Diagnosing hypertension through home blood pressure monitoring

Katarzyna Stolarz-Skrzypek,
First Department of Cardiology and Hypertension, Jagiellonian University Medical College, Kraków, Poland

Jan A. Staessen
Studies Co-ordinating Centre, Division of Hypertension and Cardiovascular Rehabilitation, Department of Cardiovascular Diseases, University of Leuven, Leuven, Belgium

Department of Epidemiology, Maastricht University, Maastricht, The Netherlands

The development over the past 20 years of cheap and properly validated devices for home blood pressure monitoring (HBPM) and the validation of HBPM in terms of cardiovascular outcomes brought HBPM to the state where it can be applied clinically.1-4 Current hypertension guidelines endorse the use of HBPM in clinical practice as a useful adjunct to conventional office measurement.5 Physicians and patients are increasingly embracing HBPM as means to refine the diagnosis and treatment of hypertension. Recently, the European Society of Hypertension (ESH) published concise and updated guidelines on the use of HBPM for practising physicians.6

HBPM – advantages and prerequisites
HBPM has several major advantages over conventional office blood pressure (BP) measurement:

1. It provides multiple measurements of BP over several days, weeks or months
2. HBPM is carried out in the usual environment of each individual, away from the medical setting and the physician’s office – conditions known to raise BP in many subjects (white-coat effect)
3. Home BP is more closely related to hypertension- induced target organ damage and predicts the risk of cardiovascular events better than conventional BP measurements in the office.

HBPM can detect white-coat and masked hypertension and it shares many features with 24- hour ambulatory BP monitoring (ABPM), another important technique for out-of-office BP monitoring.7 Compared with ABPM, HBPM can provide BP measurements over a much longer period, is cheaper, more widely applicable, and more convenient for patients, particularly for repeated measurements. HBPM improves the adherence of patients to treatment and therefore ameliorates control rates of hypertension.7-10 Moreover, HBPM is an educational tool that helps hypertensive patients to understand and take responsibility for their disease and its long-term follow-up. For diagnosis and adjustment of treatment, HBPM is often used in conjunction with ABPM as a complementary method of BP assessment.

There are important prerequisites for the optimal application of HBPM in clinical practice (Box 1). HBPM should be performed by patients who received training under medical supervision. Nurses and/or pharmacists can have an important part in the implementation of HBPM in daily practice and in the diffusion of correct recommendations. Training should include information on hypertension, BP variability, the conditions and procedures for self-monitoring, advice on equipment choice (based on validation, technical features, price and individual experience), its proper use and interpretation of results.

HBPM based on automated electronic devices is not complex and can be explained to the patient during a single training session, possibly with a subsequent observation period to verify during office visits that the patient applies the correct technique. However, in some patients – in particular in older patients with motor or cognitive impairment or in young children – help of a trained nurse or family member may be needed.

A logbook structured according to the required monitoring schedule is useful for ensuring the accuracy of reporting of HBPM values and for improving adherence to measurements schedule. Manufacturers can facilitate HBPM by providing devices with a range of cuffs for varying arm sizes and capable of automatically calculating average BP. The provision of telemonitoring facilities may be of further advantage.11

Devices and cuffs
Semi-automated (manual cuff inflation) or automated electronic devices that measure BP at the level of the upper arm are preferred for HBPM.5,7,8,12 These devices require less training, avoid observer bias and, if equipped with a memory, have the potential to prevent patients from misreporting their BP readings.13,14 Auscultatory (aneroid or mercury) devices are not recommended except under specific circumstances – for example, in case of arrhythmia, requiring repeated auscultatory measurements. Finger or wrist cuff devices should not be used for HBPM.

Among the large number of HBPM devices available on the market only those that have been validated for accuracy in independent studies performed according to internationally recognised protocols should be used.15 Up-to-date lists of validated devices are available at the dedicated websites (for example, www.dableducational.org, www.bhsoc.org and www.pressionearteriosa.net). A device that has been validated in common hypertensive patients is not necessarily accurate in special circumstances, such as obesity, patients with arrhythmias, older patients, children, or pregnant women. Devices should be specifically validated in patients with these conditions.

The selection of the appropriate size of the cuff to fit the arm of each individual is essential for an accurate BP measurement. The inflatable bladder of the cuff should cover 80–100% of the arm circumference.7,8,12 The use of a small cuff for the size of the arm can result in the overestimation of BP. Although standard cuffs are appropriate for most patients, in those with small (<24cm) or large (>32cm) arm circumference only devices available with appropriately sized cuffs should be used.

