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

Effect of estrogen receptor modulator tamoxifen on blood pressure, plasma renin activity, and renal sodium excretion

BACKGROUND

Adjuvant treatment with the estrogen receptor modulator tamoxifen is a well established long-term therapy in breast cancer. This study investigated the effect of tamoxifen on blood pressure (BP) and on factors by which it might be influenced.

METHODS

Normotensive postmenopausal women on > 12 months adjuvant tamoxifen therapy were randomized to withdraw or continue tamoxifen for 6 weeks and then to crossover to the alternative regimen for a second 6-week period. Measurements of clinic and ambulatory BP, plasma renin activity (PRA), and fractional sodium excretion (FE(Na)) were performed at baseline and at the end of each study period.

RESULTS

Twenty-three women completed the study (mean age 60.6 +/- 8.3 years). There was no effect of tamoxifen on clinic BP (mean difference between withdrawal and continuation for systolic BP, 0.4 +/- 8.4 mm Hg, 95% confidence interval [CI] -4.0 to 3.2, and diastolic 0.6 +/- 4.7, 95%CI -1.4 to 2.7) or 24-hour ambulatory BP (systolic 0.7 +/- 7.4 mmHg, 95%CI -2.6 to 3.9; diastolic BP, 1.9 +/- 5.5, 95% CI -0.5 to 4.2). Furthermore, no effect of tamoxifen on PRA (mean difference between withdrawal and continuation 0.03 +/- 0.5 ng/mL/h, 95% CI -0.3 to 0.2) or FENa (0.05 +/- 0.5, 95% CI -0.2 to 0.2) was detected.

CONCLUSIONS

Tamoxifen seems to have no effect on BP, PRA, or FE(Na) in normotensive postmenopausal women.

Association between high-normal albuminuria and risk factors for cardiovascular and renal disease in essential hypertensive men

BACKGROUND

Microalbuminuria (overnight urinary albumin excretion [UAE] > 15 microg/min) is associated with cardiovascular risk factors and predicts morbid events in hypertensive subjects. However, albuminuria is not a dichotomous variable, and a relationship with cardiovascular risk factors may extend below that conventional threshold.

METHODS

We studied 186 never-treated, glucose-tolerant, normalbuminuric (overnight UAE < or = 15 microg/min), essential hypertensive men with normal renal function (serum creatinine < 1.4 mg/dL). Study variables were 24-hour ambulatory blood pressure (BP), cardiac structure and geometry (by echocardiography), body weight, fasting insulin levels, insulin sensitivity (the Homeostasis Model Assessment index), and creatinine clearance (from overnight collections or through the Cockcroft formula) analyzed as a function of ascending urine albumin quartiles (cutoff values, 4.3, 6.3, and 9.4 microg/min; n = 47, 45, 47, and 47, respectively).

RESULTS

As compared with the three bottom fourths, patients with high-normal albuminuria (albumin, 9.4 to 15 microg/min) had a greater 24-hour BP, greater relative wall thickness, more frequent concentric left ventricular hypertrophy, heavier body size, increased fasting insulin levels, reduced insulin sensitivity, and greater creatinine clearance.

CONCLUSIONS

High-normal albuminuria in uncomplicated essential hypertensive men is associated with an adverse cardiovascular and metabolic risk profile. Furthermore, hyperfiltration in the presence of minimally increased albuminuria may underlie an augmented glomerular blood flow and hydraulic pressure conducive to glomerular hypertension and, eventually, renal insufficiency. Overall, these data confirm the appropriateness to shift downward the limits for diagnosing microalbuminuria in essential hypertension, as indicated from previous prospective studies.

Prognostic significance of left ventricular diastolic dysfunction in essential hypertension

OBJECTIVES

We sought to assess the prognostic value of alterations in left ventricular (LV) diastolic function in patients with essential hypertension.

BACKGROUND

Alterations in LV diastolic function are frequent in patients with hypertension, even in the absence of LV hypertrophy, but their prognostic significance has never been investigated.

METHODS

In the setting of the Progetto Ipertensione Umbria Monitoraggio Ambulatoriale (PIUMA) study, we followed, for up to 11 years (mean: 4.4 years), 1,839 Caucasian hypertensive patients (50 +/- 12 years, 53% men, blood pressure (BP) 156/98 mm Hg) without previous cardiovascular events, who underwent Doppler echocardiography and 24-h BP monitoring before therapy. The early/atrial (E/A) mitral flow velocity ratio was calculated and corrected for age and heart rate (HR).

RESULTS

During follow-up, there were 164 major cardiovascular events (2.04 per 100 patient-years). The incidence of cardiovascular events was 2.47 and 1.65 per 100 patient-years in patients with an age- and HR-adjusted E/A ratio below (n = 919) and above (n = 920) the median value, respectively (p < 0.005 by the log-rank test). In Cox analysis, controlling for age, gender, diabetes, cholesterol, smoking, LV mass and 24-h systolic BP (all p < 0.05), a low age- and HR-adjusted E/A ratio conferred an increased risk of cardiovascular events (odds ratio 1.57, 95% confidence interval [CI] 1.11 to 2.18, p < 0.01). A 21% excess risk was found for each 0.3 decrease of the adjusted E/A ratio (95% CI from +2% to +43%; p = 0.03).

