Hypertension

Hypertension
Hypertension (HTN) or high blood pressure is a chronic medical condition in which the blood pressure in the arteries is elevated. It is classified as either primary (essential) or secondary. About 90-95% of cases are termed "primary hypertension", which refers to high blood pressure for which no medical cause can be found.
The remaining 5-10% of cases (Secondary hypertension) are caused by other conditions that affect the kidneys, arteries, heart, or endocrine system.

Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure and arterial aneurysm, and is a leading cause of chronic kidney failure.
Moderate elevation of arterial blood pressure leads to shortened life expectancy. Both dietary and lifestyle changes as well as medicines can improve blood pressure control and decrease the risk of associated health complications

Classification
The variation in pressure in the left ventricle (blue line) and the aorta (red line) over two cardiac cycles ("heart beats"), showing the definitions of systolic and diastolic pressure.

Classification     Systolic pressure     Diastolic pressure
mmHg     kPa     mmHg     kPa
Normal     90–119     12–15.9     60–79     8.0–10.5
Prehypertension     120–139     16.0–18.5     80–89     10.7–11.9
Stage 1     140–159     18.7–21.2     90–99     12.0–13.2
Stage 2     ≥160     ≥21.3     ≥100     ≥13.3
Isolated systolic
hypertension     ≥140     ≥18.7     <90     <12.0
Source: American Heart Association (2003).

Classification :
Blood pressure is usually classified based on the systolic and diastolic blood pressures. Systolic blood pressure is the blood pressure in vessels during a heart beat. Diastolic blood pressure is the pressure between heartbeats. A systolic or the diastolic blood pressure measurement higher than the accepted normal values for the age of the individual is classified as prehypertension or hypertension.

Hypertension has several sub-classifications including, hypertension stage I, hypertension stage II, and isolated systolic hypertension. Isolated systolic hypertension refers to elevated systolic pressure with normal diastolic pressure and is common in the elderly. These classifications are made after averaging a patient's resting blood pressure readings taken on two or more office visits. Individuals older than 50 years are classified as having hypertension if their blood pressure is consistently at least 140 mmHg systolic or 90 mmHg diastolic. Patients with blood pressures higher than 130/80 mmHg with concomitant presence of diabetes or kidney disease require further treatment.

Hypertension is also classified as resistant if medications do not reduce blood pressure to normal levels.

Exercise hypertension is an excessively high elevation in blood pressure during exercise.
The range considered normal for systolic values during exercise is between 200 and 230 mm Hg.[8] Exercise hypertension may indicate that an individual is at risk for developing hypertension at rest.

Signs and symptoms
Mild to moderate essential hypertension is usually asymptomatic.

Accelerated hypertension
Accelerated hypertension is associated with headache, drowsiness, confusion, vision disorders, nausea, and vomiting symptoms which are collectively referred to as hypertensive encephalopathy. Hypertensive encephalopathy is caused by severe small blood vessel congestion and brain swelling, which is reversible if blood pressure is lowered.

Children
Some signs and symptoms are especially important in newborns and infants such as failure to thrive, seizures, irritability, lack of energy, and difficulty breathing.
In children, hypertension can cause headache, fatigue, blurred vision, nosebleeds, and facial paralysis.

Secondary hypertension
Some additional signs and symptoms suggest that the hypertension is caused by disorders in hormone regulation. Hypertension combined with obesity distributed on the trunk of the body, accumlated fat on the back of the neck ('buffalo hump'), wide purple marks on the abdomen (abdominal striae), or the recent onset of diabetes suggests that an individual has a hormone disorder known as Cushing's syndrome. Hypertension caused by other hormone disorders such as hyperthyroidism, hypothyroidism, or growth hormone excess will be accompanied by additional symptoms specific to these disorders. For example, hyperthyrodism can cause weight loss, tremors, heart rate abnormalities, reddening of the palms, and increased sweating.
Signs and symptoms associated with growth hormone excess include coarsening of facial features, protrusion of the lower jaw,

enlargement of the tongue,
excessive hair growth, darkening of the skin color, and excessive
sweating.
Other hormone disorders like hyperaldosteronism may cause less specific symptoms such as numbness, excessive urination, excessive sweating, electrolyte imbalances and dehydration, and elevated blood alkalinity.

Pregnancy
Hypertension in pregnant women is known as pre-eclampsia. Pre-eclampsia can progress to a life-threatening condition called eclampsia, which is the development of protein in the urine, generalized swelling, and severe seizures. Other symptoms indicating that brain function is becoming impaired may precede these seizures such as nausea, vomiting, headaches, and vision loss.

