High blood pressure: what is it?

High blood pressure (or hypertension) is a condition in which the blood pressure in your arteries is higher than normal. High blood pressure doesn't usually present any symptoms until a vital organ is damaged. If left untreated, high blood pressure can lead to stroke, aneurysm, heart failure, heart attack, kidney damage, and other problems.

To check for high blood pressure, your systolic and diastolic pressures must be recorded. The systolic value, which is the higher value, is checked when your heart contracts. The diastolic value, or lower value, is checked when your heart relaxes, between beats. Blood pressure is written as the systolic pressure followed by a slash, followed by the diastolic pressure. For example: 120/80mm Hg (millimeters of mercury), or "one twenty over eighty."

High blood pressure is generally defined by a systolic pressure, that averages or is greater than 140 mm Hg; and by diastolic pressure that averages or is greater than 90 mm Hg. Recent studies, however, indicate that for many people even lower readings than 140/90 would be best.

Isolated Systolic Hypertension (ISH) occurs when your systolic pressure is 140 mm Hg or more but your diastolic pressure is less than 90 mm Hg - or in the normal range. Just as the risk of high blood pressure increases with age, so too does the risk of ISH.

Malignant hypertension is a severe and fairly rare form of very high blood pressure. If left untreated, malignant hypertension can lead to death, sometimes within three to six months. Malignant hypertension is considered a medical emergency.

In many people, the cause of high blood pressure is unknown, and the condition is referred to as essential or primary hypertension. It is likely that essential hypertension may have more than one cause, wherein several changes in the heart and blood vessels could combine to elevate the blood pressure.

When the cause of high blood pressure is known, it is referred to as secondary hypertension. Obesity, a sedentary lifestyle, stress, alcohol, smoking and bad diet - too much fat and salt - can all contribute to the development of high blood pressure, which can lead to heart disease, if left untreated.

If you have been diagnosed with high blood pressure, your doctor will also want to evaluate its effects on your blood vessels, heart, brain and kidneys, and other key organs.