![ارتفاع الضعط[HYPERTENSION] Empty](https://2img.net/i/empty.gif)
Hypertension
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about arterial hypertension. For other forms of hypertension, see Hypertension (disambiguation).
Hypertension
Classification and external resources
Automated arm blood pressure meter showing arterial hypertension (shown a systolic blood pressure 158 mmHg, diastolic blood pressure 99 mmHg and heart rate of 80 beats per minute).
ICD-10 I10.,I11.,I12.,
I13.,I15.
ICD-9 401
OMIM 145500
DiseasesDB 6330
MedlinePlus 000468
eMedicine med/1106 ped/1097 emerg/267
MeSH D006973
Hypertension (HTN) or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. It is the opposite of hypotension. Hypertension 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.[1] The remaining 5–10% of cases (Secondary hypertension) are caused by other conditions that affect the kidneys, arteries, heart, or endocrine system.[2]
Persistent hypertension is one of the risk factors for stroke, myocardial infarction, heart failure and arterial aneurysm, and is a leading cause of chronic kidney failure.[3] Moderate elevation of arterial blood pressure leads to shortened life expectancy. Dietary and lifestyle changes can improve blood pressure control and decrease the risk of associated health complications, although drug treatment may prove necessary in patients for whom lifestyle changes prove ineffective or insufficient.[4]
Contents
[hide]
* 1 Classification
* 2 Signs and symptoms
o 2.1 Accelerated hypertension
o 2.2 Children
+ 2.2.1 Secondary hypertension
o 2.3 Pregnancy
* 3 Causes
o 3.1 Essential hypertension
o 3.2 Secondary hypertension
* 4 Pathophysiology
* 5 Diagnosis
* 6 Prevention
* 7 Treatment
o 7.1 Lifestyle modifications
o 7.2 Medications
o 7.3 In the elderly
o 7.4 Resistant
* 8 Complications
* 9 Epidemiology
o 9.1 Pediatrics
* 10 History
* 11 Society and culture
o 11.1 Economics
o 11.2 Awareness
* 12 References
* 13 Further reading
* 14 External links
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).[5]
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[6] 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.[5]
Hypertension is also classified as resistant if medications do not reduce blood pressure to normal levels.[5]
Exercise hypertension is an excessively high elevation in blood pressure during exercise.[7][8][9] The range considered normal for systolic values during exercise is between 200 and 230 mm Hg.[10] Exercise hypertension may indicate that an individual is at risk for developing hypertension at rest.[9][10]
Signs and symptoms
Mild to moderate essential hypertension is usually asymptomatic.[11]
Accelerated hypertension
Accelerated hypertension is associated with headache, drowsiness, confusion, vision disorders, nausea, and vomiting symptoms which are collectively referred to as hypertensive encephalopathy.[12] Hypertensive encephalopathy is caused by severe small blood vessel congestion and brain swelling, which is reversible if blood pressure is lowered.[13]
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.[14] In children, hypertension can cause headache, fatigue, blurred vision, nosebleeds, and facial paralysis.[14]
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.[15]
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, accumulated 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.[16] Signs and symptoms associated with growth hormone excess include coarsening of facial features, protrusion of the lower jaw, enlargement of the tongue,[17] excessive hair growth, darkening of the skin color, and excessive sweating.[18]:499. 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.[19] and also cause of mental pressure.
Pregnancy
Hypertension in pregnant women is one symptom of 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.[20]
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.[21]
Causes
Essential hypertension
Main article: Essential hypertension
Essential hypertension is the most prevalent hypertension type, affecting 90–95% of hypertensive patients.[1] Although no direct cause has been identified, there are many factors such as sedentary lifestyle,[22] smoking, stress, visceral obesity, potassium deficiency (hypokalemia),[22] obesity[23] (more than 85% of cases occur in those with a body mass index greater than 25),[24] salt (sodium) sensitivity,[25] alcohol intake,[26] and vitamin D deficiency that increase the risk of developing hypertension.[27][28] Risk also increases with aging,[29] some inherited genetic mutations,[30] and having a family history of hypertension.[31] An elevated level of renin, a hormone secreted by the kidney, is another risk factor,[32] as is sympathetic nervous system overactivity.[33] Insulin resistance, which is a component of syndrome X (or the metabolic syndrome), is also thought to contribute to hypertension.[32][34] Recent studies have implicated low birth weight as a risk factor for adult essential hypertension.[35]
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 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,[36] which is a condition where the adrenal glands overproduce the hormone cortisol.[36] 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.
