Use and interpretation of ambulatory blood pressure monitoring: recommendations of the British hypertension society

Comparison of ambulatory blood pressure values in patients with glaucoma and ocular hypertension

PURPOSE

To compare systemic arterial blood pressure (BP) and nocturnal hypotension in patients with normal-tension glaucoma (NTG), high-tension glaucoma (HTG), and ocular hypertension.

METHODS

Systemic BP was recorded by a portable automated BP monitoring device every 20 min during the day and every 30 min at night in patients with NTG (n=18), HTG (n=22), and ocular hypertension (n=19). Mean systolic, diastolic, and mean arterial BPs were calculated for 24 h, during the day and at night. The mean and maximum nocturnal dip rates were determined for each patient. The number of readings that declined below 90 mmHg for systolic BP and below 60 and 50 mm Hg for diastolic BP was recorded for each group. Statistical significance was set at P<0.05.

RESULTS

Minimum, maximum, and mean values of the systolic, diastolic, and mean arterial BPs were not significantly different among groups. There was no difference among groups in the nocturnal dip percentages of systolic and diastolic BPs. The number of systolic BP readings below 90 mmHg was significantly higher in the NTG group compared with the other groups (P<0.001, chi(2) test).

CONCLUSION

There may not be any difference among NTG, HTG, and ocular hypertension patients in terms of mean ambulatory BP values. On the other hand, when each individual's ambulatory reading is reviewed, readings may reveal that excessive and repetitive nocturnal drops occur more frequently in some patients with NTG. These hypotensive episodes may be related to the development of glaucomatous damage.

Premier: a clinical trial of comprehensive lifestyle modification for blood pressure control: rationale, design and baseline characteristics

PURPOSE

To describe PREMIER, a randomized trial to determine the effects of multi-component lifestyle interventions on blood pressure (BP).

METHODS

Participants with above optimal BP through stage 1 hypertension were randomized to: 1) a behavioral lifestyle (BLS) intervention that implements established recommendations, 2) a BLS intervention that implements established recommendations plus the DASH diet, or 3) an advice only standard of care group. The two BLS interventions consist of group and individual counseling sessions for 18 months. The primary outcome is systolic BP at 6 months. Additional outcomes include diastolic BP and homocysteine at 6 months; systolic and diastolic BP at 18 months; fasting lipids, glucose and insulin at 6 and 18 months; and effects in subgroup.

CONCLUSION

Results from the PREMIER trial will provide scientific rationale for implementing multi-component behavioral lifestyle intervention programs to control BP and prevent CVD.

Increased nocturnal blood pressure in healthy prepubertal twins

AIM

To compare ambulatory blood pressure monitoring (ABPM) in twin children to a published singleton population, and to examine the influence of birthweight and fasting plasma cortisol on blood pressure.

DESIGN

A cross-sectional study of monozygotic and dizygotic twins compared with a similar previously published normative control population.

METHODS

Forty-four healthy prepubertal twin children aged 4-11 years (20 monozygotic, 22 male) were studied. All subjects had 24-h ABPM and a fasting early morning plasma cortisol.

RESULTS

Twins had higher 24-h systolic blood pressure (BP) compared with controls with similar daytime and elevated night-time systolic BP (P > 0.3 and P < 0.01, respectively). Twins had reduced systolic and diastolic nocturnal BP dipping compared with controls (P < 0.0001 for both), and 61% of twins exhibited a < 10% fall in nocturnal BP. In the twin cohort there was no association between birth weight and daytime systolic BP (P = 0.6), nor any other ABPM parameter. There was no difference in BP parameters between dizygotic and monozygotic twins, and no difference between the lighter and heavier birthweight twins for any ABPM parameter. Fasting plasma cortisol was not associated with either birthweight (P = 0.2) or daytime systolic BP (P = 0.4).

CONCLUSIONS

Healthy prepubertal twins have increased nocturnal BP and reduced nocturnal BP dipping independent of zygosity or birthweight. These abnormalities may be a risk factor for the later development of hypertension in twins. As these BP abnormalities are not associated with twin birth weight, the twin model may not be appropriate in investigating the fetal origins of disease in later adult life.

Ambulatory blood pressure monitoring

Noninvasive, 24-hour ambulatory blood pressure monitoring (ABPM) has evolved over the past 25 years from a novel research tool of limited clinical use into an important and useful modality for stratifying cardiovascular risk and guiding therapeutic decisions. Early clinical uses of ABPM were mostly focused on identifying patients with white-coat hypertension; however, accumulated evidence now points to greater prognostic significance in determining risk for hypertensive end-organ damage compared with office blood pressure measurements. Ambulatory measurement of blood pressure using automated devices has also demonstrated benefit in other indications, such as treatment resistance and borderline hypertension, and is recommended by the Joint National Committee for the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure in a number of clinical scenarios. Medicare recently announced plans to begin reimbursement for ABPM, which will likely increase demand for ABPM services. Clinicians should become familiar with the role of this technology in the care of the hypertensive patient.