CONCLUSIONS

Impaired LV early diastolic relaxation, detected by pulsed Doppler echocardiography, identifies hypertensive patients at increased cardiovascular risk. Such association is independent of LV mass and ambulatory BP.

Ambulatory blood pressure monitoring

End-organ damage associated with hypertension is more closely related to ambulatory blood pressure (ABP) than clinic or casual blood pressure measurements. ABP measurements give better prediction of clinical outcome than clinic or casual blood pressure measurements. The technique of ABP monitoring (ABPM) is specialised; validated monitors and appropriate quality control measures should be used. Interpretation of ABP profile should include mean daytime, night-time (sleep) and 24-hour measurements, and consideration of diary information and time of drug treatment. Reports may also include ABP "loads" (percentage area under the blood pressure curve above set limits) for daytime and night-time periods. Normal blood pressure values for adults are < 135/85 mmHg for daytime, < 120/75 mmHg for night-time, and < 130/80 mmHg for 24 hours. ABPM is indicated to exclude "white coat" hypertension and has a role in assessing apparent drug-resistant hypertension, symptomatic hypotension or hypertension, in the elderly, in hypertension in pregnancy, and to assess adequacy of control in patients at high risk of cardiovascular disease. White coat hypertension requires continued surveillance; patients who display this phenomenon may, in time, develop established hypertension. Appropriate use of ABPM may result in cost savings. Randomised controlled trials comparing management based on clinic or casual versus ABP measurements are needed.

Beneficial effects on blood pressure and lipid profile of programmed exercise training in subjects with white coat hypertension

BACKGROUND

Patients with white coat hypertension comprise a substantial portion of the hypertensive population. Previous reports have shown that moderate-intensity regular exercise training in patients with mild hypertension usually reduces blood pressure (BP), but there is a lack of data regarding individuals with white coat hypertension. This study was performed to evaluate whether programmed exercise was effective in reducing BP in patients with white coat hypertension and whether it also had beneficial effects on other biochemical parameters.

METHODS

A total of 42 patients (23 men and 19 women) with white coat hypertension (mean 24-h ambulatory BP 119.2 +/- 6.6/78.3 +/- 5.8 mm Hg) were divided randomly into two groups: control (n = 20) (no exercise), and moderate-intensity exercise (n = 22). The training group exercised three times per week at the prescribed exercise intensity using a treadmill exercise program. Blood pressure, heart rate, and biochemical parameters were monitored every 4 weeks for 12 weeks.

RESULTS

Significant reductions in clinic and ambulatory BPs were seen in the exercise group after only 4 weeks regular exercise training and these persisted over the 12-week study. The mean maximal reductions in clinic BP were 11 mm Hg for systolic and 5 mm Hg for diastolic pressure. Significant reductions were found in plasma total cholesterol (-6.1%), low-density lipoprotein cholesterol (LDL-C) (-14.1%), and triglyceride (-11.4%). Elevation of high-density lipoprotein cholesterol (HDL-C) (+11.2%) was also noted.

CONCLUSIONS

These data, which are clinically significant, suggest that 12 weeks of exercise training can result in successful reduction of BP and favorable changes in the lipid profile that would be beneficial to patients with white coat hypertension.

Systemic hypertension and obstructive sleep apnoea

This article is a review of the current evidence that links systemic hypertension with obstructive sleep apnoea. Whilst a causal association has been suspected for some time, the day to day variability of both blood pressure and sleep apnoea severity, and clustering of confounding cardiovascular risk factors in sleep apnoea patients has made this association difficult to prove. There is unassailable evidence that obstructive apnoeas raise blood pressure acutely in both animal models and humans, through a combination of autonomic and state dependent arousal with some mechanical influences, and these rises can be controlled by nasal continuous positive airway pressure. Thus, although repetitive apnoeas alter the blood pressure variability and raise sleeping blood pressure in patients with OSA and sophisticated animal models have demonstrated increases in daytime blood pressure after the onset of OSA in the short term, such effects on diurnal BP have yet to be proven in humans. Recent rigorously designed large epidemiological studies have proven an independent association between OSA and systemic hypertension in both general and sleep clinic populations, with closely matched case control series also reporting raised blood pressure in OSA patients. A direct temporal causal association between the onset of obstructive sleep apnoea and raised blood pressure is expected to be confirmed by longitudinal data from the continuing epidemiological population studies. Finally, several studies on the beneficial effects of nasal continuous positive airway pressure in reducing blood pressure in OSA patients have preliminary results in abstract form, with one published in full.

Noninvasive 24-hour ambulatory blood pressure monitoring: overview of technology and clinical applications

During the last 25 years, 24-hour noninvasive ambulatory blood pressure monitoring (ABPM) has evolved from a research tool of limited clinical use into an important tool for stratifying cardiovascular risk and guiding therapeutic decisions. Until recently, clinical use of ABPM focused on identifying patients with white-coat hypertension, but accumulated evidence now points to greater prognostic significance of ABPM in determining risk for target-organ damage compared with that of office blood pressure measurements. Clinicians involved in the care of patients with hypertension should familiarize themselves with the role of this technology and how to use it in an appropriate and cost-effective manner.

[Blood pressure differences between consecutive days of ambulatory monitoring in hypertensive patients: the ABPM effect]

BACKGROUND

Ambulatory blood pressure monitoring is a method of blood pressure assessment that compensates for some of the limitations of office values. While a white-coat pressor effect on conventional determination has been defined and frequently used for the improved evaluation of hypertensive patients, there is no evidence that the ambulatory technique could also influence blood pressure.