Causes
Essential hypertension
Main article: Essential hypertension

Essential hypertension is the most prevalent hypertension type, affecting 90-95% of hypertensive patients.
Although no direct cause has identified itself, there are many factors such as sedentary lifestyle, stress, visceral obesity, potassium deficiency (hypokalemia),
obesity (more than 85% of cases occur in those with a body mass index greater than 25), salt (sodium) sensitivity, alcohol intake, and vitamin D deficiency that increase the risk of developing hypertension.
Risk also increases with aging, some inherited genetic mutations, and having a family history of hypertension.
An elevation of renin, an enzyme secreted by the kidney, is another risk factor, as is sympathetic nervous system overactivity.
Insulin resistance which is a component of syndrome X, or the metabolic syndrome is also thought to contribute to hypertension.
Consuming foods that contain high fructose corn syrup may increase one's risk of developing hypertension.
Recent studies have implicated low birth weight as a risk factor for adult essential hypertension.

Secondary hypertension
Main article: Secondary hypertension
Secondary hypertension by definition results from an identifiable cause. This type is important to recognize since it's treated differently than essential hypertension, by treating the underlying cause of the elevated blood pressure. Hypertension results compromise or imbalance of the pathophysiological mechanisms, such as the hormone-regulating endocrine system, that regulate blood plasma volume and heart function. Many conditions cause hypertension, some are common and well recognized secondary causes such as Cushing's syndrome, which is a condition where the adrenal glands overproduce the hormone cortisol.In addition, hypertension is caused by other conditions that cause hormone changes such as hyperthyroidism, hypothyroidism, and adrenal gland cancer. Other common causes of secondary hypertension include kidney disease, obesity/metabolic disorder, pre-eclampsia during pregnancy, the congenital defect known as coarctation of the aorta, and certain prescription and illegal drugs.

Pathophysiology
Main article: Pathophysiology of hypertension
A diagram explaining factors affecting arterial pressure

Most of the mechanisms associated with secondary hypertension are generally fully understood. However, those associated with essential (primary) hypertension are far less understood. What is known is that cardiac output is raised early in the disease course, with total peripheral resistance (TPR) 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 factors such as Atrial Natriuretic Factor being       secreted to promote salt excretion with the side effect of            raising total peripheral resistance.
    * An overactive Renin-angiotensin 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.

It is also known that hypertension is highly heritable and polygenic (caused by more than one gene) and a few candidate genes have been postulated in the etiology of this condition.

Recently, work related to the association between essential hypertension and sustained endothelial damage has gained popularity among hypertension scientists. It remains unclear however whether endothelial changes precede the development of hypertension or whether such changes are mainly due to long standing elevated blood pressures.

Diagnosis
Hypertension is generally diagnosed on the basis of a persistently high blood pressure. Usually this requires three separate sphygmomanometer (see figure) measurements at least one week apart. Initial assessment of the hypertensive patient should include a complete history and physical examination. Exceptionally, if the elevation is extreme, or if symptoms of organ damage are present then the diagnosis may be given and treatment started immediately.

Once the diagnosis of hypertension has been made, physicians will attempt to identify the underlying cause based on risk factors and other symptoms, if present. Secondary hypertension is more common in preadolescent children, with most cases caused by renal disease. Primary or essential hypertension is more common in adolescents and has multiple risk factors, including obesity and a family history of hypertension.
Laboratory tests can also be performed to identify possible causes of secondary hypertension, and determine if hypertension has caused damage to the heart, eyes, and kidneys. Additional tests for Diabetes and high cholesterol levels are also usually performed because they are additional risk factors for the development of heart disease require treatment.
Tests typically performed are classified as follows:
System     Tests
Renal     Microscopic urinalysis, proteinuria, serum BUN (blood urea nitrogen) and/or creatinine
Endocrine     Serum sodium, potassium, calcium, TSH (thyroid-stimulating hormone).
Metabolic     Fasting blood glucose, total cholesterol, HDL and LDL cholesterol, triglycerides Other     Hematocrit, electrocardiogram, and Chest X-ray
Sources: Harrison's principles of internal medicineothers

Creatinine (renal function) testing is done to determine if kidney disease is present, which can be either the cause or result of hypertension. In addition, it provides a baseline measurement of kidney function that can be used to monitor for side-effects of certain antihypertensive drugs on kidney function. Additionally, testing of urine samples for protein is used as a secondary indicator of kidney disease. Glucose testing is done to determine if diabetes is present. Electrocardiogram (EKG/ECG) testing is done to check for evidence of the heart being under strain from high blood pressure. It may also show if there is thickening of the heart muscle (left ventricular hypertrophy) or has experienced a prior minor heart distubance such as a silent heart attack. A chest X-ray may be performed to look for signs of heart enlargement or damage to heart tissue.