Ambulatory blood pressure measurement is indispensable to good clinical practice

The traditional technique of blood pressure measurement is being phased out in most countries and is being replaced by automated measurement. The era of automated blood pressure measurement brings its own problems, not least being the need to evaluate blood pressure measuring devices independently for accuracy. Towards this end, the Working Group on Blood Pressure Monitoring of the European Society of Hypertension has published an international protocol with the aim of having all devices assessed for basic accuracy before being put on the market. The main thrust of this review is that if ambulatory blood pressure measurement has become indispensable to the management of patients with hypertension, it then becomes imperative to encourage the use of ambulatory blood pressure measurement (ABPM) in general practice rather than restricting its availability to specialist hospital centres. However, if ABPM is to be widely used in general practice, there is a need to establish appropriate educational processes and to improve the methods of presenting and analysing ABPM data.

[Behavior of the night decrease of arterial pressure after suppression controlled of the antihypertensive medication]

OBJECTIVE

The patients with hypertension who do not present a night decrease of the arterial pressure are a bigger degree of target organ damage due to the supported hypertension. In our work we analyzed after ambulatory blood pressure monitoring (ABPM) the prevalence of the condition dipper of the patients with hypertension of degree 1 and/or 2 after the suppression controlled of the antihypertensive medication; as well as the magnitude of the effect of white coat (object of another study).

DESIGN

Almost experimental study and descriptive.

SETTING

Primary care. Urban health centre. Participants measurements and results. Studies of ABPM were realized in 70 essential hypertense patients with good control of the arterial pressure after pharmacological treatment before suspending the antihypertensive medication (1 phase) and to the 4 weeks of leaving the treatment (2 phase), two periods being programmed: diurnal and night.

RESULTS

Of all 70 hypertense patients, 18 (26%) did not manage to carry out 2 ABPM since after the retreat of the medication there presented blood pressure unacceptable values that forced to re-introduce the medicaments. The 79% of the hypertense patients were dipper after the 1 monitoring and that after the suppression of the antihypertensive medication, 83% was continuing being dipper. Depending on the gender there were no statistically significant differences as for the night decrease of the arterial pressure in both periods. Finally, 75% and 11.5% of the patients were dippers or not dippers, respectively, in both phases and only 13.5% of the patients it changed its condition.

CONCLUSIONS

The retreat of the medication in hypertense of degree 1 and/or 2 well controlled does not modify the patients' percentage with night decreases of the blood pressure.

Casual blood pressure and ambulatory blood pressure measurement in children

Some epidemiological studies on blood pressure among children and adolescents have revealed that blood pressure levels in childhood are the strongest predictors of adult blood pressure levels. In the adult population, hypertension causes a two to threefold increase in an individual's risk of cardiovascular morbidity. Cardiovascular risk depends on blood pressure itself, coexistent risk factors and whether there is hypertensive end-organ damage. Therefore, accuracy in determining blood pressure is essential and a standardized protocol should be considered for blood pressure measurement, which would make the comparison of results obtained by different studies in different countries possible. This article reviews the main determinants of accuracy for casual and ambulatory blood pressure measurements in children.

E-selectin-inducing activity in plasma from type 2 diabetic patients with maculopathy

Diabetic maculopathy (DMa) is a leading cause of visual loss in the western world. We examined whether plasma from type 2 diabetic patients with DMa contains factor(s) capable of inducing expression of the adhesion molecules E-selectin and VCAM-1 or cellular proliferation in cultured endothelial cells. Four gender-, age-, and duration (diabetes groups)-matched groups of 20 subjects each participated: 1) subjects with normal glucose tolerance (NGT), 2) subjects with impaired glucose tolerance (IGT), 3) type 2 diabetic patients without retinopathy, and 4) type 2 diabetic patients with DMa. Fasting plasma was added to in vitro-grown human umbilical vein endothelial cells for 6 h, after which E-selectin and VCAM-1 expression was measured. Proliferation was evaluated by thymidine incorporation. The individuals were characterized by measurement of 24-h ambulatory blood pressure, urinary albumin excretion rate, Hb A(1c), and blood lipids. Plasma from type 2 diabetic patients with DMa induced a significantly higher expression of E-selectin in endothelial cells than did plasma from subjects with NGT (259 +/- 23 x 10(3) vs. 198 +/- 19 x 10(3); arbitrary absorbance units; P < 0.05). There were no significant differences in plasma stimulatory effects on VCAM-1 expression or on thymidine incorporation between groups. These findings suggest that plasma from type 2 diabetic patients with DMa contains factor(s) capable of inducing the expression of E-selectin in endothelial cells. Enhanced expression of E-selectin may contribute to the development of DMa in type 2 diabetes.

