Hypertension which is also referred to as high blood pressure is a medical condition in which the blood pressure is chronically elevated. It is considered to be present when a person's systolic blood pressure is consistently 140 mm Hg or greater, and/or their diastolic blood pressure is consistently 90 mmHg or greater. Hypertension may be systemic or pulmonary. But the term hypertension usually refers to systemic hypertension
Different populations have different levels of blood pressure. This level varies with age, sex, race & country. African origin people have a tendency of high blood pressure than Caucasians. For practical purposes, the cut-offs from normal levels to high blood pressure are as follows:
(A) Optimal: Blood pressure is considered to be optimal when systolic pressure is less than 120 mm Hg; diastolic pressure is less than 80 mm Hg.
(B) Normal: Blood pressure is considered to be normal when systolic pressure is less than 130 mm Hg, diastolic pressure is less than 85 mm Hg.
(C) High normal: Blood pressure is considered to be high normal when systolic pressure is 130-139 mm Hg, diastolic pressure is 85-89 mm Hg.
(D) High blood pressure: Blood pressure is considered to be high when systolic pressure is above 140 mm Hg, diastolic pressure is above 90 mm Hg. It may also be graded into-
1) Mild- When systolic pressure is 140-159 mm Hg, diastolic pressure is 90-99 mm Hg.
2) Moderate- When systolic pressure is 160-179 mm Hg, diastolic pressure is 100- 109 mm Hg.
3) Severe- When systolic pressure is 180-209 mm Hg, diastolic pressure is 110-119 mm Hg.
But according to another school, blood pressure is supposed to be normal if it is below 120/80. The range of blood pressure from 120/80 mmHg to 139/89 mmHg is regarded as “Prehypertension” which though not a disease category but is definitely a designation chosen to identify people at high risk of developing hypertension. In patients with diabetes mellitus or kidney diseases, however, blood pressure over 130/80 mmHg should be considered high and warrants further treatment.
Classification According to Causes-
(I) Primary or essential hypertension-In large majority of cases, no cause can be found & this constitutes what is known as primary or essential hypertension.
Causes of essential hypertension are the following-
(A) Genetic factors- Racial & familial tendencies to hypertension are found. It is postulated that the inheritance is probably multifactorial or that a number of different genetic defects each have an elevated blood pressure as one of their phenotypic expressions.
(B) Sex-Males are at a higher risk for hypertension at earlier ages than females.
(C) Age- Usually above 40 years. Age plays its role by the fact that with increasing age the number of collagen fibers in artery and arteriole walls increases, making blood vessels stiffer. With reduced elasticity the cross-sectional area of the vessel becomes smaller in systole with the result of a raised mean arterial blood pressure.
(D) Environmental factors- Of the various factors related to the development of hypertension the following are important-
1) Obesity- BP rises with increasing obesity.
2) Alcohol intake- Alcohol ingestion acutely raises BP & at the same time alcohol intake seems to be higher in hypertensives.
3) Salt intake- Salt plays a controversial role in hypertension but has drawn a tremendous attention as an environmental factor in the causation of hypertension. It is claimed by many researchers that a portion of the essential hypertensive population is responsive to sodium intake. This is due to the fact that due to osmotic pressure, increasing amounts of salt in a person's bloodstream cause cells to release water to make an equilibrium of concentration gradient of salt between the cells and the bloodstream which in turn increases the pressure on the blood vessel walls. But it is argued by some others that salt intake may increase intravascular volume in the initial stages causing hypertension, but once peripheral vascular resistance increases, alteration salt intake may play little part in the regulation of BP.
(E) Humoral factors-These including catecholamines, rennin-angiotensin system, atrial natriuretic peptide have been implicated as causative factors for hypertension which is yet to be proved.
(II) Secondary hypertension- In rest of the cases which is usually less than 10%, an underlying cause can be found & this constitutes what is known as secondary hypertension. Secondary hypertension is more common in preadolescent children, with most cases caused by kidney diseases. Secondary hypertension should always be excluded in any case of hypertension by careful search & necessary investigations, particularly in hypertensive patients below the age of 35 years.
Causes of secondary hypertension are the following-
(1) Renal causes- Renal diseases are the most frequent causes of secondary hypertension, accounting for more than 80% of cases. Renal causes usually include chronic glomerulonephritis, polycystic kidney, renal artery stenosis etc.
(2) Endocrinal causes- Endocrinal causes usually include Conn’s syndrome, Acromegaly, Phaeochromocytoma, Cushing’s syndrome etc.
