studied, and different definitions of MH. Self-measured BP and ambulatory BP (ABP) have been widely used to identify subjects with MH. Various factors have been identified as possible determinants of MH. Cigarette smoking, alcohol, physical activity, job, and psychological stress may increase BP out of the clinical environment in otherwise normotensive individuals, leading to MH. In most studies, target organ damage was comparable in subjects with MH and those with sustained hypertension, and greater than in those with true normotension. Subjects with MH showed a 1.5- to 3-fold higher risk of major cardiovascular (CV) disease than those with normotension, and their risk was not different from that of patients with sustained hypertension. In an overview of literature, we found that the risk of major CV disease was higher in subjects with MH than in the normotensive subjects regardless of the definition of MH based on self-measured BP (hazard ratio (HR) 2.13; 95% confidence interval (CI): 1.35-3.35; P = 0.001) or 24-h ABP (HR 2.00; 95% CI: 1.54-2.60; P < 0.001). MH is an insidious and prognostically adverse condition that can be reliably diagnosed by self-measured BP and ABP. MH should be searched for in subjects who appear to be more likely to have this condition. Antihypertensive treatment is envisaged in these subjects, although the associated outcome benefits are still undetermined.

Treatment strategies for osteoarthritis patients with pain and hypertension

Out of 100 patients with osteoarthritis (OA), almost 40 have a concomitant diagnosis of hypertension. Nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX-2) inhibitors may trigger a rise in blood pressure (BP), which is more marked in patients with established hypertension. NSAIDs and COX-2 inhibitors attenuate the antihypertensive effect of several antihypertensive agents. Frequent BP controls are needed in treated hypertensive patients who are concomitantly receiving NSAIDs or COX-2 inhibitors because even a small increase in BP may be associated with an important rise in the risk of major cardiovascular complications. In meta-analyses, an increase in systolic BP of 5mmHg was associated with a 25% higher risk of cardiovascular events. These data have been confirmed in randomized studies with rofecoxib and celecoxib, where a modest increase in BP was associated with a significantly higher risk of cardiovascular disease. There is emerging evidence that the COX-inhibiting nitric oxide donator (CINOD) class is promising in the treatment of patients with OA. Naproxcinod, the first CINOD investigated in clinical trials, is composed of the traditional NSAID naproxen covalently bound to the nitric oxide (NO)-donating moiety butanediol mono-nitrate (BDMN). The molecule has the potential to provide a sustained release of NO. In clinical studies, naproxcinod prevented the BP rise in normotensive and hypertensive patients observed with naproxen. The BP benefit of naproxcinod over naproxen was greater in patients concomitantly receiving angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. These investigational data suggest that naproxcinod is a valuable alternative to NSAIDs and COX-2 inhibitors for treatment of OA patients.

Cardiovascular risk stratification in unselected primary care patients with newly detected arterial hypertension

Cardiovascular risk (CVR) stratification in patients with arterial hypertension is essential. Few data are available on CVR factors (CVRFs), hypertensive target organ damage (TOD) and overall CVR in medical outpatients with newly detected arterial hypertension. General medical patients entering the Medical Outpatient Department of the University Hospital Basel, Switzerland, were screened for elevated office blood pressure (OBP of >140/90 mm Hg). Patients with newly detected arterial hypertension (elevated OBP at two consultations) underwent a work-up that included fundoscopy, urinalysis, ambulatory blood pressure (ABP) monitoring, ECG and echocardiography. CVR was calculated according to the 1999/2003 World Health Organization/International Society of Hypertension (WHO/ISH) guidelines. A total of 2615 outpatients were screened. Of 580 patients with elevated first OPB, 207 were treated for hypertension, 98 refused to participate, 8 were early dropouts and 36 had a normal second OBP. Data from 212 patients were analyzed (mean age 53+/-14 years). The first and second OBP readings were 162+/-6/100+/-6 and 153+/-14/96+/-9 mm Hg, respectively. Mean ABP was 134+/-12/83+/-9 mm Hg, and sustained hypertension was found in 76.9% of patients. Among patients with hypertension according to OPB monitoring, 61.3% had 1 or 2 CVRFs, and 33.0% had >or=3 CVRFs. Evidence of TOD, diabetes or associated clinical conditions (ACCs), such as renal or cardiovascular disease, was found in 26.4, 5.6 and 7.1% of patients, respectively. In terms of CVR, 2.4% of patients were at low risk, 25.9% at medium risk and 71.7% at high risk. No differences existed between white coat and sustained hypertensives regarding CVRFs, TOD or ACCs. Comprehensive analysis in patients with newly detected arterial hypertension revealed a surprisingly high prevalence of CVRFs, TOD and ACCs, indicating high CVR in the majority of these patients.

Elevated myocardial repolarization lability and arterial baroreflex dysfunction in healthy individuals with nondipping blood pressure pattern

BACKGROUND

The "nondipping" pattern (NDP) of blood pressure, characterized by the absence of the reduction in blood pressure (BP) that typically takes place during the night time, has been associated with elevated cardiovascular morbidity, including stroke, myocardial infarction, and sudden cardiac-related death. In various cardiovascular diseases, reduced vagal control of cardiac function and elevated lability of cardiac repolarization have been associated with increased risk for ventricular arrhythmia and sudden death. The aim of this study was to assess temporal QT variability, arterial baroreflex sensitivity (BRS), and baroreflex effectiveness index (BEI) in two groups of otherwise healthy subjects, one group consisting of those with a normal BP pattern and the other with a nondipping BP pattern.

