Hypertension is a disorder of the cardiovascular system characterized by elevated arterial blood pressure. The blood pressure in the arteries is dependent on the energy of cardiac contractions, elasticity, and contractile state of arterial walls, as well as on the volume and viscosity of the blood. It fluctuates with every heartbeat. The maximal pressure occurs near the end of the stroke output and is termed systolic. The minimal pressure occurs late in ventricular diastole and is termed diastolic.
Individuals with a systolic blood pressure at or under 120mmHg and diastolic pressure at or under 80 mmHg are considered normotensive. The term 'prehypertensive' is used for individuals with a systolic pressure under 140, but above 120 mmHg and diastolic pressure under 90, but above 80 mmHg. Patients with 140-159 mmHg systolic and over 90 mmHg diastolic have phase I hypertension, while patients with systolic pressure over 160 mmHg and diastolic pressure over 100 mmHg have phase II hypertension.1
It has been estimated that up to 50 million, or over 20%, Americans are likely to be hypertensive. Only 70% of hypertensive patients are aware of their disease, 59% are treated, and only 34% are controlled.1-3 The prevalence of hypertension in Europe has been estimated as 13%, but in reality may not be any different from that in the US, since definitions of hypertension and populations studied were different. In the UK 12% of adults over 16 years of age have blood pressure values above 160/95 mmHg, and a further 21% have values above 140/90 mmHg.5 In Spain 68% of elderly people are hypertensive and systolic blood pressure is controlled in only 32% of them.6
Most hypertensive patients have the so-called essential or idiopathic hypertension, a polygenic multifactorial disorder that involves the interaction of several genes with environmental factors.7 Genetic abnormalities have been demonstrated in only a small percentage of patients with essential hypertension.
Risk factors for hypertension include ethnicity, obesity, psychosocial stress, limited physical activity, and diet. Hypertension itself is the major risk factor for atherosclerosis and for mortality from cardiovascular disease. The incidence of cardiovascular events increases starting with a systolic pressure of 115 and diastolic of 75 mmHg. There is a substantial risk of cardiovascular disease with a systolic pressure of 130-139 mmHg, even though these levels are not considered hypertensive.
Hypertension is the primary cause of stroke and a risk factor for coronary heart disease, myocardial infarction, sudden cardiac death, cardiac failure, and renal insufficiency. Patients with extremely high and sustained blood pressure levels over 210 mmHg systolic are likely to have malignant hypertension, a microvascular occlusive disease that affects the kidneys, brain, retina, and other organs. Malignant hypertension is fatal if untreated.
In the US, the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC) establishes and reviews guidelines for the prevention, diagnosis, and management of hypertension. According to the last published guidelines of JNC (JNC VII),1 the primary target for therapy should be systolic rather than diastolic blood pressure. All patients with a systolic pressure over 160 mmHg should receive drug therapy. To achieve goal blood pressure levels with minimal side effects, two drugs acting by different mechanisms are usually prescribed. The decision to start therapy should be based on the blood pressure level as well as on the evidence of organ damage. The presence of organ (e.g., kidney) damage calls for an immediate initiation of therapy. In patients without organ damage initial home measurements or 24-h monitoring of arterial pressure prior to the start of therapy are recommended. This recommendation is based on the existence of the so-called 'white-coat' hypertension - blood pressure elevation in the physician's office or clinic only. 'White-coat' hypertension is considered relatively benign; it carries only a low risk of cardiovascular mortality.
In the diagnosis of hypertension it is important to determine whether hypertension is primary or secondary to another disease. Only 5-10% of hypertensive patients have secondary hypertension, but it should be suspected if onset is sudden, particularly in childhood or in patients older than 50 years of age, if it is severe, resistant to therapy, and/or accompanied by unusual symptoms. Conditions that may cause secondary hypertension include aortic coarctation, eclampsia or preeclampsia, brain tumors, lead or mercury poisoning, illicit or prescribed drugs, renal disease, adrenal tumors, primary aldosteronism, Cushing's disease, and obstructive sleep apnea. Elimination or specific therapy of the cause of secondary hypertension should be attempted as the initial therapeutic approach.
Hypertension is usually systemic, but it may be limited to certain organs. The term 'pulmonary hypertension' is used to describe a selective elevation of pressure in pulmonary arteries. Portal hypertension, a persistent elevation of pressure in portal veins, is usually a secondary hypertension that often occurs as a consequence of liver cirrhosis.
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Do You Suffer From High Blood Pressure? Do You Feel Like This Silent Killer Might Be Stalking You? Have you been diagnosed or pre-hypertension and hypertension? Then JOIN THE CROWD Nearly 1 in 3 adults in the United States suffer from High Blood Pressure and only 1 in 3 adults are actually aware that they have it.