PATIENTS AND METHOD

Aimed at testing and quantifying the extent and duration over time of a possible pressor effect due to ambulatory monitoring, we studied 387 mild-to-moderate hypertensive patients (160 men), aged 54.2 (14.3) (mean [SD]). Blood pressure and heart rate were measured at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours, and physical activity was simultaneously evaluated at 1-min intervals by means of a wrist actigraph. One third of patients were evaluated twice or more times.

RESULTS

In hypertensive patients who were evaluated for the first time, results indicate a highly significant (p < 0.001) reduction, in the second day of monitoring as compared to the first, in the diurnal mean of systolic and diastolic blood pressure, but not in heart rate or physical activity. This pressor effect remains significant for at least the first 5 hours of monitoring. The nocturnal mean of blood pressure was, however, similar in the two days of sampling. This ambulatory monitoring effect could not be observed when patients were evaluated following the same sampling scheme at the second or further times.

CONCLUSIONS

Ambulatory monitoring for 48 consecutive hours reveals a statistically significant pressor response that could reflect a novelty effect in the use of the monitoring device for the first time. This effect has notable implications in both research and clinical daily practice, both for proper diagnosis of hypertension and evaluation of treatment efficacy.

Risk of cardiovascular disease in relation to achieved office and ambulatory blood pressure control in treated hypertensive subjects

OBJECTIVE

We investigated the prognostic impact of 24-h blood pressure control in treated hypertensive subjects.

BACKGROUND

There is growing evidence that ambulatory blood pressure improves risk stratification in untreated subjects with essential hypertension. Surprisingly, little is known on the prognostic value of this procedure in treated subjects.

METHODS

Diagnostic procedures including 24-h noninvasive ambulatory blood pressure monitoring were undertaken in 790 subjects with essential hypertension (mean age 48 years) before therapy and after an average follow-up of 3.7 years (2,891 patient-years).

RESULTS

At the follow-up visit, 26.6% of subjects achieved adequate office blood pressure control (<140/90 mm Hg), and 37.3% of subjects achieved adequate ambulatory blood pressure control (daytime blood pressure <135/85 mm Hg). Months or years after the follow-up visit, 58 patients suffered a first cardiovascular event. Event rate was lower (0.71 events/100 person-years) among the subjects with adequate ambulatory blood pressure control than among those with higher blood pressure levels (1.87 events/100 person-years) (p = 0.0026). Ambulatory blood pressure control predicted a lesser risk for subsequent cardiovascular disease independently of other individual risk factors (RR 0.36; 95% confidence intervals: 0.18 to 0.70; p = 0.003), including age, diabetes and left ventricular hypertrophy. Office blood pressure control was associated with a nonsignificant lesser risk of subsequent events (RR 0.63; 95% confidence intervals: 0.31 to 1.31; p = NS). In-treatment ambulatory blood pressure was more potent than pre-treatment blood pressure for prediction of subsequent cardiovascular disease.

CONCLUSIONS

Ambulatory blood pressure control is superior to office blood pressure control for prediction of individual cardiovascular risk in treated hypertensive subjects.

Hormone replacement therapy and hypertension

Hypertension, particularly systolic hypertension, affects postmenopausal women and is an important risk factor for cardiovascular disease in this group. In the last year, several papers have better defined the mechanisms by which hormone replacement therapy influences blood pressure in postmenopausal women, including effects on nitric oxide, angiotensin II and vascular stiffness (compliance). Currently, data concerning the influence of hormone replacement therapy on blood pressure in postmenopausal women are inconclusive because of the limitations of published studies. It is clear, however, that hypertension is not a contraindication to starting hormone replacement therapy.

Microalbuminuria, an integrated marker of cardiovascular risk in essential hypertension

This paper reviews the existing epidemiological and clinical evidence about the relationships of non-diabetic microalbuminuria with cardiovascular risk factors such as elevated blood pressure (BP), systolic particularly, cardiac hypertrophy, adverse metabolic status, smoking habits, elevated angiotensin II levels, endothelial dysfunction, acute and perhaps subclinical inflammation. Because of that unique property of reflecting the influence of so many clinically relevant parameters, microalbuminuria may legitimately be defined as an integrated marker of cardiovascular risk, an unique profile among the several prognostic predictors available to stratify risk in hypertensive patients. Recent cohort studies also showed associations with cardiovascular morbidity and mortality independently from conventional atherogenic factors. This behaviour, whose understanding still needs further elucidation, suggests to measure albuminuria and to screen patients at a higher absolute risk in whom preventive treatment is expected to be more beneficial than in those with a lower absolute risk.