(3) Cardiovascular causes- Coarctation of aorta is occasionally a cause of secondary hypertension in young patients.
(4) Metabolic causes- These usually include diabetes mellitus, toxaemia of pregnancy etc.
(5) Iatrogenic causes- Oestrogen-containing contraceptives, other steroids, carbenoxolone, liquorice & vasopressine may sometimes cause secondary hypertension.
Clinical features- A patient with mild hypertension is occasionally asymptomatic. Nasal bleeding & headaches may be there but are probably no commoner than in the general population. In the majority of cases, the only sign is the high blood pressure & in some others features of the target organ involvement or risk factors may be noted. Secondary hypertension may have additional symptoms of the associated causative disease. In brief in addition to the features of the target organ involvement or risk factors or the associated causative disease, the following symptoms may be present which may be headache, easy fatigue, dizziness, lack of concentration, interference with memory, blurred vision, facial flushing, transient insomnia or difficulty in sleeping, breathlessness, occasional palpitation etc.
On examination-
(A) General examination-
BP- Above140/90 mm Hg.
Pulse- Rate may be slow at times, volume is high, bounding in nature. Vessel wall may be thick. There may be delayed femoral pulses in case of coarctation of aorta.
(B) Examination of the heart- Apex beat may be more down & forceful. If there is left ventricular hypertrophy, the character of the apex beat may be heaving. Over the mitral area the first heart sound may be loud & booming. There may occasionally be a soft systolic murmur due to dilatation of the heart. Aortic second sound is loud, accentuated & ringing in nature.
(C) Examination of the abdomen- Auscultation over the lumbar area may reveal a soft bruit, which indicates renovascular obstruction. Signs of enlarged kidneys, masses etc may also be found.
(D) Examination of the eye- Ophthalmoscopic examination may show arteriolar narrowing, focal arteriolar constrictions, arteriovenous crossing changes, hemorrhages, exudates, disc edema. The presence of haemorrhages, exudates or papilloedema is diagnostic of malignant hypertension.
(E) Examination of the neck- It may reveal carotid bruits, distended veins, or an enlarged thyroid gland.
(F) Examination of the lungs- Auscultation over the chest area may reveal rales and evidence for bronchospasm.
Investigations- In most cases, extensive tests are not needed to diagnose high blood pressure. If a blood pressure measurement at any time shows a high systolic and/or diastolic blood pressure, usually two more measurements at separate times are to be done to confirm a case of hypertension. But investigations are required to detect any underlying cause, to detect extent of damage of any target organ & to detect the associated risk factors. Moreover it helps to get a baseline of organ health prior to the start of drug therapies, and to monitor hypertension control and organ status over time.
Routine investigations of a case of hypertension should include the following-
(A) Chest X –ray- This is done for signs of cardiac enlargement or evidence of cardiac failure. It may also reveal pulmonary congestion if there is heart failure or rib notching if there is coarctation of aorta.
(B) ECG - This is necessary for getting any evidence of the heart being under strain from working against a high blood pressure as well as to detect any damage already done to the heart. Very rarely features of hyperkalemia or hypokalemia may be detected.
(C) Echocardiogram- This also may be done to determine whether there is any damage to the heart.
(D) Urinanalysis - This helps to assess kidney function.
(E) BUN (Blood Urea Nitrogen) and/or and/or Creatinine - This is necessary to detect and monitor kidney dysfunction or to monitor the effect of medications on the kidneys.
(F) Fasting blood lipids- Lipid profile (total cholesterol, high density lipoprotein [HDL]-cholesterol, low density lipoprotein [LDL]-cholesterol and triglycerides) is necessary because both elevated LDL cholesterol & low HDL cholesterol are major risk factors.
(G) Blood glucose- Diabetes mellitus being additional risk factor for the development of cardiovascular disease, blood glucose estimation is essential.
Additional laboratory and diagnostic studies may be required in individuals with suspected secondary hypertension and/or evidence of target-organ disease. Some of these tests are needed for determining presence of target organ disease and possible causes of hypertension. Others relate to cardiovascular risk factors or provide baseline values for judging biochemical effects of therapy.
Complications-
(1) Cardiac & vascular- These usually include hypertensive heart disease, coronary artery disease, dissecting aortic aneurysms & peripheral vascular disease.
(2) Cerebral- These usually include cerebral haemorrhage, cerebral thrombosis, hypertensive encephalopathy.
