|March 26, 2016|
Hypertension (HTN) or high blood pressure is a chronic medical condition in which the systemic arterial blood pressure is elevated. It is the opposite of hypotension. 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.
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 mellitus 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. Exercise hypertension may indicate that an individual is at risk for developing hypertension at rest.
Mild to moderate essential hypertension is usually asymptomatic.
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 .
Even with the above clinical symptoms, the true incidence of pediatric hypertension is not known. In adults, hypertension has been defined due to the adverse effects caused by hypertension. However, in children, similar studies have not been performed thoroughly to link any adverse effects with the increase in blood pressure. Therefore, the prevalence of pediatric hypertension remains unknown due to the lack of scientific knowledge.
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 on set 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. and also cause of mental pressure.
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 .
In addition, the systemic vascular resistance and blood pressure decrease during pregnancy. The body must compensate by increasing cardiac output and blood volume to provide sufficient circulation in the utero-placental arterial bed.
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,
Secondary hypertension by definition results from an identifiable cause. This type is important to recognize since it's treated differently to essential hypertension, by treating the underlying cause of the elevated blood pressure. Hypertension results in the 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 (citation needed), and certain tumors of the adrenal medulla (e.g., pheochromocytoma). 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.
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:
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.
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:
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 mellitus 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.
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 diagnosis of prehypertension or at risk for hypertension. A prolonged assessment in 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:
Limiting alcohol intake to less than 2 standard drinks per day can reduce systolic blood pressure by between 2-4mmHg.
Increasing omega 3 fatty acids can help lower hypertension. Fish oil is shown to lower blood pressure in hypertensive individuals. The fish oil may increase sodium and water excretion.
The first line of treatment for hypertension is the same as the recommended preventative lifestyle changes
Regarding dietary changes, a low sodium diet is beneficial; A Cochrane review published in 2008 concluded that a long term (more than 4 weeks) low sodium diet in Caucasians has a useful effect to reduce blood pressure, both in people with hypertension and in people with normal blood pressure. Also, the DASH diet (Dietary Approaches to Stop Hypertension) is a diet promoted by the National Heart, Lung, and Blood Institute (part of the NIH, a United States government organization) to control hypertension. A major feature of the plan is limiting intake of sodium, and it also generally encourages the consumption of nuts, whole grains, fish, poultry, fruits and vegetables while lowering the consumption of red meats, sweets, and sugar. It is also "rich in potassium, magnesium, and calcium, as well as protein".
Several classes of medications, collectively referred to as antihypertensive drugs, are currently available for treating hypertension. Agents within a particular class generally share a similar pharmacologic mechanism of action, and in many cases have an affinity for similar cellular receptors. An exception to this rule is the diuretics, which are grouped together for the sake of simplicity but actually exert their effects by a number of different mechanisms.
Reduction of the blood pressure by 5 mmHg can decrease the risk of stroke by 34%, of ischaemic heart disease by 21%, and reduce the likelihood of dementia, heart failure, and mortality from cardiovascular disease. The aim of treatment should be reduce blood pressure to <140/90 mmHg for most individuals, and lower for individuals with diabetes or kidney disease (some medical professionals recommend keeping levels below 120/80 mmHg). Comorbidity also plays a role in determining target blood pressure, with lower BP targets applying to patients with end-organ damage or proteinuria.
Often multiple drugs are combined to achieve the goal blood pressure. Commonly used prescription drugs include:
Some examples of common combined prescription drug treatments include:
Combinations of an ACE inhibitor or angiotensin II???receptor antagonist, a diuretic and an NSAID (including selective COX-2 inhibitors and non-prescribed drugs such as ibuprofen) should be avoided whenever possible due to a high documented risk of acute renal failure. The combination is known colloquially as a "triple whammy" in the Australian health industry.
In the elderly
Treating moderate to severe high blood pressure decreases death rates in those under 80 years of age however there is no decrease in those over 80 years old.
Even though there was no decrease in total mortality, the results showed similarities between cardiovascular mortality and morbidity.
Guidelines for treating resistant hypertension have been published in the UK
Hypertension is the most important risk factor for death in industrialized countries.
Types of heart disease that may occur include: myocardial infarction, heart failure,
Other complications include:
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. 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 to 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%.
The prevalence of high blood pressure in the young is increasing.
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 BCE. 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, and Hipocrates advocated 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.
Studies in the 1920s demonstrated the public health impact of untreated high blood pressure; treatment options were limited at the time, and deaths from malignant hypertension and its complications were common. A prominent victim of severe hypertension leading to cerebral hemorrhage was Franklin D. Roosevelt (1882???1945). The Framingham Heart Study added to the epidemiological understanding of hypertension and its relationship with coronary artery disease. The National Institutes of Health also sponsored other population studies, which additionally showed that African Americans had a higher burden of hypertension and its complications. Before pharmacological treatment for hypertension became possible, three treatment modalities were used, all with numerous side-effects: strict sodium restriction, sympathectomy (surgical ablation of parts of the sympathetic nervous system), and pyrogen therapy (injection of substances that caused a fever, indirectly reducing blood pressure).
The first chemical for hypertension, sodium thiocyanate, was used in 1900 but had many side effects and was unpopular. Several other agents were developed after the Second World War , the most popular and reasonably effective of which were tetramethylammonium chloride and its derivative hexamethonium, hydralazine and reserpine (derived from the medicinal plant Rauwolfia serpentina). A randomized controlled trial sponsored by the Veterans Administration using these drugs had to be stopped early because those not receiving treatment were developing more complications and it was deemed unethical to withhold treatment from them. These studies prompted public health campaigns to increase public awareness of hypertension and the advice to get blood pressure measured and treated. These measures appear to have contributed at least in part of the observed 50% fall in stroke and ischemic heart disease beween 1972 and 1994.
A major breakthrough was achieved with the discovery of the first well-tolerated orally available agents. The first was chlorothiazide, the first thiazide and developed from the antibiotic sulfanilamide, which became available in 1958; it increased salt excretion while preventing fluid accumulation. In 1975, the Lasker Special Public Health Award was awarded to the team that developed chlorothiazide.
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 . 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.
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.
GNU Free Documentation License. It uses material from the Wikipedia article "Hypertension Prevention".
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