Because your heart pumps in pulses, your blood pressure naturally rises and falls with each surge, even when you are at rest. Blood pressure peaks when the heart’s ventricles contract (the pumping or systolic phase) and falls to its lowest level after the contractions (the resting or diastolic phase). To accurately assess blood pressure, you need a reading for both phases, systolic and diastolic.
You have probably had your blood pressure measured many times—just about every time you have any kind of a physical checkup. The familiar instrument your doctor uses, the blood pressure cuff and pressure gauge, has an unfamiliar name: sphygmomanometer.

This instrument works by measuring how high the pressure in an artery in your arm can raise a column of mercury, so the measurement is expressed in millimeters of mercury (mm Hg). The reading is always expressed with the sys- tolic (pumping) pressure on the top and the diastolic (resting) pressure on the bottom. A healthy reading in an adult is less than 120/80 mm Hg.

6

Checking your blood pressure
If you have been diagnosed with high blood pressure, your doctor will encourage you to acquire and use a device for monitoring your own blood pressure at home. This is especially important if you are taking new medica- tions or if your drug dose has been changed.

Healthy adults should have their blood pressure checked at least every two years. If you have not had it checked recently, make an appointment to do so soon. It is an easy, pain- less, and inexpensive test. You can have a reli- able blood pressure check in many different settings—a hospital clinic, a nurse’s office, a company clinic. You may be tempted to consult the free blood pressure testing units that you see at some drugstores or shopping malls, but you should not rely on them alone. They may not be checked regularly for accuracy, and they may suffer from wear and tear. If you try out one of these machines, record the reading and then compare it with a read- ing from your doctor’s of?ce.
When you know you are going to have your blood pressure checked, you can do several things to help ensure an accurate reading:
• Do not drink coffee or smoke 30 minutes before the check; both caffeine and nicotine raise your blood pressure temporarily.
• Try to arrive at your doctor’s of?ce at least 5 minutes before the check and sit comfortably, so you are not feeling hurried.
• Wear short sleeves.
Some people have a response called “white-coat hypertension,” which means that their blood pressure actually rises when they are undergoing a checkup. This phenomenon is quite common. If you or your doctor thinks you may be responding this way, you can try having your blood pressure checked in another setting, or you can buy a blood pressure device to do your own reading at home (see page 55). Your doctor can compare your home and of?ce readings to get a clearer idea of your average blood pressure.

If your doctor is concerned about your blood pressure, he or she will initially take measurements on several different days, because there are so many normal variations. It is not unusual to have a high measure- ment on a single day and then have it return to normal when you are tested again. Your doctor will probably not diagnose you as having high blood pressure unless your measurement is high on two or more read- ings taken at separate visits.
If your readings are 120/80 mm Hg or greater over several different days, your doctor will evaluate your condition in other ways. He or she will take a detailed medical history to determine if you have other risk factors for heart disease or stroke. He or she may use an instrument called an ophthalmoscope to look at the blood vessels in your eyes. This is the only place in your body where a doctor can directly look at your blood vessels to see if they are damaged. Thickened, narrowed, or burst vessels in the eyes can be another indication of high blood pressure.

If your doctor diagnoses high blood pressure, he or she may order several tests. These tests are used to determine if there is an underlying cause of high blood pressure, to detect any organ damage, to assess other risk factors for heart disease, and to identify other conditions that might affect the course of treatment.
In addition to conducting blood tests, your doctor also might order a chest X-ray (see page
128) to check the size and condition of your heart and lungs. An electrocardiogram (ECG; see page 122) may provide evidence about whether your heart is enlarged and if there is any damage to the heart muscle. It is not uncommon to have a routine ECG in the doc- tor’s office that reveals signs of an enlarged heart or a previously unknown heart attack.
You may have blood and urine tests to deter- mine if your kidneys are working properly or if there are any underlying problems causing the blood pressure to rise. In rare cases, people may have an intravenous pyelography, a procedure that examines kidney function by injecting a harmless dye into an artery and watching its passage on an X-ray screen. A few people may need more advanced tests to evaluate blood ?ow, such as an MRI (magnetic resonance imaging; see page 141), a nuclear scan stress test (see page 135), or a coronary angiogram echocardiogram.

How Blood Pressure
Testing Works

The instrument used to test your blood pressure has four parts: an inflatable cuff, a pump, a pressure gauge, and a stethoscope. When you have a checkup, the tester wraps the cuff around your arm and inflates it so that the pressure in the cuff is higher than the pressure in your artery. The flow of blood is momentarily stopped and your heart- beat is inaudible through the stetho- scope. As the cuff deflates, the tester checks the pressure gauge as soon as he or she hears your heartbeat again. At this moment, the pressure in the cuff is the same as the pressure in your artery, and the reading is your systolic pres- sure. As the cuff deflates further, the tester listens for the moment the sound of the heartbeat disappears again— when the cuff pressure goes below the resting pressure in your artery. This reading is your diastolic pressure.