Effects of the long-acting calcium channel blocker barnidipine hydrochloride on 24-h ambulatory blood pressure

The effect of the long acting calcium channel blocker, barnidipine hydrochloride (barnidipine) on 24-h ambulatory blood pressure (ABP) was evaluated in J-MUBA (Japanese Multicentre Study on Barnidipine with Ambulatory Blood Pressure Monitoring). Following an observation period of two weeks, antihypertensive treatment with barnidipine was continued for at least six months. At the end of each period, ABP were measured. The patients were divided into high- and low-range groups based on ABP measurement. Throughout the 24 h, barnidipine exerted an excellent antihypertensive effect in the high-range group, but not in the low-range group. Barnidipine had comparable effects in the daytime and nighttime in inverted dippers and non-dippers, but it was more effective on daytime ABP than on nighttime ABP in dippers and in extreme dippers. Morning blood pressure before and after waking was evaluated before and after barnidipine administration in 233 patients. Barnidipine inhibited increases in blood pressure before and after waking, especially in surge-type patients whose blood pressure increased rapidly after waking. A positive correlation among 24-h ABP, daytime and night time ABP, morning blood pressure, and clinic blood pressure during the observation period and the antihypertensive effect of barnidipine was observed, with barnidipine exhibiting stronger antihypertensive effects in patients with persistently high blood pressure. It was concluded that the antihypertensive effects of barnidipine are maintained for 24 h but it has no excessive hypotensive effects on lower blood pressure and is thus a safe antihypertensive agent.

Blood pressure measurement in research

OBJECTIVE

The aim of this paper is to summarize the issues raised during a consensus conference on the role of different blood pressure (BP) monitoring techniques in research, including pathophysiological studies, clinical outcome trials and clinical pharmacology trials.

METHODS

This review includes the contribution of the participants in a task force at the Eighth Consensus Conference on Ambulatory BP Monitoring (October 28-31, 2001, Sendai, Japan) and the results of a discussion open to all conference participants. Individual contributions have been summarized together with the points raised during the subsequent discussion, and the main statements are also presented in a table format.

POINTS OF CONSENSUS

(1) BP monitoring in pathophysiological studies. The essential role played by continuous BP monitoring in this field had been acknowledged, and further development of non-invasive beat-by-beat monitoring techniques has been advocated. (2) BP monitoring in clinical trials. In clinical trials automated ambulatory BP monitoring (ABPM) and self BP measurements (SBPM) at home share similar advantages, with specific features that make these approaches not alternative solutions but rather approaches able to complement each other. A few examples of application of ABPM and SBPM in clinical trials include the Treatment of Hypertension according to Home or Office Blood Pressure (THOP) trial and the Trial of Preventing Hypertension (TROPHY). (3) Use of ABPM in clinical pharmacology studies. Use of ABPM is now an established routine, aimed at describing the 24-h effect of new antihypertensive drugs. An example of these applications that was discussed in the conference is the use of ABPM in the evaluation of a new long-acting calcium channel blocker (Barnidipine) (J-MUBA study). (4) Specific models for the analysis of BP fluctuations. The features characterizing the chronobiological approach to description of 24-h BP profiles and its limitations (mainly consisting of the high risk of data over-modelling) are discussed. Also the possible occurrence of a circaseptan (approximately with a 7-day period) rhythm in BP has been addressed, although repeated performance of 24-h ABPM over a week obviously faces a number of practical problems. (5) Progress in technology: BP monitoring and telemedicine. The possibility to implement an interactive telemonitoring system of home SBPM values and the perspectives for a clinical application of this technology in the Hypertension Objective treatment based on Measurement by Electrical Devices of Blood Pressure (HOMED-BP) trial is discussed.

Ambulatory blood pressure after therapeutic and subtherapeutic nasal continuous positive airway pressure for obstructive sleep apnoea: a randomised parallel trial

BACKGROUND

Obstructive sleep apnoea is associated with raised blood pressure. If blood pressure can be reduced by nasal continuous positive airway pressure (nCPAP), such treatment could reduce risk of cardiovascular disease in patients with obstructive sleep apnoea. Our aim was to see whether nCPAP for sleep apnoea reduces blood pressure compared with the most robust control intervention subtherapeutic nCPAP.

METHODS

We did a randomised parallel trial to compare change in blood pressure in 118 men with obstructive sleep apnoea (Epworth score > 9, and a > 4% oxygen desaturation index of > 10 per h) who were assigned to either therapeutic (n=59) or subtherapeutic (59) nCPAP (about 1 cm H(2)O pressure) for 1 month. The primary outcome was the change in 24-h mean blood pressure. Secondary outcomes were changes in systolic, diastolic, sleep, and wake blood pressure, and relations between blood pressure changes, baseline blood pressure, and severity of sleep apnoea.

FINDINGS

Therapeutic nCPAP reduced mean arterial ambulatory blood pressure by 2.5 mm Hg (SE 0.8), whereas subtherapeutic nCPAP increased blood pressure by 0.8 mm Hg (0.7) (difference -3.3 [95% CI -5.3 to -1.3]; p=0.0013, unpaired t test). This benefit was seen in both systolic and diastolic blood pressure, and during both sleep and wake. The benefit was larger in patients with more severe sleep apnoea than those who had less severe apnoea, but was independent of the baseline blood pressure. The benefit was especially large in patients taking drug treatment for blood pressure.

INTERPRETATION

In patients with most severe sleep apnoea, nCPAP reduces blood pressure, providing significant vascular risk benefits, and substantially improving excessive daytime sleepiness and quality of life.

