Introduction
Arterial hypertension, or high blood pressure is a medical condition where the blood pressure is chronically elevated. 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 measured on both arms at two instances (several weeks apart) is considered high blood pressure. The complications of hypertension are often referred to as end-organ damage because damage to these organs is the end result of chronic high blood pressure. Uncontrolled hypertension can cause strokes, which can lead to brain or neurological damage. The strokes are usually due to a hemorrhage or a thrombosis of the blood vessels that supply blood to the brain. The patient's symptoms and signs are evaluated to assess the neurological damage. A stroke can cause weakness, tingling, or paralysis of the arms or legs and difficulties with speech or vision. Multiple small strokes can lead to dementia. The best prevention for this complication of hypertension or, for that matter, for any of the complications, is control of the blood pressure.
Epidemiology
The level of blood pressure regarded as deleterious has been revised down during years of epidemiological studies. A widely quoted and important series of such studies is the Framingham Heart Study carried out in an American town: Framingham, Massachusetts. The results from Framingham and of similar work in Busselton, Western Australia have been widely applied. To the extent that people are similar this seems reasonable, but there are known to be genetic variations in the most effective drugs for particular sub-populations.
High blood pressure does not mean excessive emotional tension, although emotional tension and stress can temporarily increase the blood pressure. While chronic anxiety is associated with poor outcomes in people with hypertension, it alone does not cause it.
Prevalence
Cardiovascular diseases (CVD), most of which are due to atherosclerosis (mainly heart attack and stroke) and often related to arterial hypertension (AH), are responsible for nearly 20% of all deaths world-wide (nearly 10 million). They are the principal cause of death in all developed countries accounting for 50% of all deaths and are also emerging as a prominent public health problem in developing countries, ranking third with nearly 16% of all deaths. It is known that more than 95 % of hypertensive patients in the community are of essential or idiopathic/unknown aetiology, and only a small percentage have an identifiable cause (secondary hypertension).
Essential hypertension affects approximately 75 million Americans, almost 1 in 4 adults in the United States. It is thus a major public health problem. African American patients with poorly controlled hypertension are at a higher risk than Caucasians for most end-organ damage and particularly kidney damage. These differentials are more pronounced in young adult women. Among the very old, race differentials in hypertension prevalence rates are less pronounced. The reasons for the epidemic hypertension rates in the United States are largely environmental: Obesity and physical inactivity probably account for a significant proportion of the premature excess hypertension in African Americans relative to white women.
According to a recent survey, 1.0% of the adult American population use complementary and alternative medicine to treat hypertension.
Age
Mean systolic and diastolic blood pressure and prevalence of AH increase with age throughout childhood, adolescence and adulthood in most populations of developed and developing countries. However, in some isolated populations, this age-related rise of blood pressure (BP) is not evident.
Sex/gender
Men tend to display higher blood pressure than women, more evident in youth and middle-age. Later in life (over 50 years old), the difference narrows and the pattern may be reversed.
Heredity
Although the precise mode of heredity/inheritance has not yet been demonstrated, a high occurrence of hypertension is observed among subjects with a family history of hypertension and it is higher and more severe when both parents are concerned.
Ethnicity/race
Studies have also revealed higher blood pressure levels in the black community than in other ethnic groups, mainly in black Afro-Americans with early onset, severity and appearance of complications.
Causes
Over 90% of all hypertension has no known cause and is therefore called "essential/primary hypertension". Approximately 30 % of cases of essential hypertension are attributable to genetic factors. Often, it is part of the Syndrome X in patients with insulin resistance as it occurs in combination with diabetes mellitus (type 2), combined hyperlipidemia and central obesity.
