Diurnal variation of hemodynamic indices in non-dipper hypertensive patients

Temporal haemodynamic changes after bisoprolol treatment in patients with uncontrolled hypertension

Background

Anti-hypertensive drugs are widely used to control blood pressure, yet their effects on haemodynamics, especially in Chinese populations, and the potential for non-invasive methods to monitor these changes, are poorly understood. This study aimed to determine the early and late effects of bisoprolol treatment on blood pressure, cardiac output (CO), stroke volume (SV), heart rate (HR), systematic vascular resistance (SVR), and inotropy measured in Chinese patients with hypertension.

Methods

Twelve Chinese subjects (median age: 55 years, interquartile range: 52-58 years; 33% male) with uncontrolled hypertension were recruited at the Prince of Wales Hospital in Hong Kong and haemodynamic measurements were assessed using a non-invasive Ultrasonic Cardiac Output Monitor (USCOM). Seven hourly measurements were taken before and after bisoprolol 2.5 mg on day 1 (T0 to T6), and in nine patients this was repeated six weeks later (TF0 to TF6). Any BP change of 5 mmHg was considered clinically significant and P<0.05 was considered statistically significant.

Results

On day 1 (N=12), there was a significant drop in median CO [4.9 (4.7-5.6) vs. 3.8 (3.3-4.7) L/m², P<0.0001] associated with a compensatory increase in SVR [1,698.1 (1,584.6-1,894.3) vs. 2,222.6 (1,777.4-2,712.5) d·s·cm^-5, P<0.0001] at T2. The median dBP {92 [87-95] vs. 86 [79-89] mmHg, P=0.0002} and MAP {110 [104-114] vs. 104 [101-109] mmHg, P=0.038} reduced significantly 6 hours after bisoprolol treatment. Except for HR, all other measured haemodynamics returned to baseline at T6. On week 6 (N=9), SVR was generally reduced, but major parallel swings in CO and SVR were still evident. All patients showed a trend to lower blood pressure, SVR, and inotropy (P<0.05), but HR, SV, and CO returned to baseline values after 6 weeks treatment (P>0.05).

Conclusions

The acute haemodynamic changes between 6 hours of the first dose and the dose after 6 weeks of bisoprolol treatment are similar. Long-term therapy can effectively reduce blood pressure by reducing SVR.

Association of vitamin D deficiency with arterial stiffness in newly diagnosed hypertension

OBJECTIVE

Vitamin D has beneficial effects on vascular endothelial function, blood pressure (BP) and arterial stiffness. Arterial stiffness increases in early-stage hypertensive patients and it is a strong predictor of cardiovascular morbidity and mortality. The purpose of this study was to assess the association between serum 25-hydroxyvitamin D (25-OH D) levels and arterial stiffness in patients with newly diagnosed hypertension.

METHOD

Our study included 100 newly diagnosed hypertensive patients (63 male, 37 female and mean age: 51.7 ± 10.3 years) without cardiovascular disease, malignancy, chronic kidney disease and diabetes mellitus. Patients were divided into two groups: vitamin D deficiency group (<20 ng/ml) and normal vitamin D group (≥20 ng/ml). Twenty-four-hour, daytime and nighttime ambulatory BP readings were recorded. Mobil-O-Graph ARC solver algorithm was used to evaluate arterial stiffness parameters of pulse wave velocity (PWV) (m/s), augmentation index normalized with 75/min heart rate (Alx@75).

RESULTS

Patients with vitamin D deficency had higher values of Alx@75 and PWV values (20.9 ± 9 vs. 16.8 ± 6.9, P = 0.018 and 8.37 ± 1.16 vs. 6.9 ± 0.9, P = 0.001, respectively) despite similar 24-hour ambulatory BP monitoring in both groups. Level of serum calcium was significantly higher in vitamin D deficiency group (9.5 ± 0.23 vs. 9.3 ± 0.12, P = 0.007). Nighttime SBP was higher in vitamin D deficiency group (133.2 ± 14.3 mmHg vs. 126.3 ± 17.2 mmHg; P = 0.03) and also, vitamin D deficiency group had non-dipping SBP pattern compared to normal Vitamin D group (P = 0.013).

CONCLUSION

Vitamin D deficiency is associated with increased arterial stiffness in newly diagnosed hypertensive patients in terms of increased PWV and Alx@75 values.

Blood Pressure Increases Before Pulse Rate During the Nocturnal Period in Hypertensive Patients

Ambulatory blood pressure monitoring (ABPM) is used for the evaluation of out-of-office blood pressure (BP), however, knowledge concerning the detailed behavior of nocturnal blood pressure (BP) and pulse rate (PR) is limited.A total of 190 participants (64 ± 15 years, 46.3% males) underwent ABPM for diagnosis of hypertension or evaluation of hypertensive therapy. BP and PR were measured automatically by the oscillometric method. From the hourly average ABPM values, the nocturnal time courses (0 AM to 6 AM) of SBP and PR were determined and compared to each other.In general, SBP fell to the lowest level at around midnight and started to increase progressively towards dawn while PR stayed unchanged until 7 AM. Age and gender affected the time course of SBP, most distinctly in the female patients aged ≥ 60 years. The time course of the increase of SBP was very similar in the patients, with BP dipping and non-dipping. The cardiothoracic ratio (CTR) slightly and renal dysfunction modestly facilitated the increase of nocturnal SBP. The nocturnal increase in SBP was not accompanied by an increase of PR in any group or subgroup. The pathophysiology and clinical significance of the early and exclusive increase in nocturnal BP need to be investigated.Average ABPM values in these hypertensive patients showed that BP starts to increase toward dawn without an increase in PR and that this discrepant behavior between BP and RP was most distinct in females 60 or older. The mechanism and clinical significance of such a discordant variation in BP and PR need to be elucidated.

