Hypertension is high blood pressure. Normal blood pressure is below 120/80. Hypertension is defined as the top number, or systolic pressure, as being over 139, or the bottom number, the diastolic pressure, as over 89. High blood pressure is caused by unknown factors 90 to 95 percent of the time, and caused by another treatable condition the remainder of the time. Hypertension is dangerous if it is extremely high—a condition called malignant hypertension—and causes a number of dangerous systemic effects over the long term.
Heart
According to the National Institutes of Health, high blood pressure is a known risk factor for coronary artery disease, or CAD, which is a narrowing of the arteries supplying blood to the heart. A heart attack results when an artery in the heart becomes completely occluded. Hypertension is also a risk factor for the development of congestive heart failure. In this disorder, the heart is unable to pump enough blood to the body and fluid builds up in the blood vessels and tissues.
Blood Vessels
The blood vessels throughout the body are more susceptible to arteriosclerosis in people with high blood pressure. Arteriosclerosis is a hardening of the arteries, placing strain on the organs because they do not receive as much blood. Plaques made of fat, cholesterol and immune cells can build up further occluding the blood vessels in the process of atherosclerosis.
Kidneys
The kidneys are responsible for filtering the blood to regulate its composition and expel wastes in urine. According to the Mayo Clinic, high blood pressure damages the tiny blood vessels in the kidneys that help filter blood, called glomeruli. Over time, this can lead to kidney failure. If that occurs, the kidney will not regulate the blood, and toxins and fluid will build up, requiring dialysis or a kidney transplant.
Brain
Largely due to the negative impact hypertension has on blood vessels, the brain is at risk of several conditions. According to the Mayo Clinic, these include stroke, transient ischemic attack, mild cognitive impairment and dementia. In a stroke, part of the brain is damaged, leading to a loss of function. This may be motor function, such as the ability to move an arm or leg; sensory, such as feeling a limb; or cognitive, such as the ability to understand speech. A transient ischemic attack is similar but only lasts 24 hours and then resolves. However, it is a major risk factor for stroke. Dementia is a progressive loss of brain function, particularly memory. Mild cognitive impairment is mild dementia.
Eyes
According to the Mayo Clinic, hypertension damages the eyes in several ways as well. It can damage the the optic nerve, the main nerve serving the eyes. In addition, the blood vessels in the eye can be damaged, destroying all or part of the retina, which is situated at the back of the eye and transfers light signals back to the optic nerve. Hypertension can also cause fluid to build up in the eyes.
