Hypertension, also referred to as high blood pressure, arises when the blood pressure is abnormally high. It occurs when the body’s smaller blood vessels narrow, causing the blood to exert excessive pressure against the vessel walls and forcing the heart to work harder to maintain the pressure. Although the heart and blood vessels can tolerate increased blood pressure for months and even years, eventually the heart may enlarge (a condition called hypertrophy) and become weak to the point of failure. Injury to blood vessels in the kidneys, brain, and eyes also may occur.
Blood pressure is actually a measure of the systolic and the diastolic pressures. The systolic pressure is the force that blood exerts on the artery walls as the heart contracts to pump the blood to the organs and tissues. The diastolic pressure is the residual pressure exerted on the arteries as the heart relaxes between beats. A diagnosis of hypertension is made when blood pressure reaches or exceeds 140/90 mmHg in three different days.
When there is no demonstrable underlying cause of hypertension, the condition is classified as essential hypertension. This is by far the most common type of high blood pressure, occurring in 90 to 95 percent of patients. Genetic factors appear to play a major role in the occurrence of essential hypertension. Secondary hypertension is associated with an underlying disease, which may be renal, neurologic, or endocrine in origin. In cases of secondary hypertension, correction of the underlying cause may cure the hypertension. Various external agents also can raise blood pressure. These include cocaine, amphetamines, cold remedies, thyroid supplements, corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), and oral contraceptives.
Malignant hypertension is defined as a sustained or sudden rise in diastolic blood pressure exceeding 120 mmHg, with accompanying evidence of damage to organs such as the eyes, brain, heart, and kidneys. Malignant hypertension is a medical emergency and requires immediate therapy and hospitalization.
Elevated blood pressure is one of the most important public health problems in developed countries. In the United States, for instance, nearly 1/3 of the adult population is hypertensive. High blood pressure is significantly more prevalent and serious among African Americans. Age, race, sex, smoking, alcohol intake, high cholesterol, salt intake, glucose intolerance, obesity and stress all may contribute to the degree and prognosis of the disease. In both men and women, the risk of developing high blood pressure increases with age.
Hypertension has been called the “silent killer” because it usually produces no symptoms. It is important, therefore, for anyone with risk factors to have their blood pressure checked regularly and to make appropriate lifestyle change.
The most common immediate cause of hypertension-relate death is heart disease, but death from stroke or renal failure is also frequent. Complications result directly from the increased pressure (cerebral hemorrhage, retinopathy, left ventricular hypertrophy, congestive heart failure, arterial aneurysm, and vascular rupture), from atherosclerosis (increased coronary, cerebral, and renal vascular resistance), and from decreased blood flow and ischemic myocardial infraction, cerebral thrombosis and infarction, and renal nephrosclerosis). The risk of developing many of these complications is greatly elevated when hypertension is diagnosed in young adulthood.
Effective treatment will reduce overall cardiovascular morbidity and mortality. Nondrug therapy consists of: (1) relief of stress, (2) dietary management (restricted intake of salt, calories, cholesterol, and saturated fats; sufficient intake of potassium, magnesium, calcium and vitamin C), (3) regular aerobic exercise (4) weight reduction, (5) smoking cessation, and (6) reduced intake of alcohol and caffeine.
Mild to moderate hypertension may be controlled by a single-drug regimen, although more severe cases often require a combination of two or more drugs.
Diuretics are a common medication class; these agents lower blood pressure primarily by reducing body fluids and thereby reducing peripheral resistance to blood flow. However, they deplete the body’s supply of potassium, so it is recommended that potassium supplements be added or that potassium-sparing diuretics be used.
Beta-adrenergic blockers, beta-blockers, block the effects of epinephrine (adrenaline), thus easing the heart’s pumping action and widening blood vessels.
Vasodilators act by relaxing the smooth muscles in the walls of blood vessels, allowing small arteries to dilate and thereby decreasing total peripheral resistance.