Non-dipping blood pressure patterns and arterial stiffness parameters in patients with Behcet's disease

Behcet's disease is a multisystemic vasculitis involving veins and arteries of various sizes. Non-dipping status, augmentation index and pulse wave velocity are important determinants of cardiovascular mortality and morbidity. We investigated the non-dipping status and arterial stiffness in patients with Behcet's disease. In this cross-sectional study, we examined the vascular parameters of 96 patients with Behcet's disease (53% female) and 60 age- and sex-matched control subjects. The non-dipping status and arterial distensibility were assessed using a Mobil-O-Graph Arteriograph, an automatic oscillometric device. In total, 65.6% of 96 patients were systolic non-dippers, and 34.4% exhibited high augmentation indices. Ten percent of the control subjects were systolic non-dippers, and 11.7% exhibited high augmentation indices. Nocturnal decreases in systolic blood pressure correlated with central systolic blood pressure and diastolic blood pressure, as well as nocturnal decreases in diastolic blood pressure. Furthermore, non-dipper patients with Behcet's disease exhibited higher nocturnal cardiac outputs than did dipper patients with Behcet's disease. Augmentation index correlated negatively with C-reactive protein and correlated positively with both 24 h and nocturnal peripheral resistance, as well as 24 h pulse wave velocity. The patients with high augmentation indices exhibited lower creatinine clearance, as well as lower nocturnal cardiac outputs, higher 24 h peripheral resistance and higher 24 h pulse wave velocities. Non-dipping status and arterial stiffness may exacerbate the harmful cardiovascular effects of the other. In addition to conventional risk factors, non-dipping status and arterial stiffness should be examined during the follow-up evaluations of patients with Behcet's disease.

Determination of correlation among heart rate variability, left atrium global strain, and nighttime blood pressure among patients with tinnitus

Background

We aimed to examine the correlation among nighttime blood pressure, heart rate variability, and left atrium peak systolic global longitudinal strain among patients with subjective tinnitus.

Material/Methods

Eighty patients with tinnitus were assigned to Group 1 and 80 healthy individuals were assigned to Group 2. Clinical blood pressure measurements, ambulatory blood pressure monitoring, and Holter electrocardiography monitoring were performed. All of the cases included in the study were examined with conventional echocardiography and 2-dimensional speckle tracking echocardiography.

Results

Mean nighttime systolic blood pressure (130.3±5.4) and mean nighttime diastolic blood pressure (82.8±3.9) in Group 1 were higher than in Group 2 (125.1±5.4 and 80.7±4.7, respectively) (p<0.05). Mean heart rate in Group 1 was significantly lower than in Group 2 but there was no statistically significant difference between the groups in terms of heart rate variability parameters and left atrium peak systolic global longitudinal strain values (p>0.05).

Conclusions

Nighttime systolic blood pressure and nighttime diastolic blood pressure were higher among the patients with tinnitus. In light of these results, we can conclude that both clinical blood pressure measurement and ambulatory blood pressure monitoring are important for patients with tinnitus.

African Caribbeans have greater subclinical cerebrovascular disease than Europeans: this is associated with both their elevated resting and ambulatory blood pressure and their hyperglycaemia

OBJECTIVES

Stroke is elevated in people of black African descent, but evidence for excess subclinical cerebrovascular disease is conflicting, and the role of risk factors in determining any ethnic differences observed unexplored.

METHODS

We compared prevalence of brain infarcts, and severe white matter hyperintensities (WMHs) on cerebral MRI, in a community-based sample of men and women aged 58-86 of African Caribbean (214) and European (605) descent, in London, UK. Resting, central and ambulatory blood pressure (BP) were measured; diabetes was assessed by blood testing and questionnaire.

RESULTS

Mean age was 70. Multiple (≥4) brain infarcts and severe WMH occurred more frequently in African Caribbeans (18/43%), than Europeans (7/33%, P=0.05/0.008). Separately, clinic and night-time ambulatory BP were significantly associated with severe WMH in both ethnic groups; when both were entered into the model, the association for clinic SBP was attenuated and lost statistical significance [1.00 (0.98-1.02) P=0.9 in Europeans, 1.00 (0.97-1.04) P=0.9 in African Caribbeans], whereas the association for night-time SBP was retained [1.04 (1.02-1.07) P<0.001 in Europeans, 1.08 (1.03-1.12), P=0.001 in African Caribbeans]. The greater age-adjusted and sex-adjusted risk of severe WMH in African Caribbeans compared with Europeans [2.08 (1.15-3.76) P=0.02], was attenuated to 1.45 [(0.74-2.83) P=0.3] on adjustment for clinic and night-time systolic pressure, antihypertensive medication use and glycated haemoglobin.