Prevention
The degree to which hypertension can be prevented depends on a number of features including: current blood pressure level, sodium/potassium balance, detection and omission of environmental toxins, changes in end/target organs (retina, kidney, heart - among others), risk factors for cardiovascular diseases and the age at the time of diagnosis of prehypertenion or at risk for hypertension. A prolonged assessment period within which repeated measurements of blood pressure are taken provides the most accurate assessment of blood pressure levels. Following this, lifestyle changes are recommended to lower blood pressure, before the initiation of prescription drug therapy. The process of managing prehypertension according the guidelines of the British Hypertension Society suggest the following lifestyle changes;

    * Weight reduction and regular aerobic exercise (e.g., walking): Regular exercise improves blood flow and helps to reduce the resting heart rate and blood pressure.
    * Reducing dietary sugar intake
    * Reducing sodium (salt) in the diet: This step decreases blood pressure in about 33% of people (see above). Many people use a salt substitute to reduce their salt intake.
    * Additional dietary changes beneficial to reducing blood pressure include the DASH diet (dietary approaches to stop hypertension) which is rich in fruits and vegetables and low-fat or fat-free dairy products. This diet has been shown to be effective based on research sponsored by the National Heart, Lung, and Blood Institute.
In addition, an increase in dietary potassium, which offsets the effect of sodium has been shown to be highly effective in reducing blood pressure.
    * Discontinuing tobacco use and alcohol consumption has been shown to lower blood pressure. The exact mechanisms are not fully understood, but blood pressure (especially systolic) always transiently increases following alcohol or nicotine consumption. Abstaining from cigarette smoking reduces the risk of stroke and heart attack which are associated with hypertension.
    * Reducing stress, for example with relaxation therapy, such as meditation and other mindbody relaxation techniques,by reducing environmental stress such as high sound levels and over-illumination can also lower blood pressure. Jacobson's Progressive Muscle Relaxation and biofeedback are also beneficial, such as device-guided paced breathing,although meta-analysis suggests it is not effective unless combined with other relaxation techniques.

Treatment
Lifestyle modifications
The first line of treatment for hypertension is the same as the recommended preventative lifestyle changes such as the dietary changes, physical exercise, and weight loss, which have all been shown to significantly reduce blood pressure in people with hypertension.
If hypertension is high enough to justify immediate use of medications, lifestyle changes are still recommended in conjunction with medication. Different programs aimed to reduce psychological stress such as biofeedback, relaxation or meditation are advertised to reduce hypertension. However, in general claims of efficacy are not supported by scientific studies, which have been in general of low quality.

Medications
See also: Antihypertensive drugs
There are many classes of medications for treating hypertension, together called antihypertensives, which — by varying means — act by lowering blood pressure. Reduction of the blood pressure by 5–6 mmHg can decrease the risk of stroke by 40%, decrease the risk of heart disease by 15–20%, and reduce the likelihood of dementia, heart failure, and death.

The aim of treatment should be reduce blood pressure to <140/90 mmHg for most individuals, and lower individuals with diabetes or kidney disease (some medical professionals recommend keeping levels below 120/80 mmHg).[56] Each drug reduces systolic blood pressure by about 5–10 mmHg, so often multiple drugs are combined to achieve the goal blood pressure.

Commonly used prescription drugs include:

    * ACE inhibitors such as ramipril
    * Angiotensin II receptor antagonists may be used where ACE inhibitors are not tolerated: e.g., candesartan
    * Calcium channel blockers such as nifedipine
    * Diuretics: e.g. hydrochlorothiazide (aHCTZ).
    * Diuretics such a furosemide or low-dosages of spironolactone
    * Alpha blockers such as terazosin. Doxazosin has been shown to the increase risk of heart failure, and to be less effective than a diuretics.
    * Beta blockers such as metoprolol. Whilst once were first line agents, now they are less commonly used because they increase the risk of diabetes.
    * Direct renin inhibitors such as aliskiren.


Common combined prescription drug treatments:
    * The durietic HCTZ and one other drug combined in one pill.
    * A fixed combination of the ACE inhibitor perindopril and the calcium channel blocker amlodipine, recently been proved to be very effective even in individuals with glucose intolerance or metabolic syndrome.

Resistant
Guidelines for treating resistant hypertension have been published in the  Complications
Main article: Complications of hypertension
Diagram illustrating the main complications of persistent high blood pressure.

Hypertension is the most important risk factor for death in industrialized countries.
It increases hardening of the arteries thus predisposes individuals to heart disease[66], peripheral vascular disease, and strokes. Types of heart disease that may occur include: heart attack, heart failure, and left ventricular hypertrophy Other complications include:

    * Hypertensive retinopathy
    * Hypertensive nephropathy
    * It blood pressure is very high hypertensive encephalopathy       may result.

