Cardiovascular abnormalities in never-treated hypertensives according to nondipper status

Cardiac Remodeling According to the Nocturnal Fall of Blood Pressure in Hypertensive Subjects: The Whole Assessment of Cardiac Abnormalities in Non-Dipper Subjects with Arterial Hypertension (Wacanda) Study

Objective: Several epidemiological studies suggest that the preservation of the physiological circadian rhythm of blood pressure or its disruption affects the extent of the organ damage developed by the patient. If we classify the circadian rhythm of blood pressure into four nocturnal profiles, significant differences emerge in terms of organ damage burden and prognosis: reverse dippers have the worst prognosis while dippers and mild dippers fall into an intermediate risk range. The risk profile of extreme dippers is still debated, and the available data are very conflicting and inconclusive. Starting from this gap of knowledge, we aimed to evaluate, retrospectively, in a cohort of hypertensive subjects, the degree of cardiac involvement in relation to the different nocturnal blood pressure profiles. Methods: We retrospectively evaluated 900 patients with essential hypertension, of whom 510 met our study criteria. We graded the 510 patients in relation to the percentage of reduction in mean systolic blood pressure (SBP) at night-time compared with day-time, considering this as a continuous variable, and then compared the extreme quintiles with each other and with the middle quintile (considered as reference). Results: Patients with less (or no) reduction in nocturnal SBP (reverse dipper) showed a higher level of organ damage and comorbidities. With regard to echocardiographic indexes, patients with maximum nocturnal pressure reduction (extreme dipper) showed a lower level of remodeling and/or impairment of E/e’ ratio, Right Atrium Area, Basal Right Ventricular Diameter, Inferior Vena Cava Average Diameter, and Tricuspidal Anular Plane Systolic Excursion compared also with hypertensive patients with a physiological nocturnal pressure reduction, even after correction for the main confounders. Conclusions: These data suggest that extreme dippers may constitute the subgroup of hypertensive patients with the lowest 24-h pressure load and, therefore, less cardiac remodeling.

Effect of non-dipper pattern on echocardiographic myocardial work parameters in normotensive individuals

BACKGROUND

It is known that non-dipper pattern (NDP) is associated with adverse outcomes in hypertensive patients. However, there is insufficient data on the outcome of NDP in normotensive individuals. Using myocardial work (MW) analysis, as a new echocardiographic examination method, this study aimed to determine the early myocardial effects of NDP in normotensive individuals.

METHODS

This study included 70 normotensive individuals who were followed by ambulatory blood pressure monitoring (ABPM). The subjects were divided into two groups according to dipper pattern (DP) and NDP. Conventional, strain, and MW findings were compared between the groups by making echocardiographic evaluations.

RESULTS

The demographic characteristics, laboratory parameters, and measurements of cardiac chambers, and left ventricular (LV) walls were similar between the groups. There was no statistical difference between the groups in terms of LV 3-2-4 chambers strains and global longitudinal strain (GLS) values. LVMW parameters, global work index (GWI), and global constrictive work (GCW) were not statistically different between groups (2012 ± 127, 2069 ± 137, p = 0.16; 2327 ± 173, 2418 ± 296, p = 0.18, respectively). However, global waste work (GWW) and global work efficiency (GWE) parameters were different between the groups (144 ± 63.9, 104 ± 24.8, p < 0.001; 93.2 ± 3.17, 95.4 ± 1.28, p < 0.001, respectively). In regression analysis, GWW was independently associated with NDP. GWW model showed better results with higher likelihood chi-square and R² values than GLS model in discriminating the predictable capability for NDP status.

CONCLUSION

The results of MW analysis in this study showed that GWW values were higher and the GWE values were lower in normotensive individuals with NDP.

The relation between blood pressure components and left atrial volume in the context of left ventricular mass index

Left atrial enlargement (LAE) is a risk factor for cardiovascular complications and death. In hypertensive patients, LAE is usually due to left ventricular (LV) hypertrophy and diastolic dysfunction. We aimed to identify factors associated with LAE in patients with increased and normal left ventricular mass index (LVMI) with reference to pulsatile and steady components of blood pressure (BP).The study was carried out as a cross-sectional observation. In a group of inhabitants of suburban area of Cracow, Poland, we measured office, ambulatory and central BP, carotid-femoral pulse wave velocity (PWV), as well as echocardiographic indices and gathered anthropometric data, information on habits and relevant medical history. Further, with division according to sex-stratified dichotomised LVMI, we performed correlation analysis to identify possibly significant relations between measures of left atrial volume and other studied parameters. We also fitted regression models in order to assess the respective value of steady and pulsatile BP components as factors related to measures of left atrial volume.The mean age of 205 patients (136 females-66%) was 53.6 ± 8.3 years. We found higher values of PWV, office, ambulatory and central BPs in the group of LVMI above median value. This group had also greater left atrial volume index (LAVI), which correlated with LVMI (r = 0.36, P < .001) and ratio of early diastolic mitral peak flow velocity to early diastolic mitral annulus mean velocity in tissue Doppler imaging (E/e') (r = 0.24, P = .04).In the group of LVMI below the median, LAVI correlated with pulsatile and steady BP components. LAVI was independently predicted by mean arterial pressure (MAP) obtained from both ambulatory (MAP24h, β= 0.15; P = .045) and office measurements (MAPoffice, β = 0.35; P = .004), but not by pulse pressure.LV mass and function are the main determinants of LAVI. However, in persons with lower LV mass, LAVI depends on the steady component of blood pressure, but not pulsatile one. Increased LAVI reflects early changes in response to systemic blood pressure elevation.

