Medical Author: Benjamin C. Wedro, MD, FACEP, FAAEM
Medical Editor: William C. Shiel Jr., MD, FACP, FACR
The concept of blood pressure is sometimes difficult to understand because it is usually described with numbers. However, adequate pressure within arteries is important to allow blood to be pumped throughout the body to deliver oxygen and other nutrients to areas of the body. This allows for normal metabolism and organ function.
The blood pressure recording, measures pressures within the arteries at two different times. The first reading, the systolic pressure, measures the pressure when the heart is pumping blood to the body through the arteries. The second reading, the diastolic pressure, measures the pressure within the arteries when the heart is receiving blood returning from the body.
There needs to be an underlying pressure within arterial blood vessels regardless of whether the heart is pumping or not. This intrinsic pressure is maintained by smooth muscle cells that surround all artery walls, great and small, and in effect squeeze and support the walls. Without this wall support, arteries would collapse in diastole (between each heart beat).
Blood pressure measurement is listed with two numbers with normal being less than 120/80, with 120 being the systolic blood pressure when the heart is pushing blood through the arterial system; and 80 being the diastolic blood pressure when the arteries are at rest and the heart is refilling.
In people with a normal blood reading pressure, the arterial walls are flexible and allow relaxation of the artery walls. In patients with high blood pressure (hypertension), the artery walls are stiffer and present increased resistance to the blood that is trying to flow through them. This requires the heart to beat more forcefully and increases the pressure of blood leaving the heart.
In recent years, the guidelines to decide what a normal blood pressure reading is have become much more stringent. There are now four categories of blood pressure.
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The chart below outlines the new blood pressure categories and the corresponding pressures in mm Hg (mercury):
Blood Pressure Guidelines
|Hypertension Stage I||140-159||OR||90-99|
|Hypertension Stage II||> 160||OR||>100|
High blood pressure is often called the silent killer because in the initial stages it presents with no symptoms. It is only after an organ in the body is irritated or damaged, that the consequences of high blood pressure are realized.
High blood pressure is a risk factor for many diseases including heart attack (myocardial infarction) and stroke (cerebrovascular accident). Poorly controlled blood pressure can also directly lead to kidney failure and blindness. Moreover, heart failure can occur because the heart muscle has to push against increased resistance.
Hypertension is usually a diagnosis that requires life-long attention and control. Diet, exercise, and medication are the cornerstones of treatment. Many patients are able to minimize the amount of medication required by living a healthier lifestyle, while others may require two, three or more types of medications to maintain blood pressures in a relatively normal range.
The type of medication prescribed to treat high blood pressure will depend upon the patient and any other underlying illnesses that they might have. Medications that are often used include:
- Diuretics: Often called "water pills," they cause the kidneys to make more
urine and decrease the amount of fluid in the body.
- Beta blockers: These medications are named because they block the beta
adrenaline receptors in the heart and blood vessels. They tend to relax the
smooth muscles in artery walls decreasing the resting diastolic pressure.
Additionally, they cause the heart to beat less forcefully, decreasing systolic
- Calcium channel blockers: These drugs work at the heart cell level,
blocking the flow of calcium in and out of the cell, which causes the heart to
contract less forcefully, and decreasing the systolic pressure it generates.
- Angiotensin receptor blockers (ARBs): These medications affect a group of hormones in the body that are associated with the kidney and blood pressure control, including renin, angiotensin, vasopressin and aldosterone. These medications cause arterial dilation and also affect the secretion of vasopressin and aldosterone.
Most patients with high blood pressure have primary or essential hypertension (high blood pressure for no specific reason). However, approximately 5% to 10% of patients may have secondary hypertension (high blood pressure due to an underlying cause or disease). These may include kidney or adrenal gland abnormalities, fibromuscular hyperplasia of an artery to the kidney, or side effects from medications or drugs. For that reason, it is wise that patients with high blood pressure readings seek care from a health professional.
National Heart Lung and Blood Institute, National Institutes of Health, "The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure."
Rosendorff, C., Black, H., Cannon, C., Gersh, B., Gore, J., Izzo, J., Kaplan, N., O'Connor, C., O'Gara, P., Oparil, S.; "Treatment of Hypertension in the Prevention and Management of Ischemic Heart Disease." Circulation. 2007;115:2761-2788