METHODS

Ninety-five healthy subjects underwent 24-h ambulatory BP (AMBP) monitoring. A minimum of 10% reduction in BP during the night relative to daytime levels is considered normal (as found in "dippers"). These individuals were classified as "dippers" (n = 59) and individuals without 10% reduction in BP during night were classified as "nondippers" (n = 36). Electrocardiogram (ECG) readings and beat-to-beat BP were recorded at 1,000 Hz with the subjects at rest in the supine posture for 20 min. BRS, BEI, and QT variability index (QTVI) were calculated.

RESULTS

There were no differences between the study groups with respect to age, gender, and average BP. Nondippers showed an increase in QTVI (-1.28 +/- 0.48 in nondippers vs. -1.52 +/- 0.29 in dippers, P < 0.05) and a decrease in BEI (0.34 +/- 0.17 in nondippers vs. 0.43 +/- 0.17 in dippers, P < 0.05), whereas BRS did not differ between the groups.

CONCLUSION

A nondipping BP pattern in healthy subjects is associated with elevated myocardial repolarization lability and impaired baroreflex function, suggesting dysfunction of the autonomic nervous system.

Androgenic anabolic steroid abuse and the cardiovascular system

Abuse of anabolic androgenic steroids (AAS) has been linked to a variety of different cardiovascular side effects. In case reports, acute myocardial infarction is the most common event presented, but other adverse cardiovascular effects such as left ventricular hypertrophy, reduced left ventricular function, arterial thrombosis, pulmonary embolism and several cases of sudden cardiac death have also been reported. However, to date there are no prospective, randomized, interventional studies on the long-term cardiovascular effects of abuse of AAS. In this review we have studied the relevant literature regarding several risk factors for cardiovascular disease where the effects of AAS have been scrutinized:(1) Echocardiographic studies show that supraphysiologic doses of AAS lead to both morphologic and functional changes of the heart. These include a tendency to produce myocardial hypertrophy (Fig. 3), a possible increase of heart chamber diameters, unequivocal alterations of diastolic function and ventricular relaxation, and most likely a subclinically compromised left ventricular contractile function. (2) AAS induce a mild, but transient increase of blood pressure. However, the clinical significance of this effect remains modest. (3) Furthermore, AAS confer an enhanced pro-thrombotic state, most prominently through an activation of platelet aggregability. The concomitant effects on the humoral coagulation cascade are more complex and include activation of both pro-coagulatory and fibrinolytic pathways. (4) Users of AAS often demonstrate unfavorable measurements of vascular reactivity involving endothelial-dependent or endothelial-independent vasodilatation. A degree of reversibility seems to be consistent, though. (5) There is a comprehensive body of evidence documenting that AAS induce various alterations of lipid metabolism. The most prominent changes are concomitant elevations of LDL and decreases of HDL, effects that increase the risk of coronary artery disease. And finally, (6) the use of AAS appears to confer an increased risk of life-threatening arrhythmia leading to sudden death, although the underlying mechanisms are still far from being elucidated. Taken together, various lines of evidence involving a variety of pathophysiologic mechanisms suggest an increased risk for cardiovascular disease in users of anabolic androgenic steroids.

Pathophysiology of sleep apnea

Sleep-induced apnea and disordered breathing refers to intermittent, cyclical cessations or reductions of airflow, with or without obstructions of the upper airway (OSA). In the presence of an anatomically compromised, collapsible airway, the sleep-induced loss of compensatory tonic input to the upper airway dilator muscle motor neurons leads to collapse of the pharyngeal airway. In turn, the ability of the sleeping subject to compensate for this airway obstruction will determine the degree of cycling of these events. Several of the classic neurotransmitters and a growing list of neuromodulators have now been identified that contribute to neurochemical regulation of pharyngeal motor neuron activity and airway patency. Limited progress has been made in developing pharmacotherapies with acceptable specificity for the treatment of sleep-induced airway obstruction. We review three types of major long-term sequelae to severe OSA that have been assessed in humans through use of continuous positive airway pressure (CPAP) treatment and in animal models via long-term intermittent hypoxemia (IH): 1) cardiovascular. The evidence is strongest to support daytime systemic hypertension as a consequence of severe OSA, with less conclusive effects on pulmonary hypertension, stroke, coronary artery disease, and cardiac arrhythmias. The underlying mechanisms mediating hypertension include enhanced chemoreceptor sensitivity causing excessive daytime sympathetic vasoconstrictor activity, combined with overproduction of superoxide ion and inflammatory effects on resistance vessels. 2) Insulin sensitivity and homeostasis of glucose regulation are negatively impacted by both intermittent hypoxemia and sleep disruption, but whether these influences of OSA are sufficient, independent of obesity, to contribute significantly to the "metabolic syndrome" remains unsettled. 3) Neurocognitive effects include daytime sleepiness and impaired memory and concentration. These effects reflect hypoxic-induced "neural injury." We discuss future research into understanding the pathophysiology of sleep apnea as a basis for uncovering newer forms of treatment of both the ventilatory disorder and its multiple sequelae.