Effects of Low and High Doses of Atorvastatin on Arterial Compliance

At the beginning of atherosclerosis before evidence of morphological lesions or plaques, vascular distensibility or arterial compliance decreased gradually. This endothelial dysfunction is regarded as an early feature of atherosclerosis. In a randomized, double-blind study design, group 1 (12 patients; 7 males, 5 females) with serum LDL-C levels higher than 170 mg/dL and without any other risk factor for atherosclerosis received three months of 20 mg/day atorvastatin treatment while group 11 (8 males, 4 females) with the same characteristics received 80 mg/day. Baseline and posttreatment serum lipid fractions and arterial compliance were measured. Arterial compliance was measured noninvasively in the left common carotid artery with color Doppler ultrasound. Atorvastatin reduced total cholesterol (TC), LDL-C, and triglyceride levels by 32% (P < 0.001), 40.8% (P < 0.001), and 19% (P < 0.001), respectively, and increased HDL-C by 6.9%, (P = 0.002) in the first group. In the second group these reductions were 38.5% (P < 0.001), 46.2% (P < 0.001), and 26.78% (P < 0.001), respectively, and the increase in HDL was 7.8% (P = 0.03). It was observed that the decrease in serum TC, LDL-C and triglyceride levels were significantly higher in the second group than the first group. With atorvastatin, the distensibility coefficient (DC) and compliance coefficient (CC) increased from 18.7 +/- 3.4 to 21.3 +/- 2.9 10(-3) x kPa(-1) (P < 0.001) and from 0.69 +/- 0.05 to 0.77 +/- 0.03 mm2 x kPa(-1) (P < 0.001) in the first group while they changed from 18.3 +/- 3.6 to 21.9 +/- 3.0 10(-3) x kPa(-1) (P < 0.001) and from 0.70 +/- 0.04 to 0.81 +/- 0.01 mm2 x kPa(-1) (P < 0.001) respectively, in the second group. DC and CC increased in both groups, but the differences between the groups were not significant. High doses of atorvastatin reduce blood lipid levels more than conventional doses, however, the change in compliance is not dose-dependent. As endothelial dysfunction is regarded as an early feature of atherosclerosis, there would be no need to administer aggressive doses in a patient without any risk factors other than hyperlipidemia.

Macular edema reflects generalized vascular hyperpermeability in type 2 diabetic patients with retinopathy

OBJECTIVE

Diabetic maculopathy (DMa) is the most prevalent sight-threatening type of retinopathy in type 2 diabetes and a leading cause of visual loss in the western world. The disease is characterized by hyperpermeability of retinal blood vessels and subsequent formation of hard exudates and macular edema, the degree of which can be estimated by measurement of retinal thickness. We examined associations between retinal thickness as evaluated by optical coherence tomography scanning (OCT), glomerular leakage as evaluated by urinary albumin excretion rate (UAE), and general vascular leakage as evaluated by the transcapillary escape rate of albumin (TER(alb)) in type 2 diabetic patients with and without DMa.

RESEARCH DESIGN AND METHODS

In 20 type 2 diabetic patients with DMa and 20 type 2 diabetic patients without retinopathy matched for age, sex, and duration of diabetes, we performed OCT, fundus photography, fluorescein angiography, and 24-h ambulatory blood pressure measurement. UAE was determined by radioimmunoassay. TER(alb) was determined as the initial disappearance of intravenously injected (125)I-labeled human serum albumin.

RESULTS

Patients with diabetic maculopathy had higher HbA(1c) (8.5 +/- 1.5 vs. 7.4 +/- 1.2%, P < 0.05) and higher total cholesterol (5.8 +/- 0.7 vs. 5.2 +/- 0.9 mmol/l, P < 0.05) than patients without retinopathy. UAE was higher in the DMa group than in the group with no retinopathy (9.3 x// 3.1 vs. 3.9 x// 1.9 micro g/min, P < 0.01). There was no difference in TER(alb) between the two groups (6.0 +/- 1.6 vs. 6.6 +/- 1.5%, NS). In the group with DMa, OCT, TER(alb), and UAE correlated significantly (OCT versus TER(alb): r = 0.55, P < 0.05; OCT versus UAE: r = 0.58, P < 0.01; UAE versus TER(alb): r = 0.81, P < 0.01). Conversely, there were no correlations between these three parameters in the group without retinopathy.

CONCLUSIONS

Macular edema seems to reflect a generalized vascular leakage in type 2 diabetic patients.

