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Monitoring hypertension: how and whyHow many of your patients know their last blood pressure measurement? And forthe few who do, what are the important numbers? Jon Waterfield focuses on someof the more pragmatic questions associated with hypertension and looks at some ofthe current debates in terms its monitoring and assessing cardiovascular risk

Evaluate Plan

Reflect

Act

REFLECT 1What are the advantages and disadvantagesof monitoring blood pressure at home?

2What extent of blood pressure lowering canbe expected through lifestyle modifications?

3What are the thresholds for initiatingantihypertensive treatment?

Before reading on, think about how this articlemay help you to do your job better.

Hypertension is a major but modifiablecontributory factor in cardiovascular diseasessuch as stroke and coronary heart disease. Themain driver for the close monitoring andmanagement of hypertension is the reductionin cardiovascular morbidity and mortality.

What are the important numbers?Hypertension is defined as persistent raisedblood pressure above 140/90mmHg. Panel 1shows the classification of blood pressure interms of numbers, as accepted by the BritishHypertension Society, the European Societyof Hypertension and the European Society ofCardiology. This does not take into accountthe rise in blood pressure seen with increasingage, but current treatment targets are notgenerally based on the age of the patient.

Hypertension should be confirmed byasking the patient to return for at least twosubsequent measurements under quiet andcalm conditions. The period over which this isconfirmed will depend on the initial bloodpressure readings and, in most cases, whetherthe patient has cardiovascular complications.For example, an initial reading of180–219mmHg systolic or 110–119mmHg

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PANEL 1: BLOOD PRESSURE CLASSIFICATION*

Category Systolic blood pressure Diastolic blood pressure(mmHg) (mmHg)

Optimal <120 and <80Normal 120–129 and <85High normal 130–139 and/or† 85–89Mild hypertension (grade 1) 140–159 and/or† 90–99Moderate hypertension (grade 2) 160–179 and/or† 100–109Severe hypertension (grade 3) ≥180 and/or† ≥110Isolated systolic hypertension (grade1) ≥140 and <90

* In patients without diabetes† The higher blood pressure reading is used to determine the blood pressure category whensystolic and diastolic readings are in different categories

PANEL 2: ADVICE FOR HOME BLOOD PRESSURE MEASUREMENT

• Only upper arm devices should be used because finger and wrist monitors are less accurate.• The machine should be validated. (A list of validated monitors is available on the British

Hypertension Society website, which is updated regularly.)• To ensure accurate measurements, the machine should be calibrated regularly (usually annually),

in accordance with manufacturer’s guidelines.• Wearing loose fitting clothing makes the upper arm more easily accessible.• The person should sit at a table, with his or her arm resting on its surface. The arm should be

relaxed. The cuff of the device should be at the same height as the heart.• The person should be still and silent during the measurement because readings can be affected

by movement and talking.• The person should avoid caffeinated drinks, strenuous exercise or having a full bladder before

blood pressure is measured because these factors can influence readings.

Ask the

expertwww.pjonline.com/ask-expert

Jon Waterfield will be available to answerquestions online on the topic of this articleuntil 25 October 2010

diastolic should be confirmed within twoweeks. In comparison, an initial reading of140–159mmHg systolic or 90–99mmHgdiastolic in a patient with diabetes requiresconfirmation within 12 weeks.1

In the diagnosis of hypertension it is alsonecessary to exclude “white coat”hypertension — where blood pressurereadings are artificially raised in the clinic. Inaddition, patients sometimes claim to havelower readings (using a home blood pressuremonitor) and this can complicate matters.

Thresholds and targetsSuggested thresholds and targets for treatmentare outlined in the British National Formulary.They are based on blood pressure readings ina clinical setting rather than readings taken at home.

The decision to initiate drug treatment willalso be influenced by factors such as co-morbidities (eg, cardiovascular complicationsand diabetes) and 10-year cardiovascular risk.Unless blood pressure is over 179mmHgsystolic or 109mmHg diastolic, patients withno complications may first be advised to makelifestyle changes and be reassessed beforedrug treatment is considered. Those withcomplications tend to be given drug treatment earlier.

The aim of treatment is to get bloodpressure down to below140/90mmHg.1 (Forpatients with diabetes or atheroscleroticcardiovascular disease the targets are lower

and the aim is to maintain systolic pressurebelow 130 mmHg and diastolic pressurebelow 80mmHg.1)

The Panel also highlights the need to lookout for isolated systolic or diastolichypertension. For example, grade 2 isolatedsystolic hypertension, defined as a systolicpressure greater than 160mmHg and adiastolic pressure of less than 90mmHg, isassociated with an increased cardiovascularrisk, particularly in those aged over 60 years.If grade 2 isolated systolic hypertensionpersists over three to six months afterattempting appropriate lifestyle interventions,it should be treated in those aged over 60years. ISH is not as common in patients underthe age of 60 years but if a patient is atincreased risk of cardiovascular disease andhas persistent raised systolic pressure,treatment should be considered.

