Hypertension, also known as high blood pressure, is a very common and serious condition that can lead to and/or complicate many health problems. These include coronary heart disease, stroke, kidney failure and heart failure. About one in three adults in the U.S. have hypertension, according to the National Heart, Lung and Blood Institute. There are three general types of hypertension. Essential hypertension occurs when the condition has no known cause. When hypertension is caused by another condition or disease process, it is called secondary hypertension. When only the systolic blood pressure number (the top number) is high, it is called isolated systolic hypertension, which is common in older adults.