Hypertension (HTN) or high blood pressure, sometimes called arterial hypertension, is a chronic medical condition in which the blood pressure in the arteries is elevated.[1]
This requires the heart to work harder than normal to circulate blood through the blood vessels. Blood pressure is summarised by two measurements, systolic and diastolic, which depend on whether the heart muscle is contracting (systole) or relaxed between beats (diastole) and equate to a maximum and minimum pressure, respectively.
Normal blood pressure at rest is within the range of 100-140mmHg systolic (top reading) and 60-90mmHg diastolic (bottom reading). High blood pressure is said to be present if it is persistently at or above 140/90 mmHg.
Hypertension is classified as either primary (essential) hypertension or secondary hypertension; about 90–95% of cases are categorized as "primary hypertension" which means high blood pressure with no obvious underlying medical cause.[2]
The remaining 5–10% of cases (secondary hypertension) are caused by other conditions that affect the kidneys, arteries, heart or endocrine system.
Hypertension is a major risk factor for stroke, myocardial infarction (heart attacks), heart failure, aneurysms of the arteries (e.g. aortic aneurysm), peripheral arterial disease and is a cause of chronic kidney disease.
Even moderate elevation of arterial blood pressure is associated with a shortened life expectancy.
Dietary and lifestyle changes can improve blood pressure control and decrease the risk of associated health complications, although drug treatment is often necessary in people for whom lifestyle changes prove ineffective or insufficient.
A proportion of people with high blood pressure report headaches (particularly at the back of the head and in the morning), as well as lightheadedness, vertigo, tinnitus (buzzing or hissing in the ears), altered vision or fainting episodes.[3]
These symptoms however are more likely to be related to associated anxiety than the high blood pressure itself.[4]
On physical examination, hypertension may be suspected on the basis of the presence of hypertensive retinopathy detected by examination of the optic fundus found in the back of the eye using ophthalmoscopy.[5]
Classically, the severity of the hypertensive retinopathy changes is graded from grade I–IV, although the milder types may be difficult to distinguish from each other.[5] Ophthalmoscopy findings may also give some indication as to how long a person has been hypertensive.
An abdominal bruit may be an indicator of renal artery stenosis (a narrowing of the arteries supplying the kidneys), while decreased blood pressure in the lower extremities and/or delayed or absent femoral arterial pulses may indicate aortic coarctation (a narrowing of the aorta shortly after it leaves the heart). Labile or paroxysmal hypertension accompanied by headache, palpitations, pallor, and perspiration should prompt suspicions of pheochromocytoma.[6]
A proportion of resistant hypertension appears to be the result of chronic high activity of the autonomic nervous system; this concept is known as "neurogenic hypertension".[7]
People with blood pressures in this range may have no symptoms, but are more likely to report headaches (22% of cases)[8] and dizziness than the general population.[3]
Other symptoms accompanying a hypertensive crisis may include visual deterioration or breathlessness due to heart failure or a general feeling of malaise due to renal failure.[6]
Most people with a hypertensive crisis are known to have elevated blood pressure, but additional triggers may have led to a sudden rise.[9]
A "hypertensive emergency", previously "malignant hypertension", is diagnosed when there is evidence of direct damage to one or more organs as a result of the severely elevated blood pressure.
This may include hypertensive encephalopathy, caused by brain swelling and dysfunction, and characterized by headaches and an altered level of consciousness (confusion or drowsiness). Retinal papilloedema and/or fundal hemorrhages and exudates are another sign of target organ damage.
Chest pain may indicate heart muscle damage (which may progress to myocardial infarction) or sometimes aortic dissection, the tearing of the inner wall of the aorta. Breathlessness, cough, and the expectoration of blood-stained sputum are characteristic signs of pulmonary edema, the swelling of lung tissue due to left ventricular failure an inability of the left ventricle of the heart to adequately pump blood from the lungs into the arterial system.[9]
Rapid deterioration of kidney function (acute kidney injury) and microangiopathic hemolytic anemia (destruction of blood cells) may also occur.[9]
In these situations, rapid reduction of the blood pressure is mandated to stop ongoing organ damage.[9]
In contrast there is no evidence that blood pressure needs to be lowered rapidly in hypertensive urgencies where there is no evidence of target organ damage and over aggressive reduction of blood pressure is not without risks.[6]
Use of oral medications to lower the BP gradually over 24 to 48 h is advocated in hypertensive urgencies.[9]
Most women with hypertension in pregnancy have pre-existing primary hypertension, but high blood pressure in pregnancy may be the first sign of pre-eclampsia, a serious condition of the second half of pregnancy and puerperium.[6] Pre-eclampsia is characterised by increased blood pressure and the presence of protein in the urine.[6] It occurs in about 5% of pregnancies and is responsible for approximately 16% of all maternal deaths globally.[6] Pre-eclampsia also doubles the risk of perinatal mortality.[6] Usually there are no symptoms in pre-eclampsia and it is detected by routine screening. When symptoms of pre-eclampsia occur the most common are headache, visual disturbance (often "flashing lights"), vomiting, epigastric pain, and edema. Pre-eclampsia can occasionally progress to a life-threatening condition called eclampsia, which is a hypertensive emergency and has several serious complications including vision loss, cerebral edema, seizures or convulsions, renal failure, pulmonary edema, and disseminated intravascular coagulation (a blood clotting disorder).[6][11]
This requires the heart to work harder than normal to circulate blood through the blood vessels. Blood pressure is summarised by two measurements, systolic and diastolic, which depend on whether the heart muscle is contracting (systole) or relaxed between beats (diastole) and equate to a maximum and minimum pressure, respectively.