Conditions of measurement
Conditions under which HBPM is performed can greatly affect the measured BP levels. The cuff should be wrapped around the arm with the inflatable bladder centered on the arm anterior surface. Most cuffs have an indication of proper placement with the lower edge of the cuff approximately 2– 3cm above the elbow. The bladder should be positioned at the heart level.

HBPM should be performed in a quiet room. The patient should remain seated comfortably and immobile, with the arm resting on a table or other support. The patient should remain silent during the measurements. The results should be noted in a logbook immediately after each measurement. Alternatively, memory-equipped devices, which are recommended, can store the readings with date and time of each measurement.

Patients sometimes use their device to measure BP in other family members. It is important to ensure that these measurements are excluded from the patient’s record. In rare cases of a significant (>10mmHg) and consistent BP difference between arms, the physician should advise the patient to use the arm with higher BP values also for HBPM.

Monitoring schedule
For the initial diagnosis of hypertension and for the assessment of the effects of antihypertensive treatment, including changes in types or doses of drugs, HBPM should be performed daily during at least three and preferably seven consecutive days before the doctor’s visit (Box 2). Duplicate measurements should be obtained in the morning before drug intake and in the evening.16 Measurements of the first monitoring day are usually higher and more variable and are therefore often excluded.

Treated hypertensive patients may also perform less frequent, regular HBPM as a long-term followup – for example, once or twice a week – with the additional aim to reinforce their adherence to treatment. However, isolated readings should never be used for diagnostic purposes.7,8,12 Overuse of HBPM and self-modification of treatment on the basis of HBPM should be avoided.

Interpretation of the measurements
The average of a series of measurements taken as described above should be used for the clinical decisions based on HBPM readings. Casual, isolated home measurements can be very misleading and should not by themselves constitute the basis for clinical decisions. The users should be informed that BP may vary between measurements and be instructed not to be alarmed by high or low BP levels measured on a single occasion. Only when the BP remains persistently too low or too high or is associated with symptoms of clinical relevance, such as dyspnoea or chest pain, should the patient seek medical assistance.

Hypertension on HBPM is a level of 135mmHg systolic or 85mmHg diastolic, or higher. The thresholds delineating ‘normal’ or ‘optimal’ home BP are still under investigation, but are probably less than 130mmHg systolic and less than 80mmHg diastolic.

Therapeutic decisions based on home monitored BP should always take into consideration the overall cardiovascular risk profile and co-morbidities. In high-risk subjects, for example, those with diabetes or chronic kidney disease, lower home BP values should probably be achieved, but the targets have not yet been definitely defined.

Clinical indications for HBPM
HBPM provides clinically useful information on BP level and profile to practising doctors, because it enables a more precise initial diagnosis of hypertension and more accurate titration of antihypertensive drug treatment. It also offers useful information on heart rate at home18 and on day-to-day BP variability.19,20 Therefore, if feasible, it should be used in all treated hypertensive patients.

Its use is also recommended for the identification of patients with suspected white-coat or masked hypertension, particularly among subjects with borderline or highly variable office BP, high cardiovascular risk and normal office BP, symptoms of hypotension in spite of inadequate control by treatment of the office BP, or no signs of organ damage in spite of the high office BP.21-23

HBPM is further recommended in patients with poor adherence to treatment. HBPM may increase their involvement in the management of their condition. HBPM can also be used in high-risk populations in whom close BP control is mandatory, such as patients with co-morbidities. In pregnancy, HBPM should be performed with devices validated in this condition.

A contraindication for HBPM using oscillometric devices is the presence of arrhythmias, such as atrial fibrillation, numerous extrasystoles or excessive bradycardia, which render these devices inaccurate.

Conclusions
HBPM is a valuable tool in the daily management of hypertension. However, it should be always used under medical supervision and taking into account the patients’ overall clinical conditions and cardiovascular risk profile.5, 24

Acknowledgements:
The European Union (grants IC15-CT98- 0329-EPOGH, LSHM-CT-2006-037093, and HEALTH-F4-2007-201550), the Fonds voor Wetenschappelijk Onderzoek Vlaanderen (Ministry of the Flemish Community, Brussels, Belgium; grants G.0575.06 and G.0734.09), and the Katholieke Universiteit Leuven (grants OT/00/25 and OT/05/49) gave support to the Studies Coordinating Centre in Leuven. The European Union (grants LSHM-CT-2006-037093 and HEALTH-F4-2007-201550) also supported the research group in Kraków. The authors gratefully acknowledge the secretarial assistance of Ms Sandra Covens and Ms Ya Zhu (Studies Coordinating Centre, University of Leuven, Leuven, Belgium).

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