Hypertension

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Failure of one or more mechanisms to limit the pressure of the blood is an important disease and contributor to several other important, expensive and lethal diseases. Cardio-vascular disease risk in particular can be related to both individual and population levels of blood pressure.

LogoWarningBox4.pngStopping a betablocker suddenly can produce a rebound, angina, stroke or death. Package inserts appropriately warn patients not to do so without advice from a doctor.

Introduction

The blood pressure is often measured because it can be. Blood pressure is a continuous variable. No level is definitively "normal" but higher values have been correlated with increased vascular disease. Lowering blood pressure appears to reduce incidence of stroke and renal disease and other vascular problems.

Contents

Aetiology

Essential Hypertension

This is also termed primary hypertension and has classically been defined as high blood pressure with no identifiable cause. However this is far from the case, and the condition is now understood to result from long term exposure to a number of risk factors, mainly environmental, and many of which are modifiable. George Pickering's classic observation in the 1950's that no single dividing line exists between normal and high blood pressures has been confirmed on meta-analysis of 61 prospective studies which shows how vascular risk was related in a continuous way to observed blood pressure[1]. The important risk factors are:

Info bulb.pngThere is far too much salt in processed foods.
  • Age in urbanised Western environments (not a variable in Bushman or convent residing Nuns[2])
  • dietary sodium intake salt which much work also relates to the ratio of sodium to potassium[3]
  • obesity
  • alcohol intake
  • psychological stress
    • Note "White coat hypertension" is significantly associated with mortality

Secondary Hypertension

Excluding Secondary Hypertension

This is a task we must commonly either pursue or decide when to break off pursuing, in that causes are rare, early detection is commonly of slight advantage, and absolute exclusion difficult, expensive, and time-consuming for the patient. Very high pressures hard to control occurring very quickly in ill young people should be pursued energetically and persistently but mild hypertension in well people of considerable years, easily controlled with standard treatments may better be observed.

Clinical

End-organ Damage

The end-organs affected by hypertension include the arterial lining, the heart and kidney, the eye and the brain. Twenty-four hour systolic BP is more strongly associated with mortality than one off clinic measurement. Interestingly masked hypertension in which clinic BPs are normal while 24 hour BPs are elevated is a stronger predictor of mortality than sustained hypertension (both clinic and 24 hour BP raised) or "white coat" (ie clinic only) hypertension. Blood pressures greater than 170/105 are those with a distinctly higher risk of five year death (over 40%).

Evidence of end-organ damage is an indicator for treatment.

Eyes

The fundus of the eye has a special character in that one can see arteries clearly. Classical descriptions of changes in the retinal arteries seem rather crisper than ordinary Practice provides, but the notes of every hypertensive patient should contain a record of ophthalmoscopy and it should be normal in an untreated patient.

Info bulb.pngThe ophthalmoscope was introduced in the middle of the 19th century and became standard in the latter half. (Say 1857 if we leave out early petrol driven ones[4].)
Since the end of the 20th century more advanced optical devices giving wide-angles of view have begun to become popular.

As well as visible changes in vessels, the retina may be affected by hypertension at high levels, with a leakage of fluid producing a movement of the receptors forward from the focal plane, thus a reduction in visual acuity and uneven progress of the process producing a curious pixelated appearance in the central vision similar to that of the faces of unconvicted hooligans on television.

As a very late and very urgent stage of runaway uncontrolled hypertension, papilloedema may occur.

Heart

The ECG likewise reveals at the surface the functioning of a deep part of the circulation. If the left ventricle has had to become thicker in order to push against a sustained high blood pressure then the voltage it produces in the QRS complex will rise, although confounding factors may make this harder to observe.

Info bulb.pngWhen treating a person of Chinese extraction, feel the pulse with three fingers.

The simple test in a thin person of feeling the force of the heartbeat in the praecordium is more likely to be made in retrospect, when people realise that following treatment their heart does not thump so hard. Similarly, ancient mentions of a hard pulse hale from a time before the first measurement of Blood pressure, and reasonable treatment for it if it were greatly raised, but examination of the pulse includes feeling the force.

Investigations

ECG

If left ventricular hypertrophy is present this indicates end-organ damage. Decide to initiate treatment of hypertension at a lower blood pressure if end-organ damage is present than otherwise. See also: hypertension/ECG

Blood tests

  • FBC
  • Renal profile
  • Blood glucose
  • Lipids

Radiology

Treatment

Lifestyle changes

There is no doubt that on an entire population basis these can have a significant impact on cardiovascular morbidity. On an individual basis the evidence is more complex and depends on when the intervention takes place. The earlier and more sustained the better ! In typical Western elderly populations there is no effective immediate reduction in blood pressure by providing an information booklet, using potassium chloride instead of sodium chloride with routine food preparation and encouraging a high fruit, vegetable, fibre and low fat diet.[5]. However the following inteventions do work in studies of more than 6 months:

  • weight loss
  • diet combined with sodium restriction...note 25% compliance rate of most fad diets
  • exercise

The level of effect of such interventions is of the order of 5mm/Hg which helps indicate why they are so effective on a population basis and are less effective than specific medical therapy for individuals.

Medical

In general the mainstream drugs presently utilised to treat hypertension lower the blood pressure by about 10 mm/Hg, Most opinion is also that the reduction of cardiovascular morbidity and mortality is exactly as predicted by this reduction. Certainly it is fascinating to most practitioners how those with an interest in a particular drug have tended to claim otherwise based on selected studies that later comparative studies put in their place. However there is also little doubt that selected and even general outcomes will be achievable with some drugs more easily than others. Medical treatment of hypertension is not necessarily one size fits all. There may be enough evidence to tailor choice of therapy to a particular end organ that needs protecting in an individual, or the individuals likely responsiveness to a drug. The absolute benefit of medical treatment to reduce systolic blood pressure increases with age.[6]. The secondary prevention benefit in ischaemic stroke is likely to be due to the blood pressure lowering actions of the proven drugs.[7] Accordingly treat to an appropriate goal while avoiding adverse effects.