Some patients may have only a raiseddiastolic pressure. A patient with a diastolicpressure of over 85mmHg would be regardedas being in the normal to high category andwould invite closer monitoring.

Measuring blood pressureThe accurate measurement of blood pressureis important for effective diagnosis andtreatment. The traditional method ofmeasuring blood pressure is the auscultatory(listening) method. This involves the use of astethoscope and sphygmomanometer by atrained healthcare professional. An inflatable

cuff is placed around the upper arm atapproximately the same height as the heartand attached to a mercury or aneroid (clockface) manometer. The mercury manometer isconsidered to be more accurate because it isbased on a height of a column of mercury. Ananeroid device, although more portable, ishighly sensitive to mechanical strain and ismore easily damaged by impact, so accuracycan decrease. It is also subject to calibrationdrift errors.

An appropriately-sized cuff is fitted aroundthe upper arm and inflated manually with arubber bulb until the artery is completelyoccluded. The stethoscope is then used tolisten to the brachial artery at the elbow while,at the same time, slowly releasing the pressurein the cuff. As the pressure drops to a levelthat is equivalent to the patient’s systolic bloodpressure the first Korotkoff sound — namedafter the Russian physician — is heard. Thissound can be described as a “whooshing” or“snapping” and is heard when the pressure inthe cuff reaches the pressure produced in theartery during systole. The characteristic soundis caused as the blood flows in spurts as thepressure in the cuff drops below the pressurein the artery, resulting in turbulence.

Korotkoff described five types of sound asthe pressure is slowly released from the cuff.The fourth, which is at pressures within10mmHg above the diastolic pressure, isdescribed as “thumping” or “muting”. Thefifth “sound” is silence as the cuff pressuredrops below the diastolic arterial pressure. The diastolic pressure reading is taken at this point.

Not all GPs and nurses use mercurymanometers and, according to a member ofthe British Hypertension Society bloodpressure device monitoring group, thenumber of readings that GPs and nurses haveto do make it impractical not to use anautomated device.2 (Automated devices detectoscillation in the arterial wall as blood flowsthrough at different pressures.3) However, arecent US study found that automated BPmonitors give readings an average of 2mmHglower than mercury manometers, puttingsome patients at risk. The disparity in readingswas found to be greatest in patients over 65years of age.2

Healthcare professionals trained tomeasure blood pressure should have theirperformance reviewed periodically.

Systolic versus diastolic Current guidelines and clinical practice arebased on the measurement and treatment ofboth systolic and diastolic blood pressure.

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PANEL 3: RELATIVE IMPORTANCE OF LIFESTYLE CHANGES

Weight management Ten per cent weight losscan reduce total blood pressure by 7/5mmHg.Any patient with a body mass index over25kg/m2 should be encouraged to lose weight.There is a link between obesity and insulinresistance, dyslipidaemia and sympatheticnervous system stimulation, increasing the riskof cardiovascular disease.

Exercise Aerobic exercise (eg, brisk walking,jogging or cycling) for 30 to 60 minutes, threeto five times each week reduces systolic anddiastolic blood pressure on average by2–3mmHg, but there is a wide variation inresponse. Reduction is more obvious inpatients who have previously taken little or noexercise. Shorter episodes of more frequentexercise appear to have less effect on bloodpressure reduction.

Alcohol consumption Interventions to reducealcohol consumption lower systolic anddiastolic blood pressure on average by3–4mmHg. Excessive alcohol consumption(defined as more than 21 units/week for menand more than 14 units/week for women) isassociated with raised blood pressure andpoorer cardiovascular and hepatic health.Binge drinking should be discouraged.

Salt consumption Advice to reduce dietarysalt intake to less than 6g/day (equivalent to2.4g/day of dietary sodium) has been shown toachieve a reduction in systolic and diastolicblood pressure of 2–3mmHg. This effect is variable but patients should be encouraged to keeptheir dietary sodium intake low. Tips include avoiding processed foods because many have highsalt levels. Salt substitutes containing potassium chloride may not be suitable for everyone. Otherdietary advice includes a reduction of total and saturated fat intake and increased fruit andvegetable consumption.

Caffeine consumption Consumption of five or more cups of coffee a day is associated with asmall increase in blood pressure (2/1mmHg). Excessive consumption of coffee and other caffeine-rich products should be discouraged.