Left Ventricular Mass in Dippers and Nondippers with Newly Diagnosed Hypertension

Hypertensive subjects can be subdivided into 2 groups, dippers and nondippers, according to the presence or the lack of a nocturnal fall of blood pressure of more than 10%. Several studies have investigated cardiac organ damage in the 2 groups with discordant results, but they included subjects with different onset, severity, and treatment of hypertension. The authors selected 23 dippers and 17 nondippers affected by newly (< 1 year) diagnosed grades 1 and 2 hypertension, never treated, who underwent 24-hour ambulatory blood pressure monitoring and M-mode echocardiography. They did not find significant differences between the 2 groups as regards the echocardiographic left ventricular and atrial dimensions or regarding the left ventricular mass, left ventricular mass index, or relative wall thickness. Also no significant differences were found in the rate of either left ventricular remodeling or left ventricular hyper trophy. These data suggest that nondipping status is not associated with a higher level of cardiac involvement in the early phases of hypertension compared to dipping status.

Non-Dipping Pattern and Subclinical Cardiac Damage in Untreated Hypertension: A Systematic Review and Meta-Analysis of Echocardiographic Studies

AIM

The association of non-dipping (ND) pattern with cardiac damage is debated. We performed a meta-analysis in order to provide comprehensive information on subclinical cardiac alterations in untreated ND hypertensives.

DESIGN

A computerized search was performed using PubMed, OVID, EMBASE, and Cochrane library databases from 1 January 1990 up to 31 October 2014. Full articles published in English language providing data on subclinical cardiac damage in ND as compared to dipper (D) hypertensives, as assessed by echocardiography, were considered.

RESULTS

A total of 3,591 untreated adult subjects (1,291 ND and 2,300 D hypertensives) included in 23 studies were considered. Left ventricular (LV) mass index (LVMI) was higher in ND than in D hypertensives (122±3.8 g/m2 vs. 111±3.3 g/m2, standardized mean difference, SMD: 0.40±0.07, confidence interval (CI): 0.26-0.53, P < 0.001); relative wall thickness (RWT) and left atrium (LA) diameter were greater (SMD: 0.14±0.005, CI: 0.05-0.23, P = 0.002; 0.36±0.10, CI: 0.16-0.56, P < 0.001, respectively), while mitral E/A ratio was lower in ND than in D counterparts (SMD: -0.23±0.08, CI: -0.39 to -0.08, P = 0.003). After assessing data for publication bias, the difference between groups was still significant, with the exception of E/A ratio.

CONCLUSIONS

Our meta-analysis supports an association between ND pattern and increased risk of LV structural alterations in untreated essential hypertensives. This observation supports the view that an effective BP control throughout the entire 24-hour cycle may have a key role in preventing or regressing subclinical cardiac damage associated to ND pattern.

24-hour intraocular pressure and ocular perfusion pressure in glaucoma

This review analyzes the currently available literature on circadian rhythms of intraocular pressure (IOP), blood pressure, and calculated ocular perfusion pressure (OPP) in patients with open-angle glaucoma. Although adequately powered, prospective trials are not available. The existing evidence suggests that high 24-hour IOP and OPP fluctuations can have detrimental effects in eyes with glaucoma. The currently emerging continuous IOP monitoring technologies may soon offer important contributions to the study of IOP rhythms. Once telemetric technologies become validated and widely available for clinical use, they may provide an important tool towards a better understanding of long- and short-term IOP fluctuations during a patient's daily routine. Important issues that need to be investigated further include the identification of appropriate surrogate measures of IOP and OPP fluctuation for patients unable to undergo 24-hour measurements, the determination of formulae that best describe the relationship between systemic blood pressure and IOP with OPP, and the exact clinical relevance of IOP and OPP fluctuation in individual patients. Despite the unanswered questions, a significant body of literature suggests that OPP assessment may be clinically relevant in a significant number of glaucoma patients.

Association of target organ damage with three arterial stiffness indexes according to blood pressure dipping status in untreated hypertensive patients

BACKGROUND

Subclinical organ damage represents an intermediate stage in the continuum of vascular disease and a determinant of overall cardiovascular risk. We investigated the associations of pulse wave velocity (PWV), ambulatory arterial stiffness index (AASI), and office pulse pressure (PP) with several target organ damages (TODs) in newly diagnosed and never-treated patients with essential hypertension with respect to their dipping profile.

METHODS

One hundred sixty-eight hypertensive patients with recently diagnosed and never-treated stage I-II essential hypertension were evaluated with respect to the relationship of PWV, AASI, and office PP with TOD including microalbumin (MAU) levels, cognitive function, intima-media thickness (IMT), coronary flow reserve (CFR), left ventricular mass (LVM), left ventricular filling pressures, diastolic dysfunction, and left atrium (LA) enlargement.

RESULTS

Simultaneous estimation of AASI, PWV, and office PP independently associated with the following: (i) CFR (P < 0.01), 24-h urine albumin excretion rates (P < 0.05), left ventricular diastolic dysfunction (P < 0.01), and LA enlargement (P < 0.01) in never-treated hypertensive patients; (ii) CFR (P < 0.05), IMT (P < 0.01), left ventricular diastolic dysfunction (P < 0.05), and LA enlargement (P < 0.05) in dippers; and (iii) CFR (P < 0.05) and LA enlargement (P < 0.01) in nondippers. Nonindependent relationships revealed between (i) AASI and left ventricular filling pressures and (ii) PWV and cognitive dysfunction in never-treated hypertensive patients.

CONCLUSIONS

The simultaneous estimation of three noninvasive indexes of arterial stiffness leads to valuable information regarding their association with TOD including CFR, MAU levels, IMT, left ventricular diastolic dysfunction, and LA enlargement in never-treated hypertensive patients regarding their dipping status.

Prognostic value of subdivisions of nighttime blood pressure fall in hypertensives followed up for 8.2 years. Does nondipping classification need to be redefined?