The effectiveness of health coaching, home blood pressure monitoring, and home-titration in controlling hypertension among low-income patients: protocol for a randomized controlled trial

Background

Despite the many antihypertensive medications available, two-thirds of patients with hypertension do not achieve blood pressure control. This is thought to be due to a combination of poor patient education, poor medication adherence, and "clinical inertia." The present trial evaluates an intervention consisting of health coaching, home blood pressure monitoring, and home medication titration as a method to address these three causes of poor hypertension control.

Methods/Design

The randomized controlled trial will include 300 patients with poorly controlled hypertension. Participants will be recruited from a primary care clinic in a teaching hospital that primarily serves low-income populations.

An intervention group of 150 participants will receive health coaching, home blood pressure monitoring, and home-titration of antihypertensive medications during 6 months. The control group (n = 150) will receive health coaching plus home blood pressure monitoring for the same duration. A passive control group will receive usual care. Blood pressure measurements will take place at baseline, and after 6 and 12 months. The primary outcome will be change in systolic blood pressure after 6 and 12 months. Secondary outcomes measured will be change in diastolic blood pressure, adverse events, and patient and provider satisfaction.

Discussion

The present study is designed to assess whether the 3-pronged approach of health coaching, home blood pressure monitoring, and home medication titration can successfully improve blood pressure, and if so, whether this effect persists beyond the period of the intervention.

Trial Registration

ClinicalTrials.gov identifier: NCT01013857

Plasma adiponectin concentration is associated with ambulatory daytime systolic blood pressure but not with the dipping status

The objective of this study was to analyse the relationship between the ambulatory blood pressure (ABP) measurement and plasma adiponectin levels in a population-based cohort. Non-hypertensive, non-diabetics from the Oulu Project Elucidating Risk of Atherosclerosis cohort aged 40-60 years with ABP measurement available in 226 men and 236 women were analysed. ABP was recorded using the fully automatic SpaceLabs 90207 oscillometric unit. Plasma adiponectin concentrations were assayed using the enzyme-linked immunosorbent assay method. Without adjustment the highest plasma adiponectin tertile was associated with the lowest ABP and office BP measurements (P from 0.025 to P<0.001, respectively). Only the association of plasma adiponectin concentration with systolic ABP was independent of other conventional risk factors (age, body mass index (BMI), waist, gender, insulin sensitivity index, smoking and alcohol consumption) for hypertension (P=0.017). No association was observed between systolic dipping pattern and adiponectin level. The plasma high adiponectin concentration is independently associated with low daytime systolic ABP value. The mechanisms may include effects on endothelial function and the sympathetic nervous system.

Exclusion of Influence of Physical Activity on Ambulatory Blood Pressure

OBJECTIVE

The basal blood pressure (BP) is more intimately related to hypertension severity than casual BP. BP values obtained by ambulatory blood pressure monitoring (ABPM) tend to be influenced by patients' physical activity because values are not always obtained with the patient at rest. The purpose of this study was to estimate the influence of physical activity on BP and determine daytime BP adjusted for activity as measured by ABPM.

METHODS

This study targeted three clinically different groups: healthy medical students (HS, n = 40), patients with hypertension (HT, n = 20), and patients with diabetes mellitus (DM, n = 7). The subjects' BP, heart rate (HR), and physical activity level were measured by a noninvasive portable multi-biomedical recorder. To identify the influence of physical activity on BP in the three study groups, a least squares regression analysis of the relation between BP and ACT (an index of activity with acceleration) was performed for each group.

RESULTS

ACT had a positive influence on systolic BP (SBP) in the HS, HT, and DM groups (R2 = 0.319, 0.576, 0.697, respectively). SBP adjusted for ACT (walking level) by means of the regression model with dummy variable was 0-24 mmHg lower than the value of SBP measured by ABPM, and daytime SBP (walking level) was overestimated by approximately 10 mmHg in comparison to the value of SBP at rest (ACT = 0).

CONCLUSION

Physical activity had a positive effect on SBP. The results showed that physical activity (walking-level) had a positive effect on SBP of about 10 mmHg.

Biological mechanisms of disease and death in Moscow: rationale and design of the survey on Stress Aging and Health in Russia (SAHR)

BACKGROUND

Prior research has revealed large differences in health and mortality across countries, socioeconomic groups, and individuals. Russia experiences one of the world's highest levels of all-cause and cardiovascular mortality, great mortality differences within the population, and a heavy burden of ill health. Psychological stress has been suggested as a likely explanation of health loss and premature death in Russia and Eastern Europe. However, physiological mechanisms connecting stress with health in Russia remain unclear since existing epidemiological data are scarce and limited to conventional risk factors.

