Blood pressure has gotten a bad rap. Some pressure is essential for circulation. Without it, blood couldn't move from the heart to the brain and the toes and back again. The heart provides the driving force — each contraction of the left ventricle, the heart's main pumping chamber, creates a wave of pressure that passes through all the arteries in the body. Relaxed and flexible arteries offer a healthy amount of resistance to each pulse of blood.
But too much of a good thing is a bad thing. Arteries that are tensed, constricted, or rigid offer more resistance. This shows up as higher blood pressure, and it makes the heart work harder. This extra work can weaken the heart muscle over time. It can damage other organs, like the kidneys and the eyes. And the relentless pounding of blood against the walls of arteries causes them to become hard and narrow, potentially setting the stage for a heart attack or stroke.
Most people with high blood pressure (known medically as hypertension) don't know they have it. Hypertension has no symptoms or warning signs. Yet it can be so dangerous to your health and well-being that it has earned the nickname "the silent killer." When high blood pressure is accompanied by high cholesterol and blood sugar levels, the damage to the arteries, kidneys, and heart accelerates exponentially.
High blood pressure is preventable. Daily exercise, following a healthy diet, limiting your intake of alcohol and salt, reducing stress, and not smoking are keys to keeping blood pressure under control. When it creeps into the unhealthy range, lifestyle changes and medications can bring it down.
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Atherosclerosis is a narrowing of the arteries that can significantly reduce the blood supply to vital organs such as the heart, brain and intestines. In atherosclerosis, the arteries are narrowed when fatty deposits called plaques build up inside. Plaques typically contain cholesterol from low-density lipoproteins (LDL), smooth-muscle cells and fibrous tissue, and sometimes calcium.
As a plaque grows along the lining of an artery, it produces a rough area in the artery's normally smooth surface. This rough area can cause a blood clot to form inside the artery, which can totally block blood flow. As a result, the organ supplied by the blocked artery starves for blood and oxygen. The organ's cells may either die or suffer severe damage.
Coronary artery disease (CAD) is the narrowing of coronary arteries. These are the blood vessels that supply blood and oxygen to the heart. The condition is also called coronary heart disease (CHD).
CAD is usually caused by atherosclerosis. Atherosclerosis is the buildup of plaque inside the coronary arteries. These plaques are made up of fatty deposits and fibrous tissue.
In most cases of high blood pressure (hypertension), there is no known cause. About 6% of the time, however, high blood pressure is caused by another condition or disease. When this happens, it is called secondary hypertension.
Most of the conditions that cause secondary hypertension involve the overproduction of one of the body's hormones. Some of the medical problems that can cause secondary hypertension include:
Kidney disease. Secondary hypertension can be related to damaged kidneys or to an abnormal narrowing of one or both renal arteries. The renal arteries are the major blood vessels that bring blood to each kidney. When the kidney's blood supply is reduced by a narrowing (called renal artery stenosis), the kidney produces high levels of a hormone called renin. High levels of renin trigger the production of other substances in the body that raise blood pressure, particularly a molecule called angiotensin II.
Adrenal disease. The adrenal glands sit on top of the kidneys and produce several hormones that help regulate blood pressure. Sometimes, one or both adrenal glands make and secrete an excess of one of these hormones.
Bradycardia is an abnormally slow heart rate of less than 60 beats per minute. A normal heartbeat is between 60 and 100 beats per minute.
Here's what happens during a normal heartbeat: The electrical signal that starts a heartbeat comes from the heart's sinus node, the natural pacemaker located in the upper portion of the right atrium. From the sinus node, the heartbeat signal travels to the atrioventricular (A-V) node, located between the atria, and then through the bundle of His (pronounced "hiss") -- a series of modified heart-muscle fibers located between the ventricles -- to the muscles of the ventricles. This triggers a contraction of the ventricles and produces a heartbeat.
In peripheral arterial disease (previously called peripheral vascular disease), not enough blood flows to the legs. The condition usually is caused by fatty deposits called plaques that build up along the walls of blood vessels. This buildup shrinks the size of the passageway and reduces the amount of blood that can flow through. This is a condition called atherosclerosis.