To evaluate the long-term prognostic significance of different ranges of the percentage fall in nighttime blood pressure (BP) of the nondipping pattern, 1200 hypertensive patients (645 women, age 51+/-12 years) underwent ambulatory BP monitoring under stabilized therapy. The occurrence of cardiovascular (CV) events was followed for 9833 patient-years and analyzed by the Cox hazard model. There were 152 CV fatal/nonfatal events (79 strokes, 51 coronary events, 22 others) during the 15.2 years of follow-up. According to nighttime BP fall (%) the authors noted: <0% (reverse-dippers [RD], n=83); 0%-4.9% (nondippers 1 [ND1], n=207); 5%-9.9% (nondippers 2 [ND2], n=311), 10%-19.9% (dippers [D], n=523); and > or =20% (extreme dippers [ED], n=76). After adjustment for confounding variables, hazard ratios (95% confidence interval) of CV event and stroke in RD vs D were 2.29 (1.31-3.99) and 2.46 (1.11-5.49); of ND1 vs D were 1.42 (1.12-1.79) and 1.62 (1.17-2.23); and of ND1 vs ND2 were 2.24 (1.33-3.75) and 2.30 (1.15-4.58). No differences were found in RD vs ND1 and ND2 vs D. Nondippers have a higher CV risk than dippers but only for a nighttime BP fall <5% suggesting that the limits for nondipping should be redefined for a stratification of CV risk.

Non-alcoholic fatty liver disease is associated with left ventricular diastolic dysfunction in essential hypertension

BACKGROUND AND AIM

Insulin resistance is recognized as the pathophysiological hallmark of non-alcoholic fatty liver disease (NAFLD). A relation between insulin sensitivity and left ventricular morphology and function has been reported in essential hypertension, where a high prevalence of NAFLD has been recently found. We investigated the inter-relationship between left ventricular morphology/function, metabolic parameters and NAFLD in 86 never-treated essential hypertensive patients subdivided in two subgroups according to the presence (n = 48) or absence (n = 38) of NAFLD at ultrasonography.

METHODS AND RESULTS

The two groups were similar as to sex, age and blood pressure levels. No patient had diabetes mellitus, obesity, hyperlipidemia, or other risk factors for liver disease. Body mass index, waist circumference, triglycerides, glucose, insulin, homeostasis model of assessment index for insulin resistance (HOMA-IR), aspartate aminotransferase and alanine aminotransferase were higher and adiponectin levels were lower in patients with NAFLD than in patients without NAFLD, and were associated with NAFLD at univariate analysis. Patients with NAFLD had similar prevalence of left ventricular hypertrophy compared to patients without NAFLD, but a higher prevalence of diastolic dysfunction (62.5 vs 21.1%, P < 0.001), as defined by E/A ratio <1 and E-wave deceleration time >220 ms. Diastolic dysfunction (P = 0.040) and HOMA-IR (P = 0.012) remained independently associated with NAFLD at backward multivariate analysis.

CONCLUSIONS

Non-alcoholic fatty liver disease was associated with insulin resistance and abnormalities of left ventricular diastolic function in a cohort of patients with essential hypertension, suggesting a concomitant increase of metabolic and cardiac risk in this condition.

Can nocturnal hypertension predict cardiovascular risk?

Nocturnal hypertension and non-dipping of blood pressure during sleep are distinct entities that often occur together and are regarded as important harbingers of poor cardiovascular prognosis. This review addresses several aspects related to these blood pressure abnormalities including definitions, diagnostic limitations, pathogenesis and associated patient profiles, prognostic significance, and therapeutic strategies. Taken together, persistent nocturnal hypertension and non-dipping blood pressure pattern, perhaps secondary to abnormal renal sodium handling and/or altered nocturnal sympathovagal balance, are strongly associated with deaths, cardiovascular events, and progressive loss of renal function, independent of daytime and 24-hour blood pressure. Several pharmacological and non-pharmacological approaches may restore nocturnal blood pressure and circadian blood pressure rhythm to normal; however, whether this translates to a clinically meaningful reduction in unfavorable cardiovascular and renal consequences remains to be seen.

Nocturnal non‐dipping pattern in untreated hypertensives at different cardiovascular risk according to the 2003 ESH/ESC guidelines

AIM

To evaluate in a large population of untreated, uncomplicated essential hypertensives the relationship between alterations in nocturnal blood pressure (BP) profile, i.e. non-dipping pattern, and total cardiovascular risk.

METHODS

A total of 580 consecutive patients with grade 1 or 2 hypertension, referred to our outpatient clinic, underwent the following procedures: (i) clinical and routine laboratory examinations; (ii) 24-h ambulatory BP monitoring; (iii) 24-h collection for microalbuminuria; (iv) echocardiography; and (v) carotid ultrasonography. Cardiovascular risk was assessed according to the stratification scheme suggested by the 2003 ESH/ESC guidelines.

RESULTS

According to this classification, 16.2% of the 580 patients were considered at low added risk, 42.4% at medium added risk and 41.4% at high added risk; 38.5% of the overall population was classified in the high-risk stratum because of at least one manifestation of target organ damage (TOD) and 6.3% for the presence of three or more risk factors. The prevalence rates of a non-dipping pattern (decrease in BP at night < or = 10% compared with the average daytime values) were 28.5% in low-risk, 32.6% in medium-risk and 42.2% in high-risk patients, respectively. CONCLUSIONS. Our findings show that the prevalence of a non-dipping profile is significantly greater in patients stratified at high compared with those at low and medium added risk.

Coronary flow reserve in dipper and non‐dipper hypertensive patients

BACKGROUND

Failure to decrease blood pressure (BP) normally during night-time, which is called non-dipping, in hypertensive individuals is associated with higher cardiovascular morbidity and mortality. In addition, non-dipping BP leads to structural changes in the left ventricle; however, the effect of non-dipping BP on coronary flow reserve (CFR) has not been studied yet.

METHODS

In this study, we measured CFR of 22 subjects with non-dipper hypertension, and 15 subjects with dipper hypertension using transthoracic second-harmonic Doppler echocardiography (Acuson Sequoia C256. None of the subjects had any systemic disease or coronary risk factor except hypertension.