METHOD AND DESIGN

The survey on Stress Aging and Health in Russia (SAHR) is addressing this knowledge gap by collecting an unusually rich database that includes a wide range of reported information, physical and cognitive health outcomes, and biomarkers in a sample of Muscovite men and women aged 55 and older. The total planned sample size is 2,000 individuals. The sample was randomly selected from epidemiological cohorts formed in Moscow between the mid-1970s and the 1990s and from medical population registers. The baseline data collection was carried out from December 2006 to June 2009. Interviews and medical tests were administered at hospital or at home according to standardized protocol. Questionnaire information includes health, socio-demographic characteristics, economic well-being, cognitive functioning, and batteries on stress and depression. Biomarkers include anthropometry, grip strength, resting ECG, conventional cardiovascular factors of risk such as lipid profile and blood pressure, and other biochemical parameters such as those related to inflammation, glucose and insulin resistance, coagulation, fibrinolysis, and stress hormones. In addition to these measurements, SAHR includes dynamic biomarkers provided by 24-hour ECG (Holter) monitoring. This method continuously registers the beat-to-beat heart rate in naturalistic conditions without restrictions on normal daily activities. It provides information about heart functioning, including heart rate variability and ischemic and arrhythmic events.Re-examination of the study subjects will be conducted in 2009-2011 and will focus on health, functional status, economic conditions, behaviors, and attitudes towards aging. The subjects are also followed up for mortality and non-fatal health events.

DISCUSSION

The SAHR will produce a valuable set of established and novel biomarkers combined with self-reported data for the international research community and will provide important insights into factors and biological mechanisms of mortality and health losses in Russia.

Carotid atherosclerosis mediated by visceral adiposity and adipocytokines in type 2 diabetic subjects

The aim of this study was to verify the possible association of visceral fat accumulation with carotid atherosclerosis in order to identify the practical and feasible determinants for each parameter of atherosclerosis in type 2 diabetic subjects. The subjects were 151 diabetic (DM) and age-matched 83 nondiabetic subjects (C), without atherosclerotic disease. Visceral fat area (VFA) on a CT scan at the umbilicus level was measured. Ambulatory 24-h blood pressure (BP) was recorded. Stiffness index beta, intima-media thickness (IMT) and plaque formation of carotid arteries were measured by ultrasonography. Insulin sensitivity was estimated by homeostasis model assessment (HOMA). Serum levels of adiponectin and tumor necrosis factor (TNF)-alpha were determined. Male gender, HOMA, serum non-HDL-Cholesterol (Chol) and TNF-alpha/adiponectin ratio were higher, and VFA was larger in DM than in C. The IMT, stiffness index beta and plaque formation in DM were more pronounced than in C, even after adjusting for age, sex and 24-h systolic BP (sBP). VFA was positively correlated with TNF-alpha/adiponectin ratio and serum non-HDL-Chol in DM. Furthermore, multiple regression analysis revealed that, in DM, serum non-HDL-Chol was associated with IMT, VFA probably via an increase in TNF-alpha/adiponectin ratio was associated with stiffness index beta, and 24-h sBP, HOMA and VFA were associated with plaque formation independently of age and sex, respectively, although any association was not observed in C. Thus, we conclude that visceral fat-associated alterations in adipokines may be mediating the development and progression of atherosclerosis in type 2 diabetic subjects, compared with nondiabetic subjects.

The impact of work on the night blood pressure dipping profile

OBJECTIVE

The purpose of this study was to elucidate whether ambulatory blood pressure (ABPM) performed during a work day and a non-work day had any impact on the night dipping profile.

STUDY DESIGN

A crossover randomized ABPM study in primary healthcare was retrospectively analysed for the occurrence of non-dipping (ND), dipping (D) or extreme (XD) nightly dipping. Non-dippers were defined as subjects with less than 10% and extreme dippers as subjects with more than 20% nightly blood pressure fall measured as mean arterial pressure (MAP).

SUBJECTS

Forty treated hypertensives and 40 normotensives (20 men and 20 women in each group), who had performed ABPM twice in a fortnight. They had been randomly allocated to perform a work day or a non-work day as the first period.

RESULT

Only one of the 16 subjects who at any time was a non-dipper remained so during both monitoring periods. Extreme dipping was more often reproduced in nine persons out of 29. Of all 80 subjects, 43.8% (35 persons) remained dippers during both periods. No one changed from a non-dipper to an extreme dipper or the reverse. The odds of being an ND were 3.8 times more common on a non-work day, p = 0.010. XDs were slightly more common (1.7 times) on a work day than on a non-work day, p = 0.040. There was no correlation as to the degree of MAP and the dipping profile, p = 0.629.

CONCLUSIONS

More subjects were non-dippers at the end than at the beginning of the work week. It is essential to consider this when attempting to identify a non-dipper by ABPM.