CONCLUSION

African Caribbeans have a greater burden of subclinical cerebrovascular disease than Europeans. This excess is related to elevated clinic and ambulatory BP, and to hyperglycaemia.

The mean platelet volume in patients with non-dipper hypertension compared to dippers and normotensives

OBJECTIVES

Increased platelet activation plays an important role in the development of atherosclerosis. Mean platelet volume (MPV) is a determinant of platelet activation. In our study, we aimed to determine whether MPV levels are elevated in non-dipper patients compared with dippers and healthy controls. In addition, we tried to find out if MPV levels are correlated with blood pressure measurements in hypertensive patients.

METHODS

This cross-sectional study included 56 hypertensive patients; 27 age- and sex-matched healthy volunteers were enrolled to study as a control subjects. Ambulatory blood pressure monitoring was performed for all patients. Hypertensive patients were divided into two groups: 28 dipper patients (10 male, mean age 51 +/-8 years) and 28 non-dipper patients (11 male, mean age 53+/-10 years). MPV was measured in a blood sample collected in EDTA tubes and was also used for whole blood counts in all patients.

RESULTS

In non-dipper patients, 24-h systolic blood pressure (141.5+/-10.21 vs 132.3+/-7.7 mmHg, p<0.001), 24-h diastolic blood pressure (88.2+/-8.5 vs 81.0+/-8.2 mmHg, p<0.01) and 24-h average blood pressure (105.7+/-8.5 vs 97.7+/-7.4 mmHg, p<0.001) are significantly higher than dippers. Whereas daytime measurements were similar between dippers and non-dippers, there was a significant difference between each group during night-time measurements (night-time systolic 137.1 +/-11.0 vs 120.2+/-8.0 mmHg, p<0.001; night-time diastolic 85.3+/-8.0 vs 72.8+/-7.9 mmHg, p<0.001). Non-dipper patients (9.61 +/-0.42 fl) demonstrated higher levels of MPV compared with dippers (9.24+/-0.35 fl) and normotensives (8.87+/-0.33 fl) (p<0.001 and p<0.001, respectively). There was significant correlation between MPV and ambulatory diastolic and systolic blood pressure in non-dipper hypertensives.

CONCLUSION

Our results suggest that MPV, a determinant of platelet activation, has a positively correlation with blood pressure and elevated in non-dipper compared with dippers and controls. Increased platelet activation could contribute to increase the atherosclerotic risk in non-dipper patients compared with dippers.

Platelet activation and inflammatory response in patients with non-dipper hypertension

OBJECTIVE

Non-dipper hypertensives had about three times the risk of atherosclerotic events than hypertensives whose blood pressure was >10% lower at night compared to daytime (dippers). Platelet activation and inflammatory response may derive from most atherosclerotic events. Mean platelet volume (MPV) is a determinant of platelet activation and high sensitive C-reactive protein (hs-CRP) is the best candidate assay to identify and monitor the inflammatory response. We aimed to determine whether MPV and hs-CRP levels are elevated in non-dipper patients compared to dippers and healthy controls. In addition, we tried to find out if MPV and CRP are related to each other or not in non-dipper hypertensives.

METHOD

The total 126 patients study group included 86 patients with hypertension and 40 healthy subjects (16 male, mean age; 51+/-4) as control. Ambulatory blood pressure monitoring was performed for all patients. Hypertensive patients were divided into two groups; 46 dipper patients (18 male, mean age; 50+/-9) and 40 non-dipper patients (17 male, mean age; 53+/-11). Clinical baseline characteristics were similar between groups. We measured mean platelet volume in a blood sample collected in EDTA tubes and high-sensitive CRP was measured by using BN2 model nephlometer.

RESULTS

Non-dipper patients demonstrated higher levels of MPV compared to dippers and normotensives (9.72+/-0.52 fl vs 9.38+/-0.33 fl and 8.92+/-0.42 fl, p<0.05, respectively). High-sensitive CRP levels were also significantly higher in non-dippers compared to dippers and normotensives (4.9+/-1.7mg/l vs 3.8+/-1.5mg/l and 2.7+/-0.8mg/l, p<0.05, respectively). There was significant positive correlation between MPV and CRP levels (p=0.002, r=0.482) in non-dipper hypertensives.

CONCLUSION

Our results suggest that patients with non-dipping tend to have increased platelet activation and inflammatory response. Increased platelet activation and inflammatory response could contribute to increase the atherosclerotic risk in non-dipper patients compared to dippers.

Stress, menopausal status and nocturnal blood pressure dipping patterns among hypertensive women

BACKGROUND

A less than 10% decline in blood pressure during the night is known as a nondipping blood pressure (BP) pattern. Nondipping BP has been shown to be associated with target organ damage and poorer cardiovascular outcomes. Additionally, some evidence suggests that hyper-tensive nondipping women are at greater risk for target organ damage than hypertensive nondipping men.