Blood pressure reduction in the morning yields beneficial effects on progression of chronic renal insufficiency with regression of left ventricular hypertrophy

Self-monitoring values of blood pressure may better reflect the average long-term blood pressure value than sporadic measurements in the physician's office and be more useful for blood pressure control. In the present study, we compared the results of self-monitoring of blood pressure values, especially in the morning, with office blood pressure, and related these to progression of chronic renal insufficiency and left ventricular hypertrophy (LVH). Thirty-four patients were selected from 316 subjects with chronic renal insufficiency (average serum creatinine 1.72 +/- 0.15 mg/dl, mean age 52.6 +/- 3.5 yrs) in accordance with the following criteria (1) office blood pressure was less than 140/90 mmHg, (2) blood pressure was controlled with amlodipine (5-20 mg/day) combined with benazepril (2.5 mg/day), (3) morning blood pressure was greater than 150/90 mmHg at 6-9 AM and (4) LVH had been determined by echocardiography (posterior wall thickness; PWT > or = 12 mm). The patients were assigned to 2 groups at random and were given: (1) guanabenz (GB; 2-8 mg at I I PM, n = 17) or (2) placebo (n = 17). Two years later, the average blood pressure of both groups as measured in the office was not significantly different: however, BP in the morning was significantly reduced from 158 +/- 6 to 134 +/- 4 mmHg in GB treated group (P< 0.001). In 14 of 17 patients in GB treated group, LVH resolved and there was only mild progression of nephropathy (serum creatinine: 1.69 +/- 0.18 to 1.81 +/- 0.19 mg/dl). In 12 of 14 patients in placebo group, whose morning blood pressure remained at greater than 150/90 mmHg, LVH was retained and there was moderate progression of nephropathy (serum creatinine: 1.73 +/- 0.14 to 2.62 +/- 0.50mg/dl). From these results, it is suggested that antihypertensive treatment with combination therapy based on self-monitoring BP is cardio-renoprotective in patients with chronic renal insufficiency and LVH.

Reference values for ambulatory blood pressure and self-measured blood pressure based on prospective outcome data

Although self-measured blood pressure and ambulatory blood pressure are widely used for research and clinical purposes, reference values are still scarcely supported by prospective outcome data. For self-measured blood pressure, values of 135 mmHg systolic and 85 mmHg diastolic (an average of two measurements in the morning and an additional two in the evening for at least 3 working days) have been suggested as the upper-normal reference limits. Unfortunately, these values have received limited support because only one study, the Ohasama study, examined the prognostic value of self-measured home blood pressure. For non-invasive 24 h ambulatory blood pressure, there are at least 11 reports of prospective outcome studies from independent centres that have examined the prognostic values of ambulatory blood pressure, but not all have attempted to define reference values. Currently, an average daytime blood pressure of less that 135 mmHg systolic and less than 85 mmHg diastolic is generally considered to be normal, and a level below 130/80 mmHg may be considered optimal. A reduction in blood pressure of less than 10% from day to night identifies subjects with an increased cardiovascular risk. There is some evidence that cardiovascular risk is further increased when night-time blood pressure is higher than daytime blood pressure. An average 24 h pulse pressure of over 53 mmHg identifies subjects with a raised cardiovascular risk.

Task Force II: blood pressure measurement and cardiovascular outcome

OBJECTIVE

To reach a consensus on the prognostic significance of new techniques of automated blood pressure measurement.

METHODS

A Task Force on the prognostic significance of ambulatory blood pressure monitoring wrote this review in preparation for the Eighth International Consensus Conference (28-31 October 2001, Sendai, Japan). This synopsis was amended to account for opinions aired at the conference and to reflect the common ground reached in the discussions.

POINTS OF CONSENSUS

(1) Prospective studies in treated and untreated hypertensive patients and in the general population have demonstrated that, even after adjusting for established risk factors, the incidence of cardiovascular events is correlated with blood pressure on conventional as well as ambulatory measurement. Ambulatory monitoring, however, significantly refines the prediction already provided by conventional blood pressure measurement. (2) White-coat hypertension is usually defined as an elevated clinic blood pressure in the presence of a normal daytime ambulatory blood pressure. Event-based studies in hypertensive patients have convincingly demonstrated that the risk of cardiovascular disease is less in patients with white-coat hypertension than in those with higher ambulatory blood pressure levels even after controlling for concomitant risk factors. Based on prognostic evidence, white-coat hypertension can now be defined as a conventional blood pressure that is persistently equal to or greater than 140/90 mmHg with an average daytime ambulatory blood pressure of below 135/85 mmHg. The issue of whether or not white-coat hypertension predisposes to sustained hypertension needs further research. (3) There is a growing body of evidence showing that a decreased nocturnal fall in blood pressure (<10% of the daytime level) is associated with a worse prognosis, irrespective of whether night-time dipping is studied as a continuous or a class variable. (4) Intermittent techniques of ambulatory blood pressure monitoring are limited in terms of quantifying short-term blood pressure variability. Proven cardiovascular risk factors such as old age, a higher than usual blood pressure and diabetes mellitus are often associated with greater short-term blood pressure variability. After adjusting for these risk factors, some - but not all - studies have nevertheless reported an independent and positive relationship between cardiovascular outcome and measures of variability of daytime and night-time blood pressure, for example standard deviation. (5) Reference values for ambulatory blood pressure measurement in children are currently based on statistical parameters of blood pressure distribution. In children and adolescents, functional rather than distribution-based definitions of ambulatory hypertension have yet to be developed. (6) Several studies of gestational hypertension have shown that, compared with office measurement, ambulatory blood pressure monitoring is a better predictor of maternal and fetal complications. Pregnancy is a special indication for ambulatory monitoring so that the white-coat effect can be measured and pregnant women are not given antihypertensive drugs unnecessarily. (7) Ambulatory pulse pressure and the QKD interval are measurements obtained by ambulatory monitoring that to some extent reflect the functional characteristics of the large arteries. The QKD interval is correlated with left ventricular mass, and ambulatory pulse pressure is a strong predictor of cardiovascular outcome. (8) Under standardized conditions, the self-measurement of blood pressure is equally as effective as ambulatory blood pressure monitoring in identifying the white-coat effect, but further studies are required to elucidate fully the prognostic accuracy of self-measured blood pressure in comparison with conventional and ambulatory blood pressure measurement.