Relaxation Relaxation therapies include stress management, meditation, cognitive therapies,muscle relaxation and biofeedback. The costs and feasibility of providing these type ofinterventions in primary care has not been assessed.

However, due to the increasing evidence ofthe importance of systolic hypertension interms of risk, it has been suggested thatdiastolic blood pressure need not bemeasured.4 There appears to be some debateabout the risks associated with increaseddiastolic hypertension whereas the MultipleRisk Intervention Trial found that for any levelof diastolic blood pressure, the systolic bloodpressure was the major determinant forcardiovascular risk.5

One reason diastolic pressure is notignored is that pulse pressure, which isdefined as the difference between systolic anddiastolic blood pressure, has been highlightedas an independent predictor of cardiovascularrisk.6 The use of pulse pressure as an indicator

of cardiovascular risk is a possible wayforward in the complex debate on the relativeimportance of systolic over diastolic pressure.In the meantime, however, national guidelinesand treatment targets are based on bothreadings.

Issues with monitoring at home The most recent National Institute for healthand Clinical Excellence guidelines state thatthe routine use of home monitoring devices orautomated ambulatory monitoring devices isnot recommended.7 This is because the valueof such equipment in primary care has notbeen established and NICE hasrecommended that this is an area of focus forfurther research.

In practice, however, healthcareprofessionals may encourage the use of ahome blood pressure monitor so that patientscan monitor their blood pressure betweenclinic appointments. The potential advantagesof home blood pressure monitoring include:

• A more general overview of a patient’s bloodpressure everyday life

• An indication of whether the blood pressureis higher or lower than in the clinic

• A means of observing if medication andlifestyle interventions are having an impacton blood pressure readings

On the negative side, the use of a homeblood pressure monitor can cause anxiety insome patients, which can lead to the obsessivetaking of frequent readings. It is important toestablish with individual patients whethermonitoring at home either reassures or is aform of additional stress.

In general, it is not necessary to take homereadings more than once a week. Patients withan irregular heart rate may not be able toachieve an accurate reading with an electronicdevice. Patients with problems bending ormoving their arms may also have problemsusing the cuff and home monitoring may beunsuitable.

Home blood pressure monitors are usuallysupplied with a standard cuff and if theperson’s upper arm circumference is outsidethe standard range, he or she will need to buya larger or smaller cuff because cuffs that aretoo large or small give inaccurate readings.The bladder of the cuff should cover at least80 per cent of the circumference of the armbut no more than 100 per cent. The cuffshould be tight but not too tight. (Two fingersshould be inserted between the skin and thecuff to check for tightness before ameasurement.)

Further advice associated with home blood pressure measurement can be found inPanel 2.

Ambulatory monitoring Ambulatory bloodpressure monitoring uses an automatic deviceto obtain readings over 24 hours while apatient is in his or her normal environment. Itis sometimes used in patients who haveborderline clinic readings or poorly controlledhypertension.8 Readings can be taken every30 minutes and every hour during the night. Itshould be noted that the numbers fromambulatory readings are not equivalent toclinic readings in terms of thresholds andtargets.

Frequency of monitoring In practice, the frequency of blood pressuremonitoring is usually every five years inhealthy individuals.

One of the indicators in the Quality andOutcomes Framework for the general medicalservices contract is a record of the percentageof patients with hypertension in whom there isa record of their blood pressure in theprevious nine months. There are no specificBritish Hypertension Society Guidelines onthe frequency of follow up in patients with

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The author

Jon Waterfield, MSc, MRPharmS, is aprincipal lecturer in pharmacy practice atLeicester School of Pharmacy, De MontfortUniversity

hypertension but there is an assumption thatthis will be approximately every six monthsand the audit standard is based on ninemonths. The frequency of follow up inpatients on antihypertensive medicines willdepend on factors such as the severity of thehypertension, the complexity of the treatmentregimen, patient compliance and the need fornon-pharmacological advice. If the patient hasuncontrolled hypertension the frequency ofmonitoring is usually every four to eightweeks.

Lifestyle advice: is it worth it?Pharmacological intervention is the main wayto treat hypertension, which continues to beviewed as a condition that is under-treated.However, lifestyle modifications can also beuseful. There are clear links between obesityand salt and alcohol intake in the developmentof hypertension.

An important question for the healthcareprofessional and the hypertensive patient is:how significant are lifestyle modifications inthe reduction of blood pressure readings? Thisquestion also overlaps with the questionsurrounding overall cardiovascular risk. Forexample, there is no strong direct link betweensmoking and blood pressure but smokingcessation is the most important lifestylemodification for the reduction of overallcardiovascular risk.