OBJECTIVE

To determine whether stress, demographics, menopausal status or sleep quality are associated with nondipping BP among hyperten-sive women.

METHODS

A cross-sectional study design was used to describe the rela-tionship between stress and dipping status among a sample of hypertensive women and to describe the sample by age, ethnicity, marital status, meno-pausal status, current medications and sleep quality.

RESULTS

The study sample consisted of 47 women (mean [+/- SD] age 57+/-13.9 years) with essential or office hypertension who underwent 24 h ambulatory BP monitoring, and completed stress and sleep quality measurements. Thirty-one women (66%) were classified as dippers and 16 (34%) were classified as nondippers. Nondippers were older (P=0.04), postmenopausal (P=0.003) and had lower stress scores (P=0.02) than their dipper counterparts. Postmenopausal status sig-nificantly predicted nondipping (OR 16; 95% CI 1.9 to 136.4).

CONCLUSION

These findings were of interest given that some women had a nondipping BP pattern and significantly lower stress scores. It is pos-sible that there are fundamentally different physiological mechanisms that explain this nondipping phenomenon. In the future, the identification of specific hemodynamic mechanisms associated with nondipping could potentially influence the choice of antihypertensive treatment regimens for nondipper hypertensive patients.

Night-time blood pressure patterns and target organ damage: a review

BACKGROUND

Individuals who do not have a 10% to 20% reduction in blood pressure (BP) during the night are known as 'nondippers'. The cause of this nondipping phenomenon is not fully understood; however, there is a growing body of evidence linking a nondipping BP pattern with target organ damage.

OBJECTIVE

To review the literature and present an overview of the target organ damage found to be associated with a nondipping BP pattern.

METHODS

PubMed, CINAHL and Medscape searches of all available English language articles from 1986 to 2005 were performed. Search terms included 'BP nondipping', 'BP dipping' and 'target organ damage'.

RESULTS

There is evidence to suggest that individuals with hypertension who exhibit a nondipping BP profile are at higher risk of cardiac and extracardiac morbidity and mortality. In particular, nondippers with essential hypertension have been found to have more advanced left ventricular hypertrophy, left ventricular mass and left ventricular mass index, carotid artery wall thickness, carotid artery atherosclerotic plaques, silent cerebral infarct, stroke, cognitive impairment and microalbuminuria.

CONCLUSION

A better understanding of the importance of the circadian variations of BP may help to identify those at higher risk of cardiovascular morbidity and mortality, as well as lay the foundation for interventions to prevent/treat alterations in night-time BP patterns.

Use of Plasma B-Type Natriuretic Peptide Level to Identify Asymptomatic Hypertensive Patients with Abnormal Diurnal Blood Pressure Variation Profiles: Nondippers, Extreme Dippers, and Risers

We examined the relationship between plasma B-type natriuretic peptide (BNP) level and diurnal variability pattern of blood pressure (BP). Twenty-four-hour ambulatory BP monitoring was performed in 98 patients with asymptomatic essential hypertension, and the patients were classified into four groups according to their circadian BP variation profiles: dippers (n=29), nondippers (n=36), extreme dippers (n=19), and risers (n=14). Plasma BNP was measured by enzyme immunoassay. Based on the distribution pattern of BNP values, the values were analyzed after logarithmic transformation. Significant differences in plasma BNP levels among the types of circadian BP variations were demonstrated by analysis of variance (p<0.0005). Nondippers and risers showed significantly higher plasma BNP levels (mean [range: -1 SD and +1 SD]: 16.1 [6.3, 41.6] pg/mL and 29.2 [15.9, 53.4] pg/mL, respectively) than dippers (8.4 [3.7, 19.1] pg/mL). The area under the receiver operating characteristics curve for distinguishing patients with abnormal circadian BP variation from those with normal variation was 0.72, indicating that plasma BNP levels were useful for distinguishing between these patients. Specificity of 69% and sensitivity of 72% were obtained with a cut-off value of 10.5 pg/mL (log plasma BNP, 1.02) for distinguishing the abnormal diurnal BP profile group from the normal group. In conclusion, hypertensive patients with abnormal diurnal BP variation patterns (nondippers, extreme dippers, and risers) showed higher plasma BNP levels than those with normal circadian BP variation (dippers). Plasma BNP level is clinically useful for the identification of hypertensive patients who have abnormal circadian BP variability, which increases the risk of cardiovascular events.