Baroreflex sensitivity varies during the rat estrous cycle: role of gonadal steroids

Baroreflex sensitivity (BRS) increases in women during the luteal phase of the menstrual cycle, when gonadal hormones are elevated, but whether a similar cycle-dependent variation in BRS occurs in rats is unknown. In addition, whether cyclic BRS changes depend on gonadal steroids has not been previously investigated. To test these hypotheses, BRS was determined in cycling female rats using two approaches: 1) baroreflex control of renal sympathetic nerve activity (RSNA) in anesthetized rats; 2) cardiovagal spontaneous BRS (sBRS) in conscious rats instrumented for continuous telemetric measurements of mean arterial pressure (MAP) and heart rate (HR). MAP, HR, and sBRS were also measured in rats 2-3 and 5-6 wk following ovariectomy (OVX), to eliminate gonadal steroids. In anesthetized rats, RSNA BRS gain was increased (P < 0.01) during proestrus (-4.8+/-0.5% control/mmHg) compared with diestrus/estrus (-2.8 +/- 0.3% control/mmHg). Similarly, a proestrous peak in sBRS was observed in conscious rats (1.66 +/- 0.07 ms/mmHg, proestrus; 1.48 +/- 0.06 ms/mmHg, diestrus/estrus; P < 0.001). OVX eliminated estrous cycle-induced variation in sBRS. In addition, OVX reduced (P < 0.05) diurnal variations in MAP (5.9 +/- 0.3 vs. 3.9 +/- 0.5 mmHg) and HR [54 +/- 4 vs. 39 +/- 3 beats per minute (bpm)], and abolished diurnal variations in sBRS. Finally, while MAP, HR, and sBRS were decreased 2-3 wk following OVX, approximately 3 wk later, MAP and sBRS increased, and HR decreased further. No changes in MAP, HR, or sBRS were seen with time in sham OVX controls. In summary, RSNA and cardiovagal sBRS vary during the rat estrous cycle, and this variation is abolished by OVX. We conclude that sex steroid hormones are required for both cyclic and diurnal changes in BRS in rats.

Determinants of inappropriate circadian blood pressure variability in children with essential hypertension

BACKGROUND

Inappropriate daily profile of blood pressure deteriorates the clinical outcome of hypertension and increases distant cardiovascular risk. The problem is important, especially in children and adolescents in whom early intervention helps to prevent complications of hypertension such as left ventricular hypertrophy and hypertensive retinopathy.

OBJECTIVES

To assess circadian blood pressure profile and basic determinants of inappropriate daily blood pressure variability in hypertensive children.

METHODS

The project was conducted retrospectively in 106 children six to 18 years of age (mean [+/- SD] 14.9+/-2.5 years) with essential hypertension and no use of antihypertensive drugs. The study group included 43 children with inappropriate daily blood pressure variability ('nondippers') and 63 controls with appropriate daily blood pressure variability ('dippers').

RESULTS

Nondippers, compared with dippers, had higher systolic and diastolic blood pressure at night (systolic, 123.9+/-10.3 mmHg versus 113.9+/-8.2 mmHg; diastolic, 65.1+/-7.6 mmHg versus 59.5+/-6.5 mmHg; P<0.0001), and higher blood pressure load at night (systolic, 61.9% versus 27.6%; diastolic, 20.0% versus 9.6%; P<0.0001). Male sex increased the risk for nondipping by 2.5 times (logistic OR=2.45; 95% CI 0.87 to 6.87). However, the increase was statistically nonsignificant (P=0.08). No differences were observed between dippers and nondippers in terms of anthropometric profile, family history of hypertension, morphological and biochemical blood parameters, and birth weight.

CONCLUSIONS

Among hypertensive children, nondippers have a more severe degree of hypertension. Male sex increases the risk of nondipping. To assess determinants of nondipping more precisely, further clinical investigations are needed.

Chronobiological analysis techniques. Application to blood pressure

Most variables of clinical interest show predictable changes with different frequencies, mainly, but not exclusively, along the rest-activity cycle (circadian variation). Methods of linear least-squares estimation have been designed for the detection of periodic components in sparse and noisy time series (as they are usually present in clinical situations). They include the single and population-mean cosinor methods. In cases where more than one period is statistically significant over the span of time investigated, or when the waveform is non-sinusoidal, the use of multiple components analysis to fit a model consisting of several cosine functions (harmonics or not from a given fundamental period) is recommended. We describe these methods, from the characterization of the underlying models to the process of parameter estimation. As an application example, we describe the modelling of the circadian variation of blood pressure (BP). In most individuals, BP presents a morning increase, a small postprandial valley and a deeper descent during nocturnal rest. This pattern can be easily modelled by means of a model with periods of 24 and 12 hours. Individuals that differ from this model might be considered to present increased cardiovascular risk.

Pitfalls in the measurement of the nocturnal blood pressure dip in adolescents with type 1 diabetes

OBJECTIVE

The purpose of this study was to screen adolescents with type 1 diabetes using ambulatory blood pressure monitoring (ABPM) to 1) test the hypothesis that using a preset sleep time results in an overdiagnosis of abnormal nocturnal dipping in systolic blood pressure and 2) assess the reproducibility of an abnormal nocturnal systolic blood pressure dip.

RESEARCH DESIGN AND METHODS

For aim 1, ABPM from 53 adolescent patients with type 1 diabetes was reviewed. Nocturnal dips in systolic blood pressure calculated by actual sleep time were compared with those from a preset sleep time. For aim 2, blood pressure monitoring from 98 patients using actual reported sleep time was reviewed. Reproducibility of the nocturnal dip in systolic blood pressure was assessed in a subset of "nondippers."

