According to the World Health Organization (WHO), hypertension is responsible for approximately 7.1 million premature deaths annually worldwide. It is the most important risk factor for stroke, and is also a major risk factor for cardiovascular disease (CVD). The relative risk of stroke or CVD increases as the blood pressure increases. It is for these reasons that management of hypertension is vital, and failure to control it leads to an increased risk of mortality.

 

Blood pressure within populations follows a normal distribution, with no distinct point at which individuals with hypertension may be separated from individuals with normal blood pressure. As in accordance with the WHO, the most effective classification of hypertension incorporates the values of blood pressure above which interventional pharmacological management becomes most effective. In individuals with a low risk of developing CVD or stroke, this has been found to be the following:

 

  • A consistent measurement of systolic blood pressure above 140 mmHg
  • A consistent measurement of diastolic blood pressure above 90 mmHg

 

Values are slightly lower for patients with other chronic conditions, such as diabetes and chronic kidney disease.

 

Types 

 

  • Essential/Primary Hypertension: This accounts for more than 95% of the cases of hypertension. At present there is no identifiable underlying cause for it. It is progressive, and is known as the ‘silent killer’ because of the absence of symptoms in most cases. Without being picked up early this high blood pressure can go unnoticed and increase the risk of CVD or stroke.

 

  • Secondary Hypertension: Hypertension with an identifiable underlying cause. This includes a variety of conditions, such as renal disease, endocrine disorders such as hyperthyroidism, phaeochromocytoma, Cushing's syndrome and Conn's syndrome, and alcohol. Medications which can cause secondary hypertension include NSAIDS, corticosteroids, anticonvulsants, mood-stabilizing drugs, oestrogen-containing oral contraceptives, and Parkinsonian medication (e.g. methyldopa). Pregnancy too can lead to hypertension in many mothers.

 

  • Accelerated Hypertension: Severe blood pressure (i.e. above 200/130mmHg) in conjunction with fundal haemorrhages.

 

Other types include white-coat hypertension, and pregnancy-induced hypertension.

 

Classification of Blood Pressure

Classification of Blood Pressure

 

Risk Factors

 

The aetiology of essential hypertension is not fully known. Several risk factors increase the probability of developing hypertension, including the following:

 

  • Age
  • Race
  • High salt intake
  • Low potassium intake
  • Obesity
  • Alcohol
  • Family history

 

 

Signs

 

Classically, essential hypertension rarely presents with any signs. However, signs of secondary causes may be found on clinical examination. Direct effects of chronic hypertension on organs may manifest themselves fairly late. Cardiac signs include ventricular hypertrophy, which can be detected by a thrusting apex beat. An ECG may reveal a ventricular strain, and an echocardiogram may display ventricular wall thickening. Hypertensive cardiomyopathy can also lead to heart failure, giving rise to signs such as bi-basal crackles on pulmonary auscultation, a raised JVP, and peripheral oedema. Rarely, an S3 or S4 heart sound may be heard upon auscultation of the heart. Hypertensive retinopathy may also be seen during opthalmoscopy in long-standing or malignant forms of hypertension. This is graded from I-IV. Signs of renal failure may also be found if significant damage to the kidneys has occurred. This may also include a worsening of hypertension itself.

 

Complications

 

Hypertension accelerates the rate of atherosclerosis in at-risk patients, as well as directly causing damage to smaller blood vessels, leading to various complications including the following:

 

  • Stroke
  • Cardiovascular disease
  • Cardiac failure
  • Peripheral vascular disease
  • Chronic kidney disease
  • Hypertensive retinopathy

 

Hypertension is an independant risk factor for ischaemic heart disease, and also exponentially increases the risk when present in conjunction with other risk factors, such as diabetes mellitus, obesity, smoking, and a positive family history for ischaemic heart disease. Hence it is vital to manage hypertension as early as possible.

 

Investigations

 

Blood pressure can be measured either manually with a sphygmomanometer, or with an electronic equivalent. The BHS recommends that the reduction in pressure during manual recording is no more than 2 mmHg per second, and that the blood pressure reading is recorded to the nearest 2 mmHg.

 

Hypertension is not diagnosed by a single measurement of blood pressure, but following repeated recordings over a period of days or even weeks. If the clinical blood pressure recorded is 140/90mmHg or higher, then ambulatory blood pressure monitoring (ABPM) is recommended. This involves two recordings per hour during a patient's normal waking hours, and subsequently taking the average of at least 14 of the lowest readings. Alternatively patients can undertake home blood pressure monitoring (HBPM), which looks at readings taken over one week. Once an average of 140/90 mmHg or higher has been recorded, pharmacological treatment should be offered.

