or high blood pressure is a medical condition wherein the
blood pressure is chronically elevated. While it is formally
called arterial hypertension, the word "hypertension"
without a qualifier usually refers to arterial hypertension.
Persistent hypertension is one of the risk factors for
strokes, heart attacks, heart failure and arterial aneurysm,
and is a leading cause of chronic renal failure.
Hypertension is usually
diagnosed on finding blood pressure of 140/90 mmHg or above,
measured on both arms. Because blood pressure readings in
many individuals are highly variable — especially in the
office setting — the diagnosis of hypertension should be
made only after noting a mean elevation on two or more
readings on two or more office visits, unless the elevations
are severe or associated with compelling indications such as
diabetes mellitus, chronic kidney disease, heart failure,
post-myocardial infarction, stroke, and high coronary
Recently, the JNC 7 (The Seventh Report of the Joint
National Committee on Prevention, Detection, Evaluation, and
Treatment of High Blood Pressure) has defined blood
pressure 120/80 mmHg to 139/89 mmHg as "prehypertension."
Prehypertension is not a disease category; rather, it is a
designation chosen to identify individuals at high risk of
In patients with diabetes mellitus or kidney disease studies
have shown that blood pressure over 130/80 mmHg should be
considered a risk factor and may warrant treatment.
Age. Over time, the number of
collagen fibers in artery and arteriole walls increases,
making blood vessels stiffer. With the reduced elasticity
comes a smaller cross-sectional area in systole, and so a
raised mean arterial blood pressure.
High salt intake
High levels of saturated fat in the diet
Obesity - In obese subjects, losing a kilogram of mass
generally reduces blood pressure by 2 mmHg.
Various genetic causes
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While most forms of
hypertension have no known underlying cause (and are thus
known as "essential hypertension" or "primary
hypertension"), in about 5% of the cases, there is a known
cause, and thus the hypertension is secondary hypertension.
The mechanisms behind the
factors associated with inessential hypertension are
generally fully understood, and are outlined at secondary
hypertension. However, those associated with essential
hypertension are far less understood. What is known is that
cardiac output is raised early in the disease course, with
total peripheral resistance normal; over time cardiac output
drops to normal levels but TPR is increased. Three theories
have been proposed to explain this:
Inability of the kidneys to
excrete sodium, resulting in natriuretic factor (note: the
existence of this substance is theoretical) being secreted
to promote salt excretion with the side-effect of raising
total peripheral resistance.
An overactive renin / angiotension system leads to
vasoconstriction and retention of sodium and water. The
increase in blood volume leads to hypertension.
An overactive sympathetic nervous system, leading to
increased stress responses.
Signs and symptoms
Hypertension is usually
found incidentally - "case finding" - by healthcare
professionals. It normally produces no symptoms.
(or accelerated hypertension) is distinct as a late phase in
the condition, and may present with headaches, blurred
vision and end-organ damage.
It is recognised that
stressful situations can increase the blood pressure; if a
normally normotensive patient has a high blood pressure only
when being reviewed by a healthcare professional, this is
colloquially termed white coat effect. Since most of
what we know of hypertension and its outcome with or without
modification is based on large series of readings in
doctors' offices and clinics (e.g., Framingham), it is
difficult to be sure that white-coat hypertension is not
significant. Ambulatory monitoring may help determine
whether traffic and ticket inspectors produce similar
Hypertension is often
confused with mental tension, stress and anxiety. While
chronic anxiety is associated with poor outcomes in people
with hypertension, it alone does not cause it.
Hypertensive urgencies and
Hypertension is rarely
severe enough to cause symptoms. These only surface with a
systolic blood pressure over 240 mmHg and/or a diastolic
blood pressure over 120 mmHg. These pressures without signs
of end-organ damage (such as renal failure) are termed
"accelerated" hypertension. When end-organ damage is
possible or already ongoing, but in absence of raised
intracranial pressure, it is called hypertensive emergency.
Hypertension under this circumstance needs to be controlled,
but prolonged hospitalization is not necessarily required.
When hypertension causes increased intracranial pressure, it
is called malignant hypertension. Increased intracranial
pressure causes papilledema, which is visible on
ophthalmoscopic examination of the retina.
While elevated blood
pressure alone is not an illness, it often requires
treatment due to its short- and long-term effects on many
organs. The risk is increased for:
Cerebrovascular accident (CVAs
Myocardial infarction (heart attack)
Hypertensive cardiomyopathy (heart failure due to
chronically high blood pressure)
Hypertensive retinopathy - damage to the retina
Hypertensive nephropathy - chronic renal failure due to
chronically high blood pressure
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Hypertension of pregnancy
Although few women of
childbearing age have high blood pressure, up to 10% develop
hypertension of pregnancy. While generally benign, it may
herald three complications of pregnancy: pre-eclampsia,
HELLP syndrome and eclampsia. Follow-up and control with
medication is therefore often necessary.
Measuring blood pressure
Diagnosis of hypertension is
generally on the basis of a persistently high blood
pressure. Usually this requires three separate measurements
at least one week apart. Exceptionally, if the elevation is
extreme, or end-organ damage is present then the diagnosis
may be applied and treatment commenced immediately.
Obtaining reliable blood
pressure measurements relies on following several rules and
understanding the many factors that influence blood pressure
For instance, measurements
in control of hypertension should be at least 1 hour after
caffeine, 30 minutes after smoking and without any stress.
Cuff size is also important. The bladder should encircle and
cover two-thirds of the length of the arm. The patient
should be sitting for a minimum of five minutes. The patient
should not be on any adrenergic stimulants, such as those
found in many cold medications.
