Hypertension or High Blood Pressure
[2000-04-20]

By: Dr. Stanley Lofsky MD CCFP FCFP

In this general overview of high blood pressure you will find the answers to these common questions.

• Can you tell when you have high blood pressure?

• Are newer treatments more effective than older medications?

• Is the lower reading (diastolic) more important than the higher reading (systolic)?

• Can a cause usually be found for high blood pressure?

Hypertension or elevated blood pressure affects 55 million North American adults. Of the 55 million, only a little over two thirds know about it, a little more than half are being treated and a little more than a quarter have it in control.

Every time the heart beats, a pulse of blood flows through the arteries to be distributed throughout the body. The pressure of this pulse can be measured and is called the systolic blood pressure. When the heart relaxes between each beat the pressure falls until the next beat. This pressure between beats is the diastolic blood pressure.

While brief periods of elevated blood pressure cause little problem, the prolonged strain of years of elevated blood pressure on many organs eventually causes damage. The strain on the blood vessels in the brain causes more frequent strokes, kidney function often decreases with build up of wastes in the blood, and the heart is stressed by the extra work causing thickening and enlargement of the heart muscle. This can lead to weakening of the muscle resulting in what is known as congestive heart failure. The arteries to the heart itself become more susceptible to hardening and blockage leading to an increased chance of heart attacks. The organs that can be damaged by high blood pressure are called target organs. You can expect your doctor to order tests that look for signs of target organ damage. For many years doctors believed that elevated diastolic pressure is more damaging but recent studies show that both readings are important.

For the most part, no particular cause can be found, and this kind of blood pressure elevation is called essential hypertension. It is more common when others members of your family have it, and it seems to be more common with weight gain, increasing age, and in areas where a lot of salt is eaten. This is why extensive testing to pinpoint a cause is usually done only in younger people and in individuals whose pressure is not easily controlled.

An inflatable balloon in the shape of a cuff is wrapped around the arm and blown up by a hand held pump. The standard method is to use a tube of mercury as the gauge and this is why blood pressure readings are in millimetres of mercury (mm Hg). Other types of blood pressure cuffs known as aneroid can be as accurate but need to be occasionally calibrated against a mercury unit. The most accurate blood pressure measurement is best done when you have been sitting quietly for five minutes, the arm supported at heart level, legs uncrossed, back supported and with a blood pressure cuff matching the size of your arm. Talking while blood pressure is being taken can change the reading. Hypertension is diagnosed when blood pressure is 140 mm Hg systolic and /or 90 mm Hg diastolic or higher at three separate occasions.

Many research studies have shown that lowering of blood pressure decreases the frequency and severity of most of the above complications. It is one of the most important preventive treatments that medical science can offer.

What about non-drug treatments?

It is always worthwhile taking a hard look at your lifestyle to assist in the lowering of your blood pressure before starting medications. In severe hypertension your doctor may wish to start medications along with lifestyle changes. If you are overweight, reduction is often very helpful. Limiting salt is helpful for many. A diet rich in magnesium, potassium and calcium (fruits and vegetables, low fat dairy) can lower blood pressure somewhat Alcohol consumption of more than three drinks a day on a steady basis is a common cause of hypertension. Smoking only increases the complications and should be stopped. Lowering lipid levels will reduce the rate of complications. A program of aerobic exercise (e.g. running, walking, swimming, bicycling) completes the healthy lifestyle recipe.

Of all the many hypertension medicines available, research has not shown yet shown that the newer drugs are more effective in reducing the complications of hypertension than the older medications. This is why many patients with hypertension will first be started on and be controlled by older and usually less expensive medications such as beta-blockers and diuretics. Newer drugs have the advantage of fewer side effects and often have helpful affects on other conditions that the hypertensive person may have. They also may be useful alternatives when other medications don’t work sufficiently.