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 plus vasoconstriction leads to hypertension.[37]
* An overactive sympathetic nervous system, leading to increased stress responses.[38]
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.[39]
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. Often, this entails three separate visits to the physician's office. 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.[31] 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.[1] 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 radiograph
Sources: Harrison's principles of internal medicine[40] others[41][42][43][44][45][46]
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.
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 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:
* 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.[47]
* Reducing dietary sugar.
* Reducing sodium (salt) in the body by disuse of condiment sodium and the adoption of a high potassium diet which rids the renal system of excess sodium. Many people use potassium chloride [48]salt substitute to reduce their salt intake.[49]
* 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.[50] In addition, an increase in dietary potassium, which offsets the effect of sodium has been shown to be highly effective in reducing blood pressure.[51]
* 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.[52]
Limiting alcohol intake to less than 2 standard drinks per day can reduce systolic blood pressure by between 2-4mmHg.[53]
* Reducing stress, for example with relaxation therapy, such as meditation and other mindbody relaxation techniques,[54] 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,[55] such as device-guided paced breathing,[56][57] although meta-analysis suggests it is not effective unless combined with other relaxation techniques.[58]
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. [59]
Treatment
Lifestyle modifications
The first line of treatment for hypertension is the same as the recommended preventative lifestyle changes[53] such as the dietary changes, physical exercise, and weight loss, which have all been shown to significantly reduce blood pressure in people with hypertension.[60] If hypertension is high enough to justify immediate use of medications, lifestyle changes are still recommended in conjunction with medication. Drug prescription should take into account the patient's absolute cardiovascular risk (including risk of myocardial infarction and stroke) as well as blood pressure readings, in order to gain a more accurate picture of the patient's cardiovascular profile.[4] 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.[61][62][63]
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.[64] 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,[65] 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".
Medications
Main article: Antihypertensive drug
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.[66] 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).[67] If the blood pressure goal is not met, a change in treatment should be made as therapeutic inertia is a clear impediment to blood pressure control.[68] Comorbidity also plays a role in determining target blood pressure, with lower BP targets applying to patients with end-organ damage or proteinuria.[4]
Often multiple drugs are combined to achieve the goal blood pressure. Commonly used prescription drugs include:[69]
* ACE inhibitors (e.g., captopril)
* Alpha blockers (e.g., prazosin)
* Angiotensin II receptor antagonists (e.g., losartan)
* Beta blockers (e.g., propranolol)
* Calcium channel blockers (e.g., verapamil)
* Diuretics (e.g. hydrochlorothiazide)
* Direct renin inhibitors (e.g., aliskiren)
Some examples of common combined prescription drug treatments include:
* A fixed combination of an ACE inhibitor and a calcium channel blocker. One example of this is the combination of perindopril and amlodipine, the efficacy of which has been demonstrated in individuals with glucose intolerance or metabolic syndrome.[70]
* A fixed combination of a diuretic and an ARB.
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.[53]
In the elderly
Treating moderate to severe high blood pressure with prescription medications decreases death rates in those under 80 years of age however there is no decrease in those over 80 years old.[71] Even though there was no decrease in total mortality, the results showed similarities between cardiovascular mortality and morbidity.[72]
Resistant
Guidelines for treating resistant hypertension have been published in the UK[69] and US.[73]
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.[74] It increases hardening of the arteries[75] thus predisposes individuals to heart disease,[76] peripheral vascular disease,[77] and strokes.[78] Types of heart disease that may occur include: myocardial infarction,[78] heart failure,[79] and left ventricular hypertrophy[80] Other complications include:
* Hypertensive retinopathy[81]
* Hypertensive nephropathy[82]
* If blood pressure is very high hypertensive encephalopathy may result
From Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about arterial hypertension. For other forms of hypertension, see Hypertension (disambiguation).