RESULTS

Age, gender, body mass index, lipids and echocardiographic findings including left ventricular mass index were similar between the groups. Office BP recordings were similar between non-dipper and dipper groups (147.9+/-6.1/93.9+/-4.3 vs 144.0+/-8.0/93.0+/-3.7). Daytime and 24-h ambulatory BP measurements were similar within the groups, but night-time BPs were significantly greater in non-dipper group than those were in dipper group. Left ventricular diastolic and systolic functions, and both baseline and hyperemic peak diastolic coronary velocity as well as CFR, were similar between the non-dipper and dipper groups (CFR: 2.47+/-0.59 vs 2.39+/-0.47).

CONCLUSION

CFR were similar in patients with non-dipper and dipper hypertension in the absence of excessive left ventricular hypertrophy and other cardiovascular risk factors.

The effects of nocturnal dipping on cardiovascular outcomes and proteinuria in essential hypertensive patients

Individuals who do not have a 10% to 20% reduction in blood pressure (BP) during the night are known as ‘nondippers’. Non-dipping patterns in hypertensive patients have been shown to be associated with an excess of target organ damage and other adverse outcomes. The present study was designed to investigate the relationship between nocturnal BP pattern, defined on the basis of the ambulatory blood pressure monitoring (ABPM) recording, and cardiac and renal target organ damage in a population of at least one year treated essential hypertensive subjects. The present analysis involved 123 patients with treated essential hypertension attending the outpatient clinic of our centre. Each patient was subjected to the following procedures: blood sampling for routine blood chemistry, spot urine for proteinuria, 24-hour periods of ABPM, and echocardiography. In the ABPM period, a dipping pattern was observed in 65 of the 123 patients, and a non-dipping pattern in 58 patients. Body mass index was higher in the non-dippers (26 ± 4 versus 28 ± 4, p<0.05). The proteinuria in spot urine was significantly higher in the non-dippers (10 ± 6 versus 24 ± 48, p<0.03). Left ventricular mass, interventricular septum thickness, posterior wall thickness and left ventricular systolic diameter were significantly higher in the non-dippers compared to the dippers. Left ventricular diastolic function was similar in non-dipper cases, except E-wave deceleration time. In treated essential hypertensives the blunted or absent nocturnal fall in blood pressure can be a strong predictor of cardiac and renal events. Hypertensive patients should be evaluated by ambulatory blood pressure monitoring. To prevent patients at risk for morbidity and mortality casualities as a result of hypertension, patients should be evaluated by ambulatory blood pressure monitoring. This method can be utilized for exacting future follow-ups with the patient.

WITHDRAWN: Left atrial function and arterial hypertension

Left atrial enlargement is frequently observed in many cardiac diseases. One of the main determinants of left atrial size is ventricular diastolic function. It has recently been suggested that left atrial volume might be the morphophysiologic expression of long-term modifications induced by diastolic function. Furthermore, left ventricular remodelling, such as it happens in hypertensive patients, is another important determinant of atrial volume. All the volumetric modifications of the left atrium, during cardiac cycle, are involved in hypertensive damage. Therefore, left atrial function impairment represents the result of morphological and haemodynamic alterations observed in hypertension. Actually, many techniques, invasive and non-invasive, are available with the purpose to investigate the real atrial dimensions and provide a suitable assessment of atrial function. Recently, it has been demonstrated that the degree of left atrial enlargement is associated with adverse prognosis in different clinical setting. The predictive value of left atrial volume seems to be independent of left ventricular systolic and diastolic function, but the use of left atrial volume for risk stratification is yet an evolving science: more data are required with respect to the natural history of left atrial remodelling in disease, the degree of left atrial modifiability with therapy and whether regression of left atrial size translates into improved cardiovascular outcome.Journal of Human Hypertension advance online publication, 14 August 2008; doi:10.1038/jhh.2008.96.

Longitudinal association of sleep-disordered breathing and nondipping of nocturnal blood pressure in the Wisconsin Sleep Cohort Study

STUDY OBJECTIVES

The association of sleep-disordered breathing (SDB) and blunting of normal nocturnal lowering of blood pressure (BP) (nondipping) has only been examined cross-sectionally. The purpose of this study is to investigate whether SDB is prospectively associated with nondipping.

METHODS

The longitudinal association between SDB and incident nondipping was examined in a subsample of 328 adults enrolled in the Wisconsin Sleep Cohort Study who completed 2 or more 24-hour ambulatory BP studies over an average of 7.2 years of follow-up. SDB identified by baseline in-laboratory polysomnography was defined by apnea-hypopnea index (AHI) categories. Systolic and diastolic nondipping was defined by systolic and diastolic sleep-wake BP ratios > 0.9. All models were adjusted for age, sex, body mass index at baseline and follow-up, smoking, alcohol consumption, hypertension, sleep time, length of follow-up time, and antihypertensive medication use.

RESULTS

There was a dose-response increased odds of developing systolic nondipping in participants with SDB. The adjusted odds ratios (95% confidence interval) of incident systolic nondipping for baseline AHI 5 to < 15 and AHI > or = 15, versus AHI < 5, were 3.1 (1.3-7.7) and 4.4 (1.2-16.3), respectively (P trend = 0.006). The adjusted odds ratios (95% confidence interval) of incident diastolic nondipping for corresponding SDB categories were not statistically significant: 2.0 (0.8-5.6) and 1.3 (0.2-7.1).

CONCLUSIONS

Our longitudinal findings of a dose-response increase in development of systolic nondipping of BP with severity of SDB at baseline in a population-based sample provide evidence consistent with a causal link. Nocturnal systolic nondipping may be a mechanism by which SDB contributes to increased cardiovascular disease.

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.

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.

