Complications

Hypertension places stress on several organs (called target organs), including the kidneys, eyes, and heart, causing them to deteriorate over time. High blood pressure contributes to 75% of all strokes and heart attacks. It is particularly deadly in African-Americans.

Research suggests that prehypertension is also a serious risk factor for heart complications. A 2005 study found that people with prehypertension are three times more likely to have a heart attack, and nearly twice as likely to develop coronary artery disease as people with normal blood pressure.

Emergency Conditions

Malignant hypertension, an emergency condition resulting from untreated primary hypertension, can be lethal.

Stroke

About two-thirds of people who suffer a first stroke have moderate elevated blood pressure (160/95 mm Hg) or above. Hypertensive people have up to 10 times the normal risk of stroke, depending on the severity of the blood pressure. Hypertension is also an important cause of so-called silent cerebral infarcts, blockages in the blood vessels in the brain that may predict major stroke or progression to dementia over time.

Mental Problems and Dementia

Uncontrolled chronic high blood pressure is also associated with reduced short-term memory and mental abilities. Isolated systolic hypertension may pose a particular risk for complications in the brain. Fortunately, controlling blood pressure with medications can reduce or even prevent memory loss and mental decline due to hypertension. A 2006 study of older men indicated that anti-hypertensive treatment for at least 5 years may help prevent the development of dementia. Other studies suggest that anti-hypertensive drugs may help protect against Alzheimer's disease in people with genetic susceptibility to this disease.

Heart Disease

High blood pressure is a major risk factor for heart disease.

Heart Attack. About half of people who suffer their first heart attack have moderate hypertension (160/95 mm Hg) or greater. High blood pressure increases the risk for a heart attack by up to five times, depending on the severity of the hypertension.

Heart Failure. Hypertension precedes heart failure in 75 - 90% of heart failure cases. High blood pressure has various effects that cause the heart to fail, including:

• To compensate for increased blood pressure, the heart must work harder to pump blood, and so its muscles thicken (hypertrophy), usually on the left side (left-ventricle dysfunction). These thickened muscles pump inefficiently, and, over time, the force of their contractions weakens. The heart muscles then have difficulty relaxing and filling the heart with blood. The heart begins to fail.

• The failing heart then triggers a number of hormonal and neurochemical mechanisms to correct imbalances in blood pressure and flow. This response, called remodeling, is helpful in the short run but very destructive and irreversible over time.
• As part of the remodeling process, the heart muscle cells elongate. The muscular walls of the heart dilate and become thinner and inefficient. The cells themselves undergo molecular changes that result in calcium loss, a mineral crucial for healthy heart contractions.
• The end-result of remodeling is a falling volume of blood pumped to the kidneys; the kidneys retain water and salt in response, increasing fluid buildup in the body.
• To make matters worse, the body's arteries narrow in response to a lower blood volume. This constriction forces the heart to work even harder to pump blood through these narrowed vessels, increasing blood pressure and continuing the cycle.

A 2006 analysis of ALLHAT trial data indicated that diuretics are the best first-line high blood pressure medication for preventing heart failure.

Diabetes and Kidney Disease

Diabetes. High blood pressure, and the medications used to treat it, can increase the risk for developing diabetes. Studies have reported that thiazide diuretics and beta blockers carry a higher risk for causing diabetes than other anti-hypertensive drugs. However, an important 2006 ALLHAT study compared the effects of various drug classes on blood sugar levels and diabetes development. The results suggested that while diuretics may slightly increase diabetes risk more than other types of anti-hypertensive drugs, this effect does not cause worse heart problems. Most experts believe that thiazide diuretics should remain the first choice for high blood pressure treatment, and that the benefit of blood pressure reduction outweighs the risk of diabetes development.

Diabetes-Related Kidney Disease. High blood pressure is strongly associated with diabetic nephropathy (diabetes-related kidney disease). Most patients with type 2 diabetes who show early signs of nephropathy already have high blood pressure. When patients with type 1 diabetes are diagnosed with early nephropathy, on the other hand, they usually have normal blood pressure readings in the doctor's office. A 2002 study using home monitors, however, found that patients with type 1 diabetes often have high systolic blood pressure during sleep -- before development of nephropathy. Home blood pressure monitoring, then, may help identify patients who are at risk for kidney damage due to high systolic pressure.

