High blood pressure

What Is Blood Pressure?

Blood pressure is the force of blood against the blood vessel wall. High blood pressure occurs when there is increased tension or pressure in the arteries. The greater the pressure, the harder the heart has to work.

Blood pressure is measured with a device called a sphygmomanometer, which can be either manual or electronic. The blood pressure reading is written as a fraction: for example, 120/80.

The first number is the systolic pressure, which is the point at which the heart contracts to push the blood out to the rest of the body. When blood pressure is taken manually, this is the number at which a person taking the blood pressure first hears a pulse through the stethoscope. When an electronic device is used, the number appears on the display.

The second number is called the diastolic pressure, which represents the lowest point in the pressure of blood--right before another squirt of blood enters the arteries. When the blood pressure is measured manually, this number is the point at which the person listening through the stethoscope stops hearing a pulse. On an electronic device, this number also automatically appears on the display.

Many people think that 120/80 is the perfect or normal blood pressure. But, says Robert Fenichel, M.D., deputy director of FDA's division of cardiovascular and renal drug products, "If your pressure is lower than that, good for you."

Deciding What's High

Elevated blood pressure rarely makes itself known; it usually has no symptoms. That's why it's often referred to as the silent killer. Feeling nervous or tense, for example, doesn't necessarily translate into elevated blood pressure. Getting periodic blood pressure checks is the only way to catch high blood pressure early.

According to the National Heart, Lung, and Blood Institute of the National Institutes of Health, a blood pressure reading consistently higher than 140/90 is a sign that the blood pressure needs to be brought under control.

Most doctors don't diagnose a person with high blood pressure on the basis of only one reading. People who find a visit to the doctor's office unnerving can have "white-coat hypertension," blood pressure that is only high when taken in the doctor's office. ("White coat" refers to the ubiquitous white lab coats many health professionals wear.) Others may have "labile hypertension," blood pressure that gets slightly elevated in certain situations but which is normal most of the time.

To rule these out, doctors may take a patient's blood pressure later during the office visit and ask the patient to come back for two more visits, taking two readings during each of those visits. Many doctors also ask patients with elevated blood pressure to have their blood pressure checked in a setting other than a medical one. With one of the many electronic blood pressure measuring devices that consumers can buy without a doctor's prescription, patients often can check and record their blood pressure at home. To get as accurate a reading as possible, the doctor may ask the patient to bring the device in to the office to make sure it is calibrated properly. This can usually be done by comparing the device's readings with readings taken at the same time with the doctor's blood pressure equipment.

If a patient has consistently high readings in and out of the medical setting, the doctor will decide what type of treatment is appropriate: diet modification, increased exercise, medicine, or a combination of these.

Treating Hypertension

Treatment can vary with the level of elevation of the blood pressure, as well as the patient's age and health. (See "Treating High Blood Pressure.") According to FDA's Fenichel, sometimes lifestyle changes can reduce blood pressure by 5 points or so. They include stopping smoking, reducing alcohol intake, losing excess weight, and making certain dietary changes, such as reducing sodium intake and possibly increasing potassium, calcium and magnesium intake. (See "Diet and Blood Pressure.") Some experts also recommend exercise and relaxation techniques, such as meditation.

FDA has approved numerous drugs for treating hypertension. These drugs work in different ways but the end result--reducing blood pressure--is the same.

Some of the most commonly used drugs to treat high blood pressure are:

• Diuretics. Sometimes called "water pills," these drugs flush excess water and sodium from the body by increasing urination. This reduces the amount of fluid in the blood and flushes sodium from the blood vessels so that they can open wider, increasing blood flow and thus reducing the blood's pressure against the vessels. Often diuretics are used in combination with other high blood pressure drugs. Types of diuretics include thiazides, such as Diuril (chlorothiazide) and Esidrex (hydrochlorothiazide); potassium-sparing diuretics, such as Aldactone (spironolactone); and loop diuretics, such as Lasix (furosemide).
• Beta blockers. These drugs slow the heartbeat by blocking the effect of nerve impulses to the heart and blood vessels, thereby lessening the burden on the heart. Beta blockers include Inderal (propranolol), Lopressor (metoprolol), and Tenormin (atenolol).
• ACE (angiotensin-converting enzyme) inhibitors. These inhibit formation of the hormone angiotensin II, which causes blood vessels to narrow, thus increasing blood pressure. ACE inhibitors include Altace (ramipril), Capoten (captopril), and Zestril (lisinopril).
• Calcium channel blockers. These prevent calcium from entering the muscle cells of the heart and blood vessels, thus relaxing blood vessels and decreasing blood pressure. Some calcium channel blockers are Procardia (nifedipine), Isoptin (verapamil) and Cardiazem (diltiazem).
• Alpha-beta blockers. These combine the actions of alpha blockers, which relax blood vessels, and beta blockers, which slow the heartbeat. The dual effect reduces the amount--and thus pressure--of blood through blood vessels. Alpha-beta blockers include Normodyne and Trandate (both labetalol).
  
  

Often, combinations of two drugs from different classes are used to improve the drugs' effectiveness.

Many doctors begin newly diagnosed hypertensive patients with diuretics or beta blockers. The Sixth Report of the Joint National Committee (JNC) on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure, released by NIH's National Heart, Lung, and Blood Institute in November 1997, recommends diuretics or beta blockers as the first line of treatment. However, based on a patient's situation--for example, use of other medicines--doctors may choose to start treatment with another antihypertensive drug.

Some specifics to JNC's first-line recommendation are noted in the report--for example, it recommends that in African Americans, one of the groups most at risk for hypertension, diuretics alone should be the first agent of choice--provided there are not other conditions that prohibit their use--because of this group's increased sensitivity to salt. For hypertensive people with diabetes or kidney disease, the guidelines recommend that initial drug treatments include ACE inhibitors.

Finding a Drug that Works

Like most drugs, blood pressure medicines can have side effects, ranging from the unpleasant--such as skin rash, sleepiness and weight gain--to the severe, including depression, hallucinations, heart dysfunction, and liver disease. Patients who begin a drug treatment and develop symptoms that they did not have before should discuss them with their doctors. With the great variety of medicines, it is likely that another antihypertensive drug or dosage level can help control blood pressure with few or no side effects.

Many patients have found diet and nutrition to be extremely beneficial in treating high blood pressure. To learn more about this, see the article on Diet and blood pressure.

Who's at Risk?

Those at greater risk for high blood pressure, according to the National Heart, Lung, and Blood Institute, include:

• African Americans
• people with a family history of high blood pressure
• people who drink alcoholic beverages excessively
• people who are physically inactive
• In addition, as many as 65 percent of people with diabetes have high blood pressure