Metabolic syndrome as a predictor of non-dipping hypertension

Metabolic syndrome (MS) and non-dipping hypertension both increase cardiovascular mortality. Although both clinical modalities share common pathophysiologic factors in their etiologies, previous studies did not find any association between them. We aimed to investigate the association between MS and non-dipping blood pressure by comparing different definitions of MS. One-hundred-thirty-two consecutive patients (58 men) who underwent 24-hour ambulatory blood pressure monitoring were analyzed. MS was evaluated according to the currently used Adult Treatment Panel (ATP) III definition criteria, named MS-ATP III. In order to reveal the weights of risk contributing to MS, a new diagnostic scoring method (MS-Score) was used in comparison with MS-ATP III. Nocturnal non-dipping refers to a reduction in average systolic and/or diastolic blood pressure at night (< or = 10%) compared with daytime average values. Non-dipping pattern was found in 61.4% of patients. The frequency of MS according to MS-Score, but not MS ATP III, was significantly higher in patients with non-dipping pattern than those without it (p = 0.009). Although more prominent in the nighttime, MS-Score showed positive correlation with all systolic blood pressure results (r = 0.27, p = 0.002). Adjusted for baseline characteristics, high (> or = 27.5) MS-Score remained as an independent predictor of non-dipping pattern (OR 2.64, p = 0.038). Finally, high MS-Score, but not MS-ATP III, is a predictor of non-dipping pattern. Nighttime systolic blood pressure is higher in patients with high MS-Score. Therefore, patients with high MS-Score may be more prone to cardiovascular events than those with low MS-Score.

Non-dippers are associated with adverse cardiac remodeling and dysfunction (R1)

BACKGROUND

Non-dippers are known to carry a high risk of cardiovascular complications due to higher cumulative 24-h pressure load over time. In this study, we hypothesized that non-dippers would be associated with adverse cardiac remodeling and left ventricular (LV) dysfunction in treated hypertensive patients.

MATERIALS AND METHODS

A total of 150 outpatients treated with antihypertensive drugs for at least 1 year were enrolled. The patients were classified as non-dippers if their daytime ambulatory systolic and diastolic BP did not decrease by at least 10% during the night. LV diastolic function was assessed by measuring mitral inflow velocity (E), early diastolic mitral annulus tissue velocity (E') and LV systolic function was assessed by measuring systolic tissue velocity (S'), longitudinal systolic strain and strain rate.

RESULTS

The Cornell voltage product, LA volume index and LV mass index was significantly higher in non-dippers. Early diastolic mitral annulus tissue velocity (E') was lower and E/E' was higher in non-dippers suggestive of diastolic dysfunction. Systolic tissue velocity (S'), systolic strain and strain rate were significantly lower in non-dippers suggestive of systolic dysfunction. The non-dipper status, controlled for age, sex and LV mass index showed significant correlation with E' (beta=-0.203, P=0.002), E/E' (beta=0.354, P<0.001), S' (beta=-0.231, P=0.002), strain (beta=-0.162, P=0.040) and strain rate (beta=-0.186, P=0.015).

CONCLUSIONS

This study showed the non-dippers in treated hypertensive patients were associated with adverse cardiac remodeling and early LV dysfunction. Further studies to demonstrate the long term prognostic significance of this finding is warranted.

Nondipping blood pressure patterns among individuals with essential hypertension: a review of the literature

BACKGROUND

Researchers have discovered that blood pressure (BP) varies in a diurnal manner throughout a 24-hour period, being higher during the day and lower at night. Most people have a dipping BP pattern characterized by a nighttime BP that is 10-20% lower than their daytime BP. Individuals who experience a less than 10% reduction in nighttime BP are described as having a nondipping BP pattern. Although controversial, there is a growing body of evidence suggesting that a nondipping BP pattern is associated with a greater risk of target organ damage among individuals with essential hypertension.

AIM

To review the literature on the most common factors associated with nondipping BP patterns among individuals with essential hypertension.

METHODS

CINAHL (1982-March 2006), PubMed (1950-March 2006) and Cochrane Library (1966-March 2006) databases were searched using the keywords: dipper, dipping, nondipper, nondipping, ambulatory blood pressure monitoring, ABPM, hypertension, essential hypertension, high blood pressure, blood pressure, nocturnal blood pressure, nighttime blood pressure, diurnal blood pressure, and blood pressure patterns. Published studies, abstracts, dissertations as well as the reference lists of retrieved articles were reviewed. Studies were included if they involved subjects with only treated or untreated essential hypertension or those with samples of both nomotensive and treated or untreated essential hypertensive individuals. Additionally, studies needed to evaluate 24-hour, daytime and nighttime BP patterns.

RESULTS

There is some evidence to suggest advanced age, African-American ethnicity, female sex, postmenopausal status, sodium sensitivity, sleep apnea, sleep quality, anger, hostility, depression, stress, social support, and socioeconomic status have an association with nondipping BP patterns.

CONCLUSION

Knowledge of the potential factors associated with an altered nighttime BP pattern is of importance because it can help identify persons at risk for nondipping BP patterns and potential target organ damage. Furthermore, knowledge of these factors associated with a nondipping BP profile will lay the foundation for interventions to prevent/treat alterations in nighttime BP patterns.

