High Blood Pressure

  • Diagnosis


    Most physical exams include a blood pressure reading. Patients should not smoke, exercise, or drink caffeinated beverages within 30 minutes before their blood pressure measurement.

    Measuring Blood Pressure

    • The standard instrument used to measure blood pressure is called a sphygmomanometer. Measurements are given as units of mercury, which for many years was used to fill the central column in standard sphygmomanometers. (Modern devices do not use mercury.)
    • An inflatable cuff with a meter attached is placed around the patient's arm over the artery while the patient is seated, their back is supported, and the arm being used is around the level of the heart. The inflated cuff briefly interrupts the flow of blood in the artery, which then resumes as the cuff is slowly deflated.
    • The person taking the blood pressure listens through a stethoscope.
    • The first pumping sound is recorded as the systolic pressure, and the last sound is the diastolic pressure.
    • If a first blood pressure reading is above normal, the health professional may take two or more measurements separated by 2 minutes with the patient sitting or lying down. Another measurement may be taken after the patient has been standing for 2 minutes. If the measurements are still elevated, your health care provider should take blood pressure readings from both arms.
    To measure blood pressure, your doctor uses an instrument called a "sphygmomanometer," more often referred to as a blood pressure cuff. The cuff is wrapped around your upper arm and inflated to stop the flow of blood in your artery. As the cuff is slowly deflated, your doctor uses a stethoscope to listen to the blood pumping through the artery. These pumping sounds register on a gauge attached to the cuff. The first pumping sound your doctor hears is recorded as the systolic pressure, and the last sound is the diastolic pressure.

    Although this test has been used for more than 90 years, it is not completely accurate or sensitive. The following factors can cause a falsely low pressure reading:

    • An arm cuff that is too wide
    • Dehydration

    Falsely high pressure can result from:

    • An arm cuff that is too small
    • Stress
    • Recently consuming foods or beverages (such as coffee) that raise blood pressure
    • Recent tobacco exposure
    • Recent exercise

    Office blood pressure readings taken by a doctor are more likely to be higher than readings measured at home. This can be due to "white coat hypertension," which is blood pressure that is only elevated during a doctor's office visit. Patients with white coat hypertension have high readings in the office but a daytime blood pressure reading away from the doctor's office of less than 135/85 mg Hg and no evidence of complications of blood pressure elsewhere in the body. Patients with white-coat hypertension may require additional blood pressure monitoring.

    Ambulatory Monitoring

    Doctors may ask some patients to use special ambulatory monitoring device for a 24-hour period. The device checks blood pressure about every 15 - 30 minutes during the day and night and provides a read-out of blood pressure measurements for the doctor. Ambulatory monitoring may be used for patients who have borderline high blood pressure or for those who have had difficulty keeping their blood pressure under control. It can also help distinguish between true and white-coat hypertension. Ambulatory monitoring can also be helpful for diagnosing children with suspected high blood pressure.

    Home Monitoring

    The American Heart Association (AHA) recommends that all patients with high blood pressure monitor their blood pressure at home on a regular basis. In addition to other benefits, home monitoring can help show if blood pressure medications are working.

    The AHA recommends:

    • Purchase a blood pressure monitor with cuffs that fit on the upper arm. Wrist monitors are not recommended. Make sure that the cuff is the right size (one size does not fit all).
    • Ask your doctor to show you the proper way to use the monitor. Your arm should be supported, with the upper arm at heart level and feet on floor (back supported, legs uncrossed).
    • Take two or three readings at a sitting, 1 minute apart, while resting in a seated position. It is important to take the readings at the same time each day, such as morning and night. Your doctor may suggest what specific times readings should be taken.
    • The target goal of a reading is under 135/85 mm Hg or less than 130/80 mm Hg in high-risk patients.

    Blood Pressure Variations at Home. In general, everyone's blood pressure varies in the same way throughout a given day. In monitoring at home, it is important to note these changes:

    • Blood pressure is usually highest from morning to mid-afternoon.
    • It normally dips to its lowest level during sleep. Some people (particularly postmenopausal women) have a condition called nondipper hypertension, in which blood pressure does not fall at night.
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    • Upon waking, blood pressure in most people typically increases suddenly. In people with severe high blood pressure, this is the highest risk period for heart attack and stroke.
    Click the icon to see an image of a heart attack.Click the icon to see an image about monitoring blood pressure.

    Physical Examination for Complications of Hypertension

    If blood pressure is elevated, the doctor will check the patient's pulse rate, examine the back of the eye, examine the neck for distended veins or an enlarged thyroid gland, check the heart for enlargement and murmurs, and examine the abdomen and check the leg pulses.

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    Medical History

    If hypertension is suspected, the doctor should obtain the following information:

    • A family and personal medical history, especially relating to high blood pressure, stroke, heart problems, kidney disease, or diabetes.
    • Risk factors for heart disease and stroke, including tobacco use, salt intake, obesity, physical inactivity, and unhealthy cholesterol levels.
    • Any medications being taken.
    • Any symptom that might indicate secondary hypertension (high blood pressure caused by another disorder). Such symptoms include headache, heart palpitations, excessive sweating, muscle cramps or weakness, or excessive urination.
    • Any emotional or environmental factors that could affect blood pressure.

    Laboratory and Other Tests

    If a physical examination indicates hypertension, additional tests may help determine whether organ damage is present.

    Blood Tests and Urinalysis. These tests are performed to check for a number of factors, including potassium levels, cholesterol, blood sugar (to screen for diabetes), infection, kidney function, and other possible problems. Measuring blood levels of the protein creatinine, for example, is important for all hypertensive patients in order to determine kidney damage.

    Tests to Evaluate the Heart. These tests include:

    • An electrocardiogram (ECG) is performed on most patients in the doctor's office.
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    • An exercise stress test may be needed for patients who also have symptoms of coronary artery disease.
    • An echocardiogram is needed when it would help the doctor decide whether to start treatment. Most of the time this test is not necessary for patients who have only hypertension and no other symptoms.
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    Tests to Evaluate the Kidneys. These tests include:

    • A Doppler or duplex test may be performed to see whether one of the arteries supplying blood to the kidney is narrowed, a condition called renal artery stenosis.
    • An ultrasound may also be performed to examine the kidneys.