Normal blood pressure at rest is within the range of 100-140mmHg systolic (top reading) and 60-90mmHg diastolic (bottom reading). High blood pressure is said to be present if it is persistently at or above 140/90 mmHg.
Hypertension is classified as either primary (essential) hypertension or secondary hypertension; about 90–95% of cases are categorized as "primary hypertension" which means high blood pressure with no obvious underlying medical cause.[2]
The remaining 5–10% of cases (secondary hypertension) are caused by other conditions that affect the kidneys, arteries, heart or endocrine system.
Hypertension is a major risk factor for stroke, myocardial infarction (heart attacks), heart failure, aneurysms of the arteries (e.g. aortic aneurysm), peripheral arterial disease and is a cause of chronic kidney disease.
Even moderate elevation of arterial blood pressure is associated with a shortened life expectancy.
Dietary and lifestyle changes can improve blood pressure control and decrease the risk of associated health complications, although drug treatment is often necessary in people for whom lifestyle changes prove ineffective or insufficient.
Signs and symptoms
Hypertension is rarely accompanied by any symptoms, and its identification is usually through screening, or when seeking healthcare for an unrelated problem.A proportion of people with high blood pressure report headaches (particularly at the back of the head and in the morning), as well as lightheadedness, vertigo, tinnitus (buzzing or hissing in the ears), altered vision or fainting episodes.[3]
These symptoms however are more likely to be related to associated anxiety than the high blood pressure itself.[4]
On physical examination, hypertension may be suspected on the basis of the presence of hypertensive retinopathy detected by examination of the optic fundus found in the back of the eye using ophthalmoscopy.[5]
Classically, the severity of the hypertensive retinopathy changes is graded from grade I–IV, although the milder types may be difficult to distinguish from each other.[5] Ophthalmoscopy findings may also give some indication as to how long a person has been hypertensive.
Secondary hypertension
Some additional signs and symptoms may suggest secondary hypertension, i.e. hypertension due to an identifiable cause such as kidney diseases or endocrine diseases. For example, truncal obesity, glucose intolerance, moon facies, a "buffalo hump" and purple striae suggest Cushing's syndrome.[6] Thyroid disease and acromegaly can also cause hypertension and have characteristic symptoms and signs.[6]An abdominal bruit may be an indicator of renal artery stenosis (a narrowing of the arteries supplying the kidneys), while decreased blood pressure in the lower extremities and/or delayed or absent femoral arterial pulses may indicate aortic coarctation (a narrowing of the aorta shortly after it leaves the heart). Labile or paroxysmal hypertension accompanied by headache, palpitations, pallor, and perspiration should prompt suspicions of pheochromocytoma.[6]
A proportion of resistant hypertension appears to be the result of chronic high activity of the autonomic nervous system; this concept is known as "neurogenic hypertension".[7]
Hypertensive crisis
Severely elevated blood pressure (equal to or greater than a systolic 180 or diastolic of 110 — sometime termed malignant or accelerated hypertension) is referred to as a "hypertensive crisis", as blood pressures above these levels are known to confer a high risk of complications.People with blood pressures in this range may have no symptoms, but are more likely to report headaches (22% of cases)[8] and dizziness than the general population.[3]
Other symptoms accompanying a hypertensive crisis may include visual deterioration or breathlessness due to heart failure or a general feeling of malaise due to renal failure.[6]
Most people with a hypertensive crisis are known to have elevated blood pressure, but additional triggers may have led to a sudden rise.[9]
A "hypertensive emergency", previously "malignant hypertension", is diagnosed when there is evidence of direct damage to one or more organs as a result of the severely elevated blood pressure.
This may include hypertensive encephalopathy, caused by brain swelling and dysfunction, and characterized by headaches and an altered level of consciousness (confusion or drowsiness). Retinal papilloedema and/or fundal hemorrhages and exudates are another sign of target organ damage.
