Hypertension can be classified as either essential (primary) or secondary. Essential or primary hypertension means that no medical cause can be found to explain the raised blood pressure. It is common. About 90-95% of hypertension is essential hypertension. Secondary hypertension indicates that the high blood pressure is a result of (i.e., secondary to) another condition, such as kidney disease or tumours (adrenal adenoma or pheochromocytoma).
Persistent hypertension is one of the risk factors for strokes, heart attacks, heart failure and arterial aneurysm, and is a leading cause of chronic renal failure.[6] Even moderate elevation of arterial blood pressure leads to shortened life expectancy. At severely high pressures, defined as mean arterial pressures 50% or more above average, a person can expect to live no more than a few years unless appropriately treated.[7] Beginning at a systolic pressure (which is peak pressure in the arteries, which occurs near the end of the cardiac cycle when the ventricles are contracting) of 115 mmHg and diastolic pressure (which is minimum pressure in the arteries, which occurs near the beginning of the cardiac cycle when the ventricles are filled with blood) of 75 mmHg (commonly written as 115/75 mmHg), cardiovascular disease (CVD) risk doubles for each increment of 20/10 mmHg.[8]
A recent classification recommends blood pressure criteria for defining normal blood pressure, prehypertension, hypertension (stages I and II), and isolated systolic hypertension, which is a common occurrence among the elderly. These readings are based on the average of seated blood pressure readings that were properly measured during 2 or more office visits. In individuals older than 50 years, hypertension is considered to be present when a person's blood pressure is consistently at least 140 mmHg systolic or 90 mmHg diastolic. Patients with blood pressures over 130/80 mmHg along with Type 1 or Type 2 diabetes, or kidney disease require further treatment.[8]
Resistant hypertension is defined as the failure to reduce blood pressure to the appropriate level after taking a three-drug regimen (include thiazide diuretic).[8] Guidelines for treating resistant hypertension have been published in the UK,[9] and US.[10]
Excessive elevation in blood pressure during exercise is called exercise hypertension.The upper normal systolic values during exercise reach levels between 200 and 230 mm Hg.[14] Exercise hypertension may be regarded as a precursor to established hypertension at rest.
Mild to moderate essential hypertension is usually asymptomatic.Accelerated hypertension is associated with headache, somnolence, confusion, visual disturbances, and nausea and vomiting (hypertensive encephalopathy). Retinas are affected with narrowing of arterial diameter to less than 50% of venous diameter, copper or silver wire appearance, exudates, hemorrhages, or papilledema.[20] Some signs and symptoms are especially important in infants and neonates such as failure to thrive, seizure, irritability or lethargy, and respiratory distress.[21] While in children hypertension may cause headache, fatigue, blurred vision, epistaxis, and bell palsy.[21]
Some signs and symptoms are especially important in suggesting a secondary medical cause of chronic hypertension, such as centripetal obesity, "buffalo hump," and/or wide purple abdominal striae and maybe a recent onset of diabetes suggest glucocorticoid excess either due to Cushing's syndrome or other causes. Hypertension due to other secondary endocrine diseases such as hyperthyroidism, hypothyroidism, or growth hormone excess show symptoms specific to these disease such as in hyperthyrodism there may be weight loss, tremor, tachycardia or atrial arrhythmia, palmar erythema and sweating.[22] Signs and symptoms associated with growth hormone excess such as coarsening of facial features, prognathism, macroglossia,[23] hypertrichosis, hyperpigmentation, and hyperhidrosis may occur in these patients.[24]:499. Other endocrine causes such as hyperaldosteronism may cause less specific symptoms such as numbness, polyuria, polydipsia, hypernatraemia, and metabolic alkalosis.[25] A systolic bruit heard over the abdomen or in the flanks suggests renal artery stenosis. Also radio femoral delay or diminished pulses in lower versus upper extremities suggests coarctation of the aorta. Hypertension in patients with pheochromocytomas is usually sustained but may be episodic. The typical attack lasts from minutes to hours and is associated with headache, anxiety, palpitation, profuse perspiration, pallor, tremor, and nausea and vomiting. Blood pressure is markedly elevated, and angina or acute pulmonary edema may occur. In primary aldosteronism, patients may have muscular weakness, polyuria, and nocturia due to hypokalemia. Chronic hypertension often leads to left ventricular hypertrophy, which can present with exertional and paroxysmal nocturnal dyspnea. Cerebral involvement causes stroke due to thrombosis or hemorrhage from microaneurysms of small penetrating intracranial arteries. Hypertensive encephalopathy is probably caused by acute capillary congestion and exudation with cerebral edema, which is reversible.[20]
Signs and symptoms associated with pre-eclampsia and eclampsia, can be proteinuria, edema, and hallmark of eclampsia which is convulsions, Other cerebral signs may precede the convulsion such as nausea, vomiting, headaches, and blindness.