Calcium channel blockers promote peripheral vasodilation and reduce vascular resistance.
Angiotensin-converting enzyme (ACE) inhibitors inhibit the generation of a potent vasoconstriction agent (angiotensin II), and they also may retard the degradation of a potent vasodilator (bradykinin) and involve the synthesis of vasodilatory prostaglandins. Angiotensin receptor antagonist are similar to ACE inhibitors in utility and tolerability, but instead of blocking the production of angiotensin II, they completely inhibit its binding to the angiotensin II receptor.
Statins, best known for their use as cholesterol-lowering agents, have shown promise as antihypertensive drugs because of their ability to lower both diastolic and systolic blood pressure. The mechanism by which statins act to reduce blood pressure is unknown; however, scientists suspect that these drugs activate substances involved in vasodilation.
How to monitor blood pressure at home?
- Checking your blood pressure at home is an important part of monitoring blood pressure and managing hypertension. There are many easy-to-use digital automatic blood pressure monitors in the market for home blood pressure monitoring.
- Blood pressure measurements taken casually, without following standard procedures, produce unreliable results. Imprecise measurements, even those that are off by just a few points, can lead to inappropriate treatment. So it is important to get accurate blood pressure readings.
- Here are a few tips on how to choose blood pressure monitors and how to get accurate readings:
How to choose blood pressure monitors
Arm monitor or wrist monitor:
- The common digital monitors can be fitted on the upper arm or the wrist. Upper arm devices should preferably be used as they are more accurate. Wrist monitors may be used by people for whom a large upper arm cuff is too small or cannot be used because of shape or pain from the pressure of the cuff when it inflates. Speak with a doctor or qualified health care provider about which blood pressure monitor is right for you. Devices that measure blood pressure at the finger are not recommended.
- Blood pressure cuffs of upper arm devices come in different sizes. The wrong cuff size will give incorrect readings: using a cuff that is too small for the arm may overestimate blood pressure and one that is too big may underestimate it. So make sure the cuff size fits your arm. The cuff should be wide enough to cover two thirds of the upper arm and its length should be long enough to encircle the whole arm. Most monitors will come with medium-sized cuffs which suit most adults. People with large arm or overweight people may need bigger cuff. You may seek advice from your doctor or the supplier of the blood pressure monitor.
Validation of monitor:
- Make sure the monitor you choose has been clinically validated for accuracy. Read the manual carefully and operate the device according to the manufacturer’s instructions. It is not uncommon for blood pressure readings taken at home to be different from those taken at your doctor’s office. If the blood pressure monitor is not too bulky, it is a good idea that you bring it along to your doctor’s appointment. Your doctor can help validate your monitor’s accuracy.
How to get accurate readings
When to measure:
- Measure blood pressure at around the same time each day.
- Do not measure blood pressure when you feel unwell, cold, anxious, stressed, in pain, or have a full bladder.
- Do not exercise, smoke or consume foods or drinks containing caffeine (such as tea or coffee) at least 30 minutes before measurement.
- Remember to wear loose-fitting clothes.
- Rest and relax for 5 minutes without distractions (e.g. watching television).
- Be seated comfortably with the back supported.
- Push up the sleeve to bare your upper arm and wrap the cuff around your upper arm.
- Make sure your arm is supported and your upper arm is at the same level as your heart.
- Keep feet on the floor and do not cross legs.
- Relax and do not talk while taking the reading.
- After the first measurement, release cuff pressure completely and repeat the same steps to obtain another reading of blood pressure. The two measurements should be taken at least 1 minute apart.
- Take the average value of at least two readings. If the first two readings differ by more than 5 mmHg, additional readings should be obtained before taking the average.
- Record down the readings to obtain a continuous monitoring.
- Consult a doctor or a nurse if you have any concerns.
Reviewed by Gracia Pierre-Pierre, MD CAQSM