(3) Renal- Chronic kidney disease
(4) Ocular- Hypertensive retinopathy.
Mode of termination-
(1) Acute left ventricular failure in most of the cases.
(2) Cerebral haemorrhage & other episodes in some cases.
(3) Very rarely uraemia.
Treatment- First of all the secondary causes of hypertension should be excluded, especially in young adults. In case of mild to moderate hypertension it is very difficult to persuade a patient if he is asymptomatic. But it is wise to treat it. A patient with diastolic pressure above 100 mm Hg should always be actively treated. If diastolic pressure is between 90-100 mm Hg it should be reassessed on several occasions with the patient in a comfortable, relaxed position & if the diastolic pressure is found to be above 90 mm Hg it should always be actively treated, especially in young adults & if there is any end-organ damage. Mild to moderate hypertension in case of a very old patient , especially above 80 years of age may be exempted. However, patients between 65-80 years with diastolic pressure above 90 mm Hg or systolic pressure above 160 mm Hg or both are always benefited from treatment. Nevertheless it is better to treat patients of all ages with a persistent systolic pressure above 160 mm Hg.
(A) General measures-A change in patient’s life-style & food habit may help in reduction of BP to some extent.
(1) Weight reduction- Obese patients on reduction of weight always have a true fall in blood pressure.
(2) Reduction of heavy alcohol consumption- Alcohol affects both systolic and diastolic pressures, but its effects appear to be greater on systolic pressure. So reduction of heavy alcohol consumption is also beneficial & may lead to fall in blood pressure of about 5-10 mm Hg.
(3) Salt restriction- This is usually of little value except in some persons & so it is better to advise the patient not to use additional salt at the table.
(4) Regular exercise- Aerobic physical activity is supposed to be beneficial for both prevention and treatment of hypertension.
(5) Tobacco Avoidance- This is to be strictly followed because nicotine not only may increase blood pressure but also may account for some degree of blood pressure lability. In addition, it is a major risk factor for atherosclerotic cardiovascular disease.
(6) Potassium supplementation- There is no direct evidence that potassium supplementation lowers blood pressure chronically.
(7) Meditation & Biofeed back- These techniques are claimed to lead to reduction of BP. Yoga is now practiced all over the globe for having a healthy body & mentality & it is particularly useful for essential hypertension.
(8) Reduction of stress and anxiety - This is particularly useful for essential hypertension & is done by counseling or by yoga.
(B) Drug therapy- Drug choice should be based on ‘individual care approach’ instead of ‘stepped care approach’ depending on the requirement of individual patient with the pharmacological & clinical properties of an appropriate antihypertensive agent & the usual choice is made from the following either as a single drug or a combination-
(1) Calcium channel blockers- There are a large number of chemically diverse calcium channel blockers (CCBs) with different pharmacological profiles, of which Verapamil, Nifedipine & Diltiazem represent the three most important classes. They lower BP by decreasing peripheral resistance without compromising cardiac output.
(2) Angiotensin converting enzyme (ACE) inhibitors-They act by blocking the conversion of angiotensin I to angiotensin II & thus cause vasodilatation of peripheral arterioles. Though these are extremely valuable for use in renovascular & resistant hypertension they are now regarded as one of the first choice antihypertensives in all grades of hypertension, especially where quality of life considerations are important. Used alone they can control hypertension in 50-60 % of cases & the efficacy increases on addition of a diuretic. They are found to increase life expectancy in elderly hypertensives. They can be safely used in asthmatics, diabetics & peripheral vascular disease patients. There is no rebound hypertension on withdrawal. They are also supposed to cause reverse ventricular hypertrophy which is common in hypertensives.
(3) Diuretics - Diuretics have been in use for many years & in some cases they are used as first choice agents. One important advantage of using them is that they do not lower BP in normotensives. They exert their hypotensive effect by minimizing salt content of the body & also by vasodilatation to some extent.
(4) Beta-Adrenergic blockers- They are mild antihypertensives that do not significantly lower BP in normotensives & when used alone can control hypertension in 30-40 % patients who are mostly varying from mild to moderate hypertensives. In the large majority of cases they are usefully combined with other drugs. control
(5) Alpha-Adrenergic blockers- Selective Alpha-Adrenergic blocker like Prazosin are very effective hypotensive drugs that produce vasodilatation.
