High blood pressure (HBP) or hypertension means high pressure (tension) in the arteries. Arteries are vessels that carry blood from the pumping heart to all the tissues and organs of the body.
High blood pressure does not mean excessive emotional tension, although emotional tension and stress can temporarily increase blood pressure. Normal blood pressure is below 120/80; blood pressure between 120/80 and 139/89 is called "pre-hypertension", and a blood pressure of 140/90 or above is considered high.
The top number, the systolic blood pressure, corresponds to the pressure in the arteries as the heart contracts and pumps blood forward into the arteries. The bottom number, the diastolic pressure, represents the pressure in the arteries as the heart relaxes after the contraction. The diastolic pressure reflects the lowest pressure to which the arteries are exposed.
An elevation of the systolic and/or diastolic blood pressure increases the risk of developing heart (cardiac) disease, kidney (renal) disease, hardening of the arteries (atherosclerosis or arteriosclerosis), eye damage, and stroke (brain damage). These complications of hypertension are often referred to as end-organ damage because damage to these organs is the end result of chronic (long duration) high blood pressure.
For that reason, the diagnosis of high blood pressure is important so efforts can be made to normalize blood pressure and prevent complications.
It was previously thought that rises in diastolic blood pressure were a more important risk factor than systolic elevations, but it is now known that in people 50 years or older systolic hypertension represents a greater risk.
The American Heart Association estimates high blood pressure affects approximately one in three adults in the United States - 73 million people. High blood pressure is also estimated to affect about two million Americanteens and children, and the Journal of the American Medical Association reports that many are under-diagnosed. Hypertension is clearly a major public health problem.
Mild to moderate essential hypertension is usually asymptomatic.
Accelerated hypertension is associated with headache, drowsiness, confusion, vision disorders, nausea and vomiting. These symptoms are collectively called hypertensive encephalopathy. Hypertensive encephalopathy is caused by severe small blood vessel congestion and brain swelling, which is reversible if blood pressure is lowered.
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.
Signs and symptoms associated with growth hormone excess include coarsening of facial features, protrusion of the lower jaw, enlargement of the tongue, excessive hair growth, darkening of the skin color, and excessive sweating.
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 and also cause mental pressure.
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.
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.
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.
Two forms of high blood pressure have been described: essential (or primary) hypertension and secondary hypertension. Essential hypertension is a far more common condition and accounts for 95% of hypertension.
The cause of essential hypertension is multifactorial, that is, there are several factors whose combined effects produce hypertension. In secondary hypertension, which accounts for 5% of hypertension, the high blood pressure is secondary to (caused by) a specific abnormality in one of the organs or systems of the body. Secondary hypertension is discussed further in a separate section later.
Essential hypertension affects approximately 72 million Americans, yet its basic causes or underlying defects are not always known. Nevertheless, certain associations have been recognized in people with essential hypertension. For example, essential hypertension develops only in groups or societies that have a fairly high intake of salt, exceeding 5.8 grams daily.
Salt intake may be a particularly important factor in relation to essential hypertension in several situations, and excess salt may be involved in the hypertension that is associated with advancing age, African American background, obesity, hereditary (genetic) susceptibility, and kidney failure (renal insufficiency).
The Institute of Medicine of the National Academies recommends healthy 19 to 50-year-old adults consume only 3.8 grams of salt to replace the average amount lost daily through perspiration and toachieve a diet that provides sufficient amounts of other essential nutrients.
Genetic factors are thought to play a prominent role in the development of essential hypertension. However, the genes for hypertension have not yet been identified. Genes are tiny portions of chromosomes that produce theproteins that determine the characteristics of individuals. The current research in this area is focused on the genetic factors that affect the renin-angiotensin-aldosterone system. This system helps to regulate blood pressure by controlling salt balance and the tone (state of elasticity) of the arteries.
Approximately 30% of cases of essential hypertension are attributable to genetic factors. For example, in the United States, the incidence of high blood pressure is greater among African Americans than among Caucasians or Asians. Also, in individuals who have one or two parents with hypertension, high blood pressure is twice as common as in the general population.
Rarely, certain unusual genetic disorders affecting the hormones of the adrenal glands may lead to hypertension. These identified genetic disorders are considered secondary hypertension.
The vast majority of patients with essential hypertension have in common a particular abnormality of the arteries: an increased resistance (stiffness or lack of elasticity) in the tiny arteries that are most distant from the heart (peripheral arteries or arterioles). The arterioles supply oxygen-containing blood and nutrients to all of the tissues of the body.
The arterioles are connected by capillaries in the tissues to the veins (the venous system), which returns the blood to the heart and lungs. Just what makes the peripheral arteries become stiff is not known.
Yet, this increased peripheral arteriolar stiffness is present in those individuals whose essential hypertension is associated with genetic factors, obesity, lack of exercise, overuse of salt, and aging. Inflammation also may play a role in hypertension since a predictor of the development of hypertension is the presence of an elevated C reactive protein level (a blood test marker of inflammation) in some individuals.
Your doctor may prescribe antihypertension medication if your blood pressure is high. There are several kinds of medication commonly taken alone or in combination, according to the American Heart Association (AHA).
Types of medication
Diuretics help to lower blood pressure by eliminating excess fluid and salt that accumulate in the body. The excess fluid is eliminated in the urine. Examples of commonly prescribed diuretics are furosemide (Lasix), hydrochlorothiazide (Esidrix, Hydrodiuril), chlorothiazide (Diuril), spironolactone (Aldactone) and ethacrynic acid (Edecrin).
These keep the heart from pumping too hard by blocking the action of the hormones that normally increase heart rate and cardiac output. Examples of commonly prescribed beta blockers are atenolol (Tenormin), metoprolol (Lopressor, Toprol XL), nadolol (Corgard) and propranolol (Inderal).
Alpha blockers prohibit the production of a hormone that makes the blood vessels constrict. Examples of alpha blockers are doxazosin (Cardura), prazosin (Minipress) and terazosin (Hytrin).
Calcium channel blockers
These cause blood vessels to dilate or widen by reducing the calcium concentration in their cells. Some also slow the heart rate.
Some commonly prescribed calcium channel blockers are amlodipine (Norvasc, Lotrel), verapamil (Calan, Isoptin, Verelan) and nifedipine (Adalat, Procardia).