Characterization of baroreflex gain in the domestic pigeon (Columba livia)

Birds have a remarkable capacity to regulate circulation yet little is known about the avian baroreflex. Although both linear regression and curve-fitting techniques are frequently used to assess baroreflex function in mammals, only the former technique has been used in birds. We characterized baroreflex gain in domestic pigeons (Columba livia) and compared gain values derived from applying linear regression to ramp changes in mean arterial pressure (MAP) to values derived from fitting a four-parameter sigmoidal function to steady-state alterations in MAP. We found that, unlike mammals, pigeons do not display circadian patterns in MAP, HR or gain derived from bolus injections of vasoactive drugs. The pressor, but not depressor response, was attenuated by administration of the NMDA-antagonist ketamine, suggesting that central processing of the baroreflex may be similar in birds and mammals despite anatomical differences in arterial baroreceptive zones. Because graded infusions of vasoactive drugs could not consistently produce a plateau in the HR response, fitting data to a sigmoidal curve was difficult. Thus, we propose that variations of the Oxford method and linear regression analysis are superior method to assess baroreflex gain in pigeons than curve fitting.

Physical activity, dipping and haemodynamics

OBJECTIVE

To determine the effect of physical activity on diurnal blood pressure (BP) and haemodynamic variation.

METHODS

Ambulatory measurements were performed during 24 h in 36 subjects (18 hypertensive, 13 male), aged 49.7 +/- 13.5 years. BP was recorded in the brachial artery. Physical activity and posture were measured with five acceleration sensors.

RESULTS

Of the subjects 50% were dippers (nocturnal decrease in systolic or diastolic BP >/= 10%). Dippers and non-dippers had similar daytime BP, daytime, night-time, and day-night difference in physical activity, subjective sleep quality, and nocturnal cardiac output decrease (14.9 +/- 9.6 and 16.0 +/- 5.9%). In non-dippers vascular resistance increased from day to night by 9.7 +/- 8.3%, while it remained unchanged (-1.0 +/- 13.9%) in dippers. Day-night changes in heart rate and cardiac output were correlated with day-night changes in physical activity (r = 0.39 and 0.43), whereas day-night changes in systolic BP were correlated with night-time activity (r = -0.34). By selection of the active (i.e. walking) and inactive (i.e. not walking) periods during the day, we showed that physical activity has a large potential effect on dipping status and diurnal haemodynamic variation underlying BP variation. Depending on the BP taken (systolic or diastolic, respectively) the proportion of dippers increased to 81% or decreased to 25% if only the walking period was considered, whereas it decreased to 36% or increased to 53% if only the non-walking period was considered.

CONCLUSIONS

Non-dippers differ from dippers by an increase of vascular resistance during the night. The degree of physical activity normally encountered during ambulatory monitoring has little influence on the diurnal BP profile or dipping status, but significantly influences underlying haemodynamics. Related to the different effects of posture and activity on systolic and diastolic BP, dipping classification may vary with the BP index taken.

Disruption of Ultradian and Circadian Rhythms of Blood Pressure in Nondipper Hypertensive Patients

Ultradian rhythms in blood pressure (BP) are known to exist, but their modification in hypertension is largely unknown. The present study was undertaken to assess the integrity of ultradian and 24-hour BP rhythms in dipper (n=100) and nondipper (n=20) hypertensive patients compared with 44 dipper normotensive individuals. Fourier analysis was used to fit ultradian (12, 8, and 6 hour) and 24-hour rhythms in BP and heart rate (HR). Mesor, amplitude, and acrophase were calculated for individual and overall rhythm curves. All subjects showed significant ultradian or 24-hour BP and HR rhythms. Systolic and diastolic BP mesor was higher in hypertensive patients compared with normotensive patients. The percentage of variability in ambulatory BP that could be explained by fitting ultradian and 24-hour rhythms was reduced in nondippers compared with normotensives or dippers. Amplitude of ultradian and 24-hour rhythms in BP increased in dippers and decreased in nondippers. Ultradian and 24-hour rhythms in HR did not differ among the 3 groups examined. Results indicate that in nondippers, blunted ultradian and 24-hour rhythm amplitude in BP was accompanied by a loss of rhythm integrity.

Disasters and the heart: a review of the effects of earthquake-induced stress on cardiovascular disease

There is growing evidence that stress contributes to cardiovascular disease. Chronic stress contributes to the atherosclerotic process through increased allostatic load, which is mediated by the neuroendocrine and immune systems (sympathetic nervous system and hypothalamus-pituitary adrenal axis) and related chronic risk factors (insulin resistance syndrome, hypertension, diabetes, and hyperlipidemia). In addition, acute stress can trigger cardiovascular events predominantly through sympathetic nervous activation and potentiation of acute risk factors (blood pressure increase, endothelial cell dysfunction, increased blood viscosity, and platelet and hemostatic activation). Earthquakes provide a good example of naturally occurring acute and chronic stress, and in this review we focus mainly on the effects of the Hanshin-Awaji earthquake on the cardiovascular system. The Hanshin-Awaji earthquake resulted in a 3-fold increase of myocardial infarctions in people living close to the epicenter, particularly in women, with most of the increase occurring in nighttime-onset events. There was also a near doubling in the frequency of strokes. These effects may be mediated by changes in hemostatic factors, as demonstrated by an increase of D-dimer, von Willebrand factor, and tissue-type plasminogen activator (tPA) antigen. Blood pressure also increased after the earthquake, and was prolonged for several weeks in patients with microalbuminuria.