CONCLUSIONS

Ambulatory blood pressure measurement refines the prognostic information provided by conventional blood pressure readings obtained in the clinic or the doctor's office. Longitudinal studies of patients with white-coat hypertension should clarify the transient, persistent or progressive nature of this condition, particularly in paediatric patients, in whom white-coat hypertension may be a harbinger of sustained hypertension and target-organ damage in adulthood. Finally, the applicability, cost-effectiveness and long-term prognostic accuracy of the self-measurement of blood pressure should be evaluated in relation to conventional blood pressure measurement and ambulatory monitoring.

Ambulatory blood pressure monitoring: technique and application in the study of cardiac dysfunction and congestive heart failure

Ambulatory blood pressure monitoring has become a widely used method of blood pressure and heart rate evaluation in the free-living subject. Recently, ambulatory monitoring has become covered by Medicare for the evaluation of "white-coat" hypertension. Although the technique provides only intermittent readings throughout the 24-hour period, average blood pressures obtained in this way correlate well with a variety of hypertensive disease processes and are also a better prognostic marker for future cardiovascular events than office blood pressure. Ambulatory blood pressure averages also correlate well with indices of diastolic dysfunction. In patients with congestive cardiac failure and systolic dysfunction, ambulatory monitoring suggests an impaired circadian blood pressure profile with high nocturnal blood pressure. Further research is needed on the relationship between ambulatory blood pressure and cardiac dysfunction, as well as the impact of observed circadian blood pressure changes on outcome. (c)2001 CHF, Inc.

The aftereffects of dynamic exercise on ambulatory blood pressure

PURPOSE

Despite the widespread belief that endurance exercise lowers blood pressure (BP), reports of the lack of such an effect are common when using ambulatory blood pressure (ABP) monitoring. This review examined the influence of dynamic exercise on ABP to elucidate possible reasons for conflicting reports.

METHODS

Criteria for inclusion were dynamic exercise studies that involved ABP determinations after exercise. A total of 23 studies containing 34 groups of which 12 were normotensive and 22 hypertensive met these criteria. The groups primarily consisted of unmedicated, sedentary, overweight, non-Hispanic white men and women with a mean +/- SEM age of 43.9 +/- 1.5 yr.

RESULTS

Baseline mean day systolic BP (SBP) was 137.3 +/- 2.1 mm Hg (95% confidence limits) (133.0, 141.5) and diastolic BP (DBP) was 86.7 +/- 1.5 mm Hg (83.7, 89.7). After exercise, day SBP (N = 34) was reduced an average of 3.2 +/- 1.0 (-5.2, -1.2) (P = 0.003) and DBP by 1.6 +/- 0.6 mm Hg (-2.9, -0.4) (P = 0.013); night SBP (N = 20) by 3.4 +/- 1.0 (-5.6, -1.2) (P = 0.005) and DBP by 3.0 +/- 1.4 mm Hg (-5.6, -0.4) (P = 0.025); and 24-h SBP (N = 17) by 3.2 +/- 0.8 (-4.9, -1.6) (P = 0.001) and DBP by 1.8 +/- 0.5 mm Hg (-2.9, -0.7) (P = 0.003). After detection of outlying cases using regression diagnostics, initial SBP accounted for 30% (P = 0.001) and 26% (P = 0.018) of the variance in the change in day and night SBP after exercise, respectively. Similarly, initial DBP explained 37% (P = 0.000) and 33% (P = 0.005) of the difference in day and night DBP after exercise.

CONCLUSION

The ABP difference after exercise is a function of initial values such that groups with the highest baseline BP experience the greatest postexercise ABP reductions. The ABP dynamic exercise studies raise important methodological considerations that should be attended to in future work.

Episodes of ST-segment depression is related to changes in ambulatory blood pressure and heart rate in intermittent claudication

OBJECTIVE

To study the prevalence and circadian distribution of ischaemic ST-segment depression detected with ambulatory electrocardiographic monitoring (AECG) in patients with intermittent claudication (IC) as well as to study ambulatory blood pressure (ABP) and the relation of ischaemic episodes to variations in ABP and heart rate.

DESIGN

A total of 40 patients with a history of IC and an ankle/brachial-index (ABI) <0.9 performed: (i) 24-h AECG recordings, (ii) simultaneous 24 h recordings of ABP every 15 min (Spacelabs 90207), (iii) an exercise treadmill test (ETT). An ischaemic episode was defined as a transient ischaemic ST-segment deviation > or =1 mm lasting >1 min. Eleven patients were excluded from ECG analysis because of uninterpretable ECG caused by treatment with digoxin or technical problems.