Circadian rhythm of blood pressure and the relation to cardiovascular events

Incidences of potentially life-threatening cardiovascular events display a diurnal pattern, tending to be higher in the morning than at other times of day. The recording of blood pressure at pre-defined intervals under everyday circumstances is facilitated by ambulatory blood pressure monitoring (ABPM). This technique shows that systolic and diastolic blood pressures display a circadian rhythm in most individuals. Typically, at the end of the night on arousal, blood pressure surges. This surge coincides with increased cardiovascular events. A recent prospective study conducted in Japan, where the incidence of stroke is high, provides further evidence for the link between cardiovascular events and morning blood pressure surge. Prevalence of both silent ischaemic events and multiple cerebrovascular infarcts was highest among the elderly subjects studied, with the largest increase in blood pressure on awakening. An increased risk of cardiovascular morbidity and mortality is also seen in 'non-dippers' (i.e. individuals in whom the normal nocturnal fall in blood pressure is absent or blunted). ABPM is superior to clinic blood pressure in predicting cardiovascular morbidity and mortality, and this suggests that 24-h blood pressure control may be necessary to gain complete benefit from blood pressure-lowering therapy. Antihypertensive agents with a long duration of action have the potential to provide blood pressure control throughout the dosing interval and thus cover the critical early morning period when the blood pressure surges. Clinical studies that have compared telmisartan with shorter-acting angiotensin II receptor blockers and angiotensin-converting enzyme inhibitors demonstrate that telmisartan has a sustained duration of action, with proven efficacy over the entire 24-h period between doses, including the critical early morning period.

Attenuation of heart rate recovery after exercise in hypertensive patients with blunting of the nighttime blood pressure fall

OBJECTIVES

To evaluate whether hypertensive patients with attenuation of nighttime blood pressure (BP) fall exhibit a delay of the recovery of heart rate (HR) after exercise as an index of a general decrease in the vagal tone.

METHODS

Mild-moderate hypertensive patients (n = 219, age 55 +/- 3, 77% men) underwent a maximal exercise test (Bruce > 85% heart rate limited) in whom we calculated the recovery of HR as the percent decrease of HR from peak to 1 min after stopping exercise (%HR fall-1 min), a 24-h ambulatory BP monitoring, calculating the percent decrease of nighttime vs. daytime BP (% night SBP fall). Left ventricular mass index (LVMI) was measured by echo and aortic stiffness by pulse wave velocity (PWV). Sixty percent were on antihypertensive drugs (not on beta-blockers nor on non-dihydropiridine calcium blockers); 12 subjects were type 2 diabetics.

RESULTS

The "% night SBP fall" ranged from - 6.3% to 38.9% and the "%HR fall-1 min" ranged from 3.3% to 43.7%. There was a significant positive correlation between these two variables (r = 0.594, p < 0.001). Population was divided into five groups according to quintiles of values for the "% night SBP fall". For similar daytime BP and age, the lowest quintile for % night SBP fall (- 6.3% to 7.2%) showed the lower "%HR fall-1 min" (3.1 +/- 0.5%), and the higher LVMI (92 +/- 3 g/m(2)) and PWV (12.1 +/- 0.4 m/s) values comparing to the other quintiles (p < 0.02).

CONCLUSIONS

In hypertensives, blunting of the nocturnal fall of BP is associated with a delayed recovery in heart rate after graded maximal exercise and with greater aortic stiffness and ventricular mass. This may indicate that in non-dipper subjects a relative general decrease of parasympathetic reactivation after exercise is linked to the failure of nighttime fall of BP, both of which might contribute to target-organs deterioration.

Effects of dipper and non-dipper status of essential hypertension on left atrial mechanical functions

AIM

This study was designed in order to investigate the effects of dipper and non-dipper status of hypertension on left atrial mechanical (reservoir, conduit and booster pump) functions with left atrial volume measurements by means of two-dimensional echocardiography in untreated systemic hypertensive patients.

METHOD

A total of 27 untreated dipper hypertensive patients, group I (15 female, 12 male, mean age 57+/-12 years); 23 untreated non-dipper hypertensive patients, group II (12 female, 11 male, mean age: 53+/-18 years); and 25 voluntary healthy individuals, group III (13 female, 12 male, mean age 53+/-10 years) were included into the study. Twenty-four hour blood pressure (BP) measurement was performed by the cuff-oscillometric method to evaluate the nocturnal decrease of BP. The patients whose night time mean blood pressure measurements were found 10% or more lower compared to mean day time measurements were classified as dipper hypertensive patients and the ones with a decrease of less than 10% were classified as non-dipper hypertensive patients. Left atrial (LA) volumes were measured echocardiographically according to biplane area-length method in apical four-chamber and two-chamber views. LA maximal volume (V(max)) was recorded at the onset of mitral opening, LA minimal volume (V(min)) was recorded at the onset of mitral closure and LA presystolic volume (V(p)) was recorded at the beginning of the atrial systole (p wave on ECG). All volume measurements were corrected to body surface area, and following LA emptying functions parameters were calculated: LA passive emptying volume (LAPEV)=V(max)-V(p), LA passive emptying fraction (LAPEF)=LAPEV/V(max), Conduit volume (CV)=left ventricular output volume-(V(max)-V(min)), LA active emptying volume (LAAEV)=V(p)-V(min), LA active emptying fraction (LAAEF)=LAAEV/V(p), LA total emptying volume (LATEV)=V(max)-V(min), LA total emptying fraction (LATEF)=LATEV/V(max).

RESULTS

LA volume indexes, V(max), V(min), and V(p), were significantly increased in the hypertensive subgroups (groups I and II) than in controls (p<0.001, p<0.001, p<0.001, respectively), but no significant difference was found in the V(p) values between group I and group II. V(max) and V(min) were larger in non-dipper hypertensive group than in dipper hypertensive group (p<0.05 and p<0.05, respectively). LAPEV and LAPEF were observed to be significantly reduced in both dipper and non-dipper hypertensives than in control (p<0.001 and p<0.05, respectively), and this difference was more obvious in non-dipper than dipper cases (p<0.001). Conduit volume was significantly lower in hypertensive groups than controls (p<0.05). LA active emptying volume (p<0.001) and LAA active emptying fraction (p<0.001) were significantly greater in hypertensive cases than in controls. Furthermore, LA active emptying volume in non-dipper hypertensive subjects was significantly greater than dipper hypertensive cases (p<0.05). Left atrial total emptying volume and left atrial total emptying fraction in both hypertensive groups were similar to control (p>0.05).

CONCLUSIONS

Atrial reservoir and booster pump functions increase in hypertensive patients, but this result is more prominent in non-dipper hypertensives than in dipper hypertensive patients.