Essential hypertension
Main article: Essential hypertension
Hypertension is one of the most common complex disorders. The etiology of hypertension differs widely amongst individuals within a large population.[27] Essential hypertension is the form of hypertension that by definition, has no identifiable cause. It is the more common type and affects 90-95% of hypertensive patients,[2][3][4][5] and even though there are no direct causes, there are many risk factors such as sedentary lifestyle,[28] obesity(more than 85% of cases occur in those with a body mass index greater than 25),[33] salt (sodium) sensitivity, alcohol intake,and vitamin D deficiency.[40][41][42] It is also related to aging[43] and to some inherited genetic mutations. Family history increases the risk of developing hypertension. Renin elevation is another risk factor, Renin is an enzyme secreted by the juxtaglomerular apparatus of the kidney and linked with aldosterone in a negative feedback loop.[30][51] Also sympathetic overactivity is implicated.[32][52][53][54][55] Insulin resistance which is a component of syndrome X, or the metabolic syndrome is also thought to cause hypertension.Recently low birth weight has been questioned as a risk factor for adult essential hypertension.
[edit] Secondary hypertension
Main article: Secondary hypertension
Secondary hypertension by definition results from an identifiable cause. This type is important to recognize since its treated differently than essential type by treating the underlying cause.
Many secondary cause can cause hypertension, some are common and well recognized secondary causes such as Cushing's syndrome,[58] which is a condition where both adrenal glands can overproduce the hormone cortisol. Hypertension results from the interplay of several pathophysiological mechanisms regulating plasma volume, peripheral vascular resistance and cardiac output, all of which may be increased. More than 80% of patients with Cushing's syndrome have hypertension.[58] Another important cause is the congenital abnormality coarctation of the aorta.
A variety of adrenal cortical abnormalities can cause hypertension, In primary aldosteronism there is a clear relationship between the aldosterone-induced sodium retention and the hypertension.[59] Another related disorder that causes hypertension is apparent mineralocorticoid excess syndrome which is an autosomal recessive disorder results from mutations in gene encoding 11¦Â-hydroxysteroid dehydrogenase which normal patient inactivates circulating cortisol to the less-active metabolite cortisone.[60] Cortisol at high concentrations can cross-react and activate the mineralocorticoid receptor, leading to aldosterone-like effects in the kidney, causing hypertension.[61] This effect can also be produced by prolonged ingestion of liquorice(which can be of potent strength in liquorice candy), can result in inhibition of the 11¦Â-hydroxysteroid dehydrogenase enzyme and cause secondary apparent mineralocorticoid excess syndrome. Frequently, if liquorice is the cause of the high blood pressure, a low blood level of potassium will also be present.[63] Yet another related disorder causing hypertension is glucocorticoid remediable aldosteronism, which is an autosomal dominant disorder in which the increase in aldosterone secretion produced by ACTH is no longer transient, causing of primary hyperaldosteronism, the Gene mutated will result in an aldosterone synthase that is ACTH-sensitive, which is normally not.GRA appears to be the most common monogenic form of human hypertension.[70] Compare these effects to those seen in Conn's disease, an adrenocortical tumor which causes excess release of aldosterone,[71] that leads to hypertension.