Ventricular repolarization is prolonged in nondipper hypertensive patients: role of left ventricular hypertrophy and autonomic dysfunction

OBJECTIVE

The aim of this study was to investigate the influence of circadian behavior of blood pressure, left ventricular hypertrophy, and autonomic function on QTc interval duration in untreated hypertensive patients.

DESIGN

Hypertensive patients underwent simultaneous blood pressure and ECG 24-h ambulatory monitoring. Patients were classified into two groups on the basis of a lack of nocturnal fall in blood pressure, as dippers and nondippers. A group of normotensive healthy subjects was studied as controls.

METHODS

QT and QTc intervals were automatically computed and spectral analysis was applied to RR interval time series from the same electrocardiogram (ECG) recordings. Left ventricular mass index (LVMI) was computed by echocardiogram.

RESULTS

No difference among the three groups was found concerning mean values and circadian pattern of heart rate; by contrast, QTc was significantly longer in nondippers compared to dippers or to normotensive subjects, particularly at night-time, whereas all groups exhibited similar circadian variations in heart rate. Compared to dippers, nondippers showed significantly higher LVMI, which positively correlated with QTc, and parasympathetic withdrawal, which negatively correlated with QTc.

CONCLUSIONS

Nondippers show a prolonged ventricular repolarization throughout the 24-h period, absent either in dippers or normotensives. The association of left ventricular hypertrophy and vagal deactivation may lead to prolongation of QTc, potentially facilitating ventricular arrhythmias in nondipper hypertensive patients.

Sleep disorders and the failure to lower nocturnal blood pressure

PURPOSE OF REVIEW

The failure to lower systolic blood pressure at night (called non-dipping) and sleep apnea are both associated with adverse cardiovascular outcomes. Sleep apnea is a common cause of non-dipping blood pressure.

RECENT FINDINGS

Sleep apnea increases night time blood pressure through enhanced cardiac pre-load, sleep disturbance and hypoxia. Hypoxia elicits increased levels of norepinephrine, endothelin and erythropoetin. Patients with sleep apnea tend to be elderly and obese, so they have poor endothelial nitric oxide release and blunted baroreflexes. They thus have several stimuli for high blood pressure and poor compensatory mechanisms to lower blood pressure.

SUMMARY

Non-dipping patients without sleep apnea have evidence of volume overload and correct their blood pressure pattern in response to diuretics. Individuals with sleep apnea have evidence of increased cardiac pre-load from episodes of negative intrathoracic pressure. Their daytime blood pressure responds poorly to many drugs, but beta blockers may be effective. Their night time blood pressure responds only slightly to therapy of their sleep apnea with continuous positive airway pressure, even though continuous positive airway pressure decreases their norepinephrine, erythropoetin and endothelin levels.

Hepatocyte growth factor and 24-hour ambulatory blood pressure monitoring

In recent years, many growth factors and cytokines have been shown to be related to arteriosclerosis, and hepatocyte growth factor (HGF) has been reported to be associated with hypertension. In the present study, we investigated the relationship between HGF and hypertension by measuring the serum HGF concentration and performing 24-h ambulatory blood pressure monitoring (ABPM) in 47 randomly selected male and female subjects who underwent a medical examination for cardiovascular disease. The results were as follows. 1) The mean serum HGF concentration in the subjects was 0.35+/-0.14 ng/ml. 2) The serum HGF concentration was positively correlated with both the nighttime systolic and diastolic blood pressures (r=0.42, p<0.05 and r=0.47, p<0.01, respectively). 3) No correlation was found between serum HGF concentration and daytime systolic or diastolic blood pressure. 4) When subjects were divided into two groups based on the difference between daytime and nighttime systolic blood pressure, i.e., a group in which the difference was less than 10 mmHg and a group in which the difference was 10 mmHg or more, the HGF concentration was significantly higher in the former group (0.39+/-0.14 vs. 0.30+/-0.12 ng/ml, p<0.05); similarly, when subjects were divided into a group in which the difference between daytime and nighttime diastolic blood pressure was 5 mmHg and a group in which the difference was 5 mmHg or more, the HGF concentration was significantly higher in the former group (0.42+/-0.15 vs. 0.31+/-0.12 ng/ml, p<0.05). The results indicated that there is a relationship between blood pressure measured by ABPM and serum HGF concentration, and that this relationship might be an index of damage to blood vessels in patients with hypertension.

Dietary sodium restriction restores nocturnal reduction of blood pressure in patients with primary aldosteronism