Relevance of blood pressure variation in the circadian onset of cardiovascular events

Ambulatory blood pressure monitoring (ABPM) is a highly useful diagnostic tool as it can detect non-dipping and can distinguish masked hypertension, white-coat hypertension and sustained hypertension. Furthermore, measurement of blood pressure using ABPM has greater prognostic strength than single clinic blood pressure measurements. The Systolic Hypertension in Europe study, for example, found that elevation of ambulatory systolic blood pressure, but not conventional single cuff systolic blood pressure, by 10 mmHg was associated with adverse cardiovascular outcomes. Blood pressure follows a circadian rhythm, with peak levels during the morning hours. The morning period has also been associated with a greater risk for cardiovascular events compared with the rest of the 24 h. The morning surge in blood pressure, along with haemostatic changes that promote thrombosis, is believed to contribute to this heightened risk. Long-acting antihypertensive agents that provide blood pressure control throughout the 24-h dosing interval, including the morning hours, are the most appropriate therapeutic approach to hypertension. Direct comparative studies with telmisartan and other angiotensin-II receptor blockers and with amlodipine have shown that telmisartan has a long duration of action and controls blood pressure over the 24-h dosing period.

The burden of uncontrolled hypertension: morbidity and mortality associated with disease progression

Even small elevations above optimal blood pressure values (<120/80 mm Hg) increase the likelihood of developing hypertension (blood pressure >or=140/90 mm Hg) and incurring target organ damage. Until recently, the main emphasis in hypertension treatment had been lowering diastolic blood pressure; however, in the past decade, the important contributions of systolic hypertension, increased pulse pressure, and a blunted reduction in nocturnal blood pressure have been described. Primary hypertension arises from complex, interrelated pathologies. Among the contributors are genetic, environmental, metabolic, vascular, and endothelial factors. Signs of target organ damage herald a poorer prognosis and may present in the heart, blood vessels, kidneys, brain, or eyes. Later consequences include cardiac, cerebrovascular, vascular, and renal morbidities and death. The goal in treating hypertension is to prevent cardiovascular and renal complications. Thus, hypertensive patients with high-normal blood pressure values may benefit from intensive lifestyle interventions to further reduce blood pressure. This is particularly true in patients with additional cardiovascular risk factors. Because of the complex nature of hypertension, it is not surprising that single antihypertensive agents normalize blood pressure for less than a majority of hypertensive patients. Using combination antihypertensive therapy consisting of agents from two or more different antihypertensive drug classes not only increases the likelihood of achieving the target blood pressure goal, but also offers the potential for greater protection against target organ damage by targeting separate pathologic mechanisms.

Reduced nocturnal fall in blood pressure, assessed by two ambulatory blood pressure monitorings and cardiac alterations in early phases of untreated essential hypertension

To investigate whether in recently diagnosed essential hypertensives a reduced nocturnal fall in blood pressure (BP), established on the basis of two 24-h ambulatory blood pressure monitorings (ABPM) is related to a greater cardiovascular damage. In all, 355 consecutive, recently diagnosed, never-treated essential hypertensives referred for the first time to our outpatient clinic were included in the study. Each patient underwent the following procedures: (1) two 24-h ABPMs performed within 3 weeks, (2) 24-h urinary collection for microalbuminuria, (3) nonmydriatic photography of ocular fundi, (4) echocardiography, (5) carotid ultrasonography. We defined nondipping profile as a night-day systolic and diastolic fall < or =10 % (mean of two ABPMs). A dipper BP profile was found in 238 patients, whereas in 117 patients a nondipper profile was present. The two groups were similar for age, gender, body mass index, smoking habit, clinic BP, 48-h BP and heart rate, while, by definition, night-time systolic and diastolic BP were significantly higher in nondippers than in dippers (130/81 vs 121/74 mmHg, P < 0.0001).The prevalence of left ventricular hypertrophy (LVH) defined by four different criteria: (a) LV mass index (LVMI) > or = 125 g/m(2) in both genders; (b) LVMI > or = 134 gm(2) in men and > or = 110 in women; (c) LVMI> or = 125 g/m(2) in men and > or = 110 g/m(2) in women; (d) LVMI > or = 51 g/m(2.7) in men and > or = 47 g/m(2.7) in women was significantly higher in nondippers than in dippers (a: 12 vs 7%, P < 0.05; b: 16 vs 7%, P < 0.01; c: 20 vs 11%, P < 0.01; d: 35 vs 23% P < 0.02) and this finding was associated with a significant increase in aortic root and left atrium dimensions. There were no differences between the two groups in the prevalence of carotid and retinal changes and microalbuminuria. In conclusion our findings suggest that never-treated hypertensives with a reduced BP fall in the night time, defined on the basis of two ABPMs, have a higher prevalence of TOD than dippers, in terms of echocardiographic LVH. In this population setting, cardiac structural alterations are a more sensitive marker of the impact of the nocturnal BP load on cardiovascular system than other extracardiac signs of TOD.

Non-dipper treated hypertensive patients do not have increased cardiac structural alterations

BACKGROUND

Non-dipping pattern in hypertensive patients has been shown to be associated with an excess of target organ damage and with an adverse outcome. The aim of our study was to assess whether a reduced nocturnal fall in blood pressure (BP), established on the basis of a single 24-h BP monitoring, in treated essential hypertensives is related to more prominent cardiac alterations.

METHODS

We enrolled 229 treated hypertensive patients attending the out-patient clinic of our hypertension centre; each patient was subjected to the following procedures : 1) clinic BP measurement; 2) blood and urine sampling for routine blood chemistry and urine examination; 3) standard 12-lead electrocardiogram; 4) echocardiography; 5) ambulatory BP monitoring (ABPM). For the purpose of this study ABPM was carried-out in three subgroups with different clinic BP profile: 1) patients with satisfactory BP control (BP < 140/90 mmHg; group I, n = 58); 2) patients with uncontrolled clinic BP (clinic BP values > or = 140 and/or 90 mmHg) but lower self-measured BP (< 20 mmHg for systolic BP and/or 10 mmHg for diastolic BP; group II, n = 72); 3) patients with refractory hypertension, selected according to WHO/ISH guidelines definition (group III, n = 99). Left ventricular hypertrophy (LVH) was defined by two gender-specific criteria (LV mass index > or = 125/m2 in men and 110 g/m2 in women, > or = 51/gm2.7 in men and 47/g/m2.7 in women).