RESULTS

Out of 29 patients, eight experienced a total of 15 episodes of ST-depression on AECG. The mean duration was 21+/-31 min. The majority of episodes (11 of 15) occurred between 6 and 12 a.m. In eight patients with ST-segment depression three had a history of ischaemic heart disease (IHD), four were hypertensives and four had signs of myocardial ischaemia on ETT. There were no significant differences between patients with and without ST-segment depression in ABP, walking performance or ABI. During ST-depression episodes systolic and diastolic blood pressure and heart rate were higher than day mean values; 178+/-41 vs. 166+/-30 mmHg (P= 0.09); 96+/-9 vs. 90+/-4 mmHg (P = 0.01) and 103+/-9 vs. 87+/-5 beats min(-1) (P < 0.01).

CONCLUSION

Silent myocardial ischemia occurred in about a third of patients with IC. Episodes of ischaemia were associated with an increased ABP and heart rate. Whether treatment of high blood pressure may reduce silent ischaemia and if this favourably influences outcome is a matter of further research.

Using out of office blood pressure monitoring in the management of hypertension

Self-measurement of blood pressure (BP) and 24-hour ambulatory BP monitoring (ABPM) are increasingly used in order to improve cardiovascular risk stratification over and beyond traditional methods, including sphygmomanometric BP measurement. Self-measured BP has the advantage of being cheap, quite representative of the usual BP over long periods of time, and devoid of the "white coat" effect. Only a few data exist on the prognostic value of self-measured BP. Most of the outcome studies with 24-hour ABPM have been conducted in patients with essential hypertension who were untreated at the time of execution of ABPM. Cardiovascular risk showed a direct association with ambulatory BP and an inverse association with the degree of BP reduction from day to night. White coat hypertension versus ambulatory hypertension and dippers versus nondippers are two classifications based on arbitrary operational risk categories. ABPM may be valuable for refining cardiovascular risk stratification in untreated subjects with office hypertension, as well as those with resistant hypertension.

Blood pressure determinants of left ventricular wall thickness and mass index in hypertension: comparing office, ambulatory and exercise blood pressures

Left ventricular (LV) mass relates positively and continuously to cardiac mortality and thus its regression is a rational therapeutic aim. Whilst the office blood pressure (BP) relates poorly to LV mass, it was unclear whether the 24-h ambulatory BP or the exercise systolic BP (ExSBP) was the stronger correlate of LV structural indices. We studied 49 hypertensive patients with a mean age of 45 (s.d. 12) years with a mean body mass index of 27.1(3.9) kg/m(2). The mean (s.d.) of office BP, ambulatory BP and ExSBP measured at the end of the first three stages of Bruce protocol treadmill exercise I, II and III were 161(20)/99(10), 140(13)/89(10), 190(30), 198(30) and 201(33) mm Hg respectively. The LV indices measured echocardiographically were LV septal thickness (IVSd) (1.1(0.2) cm), LV posterior wall thickness (LVPWd) (1.0(0.1) cm) and LV mass indexed to body surface area (LVMI) (123(30) g/m(2)). Age and gender (male) had the highest correlations with the LV indices. Of the BP measures, the stage II ExSBP's correlation with the LV indices was consistently higher than all other ExSBP, office systolic BP and 24-h systolic ambulatory BP. In a stepwise multiple regression analysis on IVSd, after adjusting for age and gender, the stage II ExSBP was independently associated with IVSd (beta= 0.018 (s.e. 0.008), P = 0.024). When only BP measures were considered as explanatory variables only stage II ExSBP was a significant predictor (P = 0.0001) of IVSd as was the case with LVPWd (P = 0.006) and LVMI (P = 0.0008). Submaximal exercise BP measured at a workload comparable to physical activity encountered in daily life correlated more closely with the left ventricular wall thickness and mass. The exercise BP should perhaps be normalised in hypertension management to optimise regression of LV hypertrophy.

Relationships between 24 h blood pressure load and target organ damage in patients with mild-to-moderate essential hypertension

OBJECTIVE

To analyse the relationships between 24 h blood pressure load (the percentage of systolic/diastolic blood pressures exceeding 140/90 mmHg while awake and 120/80 mmHg during sleep) and some indices of hypertensive target organ involvement, independently of the mean level of 24 h blood pressure.

METHODS

One hundred and thirty patients with mild-to-moderate hypertension underwent 24 h ambulatory blood pressure monitoring, ocular fundus examination, microalbuminuria assay and two-dimensional guided M-mode echocardiography. The study population was divided into subsets according to the systolic and diastolic 24 h blood pressure load values predicted from the regression equation relating 24 h blood pressure load to 24 h mean blood pressure. The subjects with an observed load above this predicted value were included in the higher blood pressure load groups, the remaining ones being included in the lower groups.

RESULTS

Relative myocardial wall thickness and total peripheral resistance were greater, and mid-wall fractional shortening, end-systolic stress-corrected mid-wall fractional shortening and cardiac index lower, in the subjects with a higher systolic blood pressure load. Moreover, the stroke index:pulse pressure ratio was reduced, and a greater prevalence of hypertensive retinopathy was observed in the higher systolic load group. On the contrary, no statistically significant difference was found for any of the cardiac, renal and funduscopic parameters examined when the two groups with a higher and lower 24 h diastolic blood pressure load were compared.