Hypertension
Classification and external resources
Automated arm blood pressure meter showing arterial hypertension (shown a systolic blood pressure 158 mmHg, diastolic blood pressure 99 mmHg and heart rate of 80 beats per minute).
ICD-10 I10.,I11.,I12.,
I13.,I15.
ICD-9 401
OMIM 145500
DiseasesDB 6330
MedlinePlus 000468
eMedicine med/1106 ped/1097 emerg/267
MeSH D006973
Hypertension (HTN) or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. It is the opposite of hypotension. Hypertension 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.[1] The remaining 5–10% of cases (Secondary hypertension) are caused by other conditions that affect the kidneys, arteries, heart, or endocrine system.[2]
Persistent hypertension is one of the risk factors for stroke, myocardial infarction, heart failure and arterial aneurysm, and is a leading cause of chronic kidney failure.[3] Moderate elevation of arterial blood pressure leads to shortened life expectancy. Dietary and lifestyle changes can improve blood pressure control and decrease the risk of associated health complications, although drug treatment may prove necessary in patients for whom lifestyle changes prove ineffective or insufficient.[4]
Contents
[hide]
* 1 Classification
* 2 Signs and symptoms
o 2.1 Accelerated hypertension
o 2.2 Children
+ 2.2.1 Secondary hypertension
o 2.3 Pregnancy
* 3 Causes
o 3.1 Essential hypertension
o 3.2 Secondary hypertension
* 4 Pathophysiology
* 5 Diagnosis
* 6 Prevention
* 7 Treatment
o 7.1 Lifestyle modifications
o 7.2 Medications
o 7.3 In the elderly
o 7.4 Resistant
* 8 Complications
* 9 Epidemiology
o 9.1 Pediatrics
* 10 History
* 11 Society and culture
o 11.1 Economics
o 11.2 Awareness
* 12 References
* 13 Further reading
* 14 External links
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).[5]
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[6] 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.[5]
Hypertension is also classified as resistant if medications do not reduce blood pressure to normal levels.[5]
Exercise hypertension is an excessively high elevation in blood pressure during exercise.[7][8][9] The range considered normal for systolic values during exercise is between 200 and 230 mm Hg.[10] Exercise hypertension may indicate that an individual is at risk for developing hypertension at rest.[9][10]
Signs and symptoms
Mild to moderate essential hypertension is usually asymptomatic.[11]
Accelerated hypertension
Accelerated hypertension is associated with headache, drowsiness, confusion, vision disorders, nausea, and vomiting symptoms which are collectively referred to as hypertensive encephalopathy.[12] Hypertensive encephalopathy is caused by severe small blood vessel congestion and brain swelling, which is reversible if blood pressure is lowered.[13]
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.[14] In children, hypertension can cause headache, fatigue, blurred vision, nosebleeds, and facial paralysis.[14]
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.[15]
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, accumulated 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.[16] Signs and symptoms associated with growth hormone excess include coarsening of facial features, protrusion of the lower jaw, enlargement of the tongue,[17] excessive hair growth, darkening of the skin color, and excessive sweating.[18]:499. 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.[19] and also cause of mental pressure.
Pregnancy
Hypertension in pregnant women is one symptom of 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.[20]
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.[21]
Causes
Essential hypertension
Main article: Essential hypertension
Essential hypertension is the most prevalent hypertension type, affecting 90–95% of hypertensive patients.[1] Although no direct cause has been identified, there are many factors such as sedentary lifestyle,[22] smoking, stress, visceral obesity, potassium deficiency (hypokalemia),[22] obesity[23] (more than 85% of cases occur in those with a body mass index greater than 25),[24] salt (sodium) sensitivity,[25] alcohol intake,[26] and vitamin D deficiency that increase the risk of developing hypertension.[27][28] Risk also increases with aging,[29] some inherited genetic mutations,[30] and having a family history of hypertension.[31] An elevated level of renin, a hormone secreted by the kidney, is another risk factor,[32] as is sympathetic nervous system overactivity.[33] Insulin resistance, which is a component of syndrome X (or the metabolic syndrome), is also thought to contribute to hypertension.[32][34] Recent studies have implicated low birth weight as a risk factor for adult essential hypertension.[35]
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 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,[36] which is a condition where the adrenal glands overproduce the hormone cortisol.[36] 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.