Important causes of secondary hypertension are:
* Renal artery stenosis (due to fibromuscular hyperplasia in younger individuals and atherosclerosis in older people)
* Pheochromocytoma
* Hyperaldosteronism (Conn's syndrome)
* Cushing's disease
* Steroid use
* Coarctation of the aorta
* Chronic renal failure
* Scleroderma crisis
Risk factors
* African American descendants
* Obesity and physical inactivity
* Alcohol
* High salt intake
* Psychosocial stress
* Hereditary (genetic)
Pathogenesis
High blood pressure or hypertension means high pressure (tension) in the arteries. The arteries are the vessels that carry blood from the pumping heart to all of the tissues and organs of the body. The systolic blood pressure represents the pressure in the arteries as the heart contracts and pumps blood into the arteries. The diastolic pressure represents the pressure in the arteries as the heart relaxes after the contraction. The diastolic pressure, therefore, reflects the minimum pressure to which the arteries are exposed. An elevation of the systolic and/or diastolic blood pressure increases the risk of developing heart disease, kidney disease, atherosclerosis or arteriosclerosis, eye damage, and stroke.
The vast majority of patients with essential hypertension have in common a particular abnormality of the arteries. They have an increased resistance (stiffness or lack of elasticity) in the peripheral arteries or arterioles. 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 in some individuals.
Symptoms and signs
Hypertension can progress without symptoms (silently) to finally develop any one or more of the several potentially fatal complications of hypertension such as heart attacks or strokes. As a matter of fact, uncomplicated hypertension may be present and remain unnoticed for many years, or even decades. This happens when there are no symptoms, and those affected fail to undergo periodic blood pressure screening.
Some people with uncomplicated hypertension, however, may experience symptoms such as headache, dizziness, shortness of breath, and blurred vision. The presence of symptoms can be a good thing in that they can prompt people to consult a doctor for treatment and make them more compliant in taking their medications. Not infrequently, however, a person's first contact with a physician may be after significant damage to the end-organs has occurred.
About 1% people with hypertension is diagnosed with severe high blood pressure (accelerated or malignant hypertension) at their first visit to the doctor. In these patients, the diastolic blood pressure (the minimum pressure) exceeds 140 mm Hg! Affected persons often experience severe headache, nausea, visual symptoms, dizziness, and sometimes kidney failure. Malignant hypertension is a medical emergency and requires urgent treatment to prevent a stroke.
Complications
* Malignant hypertension
* Hypertensive cardiomyopathy
* Hypertensive retinopathy
* Hypertensive nephropathy
* Atrial fibrillation
* Hypertension of pregnancy:
o Pre-eclampsia
o Eclampsia
Diagnosis
Hypertension is diagnosed using a sphygmomanometer according to the guidelines outlined in the definition above. A blood pressure of 140/90 or above measured on both arms at two instances (several weeks apart) is considered high blood pressure.
Chronic high blood pressure can lead to an enlarged heart, kidney failure, brain or neurological damage, and changes in the retina at the back of the eyes. Examination of the eyes in patients with severe hypertension may reveal damage--narrowing of the small arteries, small hemorrhages in the retina, and swelling of the optic disc.
People with high blood pressure have an increased stiffness or resistance in the peripheral arteries throughout the tissues of the body. This increased resistance causes the heart muscle to work harder to pump the blood through these blood vessels. The increased workload can put a strain on the heart, which can lead to heart abnormalities that are usually first seen as enlarged heart muscle. Enlargement of the heart can be evaluated by chest x-ray, electrocardiogram, and most accurately by echocardiography. Ecocardiography is especially useful in determining the enlargement of the left side of the heart. Heart enlargement may be a forerunner of heart failure, coronary artery disease, and cardiac arrhythmias. Proper treatment of the high blood pressure and its complications can reverse some of these heart abnormalities.
Blood and urine tests may be helpful in detecting kidney abnormalities in people with high blood pressure, although kidney damage can itself be the cause or the result of hypertension. An elevated level of serum creatinine indicates damage to the kidney. In addition, proteinuria may reflect chronic kidney damage from hypertension, even if the kidney function (as represented by the blood creatinine level) is normal. In fact, protein in the urine alone signals the risk of deterioration in kidney function if the blood pressure is not controlled. Even small amounts of protein (microalbuminuria) may be a signal of impending kidney failure and other vascular complications from uncontrolled hypertension. Recent studies have also suggested the angiotensin receptor blocking drugs may offer an additional protective effect against strokes above and beyond control of blood pressure. Other tests include testing blood glucose as hypertension co-exists with diabetes in many instances, and electrolytes (sodium and potassium) in a newly diagnosed hypertension patient, particularly in young patients when secondary hypertension is highly suspected.