RESULTS

Of the 229 study participants 119 (51.9%) showed a fall in SBP/DBP < 10% during the night (non-dippers). The prevalence of non-dippers was significantly lower in group I (44.8%) and II (41.6%) than in group III (63.9%, p < 0.01 III vs II and I). The prevalence of LVH varied from 10.3 to 24.1% in group I, 31.9 to 43.1% in group II and from 60.6 to 67.7% in group III (p < 0.01, III vs II and I). No differences in cardiac structure, analysed as continuous variable as well as prevalence of LVH, were found in relationship to dipping or non-dipping status in the three groups.

CONCLUSIONS

In treated essential hypertensives with or without BP control the extent of nocturnal BP decrease is not associated with an increase in LV mass or LVH prevalence; therefore, the non-dipping profile, diagnosed on the basis of a single ABPM, does not identify hypertensive patients with greater cardiac damage.

Determinants of left atrial size in patients with newly diagnosed untreated hypertension

The present study determined the relationships between ambulatory blood pressure, left ventricular mass, body mass index, and other clinical and demographic variables to left atrial size in previously untreated hypertensive and normotensive subjects. Left atrial size was measured uni-dimensionally using M-mode echocardiography in 58 newly diagnosed never-treated hypertensive patients (office blood pressure 149/96 +/- 15/7 mmHg) and 28 normotensive control subjects (office blood pressure, 122/78 +/- 8/8 mmHg). Left ventricular mass, septal and posterior wall thickness were significantly increased in hypertensive compared to normotensive subjects (230 +/- 63 g versus 181 +/- 45 g, 1.1 +/- 0.2 cm versus 0.94 +/- 0.2 cm, and 1.04 +/- 0.2 cm versus 0.92 +/- 0.2 cm respectively; all p < 0.001). Left ventricular internal diameter (4.9 +/- 0.6 versus 4.8 +/- 0.4 cm, = 0.54) and left atrial size (3.74 +/- 0.48 versus 3.70 +/- 0.34 cm, p = 0.86) were not different between the two groups respectively. Body mass index, weight, left ventricular mass, wall thickness, and 24-h pulse pressure were significant correlates of left atrial size in the entire group and in the hypertensive subgroup. In the normotensive subgroup, body weight, body mass index, 24-h systolic and pulse pressure, and left ventricular mass were significant correlates. Multiple regression analyses in the entire group and the hypertensive subgroup alone showed that body mass index and left ventricular mass were the two best predictors of left atrial dimension. These data demonstrate that body mass index and left ventricular mass were the main correlates of left atrial size in patients with previously untreated stage I-II hypertension.

Relation of extent of nocturnal blood pressure decrease to cardiovascular remodeling in never-treated patients with essential hypertension

The clinical significance of the extent of a decrease in nocturnal blood pressure (BP) and the resulting classification of hypertensives as "dipper" (decrease in BP >10% day BP) or "nondipper" (decrease in BP <10% day BP) has been questioned recently. The aim of our study was to evaluate if the extent of a nocturnal BP decrease, established on the basis of a single 24-hour BP monitoring, is related to cardiovascular remodeling in essential hypertension. We enrolled 253 never-treated essential hypertensives (24-hour BP > or = 140 and/or 90 mm Hg); for each patient we recorded 24-hour BP, left ventricular (LV) echocardiogram, Doppler transmitral flow velocities, and carotid-femoral pulse-wave velocities. A dipper BP profile was found in 161 patients, whereas 92 patients were nondippers. The 2 groups did not differ with regard to age, gender, body mass index, 24-hour and daytime BP, and 24-hour, daytime, and nighttime heart rate. All LV morphologic characteristics LV systolic and diastolic functional parameters, mitral Doppler-derived diastolic indexes, as well as carotid-femoral pulse-wave velocity, and aortic index distensibility were not significantly different between dippers and nondippers. The prevalence of LV hypertrophy and diastolic dysfunction was also similar between the 2 groups. The extent of a decrease in nocturnal BP did not correlate with any cardiovascular parameter. In conclusion, in never-treated hypertensives, the extent of a nocturnal BP decrease is not related to LV morpho-functional characteristics and aortic distensibility; therefore, the nondipping status established on the basis of a single 24-hour BP monitoring does not identify hypertensive patients with greater cardiovascular damage.

Night time blood pressure and cardiovascular structure in a middle-aged general population in northern Italy: the Vobarno Study

The aim was to determine, in a cross-sectional study, the relation between structural alterations in the heart and carotid arteries, and blood pressure (BP) changes from day to night time, measured by ambulatory BP (ABP). In 225 untreated subjects (107 F, 118 M, age range 48-64 years) and 59 treated subjects (24 M, 35 F, age range 50-64), living in a small town of northern Italy (Vobarno, Brescia) carotid intima media thickness as well as the occurrence of plaque, were evaluated by ultrasound. Echocardiographic left ventricular (LV) mass was measured according to the Penn Convention. BP was determined by clinic measurement and by 24-h non-invasive ABP monitoring. Subjects were divided in two groups, according to the decrease of night time systolic BP (SBP) "dippers" (SBP decreased by at least 10% during night time) and "non-dippers" (decrease of night time SBP <10%). The intima-media thickness in the common carotid, in the carotid bifurcation, in the internal carotid artery and average intima-media thickness were significantly greater in untreated non-dippers as compared with dipper subjects (ANOVA P < 0.05). A significantly higher prevalence of plaque was observed in untreated non-dippers as compared with dippers (P = 0.002). After adjusting for age, sex, 24-h SBP, and smoking, IMT in the carotid bifurcation and average intima-media thickness remained significantly greater in non-dipper subjects (P < 0.05 for all comparisons). No significant differences in LV mass were observed between dippers and non-dipper subjects. In conclusion, in a general population of unselected middle-aged subjects, night time BP values, among other risk factors, seem to represent an important determinant of carotid wall structure.