Epidemiology
In the year 2000 it is estimated that nearly one billion people or ~26% of the adult population have hypertension worldwide.
 It was common in both developed (333 million ) and undeveloped (639 million) countries.
However rates vary markedly in different regions with rates as low as 3.4% (men) and 6.8% (women) in rural India and as high as 68.9% (men) and 72.5% (women) in Poland.

In 1995 it is estimated that 43 million people in the United States had hypertension or were taking antihypertensive medication, almost 24% of the adult population.
The prevalence of hypertension in the United States is increasing and reached 29% in 2004.
It is more common in blacks and less in whites and Mexican Americans, rates increase with age, and is greater in the southeastern United States. Hypertension is more prevalent in men (though menopause tends decrease this difference) and those of low socioeconomic status.

Over 90—95% of adult hypertension is essential hypertension.The most common cause of secondary hypertension is primary aldosteronism. The incidence of exercise hypertension is reported to range from 1—10%.

Pediatrics
The prevalence of high blood pressure in the young is increasing. Most childhood hypertension, particularly in preadolescents, is secondary to an underlying disorder. Kidney disease is the most common (60—70%) cause of hypertension in children. Adolescents usually have primary or essential hypertension, which accounts for 85—95% of cases.

History
Image of veins from Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus

Some cite the writings of Sushruta in the 6th century BC as being the first mention of symptoms like those of hypertension.Others propose even earlier descriptions dating as far as 2600 years before Christ. Main treatment for what was called the "hard pulse disease" consisted in reducing the quantity of blood in a subject by the sectioning of veins or the application of leeches.
Well known individuals such as The Yellow Emperor of China, Cornelius Celsus, Galen, or Hipocrates advocated for such treatments.

Our modern understanding of hypertension began with the work of physician William Harvey (1578–1657), who was the first to describe correctly the systemic circulation of blood being pumped around the body by the heart in his book "De motu cordis". The basis for measuring blood pressure were established by Stephen Hales in 1733.
Initial descriptions of hypertension as a disease came among others from Thomas Young in 1808 and specially Richard Bright in 1836.
The first ever elevated blood pressure in a patient without kidney disease was reported by Frederick Mahomed (1849–1884).
It was not until 1904 that sodium restriction was advocated while a rice diet was popularized around 1940.
The first chemical for hypertension, Sodium thiocyanate, was used in 1900 but had many secondary effects.
Surgical and chemical sypathectomies were also used all over the 20th century.
Nevertheless the major advance was the appearance of effective diuretics after 1957 and other symptomatic medications in following years.
Society and culture
Economics
The National Heart, Lung, and Blood Institute (NHLBI) estimated in 2002 that hypertension cost the United States $47.2 billion.

High blood pressure is the most common chronic medical problem prompting visits to primary health care providers, yet it is estimated that only 34% of the 50 million American adults with hypertension have their blood pressure controlled to a level of <140/90 mm Hg [citation needed]. Thus, about two thirds of Americans with hypertension are at increased risk for heart disease. The medical, economic, and human costs of untreated and inadequately controlled high blood pressure are enormous. Adequate management of hypertension can be hampered by inadequacies in the diagnosis, treatment, and/or control of high blood pressure.
Health care providers face many obstacles to achieving blood pressure control from their patients, including resistance to taking multiple medications to reach blood pressure goals. Patients also face the challenges of adhering to medicine schedules and making lifestyle changes. Nonetheless, the achievement of blood pressure goals is possible, and most importantly, lowering blood pressure significantly reduces the risk of death due to heart disease, the development of other debilitating conditions, and the cost associated with advanced medical care.

Awareness
Graph showing, prevalence of awareness, treatment and control of hypertension compared between the four studies of NHANES
The World Health Organization attributes hypertension, or high blood pressure, as the leading cause of cardiovascular mortality. The World Hypertension League (WHL), an umbrella organization of 85 national hypertension societies and leagues, recognized that more than 50% of the hypertensive population worldwide are unaware of their condition.
To address this problem, the WHL initiated a global awareness campaign on hypertension in 2005 and dedicated May 17 of each year as World Hypertension Day (WHD). Over the past three years, more national societies have been engaging in WHD and have been innovative in their activities to get the message to the public. In 2007, there was record participation from 47 member countries of the WHL. During the week of WHD, all these countries – in partnership with their local governments, professional societies, nongovernmental organizations and private industries – promoted hypertension awareness among the public through several media and public rallies. Using mass media such as Internet and television, the message reached more than 250 million people. As the momentum picks up year after year, the WHL is confident that almost all the estimated 1.5 billion people affected by elevated blood pressure can be reached.