Too much of a good thing? A critique of overemphasis on the use of ambulatory blood pressure monitoring in clinical practice

Ambulatory blood pressure monitoring (ABPM) can be considered a major achievement in clinical medicine. However, its superiority over traditional clinical measurement has often been overemphasized in the literature. In both cross-sectional and longitudinal studies, ABPM has been compared with clinical blood pressure calculated from only a few readings taken over a short period of time. For reasons of costs and practicality, ABPM should not be considered as a routine test in the assessment of the hypertensive patient. Most patients with borderline hypertension or isolated clinical hypertension can be profitably assessed with multiple clinical readings and self-blood pressure monitoring. Patients with large short-term or long-term blood pressure oscillations appear as optimal candidates to ABPM. The many methodological problems associated with the use of this technique suggest that ABPM is performed only by experienced doctors.

Ambulatory blood pressure monitoring: is it necessary for the routine assessment of hypertension in people with diabetes?

AIMS

The British Hypertension Society (BHS) has recommended that, for people with diabetes, the target 'clinic' blood pressure should be < 140/80 mmHg. Ambulatory monitoring of blood pressure (ABPM) is used widely in the assessment of hypertension and the BHS has recommended that the target 'awake' ambulatory blood pressure for people with diabetes should be < 130/75 mmHg. The purpose of the present study was to determine the utility of ABPM in the assessment of hypertension in patients with diabetes, over and above a careful 'clinic' measurement of blood pressure.

METHODS

The records of 540 patients with diabetes who underwent ABPM (using SpaceLabs monitors) were retrospectively analysed. With respect to current BHS recommendations, the positive and negative predictive values of 'clinic' blood pressure (measured by trained nurses using mercury sphygmomanometers) on 'awake' ambulatory blood pressure (ABP) were calculated.

RESULTS

The positive predictive value of the 'clinic' BP, its ability to detect patients whose ABP was above BHS targets, was 99%. The negative predictive value of 'clinic' blood pressure was 27%.

CONCLUSIONS

With regard to current BHS guidelines, ABPM is generally unnecessary in the assessment of hypertension in patients with diabetes, provided careful 'clinic' measurements of blood pressure are made.

Comparison of agreement between different measures of blood pressure in primary care and daytime ambulatory blood pressure

OBJECTIVE

To assess alternatives to measuring ambulatory pressure, which best predicts response to treatment and adverse outcome.

SETTING

Three general practices in England.

DESIGN

Validation study.

PARTICIPANTS

Patients with newly diagnosed high or borderline high blood pressure; patients receiving treatment for hypertension but with poor control.

MAIN OUTCOME MEASURES

Overall agreement with ambulatory pressure; prediction of high ambulatory pressure (>135/85 mm Hg) and treatment thresholds.

RESULTS

Readings made by doctors were much higher than ambulatory systolic pressure (difference 18.9 mm Hg, 95% confidence interval 16.1 to 21.7), as were recent readings made in the clinic outside research settings (19.9 mm Hg,17.6 to 22.1). This applied equally to treated patients with poor control (doctor v ambulatory 21.4 mm Hg, 17.3 to 25.4). Doctors' and recent clinic readings ranked systolic pressure poorly compared with ambulatory pressure and other measurements (doctor r=0.46; clinic 0.47; repeated readings by nurse 0.60; repeated self measurement 0.73; home readings 0.75) and were not specific at predicting high blood pressure (doctor 26%; recent clinic 15%; nurse 72%; patient in surgery 81%; home 60%), with poor likelihood ratios for a positive test (doctor 1.2; clinic 1.1; nurse 2.1, patient in surgery 4.7; home 2.2). Nor were doctor or recent clinic measures specific in predicting treatment thresholds.

CONCLUSION

The "white coat" effect is important in diagnosing and assessing control of hypertension in primary care and is not a research artefact. If ambulatory or home measurements are not available, repeated measurements by the nurse or patient should result in considerably less unnecessary monitoring, initiation, or changing of treatment. It is time to stop using high blood pressure readings documented by general practitioners to make treatment decisions.

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.

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.

Reversible hypertension following coeliac disease treatment: the role of moderate hyperhomocysteinaemia and vascular endothelial dysfunction