Strokes can damage brain tissue in the outer part of the brain (the cortex) or deeper structures in the brain underneath the cortex. A stroke in a deep area of the brain (for example, a stroke in the thalamus, the basal ganglia or pons) is called a lacunar stroke. These deeper structures receive their blood flow through a unique set of arteries. Because of the characteristics of these arteries, lacunar strokes happen a little bit differently from other strokes.
A lacunar stroke occurs when one of the arteries that provide blood to the brain's deep structures is blocked. These arteries are small, and are uniquely vulnerable. Unlike most arteries, which gradually taper to a smaller size, the arteries of a lacunar stroke branch directly off of a large, high-pressure, heavily muscled main artery. High blood pressure (hypertension) can lead to lacunar strokes because it causes a pounding pulse. Since the arteries don't gradually taper down in their size, high blood pressure can directly damage these arteries. High blood pressure also can cause atherosclerosis, a condition in which fatty deposits (plaques) build up along the walls of blood vessels. When atherosclerosis is present, a clot can form inside of one of these small arteries, blocking blood flow in the artery.
Polyarteritis nodosa is a rare, but potentially life threatening, inflammation of the blood vessels (vasculitis) that damages the walls of the body's small- and medium-sized arteries. This damage slows the supply of blood and nourishment to the arteries, causing nearby tissue in many parts of the body to be injured or even destroyed. The disease most commonly affects the kidneys, the nerves of the arms and legs and the abdominal organs, although it can also involve the skin, joints, muscles, brain, heart, eyes and reproductive organs.
Vasculitis means inflammation of blood vessels. The inflammation can be short term (acute) or long term (chronic), and it can be so severe that it reduces blood flow to tissues and organs. This can cause significant organ and tissue damage, especially when vasculitis affects blood vessels in the brain, lungs, kidneys or other vital areas.
Although the cause of most forms of vasculitis remains unknown, many forms probably are related to a problem with the immune system. One theory is that, for unknown causes, the immune system attacks the blood vessels, which causes them to become inflamed. Some researchers think this immune attack might be triggered by an infection, drug or something else in the environment.
Edema is swelling of both legs from a buildup of extra fluid. Edema has many possible causes:
Prolonged standing or sitting, especially in hot weather, can cause excess fluid to accumulate in the feet, ankles and lower legs.
Tiny valves inside the veins of the legs can become weakened, causing a common problem called venous insufficiency. This problem makes it more difficult for the veins to pump blood back to the heart, and leads to varicose veins and buildup of fluid.
Severe chronic (long-term) lung diseases, including emphysema and chronic bronchitis, increase pressure in the blood vessels that lead from the heart to the lungs. This pressure backs up in the heart. The higher pressure causes swelling in the legs and feet.
Congestive heart failure, a condition in which the heart can no longer pump efficiently, causes fluid buildup in the lungs and other parts of the body. Swelling is often most visible in the feet and ankles.
Pregnancy can cause edema in the legs as the uterus puts pressure on the vena cava, a major blood vessel that returns blood to the heart from the legs. Fluid retention during pregnancy also can be caused by a more serious condition called preeclampsia.
Low protein levels in the blood caused by malnutrition, kidney and liver disease can cause edema. The proteins help to hold salt and water inside the blood vessels so fluid does not leak out into the tissues. If a blood protein, called albumin, gets too low, fluid is retained and edema occurs, especially in the feet, ankles and lower legs.
Blood pressure has two components:
Systolic pressure is the top number. It represents the pressure the heart generates when it beats to pump blood to the rest of the body.
Diastolic pressure is the bottom number. It refers to the pressure in the blood vessels between heartbeats.
Blood pressure is measured in millimeters of mercury (mmHg). So blood pressure would be expressed, for example, as 120/80 mmHg.
High blood pressure is diagnosed when one or both of these numbers is too high. High blood pressure is also called hypertension.
Blood pressure is categorized as follows:
Normal: Less than 120/80 mmHg
Prehypertension: 120/80 to 139/89 mmHg
Stage 1 hypertension: 140/90 to 159/99 mmHg
Stage 2 hypertension: 160/100 mmHg and above
Usually, systolic pressure increases as we age. However, after age 60, diastolic pressure usually begins to decline.
Prehypertension is not a disease—yet. But it does mean you are at increased risk for developing high blood pressure.
Although high blood pressure can cause symptoms such as headache and pounding heartbeat, it often causes no symptoms at all.