High blood pressure and beta blockers

One out of four Filipino adults has high blood pressure (hypertension) or a blood pressure (BP) reading equal to or higher than 140/90 millimeter mercury (mmHg). One in 10 Filipino adults has prehypertension or a BP reading in the range of 130-139/85-89 mmHg. These are among the findings of the latest 2008 National Nutrition and Health Survey (NNHeS II Philippine data) published this year.

Hypertension is a major risk factor for kidney disease, heart attack, congestive heart failure and stroke. Lifestyle modification is an effective way of controlling hypertension. This includes losing weight (if overweight/ obese), eating a healthy diet, exercising regularly, quitting smoking, and moderation in drinking alcoholic beverages. If lifestyle modification proves inadequate in controlling hypertension, the doctor will prescribe any of several classes of antihypertension medications, such as beta blockers, calcium channel blockers, diuretics, ACE inhibitors and angiotensin II receptor blockers (singly or in combination, if necessary).

Improve blood flow

Beta blockers are a class of antihypertension medication that works by widening (dilating) blood vessels and slowing heart rate to improve blood flow and decrease blood pressure. They exert their effect on heart rate by blocking the transmission of certain nerve impulses. When certain nerves are stimulated, they release a chemical (neurotransmitter) called noradrenaline. Noradrenaline then stimulates beta-adrenergic receptors, which are tiny structures on cells in various parts of the body including the heart, brain, and blood vessels.

Stimulation of the beta-adrenergic receptors on heart cells causes an increase in the force and rate of the heartbeat. The beta-adrenergic receptors are also stimulated by adrenaline, which is released into the bloodstream by the adrenal gland when a person is frightened or anxious. Adrenaline can cause, among others, an increase in heart rate.

Beta blockers “sit” on beta-adrenergic receptors and stop them from being stimulated, thereby reducing the force of contraction in the heart muscle and rate of the heartbeat. Because of their dual effect of dilating blood vessels and slowing heart rate, beta blockers are used not only to lower blood pressure but also to prevent chest pain (angina), reduce a person’s risk of suffering another heart attack, control certain abnormal heart rhythms (arrhythmias), and help treat heart failure.

There are many types of beta blockers. However, not  all beta blockers are the same in terms of the beta-adrenergic receptor they target. First-generation beta blockers slow down heart activity by blocking ß1 receptors in the heart muscles; however, they also block the ß2 receptors, which cause many of the side effects associated with older types of beta blockers (e.g. bronchoconstriction, increased blood sugar, erectile dysfunction). As such, first-generation beta blockers should not be prescribed to patients with asthma and diabetes.

Second-generation beta blockers are relatively selective for ß1 receptors, but their selectivity are lost at higher doses. Third-generation beta blockers, such as nebivolol, selectively block ß1 receptors only and therefore do not cause the side effects usually caused by older-generation beta blockers. Unlike older beta blockers, third-generation beta blockers exert the additional effect of dilating blood vessels. Because of their unique dual mode of action, third-generation beta blockers provide other benefits such as improved sexual function and neutral effect on blood sugar levels, making them safe to use in hypertensive patients with diabetes.

Life-saving benefits

There is solid scientific evidence backing up the life-saving benefits of lowering blood pressure. A meta-analysis presented in the 2003 guidelines on hypertension management showed that effective antihypertensive treatment resulted in a 30- to 40-percent reduction in strokes, 15- to 25-percent reduction in coronary heart disease and about a 20-percent reduction in cardiovascular mortality. Because uncontrolled hypertension is a risk factor for the development of congestive heart failure, hypertension treatment reduces a person’s risk of developing the life-threatening disease. The use of beta blockers in heart failure has been proven to improve ventricular function and patient well-being, reduce hospital admission for worsening heart failure, and increase patient survival.

(Dr. Romeo Divinagracia is a cardiologist (heart specialist), founder and past president of the Heart Failure Society of the Philippines. The Doctor is In column is a health information advocacy supported by Invida, a Menarini company, aimed at increasing awareness on hypertension prevention and management. For more information, e-mail [email protected].)