The vascular endothelium maintains a relatively vasodilated state via the release of nitric oxide (NO), a process that could be disrupted by hyperhomocysteinaemia. Since endothelial dysfunction is associated with increased systemic vascular resistance that is the hallmark of sustained arterial hypertension, we hypothesised that in patients with both hypertension and coeliac disease with hyperhomocysteinaemia (via malabsorption of essential cofactors), treatment of the latter disease could improve blood pressure (BP) control. A single patient with proven sustained hypertension and newly-diagnosed coeliac disease had baseline and post-treatment BP and endothelial function assessed by ambulatory BP monitoring (ABPM) and brachial artery forearm occlusion plethysmography respectively. This 49 year-old woman had uncomplicated sustained hypertension proven on repeated ABPM carried out 6 weeks apart (daytime mean 151/92 mm Hg and 155/95 mm Hg), and sub-clinical coeliac disease (gluten-sensitive enteropathy). Initial assessments revealed raised homocysteine levels with low normal vitamin B(12) level. It was likely that she had impaired absorption of essential cofactors for normal homocysteine metabolism. She adhered to a gluten-free diet and was give oral iron, folate and B(6) supplementations as well as B(12) injections for 3 months. Her BP had improved by 6 months and normalised by 15 months (daytime ABPM mean 128/80 mm Hg). There was parallel restoration of normal endothelial function with normalisation of her homocysteine levels. These observations suggest that sub-clinical coeliac disease related hyperhomocysteinaemia might cause endothelial dysfunction, potentially giving rise to a reversible form of hypertension. In addition, this case study supports the notion that irrespective of aetiology, endothelial dysfunction may be the precursor of hypertension. This highlights the need to resolve co-existing vascular risk factors in patients with hypertension.

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.

Systematic error in the determination of nocturnal blood pressure dipping status by ambulatory blood pressure monitoring

BACKGROUND

Vertical displacement of the arm relative to the heart causes inverse changes in blood pressure of approximately 0.8 mmHg for every centimetre change in arm position. Therefore a potential confounding issue in assessing diurnal variation in blood pressure during ambulatory blood pressure monitoring (ABPM) is arm position during sleep. An increase in the number of patients with 'excessive' nocturnal dipping (> 20% decrease in night/day blood pressure) was observed following the creation of an instructional videotape in which patients were advised to muffle the noise of the monitor with a pillow at night. This raised the possibility that patients were placing their arm on top of the pillow reducing nocturnal blood pressure readings.

DESIGN

Ambulatory blood pressure monitoring data from 184 patients prior to and from 193 patients following specific instructions not to put their arm on top of the pillow was examined.

RESULTS

Following the instructions, the percentage of patients with 'excessive' nocturnal dipping in blood pressure decreased (excessive systolic dipping 17.4 versus 8.8%, P = 0.014; excessive diastolic dipping 37 versus 24.4%, P = 0.01). Consistent with an increase in the ratio of nocturnal/day pressures, there was an increase in the percentage of patients with inadequate nocturnal dipping (< 10% decrease in night/day blood pressure; systolic dipping 33.7 versus 45.6%, P = 0.02; diastolic dipping 13.0 versus 31.6%, P < 0.001)

CONCLUSION

Instructing patients to avoid resting their arm on a pillow at night has a substantial effect on the classification of nocturnal dipping status. Patients need clear instructions not to place their arm on a pillow at night during blood pressure monitoring.

Self-monitored blood pressure: a role in clinical practice?

Electronic self-monitoring of blood pressure is increasing in popularity and most international guidelines on the management of hypertension approve cautious use of the technique in the assessment of potentially hypertensive individuals. A recent editorial in the Archives of Internal Medicine suggested that it was "appropriate to encourage the widespread use of self recorded BP as an important adjunct to the clinical care of the patient with hypertension". Such a statement is based on increasing evidence that self-monitoring of blood pressure gives similar information to daytime ambulatory blood pressure -- a now well-established technology in the management of hypertension. Suggested strategies for the use of self-monitoring of blood pressure include monitoring in individuals whose clinical risk status is low enough that they need not necessarily be given medical therapy simply on the basis of a clinic pressure (i.e. at a 10 year risk of cardiovascular disease below 20%). The threshold for defining 'normotension/hypertension' is now regarded as being broadly similar for ABPM and SBPM and is set at 135/85 mmHg. In a recent meta-analysis of all available studies the average difference between these techniques, using the same patients, is -1.7/1.2 mmHg. There is some evidence that careful use of self-monitoring may improve blood pressure control in patients who are otherwise resistant to care. Self-monitoring of blood pressure has now been shown in at least one major prospective study to predict outcome better than clinic pressures and in that setting it now has equivalence to the use of ABPM. There remain issues regarding the availability of validated devices, the quality of training of patients in their use and the possibility that inaccurate recording might occur, either deliberately or by accident. Self-monitoring of blood pressure may well not give the same readings as carefully measured blood pressure by research nurses but its use is clearly superior to routine clinical practice. The technique is ripe for widespread application.

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 as a surrogate end point for hypertension

OBJECTIVE

To review relevant literature and provide opinions regarding the use of blood pressure as a surrogate measure to predict cardiovascular risk.

DATA SOURCES

Primary and review articles were identified by MEDLINE search (1990-January 2001) and through secondary sources.

