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Course Sample:
Introduction
I. Epidemiology of Hypertension
Hypertension (HTN) or high blood pressure, is a medical condition in which constricted arterial blood vessels increase the resistance to blood flow, causing the blood to exert excessive pressure against vessel walls. Hypertension affects 25 percent of people living in North America, of these almost 1/3rd are unaware of their condition. In the United States, about 50 million people age six and older have high blood pressure. Hypertension is more common in men than women and in people over the age of 65 than in younger persons. More than half of all Americans over the age of 65 have hypertension. Until the age of 55, more men than women have hypertension. After that age, the condition becomes more prevalent in women. It is also more common in African-Americans than in white Americans. Hypertension is serious because people with the condition have a higher risk for heart disease and other medical problems than people with normal blood pressure Hypertension is significantly more common in African Americans of both sexes than in other racial or ethnic groups.
There are many situations wherein the blood pressure can rise - temporarily. Stressful situations can make blood pressure go up. When the stress goes away, blood pressure usually returns to normal. These temporary increases in blood pressure are not considered hypertension. A diagnosis of hypertension is made only when a person has multiple high blood pressure readings over a period of time.
The term essential hypertension describes cases when no clear cause can be identified. According to the American Heart Association, essential hypertension occurs in up to 95 percent of cases. Scientists suspect that genetic factors may play a role in this form of high blood pressure. In about 5 percent of cases, high blood pressure develops as a result of another medical disorder, such as kidney or liver disease, or as a side effect of certain medications. When a person has hypertension caused by another medical condition, it is called secondary hypertension. Secondary hypertension can be caused by a number of different illnesses. Many people with kidney disorders have secondary hypertension. Kidney infections, a narrowing of the arteries that carry blood to the kidneys (renal artery stenosis), and other kidney disorders can disturb the sodium and water balance. Cushing's syndrome and tumors of the pituitary and adrenal glands often increase levels of the adrenal gland hormones cortisol, adrenalin and aldosterone, which can cause hypertension. Other conditions that can cause hypertension are blood vessel diseases, thyroid gland disorders, some prescribed drugs, alcoholism and pregnancy. Other factors that may contribute to elevated blood pressure in some people include a diet high in sodium, physical inactivity, obesity, and heavy alcohol consumption. All of these disorders will not be discussed in this course as the focus of this course is on essential hypertension. However it is critical that secondary causes be ruled out!
II. Pathophysiology of Hypertension
Two factors determine blood pressure: the amount of blood the heart pumps and the diameter of the arteries receiving blood from the heart. When the arteries narrow, they increase the resistance to blood flow. The heart works harder to pump more blood so that the same amount of blood circulates to all the body tissues. The more blood the heart pumps and the smaller the arteries, the higher the blood pressure. As blood flows through arteries it pushes against the inside of the artery walls. The more pressure the blood exerts on the artery walls, the higher the blood pressure will be. The size of small arteries also affects the blood pressure. When the muscular walls of arteries are relaxed, or dilated, the pressure of the blood flowing through them is lower than when the artery walls narrow, or constrict. Blood pressure is highest when the heart beats (systole) to push blood out into the arteries. When the heart relaxes (diastole) to fill with blood again, the pressure is at its lowest point. Blood pressure when the heart beats is called systolic pressure. Blood pressure when the heart is at rest is called diastolic pressure.
The kidneys play a major role in the regulation of blood pressure. Kidneys secrete the hormone renin, which causes arteries to contract, thereby raising blood pressure. The kidneys also control the fluid volume of blood, either by retaining sodium or excreting sodium into urine. When kidneys retain sodium in the bloodstream, the sodium attracts water, increasing the fluid volume of blood. As a higher volume of blood passes through arteries, it increases blood pressure.
The AHA has defined the following as major risk factors for the development of hypertension:
- Age over 60
- Male sex
- Race
- Heredity
- Sodium sensitivity
- Obesity
- Inactive lifestyle
- Heavy alcohol consumption
- Use of oral contraceptives.
Obviously some of these risk factors for developing hypertension can be changed, while others cannot. Age, male sex, and race are risk factors that cannot be altered. Some people inherit a tendency to develop hypertension. People with family members who have hypertension are more likely to develop it than those whose relatives are not hypertensive. A person with these risk factors can avoid or eliminate the other modifiable risk factors to lower their chance of having high blood pressure. Non-pharmacological measures for reducing blood pressure will be discussed shortly.
III. Complications
Hypertension is serious because people with the condition have a higher risk for heart disease and other medical problems than people with normal blood pressure. Serious complications can be avoided by getting regular blood pressure checks and treating hypertension as soon as it is diagnosed. If left untreated, hypertension can lead to the following medical conditions:
- Arteriosclerosis, also called atherosclerosis
- Heart attack
- Stroke
- Enlarged heart
- Kidney damage.
If hypertension is not detected and treated, life-threatening complications develop over a course of years. Increased pressure on the inner walls of blood vessels make the vessels less flexible over time and more vulnerable to the buildup of fatty deposits in a process known as atherosclerosis. Weakened portions of the blood vessel wall may balloon, forming an aneurysm. If an aneurysm ruptures, internal hemorrhaging results. Both atherosclerosis and a ruptured aneurysm in the brain can lead to a stroke.
Hypertension forces the heart to work harder to pump adequate blood throughout the body. This extra work causes the muscles of the heart to enlarge, and eventually the enlarged heart becomes inefficient in pumping blood. An enlarged heart may lead to heart failure, in which the heart can not pump enough blood to meet the body's needs. Increased blood pressure may damage the small blood vessels within the kidney. The kidney then becomes unable to filter blood efficiently, and waste products may build up in the blood in a condition known as uremia. Without medical treatment, kidney failure will result.
IV. Screening
Screening of a population without the diagnosis of hypertension is the first element. Health care providers must identify those individuals who are in high risk populations for elevated blood pressure: smokers (30% increase in hypertension), patients with Type II diabetes (55% have hypertension), dyslipidemic patients (25% increase in hypertension). The diagnosis of hypertension is based on the average of 2 or more readings taken at each of 2 or more visits after an initial screening in patients not currently on antihypertensive drugs or who are not acutely ill. Risk classification also depends on presence or absence of target organ damage or clinical cardiovascular disease (CVD) and additional risk factors. The provider will then make the diagnosis of hypertension on the following:
Table
1:
Criteria for diagnosis of HTN.
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Stage
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Systolic
BP (mm Hg)
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Diastolic
BP (mm Hg)
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