RESULTS

For aim 1, the actual mean +/- SE decline in nocturnal systolic blood pressure was 11.6 +/- 4.7%, whereas the mean decline in nocturnal systolic blood pressure calculated using the preset sleep time was 8.8 +/- 4.9% (P < 0.0001). For aim 2, 64% of patients had a normal nocturnal decline in systolic blood pressure (14.9 +/- 3.1% mmHg), whereas 36% had an abnormal dip (5.7 +/- 2.8% mmHg). Repeat ABPM performed in 22 of the 35 nondippers revealed that only 36% had abnormal systolic dipping confirmed on the repeat ABPM.

CONCLUSIONS

The use of actual reported sleep time is required to accurately determine the nocturnal dip in systolic blood pressure. Repeating ABPM in nondippers is essential to confirm this abnormality.

Ambulatory blood pressure monitoring versus self-measurement of blood pressure at home: correlation with target organ damage

OBJECTIVE

Ambulatory blood pressure (BP) monitoring and home blood pressure measurements predicted the presence of target organ damage and the risk of cardiovascular events better than did office blood pressure.

METHODS

To compare these two methods in their correlation with organ damage, we consecutively included 325 treated (70%) or untreated hypertensives (125 women, mean age = 64.5 +/- 11.3) with office (three measurements at two consultations), home (three measurements morning and evening over 3 days) and 24-h ambulatory monitoring. Target organs were evaluated by ECG, echocardiography, carotid echography and detection of microalbuminuria. Data from 302 patients were analyzed.

RESULTS

Mean BP levels were 142/82 mmHg for office, 135.5/77 mmHg for home and 128/76 mmHg for 24-h monitoring (day = 130/78 mmHg; night = 118.5/67 mmHg). With a 135 mmHg cut-off, home and daytime blood pressure diverged in 20% of patients. Ambulatory and Home blood pressure were correlated with organ damage more closely than was office BP with a trend to better correlations with home BP. Using regression analysis, a 140 mmHg home systolic blood pressure corresponded to a 135 mmHg daytime systolic blood pressure; a 133 mmHg daytime ambulatory blood pressure and a 140 mmHg home blood pressure corresponded to the same organ damage cut-offs (Left ventricular mass index = 50 g/m, Cornell.QRS = 2440 mm/ms, carotid intima media thickness = 0.9 mm). Home-ambulatory differences were significantly associated with age and antihypertensive treatment.

CONCLUSION

We showed that home blood pressure was at least as well correlated with target organ damage, as was the ambulatory blood pressure. Home-ambulatory correlation and their correlation with organ damage argue in favor of different cut-offs, that are approximately 5 mmHg higher for systolic home blood pressure.

Short sleep duration as an independent predictor of cardiovascular events in Japanese patients with hypertension

BACKGROUND

It is not known whether short duration of sleep is a predictor of future cardiovascular events in patients with hypertension.

METHODS

To test the hypothesis that short duration of sleep is independently associated with incident cardiovascular diseases (CVD), we performed ambulatory blood pressure (BP) monitoring in 1255 subjects with hypertension (mean [SD] age, 70.4 [9.9] years) and followed them for a mean period of 50 (23) months. Short sleep duration was defined as less than 7.5 hours (20th percentile). Multivariable Cox hazard models predicting CVD events were used to estimate the adjusted hazard ratio and 95% confidence interval (CI) for short sleep duration. A riser pattern was defined when mean nighttime systolic BP exceeded daytime systolic BP. The end point was a cardiovascular event: stroke, fatal or nonfatal myocardial infarction (MI), and sudden cardiac death.

RESULTS

In multivariable analyses, short duration of sleep (<7.5 hours) was associated with incident CVD (hazard ratio [HR], 1.68; 95% CI, 1.06-2.66; P = .03). A synergistic interaction was observed between short sleep duration and the riser pattern (P = .09). When subjects were classified according to their sleep time and a riser vs nonriser pattern, the group with shorter sleep duration plus the riser pattern had a substantially and significantly higher incidence of CVD than the group with predominant normal sleep duration plus the nonriser pattern (HR, 4.43; 95% CI, 2.09-9.39; P < .001), independent of covariates.

CONCLUSIONS

Short duration of sleep is associated with incident CVD risk and the combination of the riser pattern and short duration of sleep that is most strongly predictive of future CVD, independent of ambulatory BP levels. Physicians should inquire about sleep duration in the risk assessment of patients with hypertension.