CONCLUSIONS

Our results seem to suggest that, in mild-to-moderate arterial hypertension, a high 24 h systolic blood pressure load may be associated, independently of the average level of 24 h systolic ambulatory blood pressure, with an adverse cardiovascular risk profile.

Control of blood pressure in the ambulatory setting

Control of blood pressure still relies on conventional office or clinical blood pressure measurement using mercury sphygmomanometry. However, it has long been known that office measurement, even when repeated, does not fully reflect usual blood pressure. The additional use of ambulatory devices for prolonged periods of blood pressure measurement is now clinically feasible. Previous research has indicated that ambulatory blood pressure measurement is better than office measurement at predicting individual cardiovascular risk. Guidelines for clinical use of ambulatory blood pressure measurement and for quality control of devices are available. Ambulatory measurement has revealed characteristics of circadian rhythm and variability that are promising with regard both to improving our understanding of the aetiology of high blood pressure and to individual risk assessment. Some of the latest developments in research on ambulatory blood pressure measurement are discussed.

Increased QTc dispersion is related to blunted circadian blood pressure variation in normoalbuminuric type 1 diabetic patients

A reduced nocturnal fall in blood pressure (BP) and increased QT dispersion both predict an increased risk of cardiovascular events in diabetic as well as nondiabetic subjects. The relationship between these two parameters remains unclear. The role of diabetic autonomic neuropathy in both QT dispersion and circadian BP variation has been proposed, but data have been conflicting. The aim of the present study was to describe associations between QT dispersion and circadian BP variation as well as autonomic function in type 1 diabetic patients. In 106 normoalbuminuric (urinary albumin excretion <20 microg/min) normotensive patients, we performed 24-h ambulatory BP (Spacelabs 90207) and short-term (three times in 5 min) power spectral analysis of RR interval oscillations, as well as cardiovascular reflex tests (deep breathing test, postural heart rate, and BP response). No patient had received (or had earlier received) antihypertensive or other medical treatment apart from insulin. In a resting 12-lead electrocardiogram, the QT interval was measured by the tangent method in all leads with well-defined T-waves. The measurement was made by one observer blinded to other data. The QT interval was corrected for heart rate using Bazett's formula. The QTc dispersion was defined as the difference between the maximum and the minimum QTc interval in any of the 12 leads. When comparing patients with QTc dispersion below and above the median (43 ms), the latter had significantly higher night BP (114/67 vs. 109/62 mmHg, P < 0.003/P < 0.001), whereas day BP was comparable (129/81 vs. 127/79 mmHg). Diurnal BP variation was blunted in the group with QTc dispersion >43 ms with significantly higher night/day ratio, both for systolic (88.8 vs. 86.2%, P < 0.01) and diastolic (83.1 vs. 79.5%, P < 0.01) BP. The association between QTc dispersion and diastolic night BP persisted after controlling for potential confounders such as sex, age, duration of diabetes, urinary albumin excretion, and HbA1c. Power spectral analysis suggested an altered sympathovagal balance in patients with QTc dispersion above the median (ratio of low-frequency/high-frequency power: 1.0 vs. 0.85, P < 0.01). In normoalbuminuric type 1 diabetic patients, increased QTc dispersion is associated with reduced nocturnal fall in BP and an altered sympathovagal balance. This coexistence may be operative in the ability of these parameters to predict cardiovascular events.

Prognostic value of midwall shortening fraction and its relation with left ventricular mass in systemic hypertension

We followed 1,778 subjects (up to 12 years) with essential hypertension who underwent echocardiography at the time of their initial diagnostic workup. There were 166 major cardiovascular events during follow-up and the prognostic value of the midwall shortening fraction did not remain significant after controlling for left ventricular mass.

Comparison of the actigraph versus patients' diary information in defining circadian time periods for analyzing ambulatory blood pressure monitoring data

BACKGROUND

Assessment of 24-h changes in blood pressure is one of the unique features that ambulatory blood pressure monitoring (ABPM) can provide. Most studies agree that sleep/wake periods should be based on patients' actual sleep and wake times. Actual wake and sleep time determinations are often based on patients' diary information. Several publications indicate that actigraphy is, at least, as accurate as activity diary in determining sleep/wake periods.

OBJECTIVES

To compare subjects' compliance with actigraphy and diary keeping and to compare actigraphy and diary data in determination of sleep and wake times, mean blood pressures, classification of hypertension, and assessment of nocturnal dipping status.

METHODS

We evaluated ABPM studies of 62 subjects. Blood pressure data were obtained using Spacelabs monitors for 24h. Sleep and wake times were determined by both the actigraph and patients' activity diary.

RESULTS

In the 62 studies, 56 subjects had successful actigraphy (90%), 44 had activity diary completion (71%), and 38 subjects had both (61%). There was no statistically significant difference between the mean wake and sleep onset using the two methods, but up to 3 hours' difference in wake or sleep onset was noted in some studies. Although the two methods did not significantly affect the calculated systolic blood pressure (SBP) or diastolic blood pressure (DBP) loads in either awake or sleep periods, approximately 55% of the subjects' dipping status was changed when diary information on sleep time was used compared to actigraph.

CONCLUSIONS

Our data indicate that in children and young adults, compliance with the actigraph was superior to diary completion and use of the actigraphy method rather than diary information changed the interpretation of some ABPM data. Our study suggested that actigraphy is superior to diary keeping in providing the information needed for appropriate interpretation of some ABPM data.