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 plus vasoconstriction leads to hypertension.[37]
* An overactive sympathetic nervous system, leading to increased stress responses.[38]
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.[39]
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. Often, this entails three separate visits to the physician's office. 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.[31] 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.[1] 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 radiograph
Sources: Harrison's principles of internal medicine[40] others[41][42][43][44][45][46]
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.
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 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:
* 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.[47]
* Reducing dietary sugar.
* Reducing sodium (salt) in the body by disuse of condiment sodium and the adoption of a high potassium diet which rids the renal system of excess sodium. Many people use potassium chloride [48]salt substitute to reduce their salt intake.[49]
* 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.[50] In addition, an increase in dietary potassium, which offsets the effect of sodium has been shown to be highly effective in reducing blood pressure.[51]
* 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.[52]
Limiting alcohol intake to less than 2 standard drinks per day can reduce systolic blood pressure by between 2-4mmHg.[53]
* Reducing stress, for example with relaxation therapy, such as meditation and other mindbody relaxation techniques,[54] 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,[55] such as device-guided paced breathing,[56][57] although meta-analysis suggests it is not effective unless combined with other relaxation techniques.[58]
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. [59]
Treatment
Lifestyle modifications
The first line of treatment for hypertension is the same as the recommended preventative lifestyle changes[53] such as the dietary changes, physical exercise, and weight loss, which have all been shown to significantly reduce blood pressure in people with hypertension.[60] If hypertension is high enough to justify immediate use of medications, lifestyle changes are still recommended in conjunction with medication. Drug prescription should take into account the patient's absolute cardiovascular risk (including risk of myocardial infarction and stroke) as well as blood pressure readings, in order to gain a more accurate picture of the patient's cardiovascular profile.[4] 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.[61][62][63]
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.[64] 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,[65] 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".
Medications
Main article: Antihypertensive drug
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.[66] 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).[67] If the blood pressure goal is not met, a change in treatment should be made as therapeutic inertia is a clear impediment to blood pressure control.[68] Comorbidity also plays a role in determining target blood pressure, with lower BP targets applying to patients with end-organ damage or proteinuria.[4]
Often multiple drugs are combined to achieve the goal blood pressure. Commonly used prescription drugs include:[69]
* ACE inhibitors (e.g., captopril)
* Alpha blockers (e.g., prazosin)
* Angiotensin II receptor antagonists (e.g., losartan)
* Beta blockers (e.g., propranolol)
* Calcium channel blockers (e.g., verapamil)
* Diuretics (e.g. hydrochlorothiazide)
* Direct renin inhibitors (e.g., aliskiren)
Some examples of common combined prescription drug treatments include:
* A fixed combination of an ACE inhibitor and a calcium channel blocker. One example of this is the combination of perindopril and amlodipine, the efficacy of which has been demonstrated in individuals with glucose intolerance or metabolic syndrome.[70]
* A fixed combination of a diuretic and an ARB.
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.[53]
In the elderly
Treating moderate to severe high blood pressure with prescription medications decreases death rates in those under 80 years of age however there is no decrease in those over 80 years old.[71] Even though there was no decrease in total mortality, the results showed similarities between cardiovascular mortality and morbidity.[72]
Resistant
Guidelines for treating resistant hypertension have been published in the UK[69] and US.[73]
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.[74] It increases hardening of the arteries[75] thus predisposes individuals to heart disease,[76] peripheral vascular disease,[77] and strokes.[78] Types of heart disease that may occur include: myocardial infarction,[78] heart failure,[79] and left ventricular hypertrophy[80] Other complications include:
* Hypertensive retinopathy[81]
* Hypertensive nephropathy[82]
* If blood pressure is very high hypertensive encephalopathy may result