Another adrenal related cause is Cushing's syndrome which is a disorder caused by high levels of cortisol. Cortisol is a hormone secreted by the cortex of the adrenal glands. Cushing's syndrome can be caused by taking glucocorticoid drugs, or by tumors that produce cortisol or adrenocorticotropic hormone (ACTH).[75] More than 80% of patients with Cushing's syndrome develop hypertension.[58], which is accompanied by distinct symptoms of the syndrome, such as central obesity, buffalo hump, moon face, sweating, hirsutism and anxiety.[76]
Other well known causes include diseases of the kidney. This includes diseases such as polycystic kidney disease which is a cystic genetic disorder of the kidneys, PKD is characterized by the presence of multiple cysts (hence, "polycystic") in both kidneys, can also damage the liver, pancreas, and rarely, the heart and brain.[77][78][79][80] It can be autosomal dominant or autosomal recessive, with the autosomal dominant form being more common and characterized by progressive cyst development and bilaterally enlarged kidneys with multiple cysts, with concurrent development of hypertension, renal insufficiency and renal pain.[81] Or chronic glomerulonephritis which is a disease characterized by inflammation of the glomeruli, or small blood vessels in the kidneys.[82][83][84] Hypertension can also be produced by diseases of the renal arteries supplying the kidney. This is known as renovascular hypertension; it is thought that decreased perfusion of renal tissue due to stenosis of a main or branch renal artery activates the renin-angiotensin system.[85][86][87] also some renal tumors can cause hypertension. The differential diagnosis of a renal tumor in a young patient with hypertension includes Juxtaglomerular cell tumor, Wilms' tumor, and renal cell carcinoma, all of which may produce renin.[88]
Neuroendocrine tumors are also a well known cause of secondary hypertension. Pheochromocytoma[89] (most often located in the adrenal medulla) increases secretion of catecholamines such as epinephrine and norepinephrine, causing excessive stimulation of adrenergic receptors, which results in peripheral vasoconstriction and cardiac stimulation. This diagnosis is confirmed by demonstrating increased urinary excretion of epinephrine and norepinephrine and/or their metabolites (vanillylmandelic acid).
Certain medications, especially NSAIDs (Motrin/Ibuprofen) and steroids can cause hypertension.[90][91][92][93][94] High blood pressure that is associated with the sudden withdrawal of various antihypertensive medications is called Rebound Hypertension.The increases in blood pressure may result in blood pressures greater than when the medication was initiated. Depending on the severity of the increase in blood pressure, rebound hypertension may result in a hypertensive emergency. Rebound hypertension is avoided by gradually reducing the dose (also known as "dose tapering"), thereby giving the body enough time to adjust to reduction in dose. Medications commonly associated with rebound hypertension include centrally-acting antihypertensive agents, such as clonidine[102] and beta-blockers.[101]
Few women of childbearing age have high blood pressure, up to 11% develop hypertension of pregnancy.[103] While generally benign, it may herald three complications of pregnancy: pre-eclampsia, HELLP syndrome and eclampsia. Follow-up and control with medication is therefore often necessary.[104][105]
Another common and under-recognized cause of hypertension is sleep apnea,[106][107] which is often best treated with nocturnal nasal continuous positive airway pressure (CPAP), but other approaches include the Mandibular advancement splint (MAS), UPPP, tonsillectomy, adenoidectomy, septoplasty, or weight loss. Another cause is an exceptionally rare neurological disease called Binswanger's disease, causing dementia; it is a rare form of multi-infarct dementia, and is one of the neurological syndromes associated with hypertension.[108]
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.[109][110][111]
• 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.
Initial assessment of the hypertensive patient should include a complete history and physical examination to confirm a diagnosis of hypertension. Most patients with hypertension have no specific symptoms referable to their blood pressure elevation. Although popularly considered a symptom of elevated arterial pressure, headache generally occurs only in patients with severe hypertension. Characteristically, a "hypertensive headache" occurs in the morning and is localized to the occipital region. Other nonspecific symptoms that may be related to elevated blood pressure include dizziness, palpitations, easy fatiguability, and impotence.