 

Patients who are diagnosed with hypertension require further investigations:

  • Height
  • Weight 
  • Urine dipstick for proteinuria and haematuria.
  • Serum urea, creatinine and electrolytes
  • Fasting blood glucose
  • Full lipid profile
  • Electrocardiogram (ECG)

 

Patients are also assessed for the risk of cardiovascular disease (CVD). This can be done using a cardiovascular disease chart and risk calculator. Assessment of the risk of CVD helps to guide the management of hypertensive patients. Patients who are diagnosed with severe or secondary hypertension, or have problems with therapy are referred to a specialist.

 

Management

 

Management should reflect not only the pursuit of reducing blood pressure in hypertensive patients, but also be based upon the presence of risk factors for CVD and diabetes, amongst other conditions. The patient’s social and personal factors should also be taken into consideration during the course of management. The following guidelines are recommended the British Hypertension Society (BHS) and NICE.

 

 

 

Algorithm for pharmacological intervention



As shown in the above algorithm, pharmacological management plans differ for younger and older patients, and black and non-black patients. Initially younger patients (<55 years) are started on an ACE-inhibitor, such as ramipril (typical starting dose 2.5mg once daily) (or an angiotensin-II receptor blocker (ARB) if ACE-inhibitors are contraindicated, or side effects such as a dry cough or persistent hyperkalaemia become intolerable. Examples include losartan, 25 - 100mg once daily). ACE-inhibitors are particularly useful in diabetics as it reduces microalbuminuria and proteinuria. *However, DO NOT use in those with renal artery stenosis as it lowers eGFR & worsens renal function due to its efferent arteriole dilatation effects which reduces renal perfusion.

 

In older patients (>55 years) or black patients of any age, a calcium-channel blocker such as amlodipine (2.5 - 10mg once daily) is first used. Typical side effects include peripheral oedema and flushing. If blood pressure subsequently fails to lower to desired levels for patients in either group, then both drugs are combined.

 

If two drugs still proves inadequate, then a thiazide-like diuretic such as chlortalidone (12.5 - 25.0mg once daily) or bendroflumethiazide (2.5mg once daily) can added. Blood pressure that remains high despite the use of three drugs is termed 'resistant hypertension'. Subsequently other types of drugs can be introduced, such as alpha-blockers, beta-blockers, or aldosterone antagonists.

 

Blood pressure targets for patients aged under 80 years should be lower than 140/90 mmHg, and lower than 150/90 mmHg in patients aged over 80 years. More stringent targets are employed in patients with diabetes and chronic kidney disease. (eg. below 130/80 if there is evidence of kidney, eye or cerebrovascular complications)

 

Treated patients are reviewed every 6 months to 1 year, where progress is assessed, and advice regarding adherence to medication and lifestyle modifications is reinforced.

 

Summary

 

Hypertension is a prevalent condition, which increases the risk of stroke and cardiovascular disease. It can lead to many other complications, including chronic kidney disease and hypertensive neuropathy. Diagnosing and managing hypertension early is therefore of extreme importance. Management guidelines take into account patient age and race, as well as other comorbidities. Lifestyle advice is given to hypertensive patients at first, followed by pharmacological management for patients with more severe forms. 

Selected References

 

Whitworth JA; World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. J Hypertens. 2003; 21: 1983-92.

 

MacMahon S, Peto R, Cutler J, Collins R, Sorlie P, Neaton J, Abbott R, Godwin J, Dyer A, Stamler J. Blood pressure, stroke, and coronary heart disease, part I: prolonged differences in blood pressure: prospective observational studies corrected for the regression dilution bias. Lancet. 1990; 335: 765-774.

 

Vikrant S, Tiwari SC. Essential Hypertension – Pathogenesis and Pathophysiology. Journal, Indian Academy of Clinical Medicine. 2001; 2: 140-161.

 

Williams W, Poulter NR, Brown MJ, Davis M, McInnes GT, Potter JF, Sever PS, Thom SM. British Hypertension Society guidelines for hypertension management 2004 (BHS-IV): summary. BMJ. 2004; 328: 634-640.

 

Onusko E. Diagnosing Secondary Hypertension. Am Fam Physician. 2003; 67: 67-74.

 

Practice Guidelines Writing Committee. Practice Guidelines For Primary Care Physicians: 2003 ESH/ESC Hypertension Guidelines. J Hypertens. 2003; 21: 1779-1786.

 

National Institute for Health and Clinical Excellence. Hypertension. Clinical management of primary hypertension in adults. Quick reference guide. NICE clinical guideline 127. NICE, 2011.

 

Heagerty, A. Optimizing hypertension management in clinical practice. Journal of Human Hypertension. 2006; 20: 841–849.

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