End-Stage Kidney Disease. High blood pressure causes 30% of all cases of end-stage kidney disease (medically referred to as end-stage renal disease, or ESRD). Only diabetes leads to more cases of kidney failure.

Kidney Cancer. Men with high blood pressure may also have a higher risk of kidney cancer.

Effect on the Eyes

High blood pressure can injure the eyes, causing a condition called retinopathy.

Bone Loss

Hypertension also increases the elimination of calcium in urine, potentially leading to loss of bone mineral density, a significant risk factor for fractures, particularly in elderly women. In one study, women with the highest levels of blood pressure lost bone density at nearly twice the rate of those in the lowest range. It is not clear whether this effect occurs in men or in non-Caucasian women.

Sexual Dysfunction

Sexual dysfunction is more common and more severe in men with hypertension and in smokers than it is in the general population. Many of the drugs that treat hypertension are thought to cause impotence as a side effect. In these cases, it is reversible when the drugs are stopped. More recent evidence suggests, however, that the disease process that causes hypertension is itself the major cause of erectile dysfunction in these men.

Newer anti-hypertensive drugs, including angiotensin-converting enzyme (ACE) inhibitors and angiotensin-receptor blockers (ARBs), are less associated with erectile dysfunction. ARBs, such as losartan (Cozaar), may be particularly effective in restoring erectile function in men with high blood pressure. Sildenafil (Viagra) is successful in achieving erections in almost two-thirds of patients with controlled high blood pressure. Because sildenafil has a shorter half-life and is eliminated more quickly from the body than newer erectile dysfunction drugs, it may be a safer option for men with hypertension. In a 2003 review of safety data, sildenafil did not appear to pose a risk for men who had both high blood pressure and erectile dysfunction.

Pregnancy and Preeclampsia

Severe, sudden high blood pressure in pregnant women is one component of a condition called preeclampsia (commonly called toxemia) that can be very serious for both mother and child. Preeclampsia occurs in up to 10% of all pregnancies, usually in the third trimester of a first pregnancy, and resolves immediately after delivery. Other symptoms and signs of preeclampsia include protein in the urine, severe headaches, and swollen ankles.

This condition may be caused by a failure of the placenta to embed properly in the uterus, which causes it to misconnect with the mother's blood vessels. As a result, the fetus does not receive a sufficient blood supply, and the mother's own blood pressure increases to replace it. The risk for preeclampsia is higher for first births, multiple births, and for very young women (teenagers) and those over age 35. Pre-existing high blood pressure, diabetes, and kidney disease also increase the risk for preeclampsia. There appears to be a genetic component for this condition, so women whose mothers experienced preeclampsia are also at higher risk.

The reduced supply of blood to the placenta can cause low birth weight and eye or brain damage in the fetus. Severe cases of preeclampsia can cause kidney damage, convulsion, and coma in the mother and can be lethal to both mother and child. Evidence also suggests that preeclampsia can lead to increased risks later in life for coronary heart disease and other heart problems.

Women at risk for preeclampsia (particularly those with existing hypertension) may benefit from having an ultrasound of uterine arteries at 20 - 24 weeks of pregnancy, followed (if abnormal) by 24-hour blood pressure monitoring. Blood pressure medications may be required. Delivery is the main cure for preeclampsia. In severe cases, the obstetrician will need to induce pre-term birth.

Uterine Fibroids

High blood pressure may increase the risk of developing fibroids, according to data from the Nurses’ Health Study. Tracking women for 10 years, the prospective epidemiologic study found that for every 10 mm/Hg increase in diastolic blood pressure, the risk for developing fibroids increased by 8 - 10%.

Outlook for Children with Hypertension

Children with high blood pressure should first be treated with lifestyle changes, including weight reduction, increased physical activity, and diet modification. If blood pressure is not controlled with lifestyle changes, drug treatment may be required. Although there are few clinical trials conducted in children, a 2005 study found that the angiotensin receptor blocker losartan was safe and effective in children. Results of studies evaluating outcomes of children with hypertension suggest that early abnormalities, including enlarged heart and abnormalities in the kidney and eyes, may occur even in children with mild hypertension. Children and adolescents with hypertension should be monitored and evaluated for any early organ damage. Secondary hypertension (high blood pressure due to another disease or drug) is more common in children than adults.