Prevalência da adesão ao tratamento anti-hipertensivo em hipertensos resistentes e validação de três métodos indiretos de avaliação da adesão

O estudo estimou a adesão ao tratamento anti-hipertensivo farmacológico utilizando-se três métodos indiretos em uma coorte de hipertensos resistentes no Rio de Janeiro, Brasil, 2005. Os métodos foram: avaliação pelo paciente; avaliação do médico; teste de Morisky-Green (TMG) adaptado para a língua portuguesa. Foi realizada validação preditiva comparando-se a diferença tanto de pressões de consultório como de monitorização de 24 horas (MAPA), em duas ocasiões, de pacientes com e sem adesão. As médias de pressões entre os grupos foram comparadas usando-se testes não-paramétricos. Foram entrevistados 200 pacientes com idade média de 63 anos (DP = 10,3), 73,5% do sexo feminino. A prevalência de adesão foi de 51% pelo TMG, 52% pelo médico e 80,5% pelo paciente. Ocorreram reduções das pressões arteriais de consultório e na MAPA dos pacientes com adesão por todos os métodos, mas não para os não-aderentes. O emprego de mais de um método para avaliação da adesão mostrou que indivíduos não-aderentes pelos três métodos (11,9%) tiveram pior evolução dos níveis tensionais. Esse achado sugere que a hipertensão resistente não pode ser atribuída unicamente à baixa adesão.

Clinical variables associated with non-dipping of nocturnal blood pressure in type 2 diabetes

Aim

Non-dipping of nocturnal BP (blood pressure) is common in people with type 2 diabetes and is associated with increased risk of cardiovascular morbidity and mortality. This study aimed to identify the factors associated with nocturnal non-dipping of BP in people with type 2 diabetes.

Methods

Data were examined from 100 people with type 2 diabetes who had undergone ambulatory BP monitoring. Dippers were defined as those with a systolic night-time BP dip over 15%, and non-dippers as those with a systolic night-time BP dip of under 5%.

Results

There was no significant difference between the mean awake systolic BP in the dipping (142.9 mmHg) and the non-dipping (142.0 mmHg) groups (p=0.77). Non-dippers were significantly older (p<0.0001) with a higher prevalence of albuminuria (p=0.003) and of macrovascular disease (p=0.008) when compared with the dipping group. After adjustment for age, albuminuria remained more prevalent within the non-dipping group (p=0.007). There was no significant difference in glycaemic control, type of diabetes treatment, smoking status, or gender between the groups.

Conclusion

Albuminuria is strongly associated with non-dipping of nocturnal BP in people with type 2 diabetes.

Pulse pressure or dipping pattern: which one is a better cardiovascular risk marker in resistant hypertension?

OBJECTIVE

Nocturnal blood pressure (BP) reduction and ambulatory pulse pressure (PP) are well known prognostic markers obtained from ambulatory BP monitoring (ABPM). The aim of this study is to investigate which one of these ABPM parameters is related to high cardiovascular risk profile in resistant hypertension, based on their associations with target organ damage (TOD).

METHODS

Clinical-demographic, laboratory and ABPM variables were recorded in a cross-sectional study involving 907 resistant hypertensive patients. Nocturnal systolic BP reduction and 24-h PP were assessed both as continuous and dichotomized variables (PP at the upper tertile value: 63 mmHg). Statistical analyses included bivariate tests and multivariate logistic regression with each TOD as the dependent variable.

RESULTS

Patients with the nondipping pattern and high 24-h PP shared some characteristics: they were older, had higher prevalence of cerebrovascular disease and nephropathy, higher office and 24-h BP levels, increased serum creatinine and microalbuminuria, and higher left ventricular mass index than their counterparts. Additionally, patients with high PP had a greater prevalence of diabetes and other TOD. In multivariate logistic regression, high PP was independently associated with all TODs even after adjustment for sex, age, BMI, cardiovascular risk factors, 24-h mean arterial pressure and antihypertensive treatment, whereas nondipping pattern was only associated with hypertensive nephropathy. Furthermore, PP was more strongly associated with the number of TOD than the nocturnal systolic blood pressure (SBP) fall.

CONCLUSIONS

In a large group of resistant hypertensive patients, an increased 24-h PP shows a closer correlation with high cardiovascular risk profile than the nocturnal BP reduction.

Nocturnal hypertension defined by fixed cut-off limits is a better predictor of left ventricular hypertrophy than non-dipping

The classification of subjects as nocturnal hypertensives in accordance with non-dipping (i.e. systolic blood pressure - BP - fall <10%) is less reproducible as compared to the fixed cut-off limits method (nocturnal BP means >120/70 mm Hg). The present study was carried out to assess if nocturnal hypertension defined by fixed cut-off limits may be a better predictor of left ventricular hypertrophy (LVH) than to non-dipping. Echocardiography and 24-h ambulatory blood pressure monitoring were performed in 223 subjects. Logistic regression showed that nocturnal hypertension defined by fixed cut-off limits was a significant predictor of LVH (OR=11.1, 95%CI=3.0-40.1) whereas non-dipping was not (OR=1.4, 95%CI=0.4-5.5). No interaction was detected (p<.3). These results suggest that the definition of nocturnal hypertension based on fixed cut-off values is a better predictor of left ventricular hypertrophy than non-dipping.