STUDY SELECTION AND DATA EXTRACTION

Studies and review articles that related to the interpretation of blood pressure as a surrogate measure were reviewed. Information that was relevant to this topic was included.

DATA SYNTHESIS

The measurement of blood pressure is subject to numerous sources of error and bias. Patients who perform home blood pressure testing and self-report these values frequently leave out high values and add ghost values into logbooks. Additionally, analysis of recent data suggests that at any given level of blood pressure that is achieved, cardiovascular risk reduction may not be the same with different therapeutic agents. It is also now recommended that systolic blood pressure be used in preference to diastolic blood pressure to determine risk and to assess management strategies. Although 24-hour blood pressure measurements may be the best predictors of cardiovascular risk, this has not been demonstrated in a long-term morbidity trial.

CONCLUSIONS

Blood pressure is a relatively poor surrogate measure. Unfortunately, no alternatives are available at this time. Therefore, every attempt must be made to accurately determine blood pressure and to assess risk and benefit from specific antihypertensive agents. Systolic blood pressure should be the predominant blood pressure measure used to evaluate patients, especially middle-aged and elderly individuals.

Oscillometric blood pressure measurement: progress and problems

Oscillometric blood pressure measurement has become very popular, but although a number of devices have now passed both the Association for the Advancement of Medical Instrumentation and British Hypertension Society criteria, complacency with the state of the technique is as yet premature. In individual subjects, a substantial number of readings may deviate more than a clinically relevant 5 mmHg in devices that have earned a British Hypertension Society grade A rating. The marketing of pressure-wave-simulating devices is a welcome development as monitors can now be tested for reproducibility; an intra-device standard deviation of less than 2 mmHg has been proposed as the limit. Authors suggest that these simulators are currently better suited to intra- than between-device testing since they are not yet fully confident that the simulated waveforms are indistinguishable from the man-made pressure waves. Simulators should, however, be incorporated into our standard validation protocols in order eventually to obviate the human, fallible, factor in the validation protocols. The currently employed maximal amplitude algorithm has many drawbacks as the parameter identification points for systolic and diastolic pressure depend on many factors, for example pulse pressure, heart rate and arterial stiffness. These errors have now been demonstrated in clinical studies. Modern pattern recognition algorithms are being constructed but have not yet produced convincing results. As repeatedly stated, the development of a more robust and more widely applicable algorithm than the maximal amplitude approach should be allocated a high priority.

[Variations in the prevalence and patient profile of white-coat syndrome, according to its definition using self-measurement of blood pressure at home]

OBJECTIVE

To calculate the prevalence of white-coat syndrome (WCS) in patients with hypertension, comparing the two most common definitions and their effect on the profile of the patient with WCS.

DESIGN

Cross-sectional, descriptive study.Setting. Urban health centre.Patients. Hypertense patients selected by simple randomised sampling from among those included in the hypertension programme.

MEASUREMENTS

Clinical blood pressure (CBP) from the previous year was collected. Home blood pressure (HBP) was measured by the patient with an electronic sphygmomanometer. Age, sex, further tests (analysis and electrocardiogram) and other clinical features were also recorded. WCS was defined as when CBP was above/equal to 140/90 mmHg and HBP was under 135/85 mmHg or when the difference between CBP and HBP was more than/equal to 20 mmHg systolic and/or 10 mmHg diastolic pressure.

RESULTS

In 154 hypertense patients (60.4% women) between 38 and 92 years old, mean CBP (141.1/85.3) was higher than mean HBP (136.8/79.8). WCS prevalence varied (p = 0.001), depending on the definition used (20.1% and 36.4%). The systolic and diastolic mean CBP of the last year were higher in those patients with WCS (p < 0.001 for diastolic pressure). The profile of hypertense patients with WCS varied according to the definition used.

CONCLUSIONS

WCS is common in hypertense patients treated in Primary Care and may condition an inadequate assessment of the degree of blood pressure monitoring. As the way of defining WCS conditions its prevalence, its profile and clinical decision-taking, it is essential to agree a uniform definition for practical use.

Large waist circumference and risk of hypertension

OBJECTIVE

To examine the relationship between 24 h ambulatory blood pressure monitoring and three commonest anthropometric measurements for obesity--body mass index (BMI), waist-to-hip ratio (WHR) and waist circumference (W).

DESIGN

Cross-sectional survey among outpatients at the Obesity Research Center.

SUBJECTS AND METHODS

Four-hundred and sixty-one overweight or obese subjects, non-diabetic, otherwise healthy, aged 20-70 y, of either sex, were consecutively recruited. All subjects underwent 24 h ambulatory blood pressure monitoring. The population study was separated in normotensive and hypertensive males and females and the possible risk factors for hypertension (W, WHR, BMI and age) were subdivided into different classes of values.