The purpose of this study was to elucidate the effects of dietary sodium restriction on diurnal blood pressure (BP) variation in primary aldosteronism. We studied the diurnal variation in the systemic hemodynamic indices and in baroreflex sensitivity (BRS). In 13 subjects with aldosterone-producing adenomas (2 males; mean age, 39+/-2 years), intra-arterial pressure was monitored telemetrically on a normal salt diet (NaCl 10-12 g/day). Non-dippers were defined as those with a nocturnal reduction in systolic BP (SBP) of less than 10% of daytime SBP. Ten subjects showed a non-dipper pattern. Six of these "non-dippers" underwent repetitive hemodynamic studies on the last day of a 1-week low salt diet regimen (NaCl 2-4 g/day). Stroke volume was determined using Wesseling's pulse contour method, calibrated with indocyanine green dilution. BRS was calculated every 30 min as delta pulse interval/delta SBP on spontaneous variations. Nocturnal reduction of SBP was 4.1% on the normal salt diet. With sodium restriction, urinary sodium excretion decreased from 187+/-8 to 46+/-8 mmol/day, and body weight decreased from 57.9+/-2.1 to 56.6+/-1.9 kg. Night-time BP significantly decreased with dietary modification from 154+/-7/88+/-4 to 140+/-6/78+/-4 mmHg, whereas daytime BP was unaltered. With sodium restriction, cardiac index and stroke index decreased throughout the day. No significant difference was seen in either daytime or nighttime BRS between the two diets. We conclude that the non-dipper pattern is common in patients with an aldosterone-producing adenoma on a normal salt intake, and under such conditions, volume expansion appears to play a major role in the impairment of nocturnal BP reduction.

The influence of work- and home-related stress on the levels and diurnal variation of ambulatory blood pressure and neurohumoral factors in employed women

The purpose of this study was to examine the effects of self-reported perceived stress at work and home on the levels, variation and co-variation of ambulatory blood pressure (BP), pulse rate (PR) and urinary catecholamine, cortisol, and aldosterone excretion measured at work, home and during sleep in women employed outside the home. The subjects of the study were 134 women (mean age 34.4 +/- 9.6 years, range 18 to 64 years) who were employed in managerial, technical or clerical positions at the same work place. Perceived stress at work and home was self-reported on a scale from 0 (low) to 10 (high). BP, PR and the urinary rates of excretion of epinephrine, norepinephrine, cortisol and aldosterone were averaged in the daily work environment from 11 AM to 3 PM, in the daily home environment from approximately 6 PM to 10 PM, and during sleep from approximately 10 PM to 6 AM the following morning. The results showed that systolic and diastolic BP (SBP and DBP) and the rates of urinary catecholamine, cortisol, and aldosterone excretion measured in the work environment were significantly higher than corresponding measurements taken in the home environment. SBP measured at work was also positively correlated with the difference in perceived stress between work and home (p < 0.05). PR (p < 0.001) and the rate of urinary norepinephrine excretion (p < 0.05) measured in the home environment were positively correlated with stress at home. When the subjects were divided into groups based on whether the work or home environment was perceived to be most stressful, women reporting greater stress at work (n=85) had higher work SBP (p < 0.005), work DBP (p < 0.05), and sleep SBP (p < 0.005) than women who perceived the home environment to be more stressful (n=34). There were no differences in the urinary hormonal excretion rates between these perceived-stress groups. Among women with greater perceived stress at home, the home-stress score was positively correlated with sleep SBP level (r = 0.310, p < 0.05), its variation (SD of sleep SBP: r = 0.402, p < 0.01) and home pulse rate ( r= 0.414, p < 0.01). These findings suggest that among employed women, work stress may increase ambulatory BP levels throughout the day, while home stress may induce additional sympathetic activation at home. In addition, they also show that among employed women who perceive greater stress at home than at work, higher home stress levels may also elevate sleep BP levels.

Psychological and physical stress-induced cardiovascular reactivity and diurnal blood pressure variation in women with different work shifts

There is increasing evidence that diurnal blood pressure (BP) variation, in addition to high BP per se, is related to target organ damage and the incidence of cardiovascular events. However, the determinants of diurnal BP variation are not adequately understood. This paper tests the hypothesis that cardiovascular reactivity to acute stress and/or delayed recovery predicts greater diurnal BP variation (i.e., a lower sleep/awake BP ratio). We studied the relationship of diurnal BP variation (assessed by ambulatory BP monitoring) to mental stress (mental arithmetic and anger recall tasks) and physical stress (treadmill)-induced cardiovascular reactivity and recovery in 87 female nurses who worked different shifts. The sleep/awake systolic BP (SBP) ratio was negatively correlated with relative SBP reactivity (maximum SBP increase/baseline SBP: r = -0.21, p = 0.06) and relative stress response (average of SBP during stress/baseline SBP:r = -0.23, p = 0.04) induced by anger recall, while the correlations of the sleep/awake SBP ratio with other parameters of reactivity or recovery in the anger recall or mental arithmetic task were not significant. When subjects were divided into day-shift workers (n=54) and night-shift workers (n = 33), the sleep/awake SBP ratio was negatively correlated with relative SBP reactivity (r = -0.41, p = 0.02) and relative stress response of SBP (r = -0.48, p = 0.006) induced by anger recall, and positively correlated with recovery rate (r = 0.34, p = 0.06) in the latter group, while these correlations were not significant in the former group. The sleep/awake SBP ratio was inversely correlated with the exercise-induced SBP increase in the day-shift workers (r = -0.30, p = 0.03), while this association was not found in the night-shift workers. In conclusion, cardiovascular reactivity triggered by psychological and physical stress in the laboratory may be a weak, but significant, determinant of diurnal BP variation; in addition, work shift (day or night) appears to moderate the relationship between these two pressor mechanisms.