Treatment
Lifestyle modifications
Lifestyle modifications refer to certain specific recommendations for changes in habits, diet and exercise. These modifications can lower the blood pressure as well as improve a patient's response to blood pressure medications.
Alcohol
People who drink alcohol excessively (over two drinks per day) have a one and a half to two times increase in the prevalence of hypertension. The association between alcohol and high blood pressure is particularly noticeable when the alcohol intake exceeds 5 drinks per day. Moreover, the connection is a dose-related phenomenon, thus the more alcohol is consumed, the stronger is the link with hypertension.
Smoking
Although smoking increases the risk of vascular complications in people who already have hypertension, it is not associated with an increase in the development of hypertension. Nevertheless, smoking a cigarette can repeatedly produce an immediate, temporary rise in the blood pressure of 5 to 10 mm Hg. Steady smokers however, actually may have a lower blood pressure than nonsmokers. The reason for this is that the nicotine in the cigarettes causes a decrease in appetite, which leads to weight loss. This, in turn, lowers the blood pressure.
Coffee
In one study, the caffeine consumed in 5 cups of coffee daily caused a mild increase in blood pressure in elderly people who already had hypertension, but not in those who had normal blood pressures. What's more, the combination of smoking and drinking coffee in persons with high blood pressure may increase the blood pressure more than coffee alone. Limiting caffeine intake and cigarette smoking in hypertensive individuals, therefore, may be of some benefit in controlling their high blood pressure.
Salt
The American Heart Association recommends that the consumption of dietary salt be less than 6 grams of salt per day in the general population and a lower level (for example, less than 4 grams) for people with hypertension. To achieve a diet containing less than 4 grams of salt, a person should not add salt to their food or cooking. Also, the amount of natural salt in the diet can be reasonably estimated from the labeling information provided with most purchased foods.
Obesity
Obesity is common among hypertensive patients, and its prevalence increases with age. In fact, obesity may be what determines the increased incidence of high blood pressure with age. Obesity can contribute to hypertension in several possible ways. For one thing, obesity leads to a greater output of blood because the heart has to pump out more blood to supply the excess tissue. The increased cardiac output then can raise the blood pressure. For another thing, obese hypertensive individuals have a greater resistance in their peripheral arteries throughout the body. In addition, insulin resistance and the metabolic syndrome described previously occur more frequently in the obese. Finally, obesity may be associated with a tendency for the kidneys to retain salt. Weight loss may help reverse problems related to obesity while also lowering the blood pressure. It has been estimated that the blood pressure can be decreased 0.32 mm Hg for every 1 kg (2.2 pounds) of weight lost down to ideal body weight for the individual.
Some obese people, especially if they are very obese, have a syndrome called sleep apnea. This syndrome is characterized by the periodic interruption of normal breathing during sleep. Sleep apnea may contribute to the development of hypertension in this subgroup of obese individuals. This happens because the repeated episodes of apnea cause hypoxia. The hypoxia then causes the adrenal gland to release adrenalin and related substances. Finally, the adrenalin and related substances cause a rise in the blood pressure.
Exercise
A regular exercise program may help lower blood pressure over the long term. For example, activities such as jogging, bicycle riding, or swimming for 30 to 45 minutes daily may ultimately lower blood pressure by as much as 5 to15 mm Hg. Moreover, there appears to be a relationship between the amount of exercise and the degree to which the blood pressure is lowered. Thus, the more you exercise (up to a point), the more you lower the blood pressure. The beneficial response of the blood pressure to exercise occurs only with aerobic (vigorous and sustained) exercise programs. Therefore, any exercise program must be recommended or approved by an individual's physician.