When taking manual
measurements, the person taking the measurement should be
careful to inflate the cuff suitably above anticipated
systolic pressure. A stethoscope should be placed lightly
over the brachial artery. The cuff should be at the level of
the heart and the cuff should be deflated at a rate of 2 to
3 mmHg/s. Systolic pressure is the pressure reading at the
onset of the
sounds described by
Korotkoff (Phase one). Diastolic pressure is then
recorded as the pressure at which the sounds disappear (K5)
or sometimes the K4 point, where the sound is abruptly
muffled. Two measurements should be made at least 5 minutes
apart, and, if there is a discrepancy of more than 5 mmHg, a
third reading should be done. The readings should then be
averaged. An initial measurement should include both arms.
In elderly patients who particularly when treated may show
orthostatic hypotension, measuring lying sitting and
standing BP may be useful. The BP should at some time have
been measured in each arm, and the higher pressure arm
preferred for subsequent measurements.
BP varies with time of day,
as may the effectiveness of treatment, and
archetypes used to record the data should include the
time taken. Analysis of this is rare at present.
Distinguishing primary vs.
Once the diagnosis of
hypertension has been made it is important to attempt to
exclude or identify reversible (secondary) causes.
Over 90% of adult
hypertension has no clear cause and is therefore called
essential/primary hypertension. Often, it is part of the
metabolic "syndrome X" in patients with insulin resistance:
it occurs in combination with diabetes mellitus (type 2),
combined hyperlipidemia and central obesity.
In hypertensive children most cases are secondary
hypertension, and the cause should be pursued diligently.
commonly performed in a newly diagnosed hypertension patient
Creatinine (renal function)
Electrolytes (sodium, potassium)
Glucose (to identify diabetes mellitus)
The level of blood pressure
regarded as deleterious has been revised down during years
of epidemiological studies. A widely-quoted and important
series of such studies is the
Framingham Heart Study carried out in an American town:
Framingham, Massachusetts. The results from Framingham
and of similar work in
Busselton, Western Australia have been widely applied.
To the extent that people are similar this seems reasonable,
but there are known to be genetic variations in the most
effective drugs for particular sub-populations. Recently (2004),
the Framingham figures have been found to overestimate risks
for the UK population considerably. The reasons are unclear.
Nevertheless the Framingham work has been an important
element of UK health policy.
Doctors recommend weight loss
and regular exercise as the first steps in treating mild to
moderate hypertension. These steps are highly effective in
reducing blood pressure, but easier to suggest than to
achieve, and most patients with moderate or severe
hypertension end up requiring indefinite drug therapy to
bring their blood pressure down to a safe level.
Discontinuing smoking does not directly reduce blood
pressure, but is very important for people with hypertension
because it reduces the risk of many dangerous outcomes of
hypertension, such as stroke and heart attack.
Mild hypertension is usually treated by diet, exercise and
improved physical fitness. A diet rich in fruits and
vegetables and fat-free dairy foods and low in fat and
sodium lowers blood pressure in people with hypertension.
Dietary sodium (salt) causes hypertension in some people and
reducing salt intake decreases blood pressure in a third of
people. Regular mild exercise improves blood flow, and helps
to lower blood pressure.
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There are many classes of
medications for treating hypertension, together called
antihypertensives, which — by varying means — act by
lowering blood pressure. Evidence suggests that reduction of
the blood pressure by 5-6 mmHg can decrease the risk of
stroke by 40%, of coronary heart disease by 15-20%, and
reduces the likelihood of dementia, heart failure, and
mortality from vascular disease.
Which type of medication to
use initially for hypertension has been the subject of
several large studies. The JNC7 recommends starting with a
thiazide diuretic if single therapy is being initiated and
another medication is not indicated.
This is based on a slightly better outcome for
chlortalidone in the ALLHAT study versus other anti-hypertensives
and because thiazide diuretics are relatively cheap.
A subsequent smaller study (ANBP2) published after the JNC7
did not show this small difference in outcome and actually
showed a slightly better outcome for ACE-inhibitors in older
Despite thiazides being
cheap, effective, and recommended as the best first-line
drug for hypertension by many experts, they are not
prescribed as often as some newer drugs. Arguably, this is
because they are off-patent and thus rarely promoted by the
Physicians may start with
non-thiazide antihypertensive medications if there is a
compelling reason to do so. An example is the use of
ACE-inhibitors in diabetic patients who have evidence of
kidney disease, as they have been shown to both reduce blood
pressure and slow the progression of
diabetic nephropathy. In patients with coronary artery
disease or a history of a heart attack, beta blockers and
ACE-inhibitors both lower blood pressure and protect heart
muscle over a lifetime, leading to reduced mortality.
Commonly used drugs include:
Beta blockers: eg,
metoprolol (Lopressor®), atenolol, labetalol, carvedilol (Coreg®)
ACE inhibitors: eg, lisinopril (Zestril®), quinapril,
fosinopril (Monopril®), captopril, enalapril
Angiotensin receptor blockers (ARBs): eg, losartan (Cozaar®),
valsartan (Diovan®), irbesartan (Avapro®)
Calcium channel blockers: e.g. amlodipine (Norvasc®),
Diuretics: eg, chlortalidone, hydrochlorothiazide (also
Combination products (which usually contain HCTZ and one
The aim of treatment should
be blood pressure control (<140/90 mmHg for most patients,
and lower in certain contexts such as diabetes or kidney
disease). Each added drug may reduce the systolic blood
pressure by 5-10 mmHg, so often multiple drugs are necessary
to achieve blood pressure control.