Chest pain may indicate heart muscle damage (which may progress to myocardial infarction) or sometimes aortic dissection, the tearing of the inner wall of the aorta. Breathlessness, cough, and the expectoration of blood-stained sputum are characteristic signs of pulmonary edema, the swelling of lung tissue due to left ventricular failure an inability of the left ventricle of the heart to adequately pump blood from the lungs into the arterial system.[9]
Rapid deterioration of kidney function (acute kidney injury) and microangiopathic hemolytic anemia (destruction of blood cells) may also occur.[9]
In these situations, rapid reduction of the blood pressure is mandated to stop ongoing organ damage.[9]
In contrast there is no evidence that blood pressure needs to be lowered rapidly in hypertensive urgencies where there is no evidence of target organ damage and over aggressive reduction of blood pressure is not without risks.[6]
Use of oral medications to lower the BP gradually over 24 to 48 h is advocated in hypertensive urgencies.[9]
Pregnancy
Hypertension occurs in approximately 8–10% of pregnancies.[6] Two blood pressure measurements six hours an apart of greater than 140/90 mm Hg is considered diagnostic of hypertension in pregnancy.[10]Most women with hypertension in pregnancy have pre-existing primary hypertension, but high blood pressure in pregnancy may be the first sign of pre-eclampsia, a serious condition of the second half of pregnancy and puerperium.[6] Pre-eclampsia is characterised by increased blood pressure and the presence of protein in the urine.[6] It occurs in about 5% of pregnancies and is responsible for approximately 16% of all maternal deaths globally.[6] Pre-eclampsia also doubles the risk of perinatal mortality.[6] Usually there are no symptoms in pre-eclampsia and it is detected by routine screening. When symptoms of pre-eclampsia occur the most common are headache, visual disturbance (often "flashing lights"), vomiting, epigastric pain, and edema. Pre-eclampsia can occasionally progress to a life-threatening condition called eclampsia, which is a hypertensive emergency and has several serious complications including vision loss, cerebral edema, seizures or convulsions, renal failure, pulmonary edema, and disseminated intravascular coagulation (a blood clotting disorder).[6][11]
Infants and children
Failure to thrive, seizures, irritability, lack of energy, and difficulty breathing[12] can be associated with hypertension in neonates and young infants. In older infants and children, hypertension can cause headache, unexplained irritability, fatigue, failure to thrive, blurred vision, nosebleeds, and facial paralysis.[12][13]Cause
Primary hypertension
Main article: Essential hypertension
Primary (essential) hypertension is the most common form of hypertension, accounting for 90–95% of all cases of hypertension.[2] In almost all contemporary societies, blood pressure rises with aging and the risk of becoming hypertensive in later life is considerable.[14]
Hypertension results from a complex interaction of genes and
environmental factors. Numerous common genetic variants with small
effects on blood pressure have been identified[15] as well as some rare genetic variants with large effects on blood pressure[16]
but the genetic basis of hypertension is still poorly understood.
Several environmental factors influence blood pressure. Lifestyle
factors that lower blood pressure include reduced dietary salt intake,[17][18] increased consumption of fruits and low fat products (Dietary Approaches to Stop Hypertension (DASH diet)), exercise,[19] weight loss[20] and reduced alcohol intake.[21] Stress appears to play a minor role[4] with specific relaxation techniques not supported by the evidence.[22][23] The possible role of other factors such as caffeine consumption,[24] and vitamin D deficiency[25] are less clear cut. Insulin resistance, which is common in obesity and is a component of syndrome X (or the metabolic syndrome), is also thought to contribute to hypertension.[26] Recent studies have also implicated events in early life (for example low birth weight, maternal smoking and lack of breast feeding) as risk factors for adult essential hypertension,[27] although the mechanisms linking these exposures to adult hypertension remain obscure.[27]Secondary hypertension
Main article: Secondary hypertension
Secondary hypertension results from an identifiable cause. Renal disease is the most common secondary cause of hypertension.[6] Hypertension can also be caused by endocrine conditions, such as Cushing's syndrome, hyperthyroidism, hypothyroidism, acromegaly, Conn's syndrome or hyperaldosteronism, hyperparathyroidism and pheochromocytoma.[6][28] Other causes of secondary hypertension include obesity, sleep apnea, pregnancy, coarctation of the aorta, excessive liquorice consumption and certain prescription medicines, herbal remedies and illegal drugs.[6][29]Prevention
Much of the disease burden of high blood pressure is experienced by people who are not labelled as hypertensive.[55] Consequently, population strategies are required to reduce the consequences of high blood pressure and reduce the need for antihypertensive drug therapy. Lifestyle changes are recommended to lower blood pressure, before starting drug therapy. The 2004 British Hypertension Society guidelines[55] proposed the following lifestyle changes consistent with those outlined by the US National High BP Education Program in 2002[58] for the primary prevention of hypertension:- maintain normal body weight for adults (e.g. body mass index 20–25 kg/m2)
- reduce dietary sodium intake to <100 chloride="" day="" g="" li="" mmol="" nbsp="" of="" or="" per="" sodium="">
- engage in regular aerobic physical activity such as brisk walking (≥30 min per day, most days of the week)
- limit alcohol consumption to no more than 3 units/day in men and no more than 2 units/day in women
- consume a diet rich in fruit and vegetables (e.g. at least five portions per day);
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