Flag of the United Kingdom.png

The 2011 NICE guidelines were slightly changed compared to 2006. The key changes related to new evidence with regard to race and thiazide therapy. Some inconsistecies are noted: CCBs are more cost-effective than thiazide-type diuretics when using the lowest cost drugs in their class (amlodipine compared to bendroflumethiazide) but NICE now recommends chlortalidone and indapamide as more evidenced based thiazides than bendroflumethiazide or hydrochlorothiazide. It just so happens that the doses of chlortalidone recommended are not marketted in the UK.[8]

Step one

Under 55 and not black people of African or Caribbean family origin
Over 55 or black people of African or Caribbean family origin any age

Step two

Add A + C or D

Step three

A + C + D

Step four

Add if potassium <4.5mmol/l spironolactone, if above 4.5 mmol/l a higher-dose thiazide diuretic and then either betablocker or alpha blocker. Once 4 drug combination fail get expert advice.

Secondary Hypertension

Targeted medical treatment may be appropriate. The use of a beta blocker alone, without appropriate alpha blockade would be contra-indicated with a Phaeochromocytoma. Use of ACE inhibitors or angiotension receptor blockers would not be a good idea with renal artery stenosis.

Surgical

Only in treating secondary hypertension when caused by an endocrinally active tumour.

Prevention

(See also Exercise article.)

Side Effects of Treatment

Excessive treatment can lead to

  • hypotension
    • When significant, hypotension is an important issue. A J shaped curve may exist specifically with those with ischaemic heart disease with post hoc analysis suggesting increased risk of ischaemic events if diastolic BP falls below 85 systolic. [9] Such views may be controversial in guideline authors but much less so with practising clinicians who regularly have to rescue patients from target driven therapy.
  • postural hypotension
  • Death in those over 80. Five year mortality in treated hypertensives over 80 increased as blood pressure was reduced below 139/89 mmHg[10]. This is an interesting result as in the untreated population over 80 BPs below 130/80 are associated with lowest mortality[11]. The message seems to be in this age group to aim for a BP between 130-140/80-90 mmHg as such a large proportion of the limited evidence base in the very old is consistent with increased mortality in patients treated to classic guideline goals[12].

Monitoring treatment

Reasonably accurate, and consistent blood pressure measuring devices have become cheap and deservedly popular. Monitoring BP at home is logical and clearly superior to any reasonable intensity of monitoring based on clinic or general practice attendance. It is not absolutely clear how the readings at home correlate with those in the clinic.[13].

External links

References

  1. Lewington S, Clarke R, Qizilbash N, Peto R, Collins R. Age-specific relevance of usual blood pressure to vascular mortality: a meta-analysis of individual data for one million adults in 61 prospective studies. Lancet. 2002 Dec 14; 360(9349): 1903-13.
  2. Timio M, Verdecchia P, Venanzi S, Gentili S, Ronconi M, Francucci B, Montanari M, Bichisao E. Age and blood pressure changes. A 20-year follow-up study in nuns in a secluded order. Hypertension. 1988 Oct ; 12(4): 457-61
  3. Espeland MA, Kumanyika S, Yunis C, Zheng B, Brown WM, Jackson S, Wilson AC, Bahnson J. Electrolyte intake and nonpharmacologic blood pressure control. Ann Epidemiol. 2002 Nov ; 12(8): 587-95.
  4. [1]
  5. Little P, Kelly J, Barnett J, Dorward M, Margetts B, Warm D. Randomised controlled factorial trial of dietary advice for patients with a single high blood pressure reading in primary care. BMJ. 2004 May 1; 328(7447): 1054
  6. Wang JG, Staessen JA, Franklin SS, Fagard R, Gueyffier F. Systolic and diastolic blood pressure lowering as determinants of cardiovascular outcome. Hypertension. 2005 May ; 45(5): 907-13.
  7. Macmahon S, Neal B, Rodgers A, Chalmers J. The PROGRESS trial three years later: time for more action, less distraction. BMJ. 2004 Oct 23;329(7472):970-1. Also available on-line at the BMJ on-line.
  8. Whatever happened to thiazides? DTB doi:10.1136/dtb.2011.02.0070
  9. Messerli FH, Mancia G, Conti CR, Hewkin AC, Stuart Kupfer S, Champion A, Kolloch R, Benetos A, Pepine CJ. Dogma Disputed: Can Aggressively Lowering Blood Pressure in Hypertensive Patients with Coronary Artery Disease Be Dangerous? Ann Int Med 2006;144(12):884-893
  10. Oates DJ, Berlowitz DR, Glickman ME, Silliman RA, Borzecki AM. Blood pressure and survival in the oldest old. Journal of the American Geriatrics Society. 2007 Mar; 55(3):383-8.(Link to article – subscription may be required.)
  11. Satish S, Freeman DH, Ray L, Goodwin JS. The relationship between blood pressure and mortality in the oldest old. Journal of the American Geriatrics Society. 2001 Apr; 49(4):367-74.
  12. Chobanian AV. Clinical practice. Isolated systolic hypertension in the elderly. The New England journal of medicine. 2007 Aug 23; 357(8):789-96.(Link to article – subscription may be required.)
  13. http://bmj.bmjjournals.com/cgi/content/full/329/7471/870