Predicting arterial stiffness with ambulatory blood pressure: an 11-year follow-up

No prospective data have been published on whether ambulatory blood pressure (BP) works better than casual measurements in predicting arterial stiffness. This study with 11-year follow-up was launched to evaluate the usefulness of ambulatory intra-arterial BP in predicting pulse wave velocity (PWV). Ninety-seven previously healthy men were recruited from a routine physical check-up at baseline. BP was measured with standard cuff and intra-arterial ambulatory methods. Sixty-seven subjects with no antihypertensive medication were enrolled for a visit after a follow-up of 11 years. Arterial stiffness was estimated with PWV derived with impedance cardiography. Ambulatory 24-h systolic blood pressure (SBP) (r = 0.30, P = 0.01), 24-h mean arterial pressure (r = 0.27, P = 0.03), 24-h pulse pressure (r = 0.27, P = 0.03) and daytime SBP (r = 0.26, P = 0.03) were the best BP variables in predicting future PWV. Casual BP values did not bear significant correlations with future PWV. In hierarchical regression analysis, the best predictive value for future PWV was achieved with the model including ambulatory 24-h SBP, smoking (number of cigarettes) and age (adjusted R(2) = 0.26). In conclusion, to our knowledge, this is the only prospective follow-up study to show that ambulatory BP is superior to casual BP measurement in predicting future PWV.

Early signs of left ventricular dysfunction in adolescents with type 1 diabetes mellitus: the importance of impaired circadian modulation of blood pressure and heart rate

Diabetic cardiomyopathy is a well-defined complication of diabetes that occurs in the absence of ischemic heart disease or hypertension. Moreover impaired circadian blood pressure (BP) variation has been associated with autonomic dysfunction. The aim of our study was to evaluate diurnal BP fluctuations and autonomic function and their association with left ventricular function in adolescents with Type 1 diabetes mellitus (T1DM). In 48 normotensive, normoalbuminuric diabetic adolescents, with a mean (+/-SD) age of 17.3 (+/-4.1) yr and a mean (+/-SD) diabetes duration of 8.5 (+/-3.3) yr, 24-h ambulatory BP was recorded. Moreover 24-h heart rate (HR) monitoring was performed. Myocardial structural parameters were studied by echocardiogram. Left ventricular end-diastolic (EDDLV) and end-systolic diameters (ESDLV) were estimated and left ventricular mass index (LVMI) was calculated using the Devereux formula. The patients were divided into 2 groups according to the absence of decrease (non-dippers) or the decrease (dippers) of nocturnal diastolic BP (DBP). The non-dippers showed, in comparison with the dippers, reduced mean 24-h HR (79.6 vs 84.0 beats/min, p=0.05) and reduced mean day-time HR (81.3 vs 86.0 beats/min, p=0.05). The nondippers also presented greater ESDLV (28.7 vs 25.9 mm, p=0.001) and EDDLV (47.8 vs 45.1 mm, p=0.040), and LVMI (90.2 vs 78.3 g/m2, p=0.044), in comparison with the dippers. During stepwise multiple regression, the most important variables affecting LVMI were mean HR (day): (b=-0.40, p=0.001), high frequency domain variable of HR variability (b=0.38, p=0.016) and glycosylated hemoglobin (b=0.67, p=0.001). In conclusion, we found that a group of normotensive diabetic adolescents with impaired nocturnal BP reduction, also had autonomic dysfunction, together with impaired left ventricular function. These findings suggest that there is a close relationship between autonomic function and left ventricular remodeling in patients with T1DM, which may be attributed to altered diurnal BP profile, autonomic neuropathy and poor glycemic control.

Is the use of ABPM justified in patients on 1 or 2 antihypertensive medications?

We studied the utility of ABPM in patients with elevated clinic BP on 1-2 antihypertensive medications (group B, N=117), compared with those on no medications (group A, N=76) and on > or =3 medications (group C, N=110). 35% of patients in group B had adequately controlled 24-h BP based on ABPM, compared with 22.4% in group A (P=0.06) and 19.1% in group C (P=0.007). Antihypertensive treatment was not escalated in patients with adequately controlled BP. This suggests that ABPM has an important role in therapeutic decision-making for patients on 1-2 antihypertensive medications.

Ambulatory impedance cardiography in hypertension: a validation study

The management of hypertension is improved by knowledge of the hemodynamics underlying blood pressure. Impedance Cardiography (ICG) provides data on a range of hemodynamic variables that affect blood pressure. However, ICG captures only fixed descriptions of hemodynamic characteristics. Improvements in ambulatory technology have led to the development of the Ambulatory Impedance Monitor (AIM) which records hemodynamic data during the activities of daily living. The purpose of this study was to evaluate the sensitivity of the AIM to detect hemodynamic changes associated with postural shift in persons with hypertension. Using a repeated measures cross-over design, sitting and standing hemodynamic measures were taken in seventeen persons with hypertension while wearing the AIM-BpTRU system designed for standard office use and the AIM-Spacelabs system designed for ambulatory monitoring. Both AIM-blood pressure monitoring systems detected significant changes from sitting to standing posture in heart rate (p=0.03), stroke volume (p=0.002), left ventricular ejection time (p<0.001), systemic vascular resistance (p=0.03) and diastolic blood pressure (p<0.001). Additionally, both systems generated measures of cardiac function that were positively correlated (p<0.001) and not significantly different (p>0.05). Our findings support previous work and demonstrate that the AIM provides valid and reliable estimates of cardiac function in persons with hypertension.