RESULTS

Logistic regression shows that W is the most important anthropometric factor associated with the hypertensive risk. Among males with W> or =102 cm the odds ratio (OR) for hypertension is three times that of males with W<94 cm using casual BP measure (OR 3.04), nearly four times higher using 24 h BP mean (OR 3.97), and even five times higher using day-time BP mean (OR 5.19). Females with W> or =88 cm have a risk for hypertension twice that of females with W<80 cm, whatever BP measurement was take (casual, 24 h or day-time). Males with WHR> or =0.96 and females with WHR> or =0.86 show significant OR for hypertension only by 24 h BP measurement and by day-time BP measurement. BMI seems to have no significant relationship to hypertensive risk. Age shows a significant relationship to hypertensive risk only considering males aged > or =55 y and females aged > or =50 y.

CONCLUSION

The waist circumference seems to have a strong association with the risk of hypertension, principally by the ambulatory BP monitoring, when compared with casual BP measurement.

A study of inter-arm blood pressure differences in primary care

OBJECTIVES

To investigate whether there are inter-arm blood pressure differences that are of clinical importance to general practice.

DESIGN AND SETTING

Pragmatic study with randomised order of use of left or right arm carried out in routine surgeries in an inner city and suburban general practice.

SUBJECTS

There were 237 patients presenting opportunistically for blood pressure measurement to a nurse or general practitioner.

MAIN OUTCOME MEASURES

95% limits of agreement between measurements on the left and right arm and bias between arms.

RESULTS

Large inter-arm blood pressure differences exist reflected in wide 95% limits of agreement; -16 mm Hg to 24 mm Hg for the right minus the left arm diastolic blood pressure. There is a small but statistically significant bias to the right arm blood pressure measuring higher than the left (3.7 mm Hg diastolic, 2.4 to 5 mm Hg 95% confidence intervals). An interarm difference of 10 mm Hg or greater for diastolic blood pressure occurred in 40% of subjects and a difference of 20 mm Hg or more for systolic blood pressure occurred in 23% of subjects.

CONCLUSIONS

In a primary care setting blood pressure should be measured routinely in both arms. If one arm is to be preferred for pragmatic clinical purposes, then this should be the right arm.

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.

What is hypertension in diabetes? Ambulatory blood pressure in 137 normotensive and normoalbuminuric Type 1 diabetic patients

AIMS

To establish reference data for ambulatory blood pressure (AMBP) in normotensive, normoalbuminuric Type 1 diabetic patients and characterize the relation to clinic blood pressure (BP). To evaluate the statement of the third working party of the British Hypertension Society (BHS) that a target clinic BP in diabetes < 140/80 corresponds to a target day-time AMBP < 130/75 mmHg.

PATIENTS AND METHODS

AMBP were performed in 172 normoalbuminuric, adult Type 1 diabetic patients, who had never received anti-hypertensive drugs. Clinic BP was determined as the mean of at least three auscultatory (Hawskley random zero manometer) and as the mean of at least three oscillometric (Spacelabs) BP values obtained just prior to ambulatory monitoring. Five patients with more than three missing hours/24 h were excluded.

RESULTS

For 30 patients auscultatory clinic BP exceeded 140 mmHg systolic and/or 90 mmHg diastolic. For the remaining 137 normotensive patients day-time AMBP was 125.7/77.2 mmHg and oscillometric clinic BP was 125.3/76.5 mmHg (mean difference 0.3/0.7 mmHg; 95% confidence interval (CI) -0.9 to 1.5/-0.3 to 1.7 mmHg, P = 0.6/P = 0.2). Sixty-five percent of the patients had a diastolic day-time AMBP > 75 mmHg.

CONCLUSIONS

Clinic BP and day-time AMBP measured by the same method were indistinguishable. The target for day-time diastolic AMBP (< 75 mmHg) proposed by the BHS is too low and is based on the misconception that in normotensive subjects day-time AMBP is lower than clinic BP. If the BHS guidelines are strictly adhered to, the consequence may be overtreatment in patients with normoalbuminuria and no end organ damage.

What is the magnitude of blood pressure response to a programme of moderate intensity exercise? Randomised controlled trial among sedentary adults with unmedicated hypertension

BACKGROUND

Current guidelines for the management of hypertension recommend regular, moderate intensity aerobic exercise such as brisk walking as a means of blood pressure reduction. However, there is a lack of consistent evidence regarding the magnitude of blood pressure response to such a prescription. In particular, no well designed studies have investigated the efficacy of a programme of exercise meeting current guidelines.

AIM

To investigate the effect of a six-week programme of moderate intensity exercise on daytime ambulatory blood pressure (10.00 am to 10.00 pm) among unmedicated, sedentary adults aged 25 years to 63 years with office blood pressure of 150 mmHg to 180 mmHg systolic and/or 91 mmHg to 110 mmHg diastolic.