Nocturnal non-dipping: what does it augur?

The non-dipping pattern of blood pressure (defined as a nocturnal fall of less than 10%) occurs in about 25% of hypertensives, with increased prevalence in certain sub-groups such as diabetics, African-Americans, and patients with renal disease. It almost certainly has multiple causes, including factors such as the levels of activity and arousal during both the day and the night, the depth and quality of sleep, and the activity of the sympathetic nervous system, among others. In patients with uncomplicated hypertension, the reproducibility is relatively low. There is evidence suggesting that the non-dipping pattern may have an adverse prognosis: thus, it appears to predict the progression of renal disease, to be associated with increased target-organ damage (in some studies), and also to predict increased cardiovascular morbidity. Antihypertensive drug treatment can normalize the non-dipping pattern, but the therapeutic consequences of this are unknown.

Target organ damage and non-dipping pattern defined by two sessions of ambulatory blood pressure monitoring in recently diagnosed essential hypertensive patients

OBJECTIVE

To evaluate in a selected population of patients with a recent diagnosis of hypertension whether a reduced nocturnal fall in blood pressure, confirmed by two 24 h ambulatory blood pressure monitoring (ABPM) sessions is associated with more prominent target organ damage (TOD).

METHODS

The study was structured in two phases: in the first, 141 consecutive, recently diagnosed, never-treated essential hypertensives underwent 24 h ABPM twice within 3 weeks; in the second phase, 118 of these patients showing reproducible dipping or non-dipping patterns underwent the following procedures: (1) routine blood chemistry, (2) 24 h urinary collection for microalbuminuria, (3) amydriatic photography of ocular fundi, (4) echocardiography and (5) carotid ultrasonography.

RESULTS

The 92 patients with (>10%) night-time fall in systolic blood pressure (SBP) and diastolic blood pressure (DBP) (dippers) in both monitoring sessions were similar for age, gender, body surface area, smoking habit, clinic BP, 24 h and 48 h BP to the 26 patients with a < or = 10% nocturnal fall (non-dippers) in both sessions. The prevalence of left ventricular hypertrophy (LVH) (defined by two criteria: (1) LV mass index > or = 125 g/m2 in both genders; (2) LV mass index > or = 120 and 100 g/m2 in men and women, respectively) and that of carotid intima-media (IM) thickening (IM thickness > or = 0.8 mm) were significantly higher in non-dippers than in dippers (23 versus 5%, P < 0.01; 50 versus 22%, P < 0.05; and 38 versus 18%, P < 0.05, respectively). There were no differences among the two groups in the prevalence of retinal changes and microalbuminuria. The strength of the association of LV mass index with night-time BP was slightly but significantly greater than that with daytime BP.

CONCLUSIONS

This study suggests that a blunted reduction in nocturnal BP, persisting over time, may play a pivotal role in the development of some expressions of TOD, such as LVH and IM thickening, during the early phase of essential hypertension, despite similar clinic BP, 24 h and 48 h BP levels observed in non-dippers and dippers.

A validation of the Mobil O Graph (version 12) ambulatory blood pressure monitor

OBJECTIVE

To assess the clinical accuracy of the Mobil O Graph (version 12) ambulatory blood pressure monitor in an adult population.

METHODS

The accuracy of the device was assessed by predefined criteria (British Hypertension Society, BHS) in 85 subjects recruited from the patients and staff in a teaching hospital. A series of same-arm sequential blood pressure measurements were taken: first two observers taking simultaneous mercury readings, followed by a reading with the Mobil O Graph ambulatory monitor. A total of seven readings were taken from each subject in the sitting position. The data were then analysed according to the BHS protocol and the criteria of the Association for the Advancement of Medical Instrumentation (AAMI).

RESULTS

The Mobil O Graph ambulatory monitor fulfilled the criteria of the BHS protocol, achieving a grade B for systolic blood pressure (SBP) and a grade A for diastolic blood pressure (DBP). The mean differences were -2+/-8 mmHg for SBP and -2+/-7 mmHg for DBP. The device therefore also passed the AAMI standard (the mean to be within 5+/-8 mmHg).

CONCLUSION

The Mobil O Graph ambulatory monitor performed in a satisfactory manner according to the BHS and the AAMI criteria and can therefore be recommended for clinical use in the general population.

Impact of nocturnal fall in blood pressure on early cardiovascular changes in essential hypertension

OBJECTIVE

To evaluate in a selected population of subjects with a recent diagnosis of hypertension whether a blunted nocturnal fall in blood pressure is associated with more advanced cardiac and vascular damage.

METHODS

One hundred and eleven recently diagnosed and never-treated patients with mild essential hypertension underwent 24-h ambulatory blood pressure monitoring (ABPM), echocardiography and carotid ultrasonography.

RESULTS

The 78 patients with normal (> 10%) night-time fall in systolic blood pressure (SBP) and diastolic blood pressure (DBP) (dippers) were similar to the 33 patients with a small (< or = 10 %) fall (non-dippers) for age, sex, body surface area, smoking habit, clinic and 24-h blood pressure. There were no differences between dippers and non-dippers in left ventricular mass index (104 versus 105 g/m2), common carotid internal diameter (5.8 versus 5.9 mm), intima-media thickness (0.66 versus 0.64 mm) and carotid plaques prevalence (25 versus 29%). Furthermore, no differences were found in the correlation of daytime and night-time SBP and DBP with left ventricular mass and carotid wall thickness. When the 77 men and 34 women were analysed separately, similar results were obtained.

CONCLUSION

These results suggest that a blunted reduction in night-time blood pressure does not play a major role in the development of cardiovascular changes during the early phase of essential hypertension.