Planning of therapy for the control hypertension- The target should always be to maintain BP below 140/90 mm Hg and still lower in certain associated conditions such as diabetes or kidney disease. Unless hypertension is severe, lifestyle changes are strongly recommended before initiation of drug therapy. If the general restrictions & life-style adjustments fail to lower BP to the desired level or the hypertension is severe, it is better to use either a Beta-Adrenergic blocker or a diuretic. But in no case lifestyle changes should be stopped. Diuretics are preferable if heart failure or peripheral vascular disease is present whereas Beta-Adrenergic blockers are preferable if there is angina. Calcium channel blockers may also be used as a first line therapy. If single drug therapy cannot lead to the desired result, a diuretic may be added either with a Beta-Adrenergic blocker or with a Calcium channel blocker. If this combined therapy is also found to be insufficient, more powerful vasodilators like Prazosin is to be added to this regimen. Angiotensin converting enzyme inhibitors may be used if these prove inadequate, especially if there is associated diabetes mellitus & a diuretic may be added to increase the hypotensive effect of ACE inhibitors.
Prevention- As the underlying cause of essential hypertension is yet to be established, avoidance of the known risk factors is the only way to be followed strictly to prevent essential hypertension. The best ways for avoiding the known risk factors are ensurance of a low salt diet, restrain from smoking, avoidance of high-cholesterol and fatty foods, reduction of alcohol consumption, participation in adequate regular exercise, reduction of stress and anxiety by counseling. These measures if practiced properly may help in keeping blood pressure within control.
Some points to be borne in mind-
(1) Family history of hypertension should always be kept in mind as risk is higher in people whose parents also have high blood pressure.
(2) Routine fundoscopic eye exam should always be done to look for any hypertensive changes of the retina especially for changes typical of malignant hypertension.
(3) Routine neurological assessment in details should always be done.
(4) Confirmation of hypertension should be based on the initial visit, plus two follow-up visits with at least two blood pressure measures at each visit, taken at least 2 minutes apart. Verification should be done by measuring blood pressure in the contralateral arm & if values are different, the higher value should be taken.
(5) While recording blood pressure, the patient should sit with his arms supported at heart level & before this the patient should sit down for at least 5 minutes.
(6) The patient should not smoke or ingest caffeine for 30 minutes prior to blood pressure measurement.
(7) Systolic blood pressure level should be the major factor for the detection, evaluation, and treatment of hypertension, especially in adults 50 years and older.
(8) A thiazide-type diuretic should be considered as initial therapy in most patients with uncomplicated hypertension.
(9) Fewer than 50% of patients with hypertension will be controlled with a single drug. When choosing antihypertensive drugs, preference should be given to long-acting drugs that can be dosed once daily to enhance long-term compliance.
(10) If the initial response to one drug is adequate, the same drug should be continued. But if the response is partial, the dose should either be increased or a second drug of a different class should be added. It is better to use a low-dose diuretic as a first addition.
(11) If there is little response to one drug, it should be substituted by a single drug from a different class.
(12) The use of combination agents can be effective. But two drugs of the same class should never be combined.
(13) Hypertension never goes away after a single dose or treatment & treatment is to be continued for many years or for life.
(14) Since treatment is usually life long, BP should be checked at regular intervals & the physician must try to simplify treatment regimen for better compliance.
(15) The patient should be made to understand that though poor treatment is better than no treatment at all, he should stick to the treatment schedule for avoidance of the consequences of hypertension.
Risk Assessment- The risk for cardiovascular disease in patients with hypertension is determined not only by the level of blood pressure but also by the presence or absence of target organ damage or other risk factors such as smoking, dyslipidemia and diabetes. These factors independently modify the risk for subsequent cardiovascular disease, and their presence or absence is determined during the routine evaluation of patients with hypertension like history, physical examination, laboratory tests etc.
Prognosis of hypertension- Though hypertension itself may lead to a number of complications, effective reduction of BP results in a dramatic improvement of prognosis. Untreated malignant hypertension has of course a very bad prognosis. Treatment of even mild hypertension reduces the likelihood of morbidity & mortality. Prognosis of hypertension in general depends on the following-
(1) Age- Young patients have worse prognosis than the old.
(2) Sex- Males are at more risk than the females.
(3) Degree of hypertension.
(4) Family history of hypertension.
(5) Behaviour after therapy.
(6) Degree of ischaemic myocardial changes.
(7) Degree of cardiac decompensation.
(8) History of cardiac failure.
(9) Degree of renal impairment.
(10) Ocular changes.
(11) Presence of risk factors for coronary disease like diabetes mellitus, high plasma lipids, smoking etc.
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