The reductions, in terms of mmHg,resulting from lifestyle changes (summarisedin Panel 3 [p377] using data from NICEguidelines) may appear modest. However, itshould be appreciated that the overall pictureis complex in terms of additive effects betweendifferent factors and variability betweenindividuals. For example, about 25 per cent ofpatients receiving multiple lifestyleinterventions were estimated to achieve areduction in systolic blood pressure of10mmHg systolic or more in the short term,up to a year.

Pharmacists should note, however, thatNICE concluded that patient education aboutlifestyle on its own is unlikely to be effective.Any lifestyle advice needs to be supplementedwith appropriate written or audiovisualmaterials.

Cardiovascular riskWhen an increase in blood pressure persistsand there is no previous history ofcardiovascular disease the patient should beinvited to discuss the need to assess theircardiovascular risk formally. Age is the maindeterminant of risk for cardiovasculardisease — the condition mainly affects peopleolder than 50 years.

Although it has been established thatwomen have lower coronary heart diseaserates than men, the disease is the leading causeof mortality in women as well as men in mostindustrialised countries. This suggests thatinterventions by healthcare professionals needto be targeted at both sexes.

The three modifiable risk factors that makea major contribution to CVD risk aresmoking, raised blood pressure and raisedcholesterol. These factors are present in 80 per

cent of all cases of premature coronary heartdisease. Initially, patients should be prioritisedon the basis of an estimate of their CVD risk,based on information recorded in theirmedical record, before a full formalassessment is made.

Debate over tools A cardiovascular risk assessment tool can beuseful in terms of prognosis. Assessment toolsprovide an indication of percentage risk ofcardiovascular disease over a 10-year period.This is usually undertaken by inputtinginformation, such as age, sex, systolic bloodpressure, total cholesterol, high densitylipoprotein cholesterol, smoking status andother factors, into a computer programme.

Most risk assessment models are based oninformation derived from the FraminghamHeart Study, which involved a cohort of over5,000 men and women aged between 30 and62 years of age from Framingham,Massachusetts. The subjects were followedfrom 1971 in order to assess the determinantsof cardiovascular disease. Major criticisms ofthis model include poor validation in the UKand lack of application to ethnic minoritiesand younger populations.

The University of Nottingham developedthe QRISK CVD risk assessment tool toaddress some of these issues and provide amore UK-centred tool. This is updatedannually as the population characteristicschange and comparison data improves. InScotland, the ASSIGN tool was developed byDundee University and took into accountfactors suited to Scotland, such as socialdeprivatio n. There is significant debatesurrounding both the choice and the use ofthese tools. Until recently, the Framinghamrisk calculator was the model of choice.However, this year the NICE guidanceexecutive agreed to withdraw the

recommendation that the Framingham riskequation should be the tool of choice for theassessment of CVD risk.9 The updated NICEguidance states that other risk assessmenttools can be used and it is up to the individualclinician.

Some would view the development of aspecific UK-wide, standardised CVD risk toolas a positive move. An alternative view is thatall risk equations are inaccurate to somedegree and need constant refinement. Themain issue is that they are applied consistently.The cardiovascular risk prediction charts atthe back of the BNF are based on the JointBritish Societies guidelines on prevention ofcardiovascular disease in clinical practice.10 Itshould be noted that these differ from theestimation of cardiovascular risk in the latestNICE clinical guideline.

Do you need to revise your knowledge ofhypertension treatment? A second CPDarticle, to be published online on 16 October,will summarise the current treatmentrecommendations. It will contain practicepoints, a suggested answer to the scenario inPanel 4 and references. Our “Check yourlearning” tool will be available once thissecond article is published.

CPD articles are commissioned by ThePharmaceutical Journal and are not peerreviewed.

PANEL 4: CONSIDER THIS PATIENT

James Martin is a 50-year old sales manager whoregularly collects prescriptions for his elderly mother.Your pharmacy is currently offering a blood pressurescreening service and he asks for his blood pressureto be taken. His initial reading is 160/90mmHg and asimilar reading is obtained after 15 minutes. Youexplain to Mr Martin that you would like to take hisblood pressure at a different time and suggest thathe comes back in a few days.

Mr Martin returns a week later, just before closingtime. He has had a busy day and has had difficultyparking the car near the pharmacy. His reading is163/92mmHg and you offer to take another reading.The result is similar. Mr Martin appears anxious andasks your advice about purchasing a home bloodpressure monitor so that he can take readings athome.

Two months later, Mr Martin comes in with aprescription for enalapril tablets, 5mg to be taken once daily, which you dispense. He returns to thepharmacy after a week with the box of enalapril tablets and the patient information leaflet. He saysthe tablets are giving him a cough.

Consider this scenario. (Suggested comments will appear online on 16 October 2010.)

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