Diuretics (drugs that cause the kidneys to excrete fluid) are usually inexpensive and are often a good first choice, especially in older patients. Common side effects are increases in blood sugar, uric acid (the gout chemical), cholesterol, decreases in potassium, and effects on sexual function. They are often avoided in diabetics and those with high lipids (cholesterol or triglycerides). Current practice is to use the smallest dose possible to reduce these side effects.

Beta-blockers block the stimulating affects of the nervous system on the heart and blood vessels and will as a result lower the heart rate and blood pressure. They should be avoided with asthma as they can constrict the breathing passages. Some of them may elevate the lipids while others known as ISA have less effect on the heart rate and lipids. They are often avoided in insulin needing diabetes as they make it hard for diabetics to know their blood sugar is too low. They may affect sexual function. Although they are older antihypertensives, new uses are being discovered and some hypertensive patients can doubly benefit. For example, they may be especially useful in sufferers of angina, migraine, stage fright, and certain types of tremors. They are now being used to reduce death rate following a heart attack and in those with mild to moderate heart failure.

Calcium channel blockers: By blocking the flow of calcium into the cells of the walls of blood vessels, they relax the artery walls, lowering the blood pressure. These drugs are safe with diabetics and asthmatics. They are effective treatments for angina patients and people with spastic arteries such as in the heart or limbs. Most doctors now use the longer acting versions, as the shorter acting calcium channel blockers may be associated with increased complications. Headaches, constipation and annoying ankle swellings are troublesome side effects.

Alpha Blockers: These medicines block certain nerve impulses to the arteries and thus allow them to stay open. As they may improve blood fats they may be of use to those with elevated lipids, and are also used to help men with symptoms of prostate trouble. Recent research has found that diuretics are more effective in reducing hypertension complications and thus alpha-blockers are best used with other medications for hypertension treatment.

ACE (Angiotensin-converting enzyme) inhibitors: The kidney produces renin, which acts on a protein in the blood to produce angiotensin that has a powerful effect on blood pressure. ACE inhibitors prevent or reduce the amount of angiotensin being made allowing blood pressure to fall to lower levels. ACE inhibitors are safe with asthma and diabetes and cause very little sexual dysfunction. Although they may cause a rise in chemicals in the blood signifying kidney trouble, experience has shown they actually preserve kidney function in diabetics. They are one of the few drugs that decrease mortality in heart failure and recent research on one of them (ramipril) has shown increased survival when used in individuals with various type of heart disease. It is not yet known if this is true for all ACE inhibitors. They can cause a troublesome cough, raise potassium levels and result in skin eruptions. When extra effect is needed they seem to work well with diuretics, often cancelling out the potassium effects seen with both agents. Potassium supplements should generally be avoided with ACE inhibitors.

Angiotensin receptor antagonists: Instead of preventing the production of angiotensin, these newest drugs prevent angiotensin from working on the blood vessels by blocking their attachment to tissues. Like ACE inhibitors they produce very few side effects but do not cause a cough. Whether or not they will be as helpful with heart failure or preventing heart disease is not known yet.

Some less common medications: Reserpine is an older inexpensive effective drug whose reputation was ruined by a high rate of depression. At the much smaller doses used today, this is uncommon. Methyldopa was used a lot in the past but its main niche today is with pregnancy where its safety is proven. Clonidine is another such agent with a useful effect of reducing menopausal flushes at a much lower dose. At standard doses and higher it is often used in drug withdrawal.

• If you have high blood pressure, avoid all decongestant, stimulant or diet pills that contain ephedrine, psuedoephedrine or phenylpropanolamine. Some dietary preparations may have ingredients such as ephedrea, which can elevate blood pressure.

• For unknown reasons, certain of these medications (ACE and angiotensin receptor antagonists, beta-blockers) don’t work as well in black people.

• Even if you don’t think you have high blood pressure, when you see your physician for other problems have him/her check your blood pressure. Remember that most people with elevated blood pressure don’t feel it and 40% don’t know about it.