METHOD

Randomised controlled trial of participants carrying out 30 minutes of moderate intensity exercise (brisk walking or equivalent) five days per week for six weeks compared with controls who maintained existing levels of physical activity.

RESULTS

Compliance with the exercise programme was high. The reduction in mean daytime ambulatory blood pressure between baseline and six-week follow-up was greater in the intervention group than in the control group for both systolic and diastolic blood pressure. However, this net hypotensive effect was not statistically significant (systolic = -3.4 mmHg, 95% CI = -7.4 to 0.6; diastolic = -2.8 mmHg, 95% CI = -5.8 to 0.2). Adjusting for baseline differences in mean ambulatory blood pressure in an analysis of covariance led to a reduction in the estimated magnitude of the effect (systolic = -1.9 mmHg, 95% CI = -5.4 to 1.7, P = 0.31; diastolic = -2.2 mmHg, 95% CI = -4.9 to 0.5, P = 0.11).

CONCLUSION

Despite high compliance with the exercise programme, the magnitude of the hypotensive effect of moderate intensity exercise was not as great as that found in studies of higher intensity exercise among hypertensives. Expectations of general practitioners and patients that a programme of moderate intensity exercise will lead to a clinically important reduction in the individual's blood pressure are unlikely to be realised.

Is nurse-measured blood pressure a valid substitute for ambulatory blood pressure monitoring?

BACKGROUND

Because ambulatory blood pressure monitoring (ABPM) is not available everywhere, the objective of the study was to determine whether nurse-measured blood pressure could be an acceptable substitute to ABPM.

METHODS

We analyzed the data of 2385 consecutive patients referred to our hypertension clinic for the performance of ABPM. Before ambulatory monitoring was performed, a nurse-measured BP was obtained three times using a Y-tube connecting the sphygmomanometer and the recorder. We compared the mean value of the three nurse-measured blood pressures with that of the 12h daytime ambulatory monitoring, considered as the reference.

RESULTS

The difference between the nurse-measured and the ambulatory blood pressure was small but statistically significant, indicating that nurse-measured blood pressure tends to overestimate both diastolic and systolic blood pressure. The difference between the nurse blood pressure and ABPM was greater among treated hypertensive patients than untreated patients. To diagnose hypertension, defined as a blood pressure of over 140/90mmHg by ABPM, the positive predictive value of the nurse blood pressure was 0.81 and the negative predictive value 0.63. However, these predictive values could be improved with less stringent cut-off values of blood pressure. Thus, for a diastolic blood pressure above 100mmHg, the positive predictive value of nurse blood pressure was 0.55 and the negative predictive value 0.91. These figures were relatively similar for previously treated and untreated patients.

CONCLUSION

Nurse blood pressure is less accurate than ABPM in diagnosing hypertension, defined as a blood pressure of over 140/90mmHg. It could, however, be an acceptable substitute, especially to exclude people who do not need to be treated, in situations where lower resources require a less rigorous definition of hypertension.

Modern approaches to blood pressure measurement

BACKGROUND

Blood pressure (BP) is usually measured by conventional sphygmomanometry. Although apparently simple, this procedure is fraught with many potential sources of error. This review focuses on two alternative techniques of BP measurement: ambulatory monitoring and self measurement.

REVIEW

BP values obtained by ambulatory monitoring or self measurement are characterised by high reproducibility, are not subject to digit preference or observer bias, and minimise the transient rise of the blood pressure in response to the surroundings of the clinic or the presence of the observer, the so called white coat effect. For ambulatory monitoring, the upper limits of systolic/diastolic normotension in adults include 130/80 mm Hg for the 24 hour BP and 135/85 and 120/70 mm Hg for the daytime BP and night time BP, respectively. For the the self measured BP these thresholds include 135/85 mm Hg. Automated BP measurement is most useful to identify patients with white coat hypertension. Whether or not white coat hypertension predisposes to sustained hypertension remains debated. However, outcome is better correlated with the ambulatory BP than with the conventional BP. In patients with white coat hypertension, antihypertensive drugs lower the BP in the clinic, but not the ambulatory BP, and also do not improve prognosis. Ambulatory BP monitoring is also better than conventional BP measurement in assessing the effects of treatment. Ambulatory BP monitoring is necessary to diagnose nocturnal hypertension and is especially indicated in patients with borderline hypertension, elderly patients, pregnant women, patients with treatment resistant hypertension, and also in patients with symptoms suggestive of hypotension.

CONCLUSIONS

The newer techniques of BP measurement are now well established in clinical research, for diagnosis in clinical practice, and will increasingly make their appearance in occupational and environmental medicine.