Are there different types of high blood pressure?
Yes. High blood pressure can be classified in two ways, one according to how severe it is (mainly a question of how high the blood pressure is) and the other according to what's causing it. About 95 percent of people with high blood pressure have what is known as essential hypertension, which is really a fancy way of saying that it just happens, and we don't know why. The other 5 percent of cases have secondary hypertension, where there is an identifiable and usually correctable cause. The commonest of these is renovascular hypertension, where there is narrowing of the artery to one or both kidneys. Other less common causes of secondary hypertension are small tumors of the adrenal glands that secrete blood pressure-raising chemicals (hormones) into the bloodstream.
The term essential hypertension is not a very specific one. It is thought that hypertension is the end result of a number of different factors that make the blood pressure go up, and it is probable that different mechanisms are important in different individuals. This may explain why a particular type of treatment may work very well in one person, but not at all in another.
Classification of hypertension by its severity is somewhat arbitrary because there's no precise level of pressure above which it suddenly becomes dangerous. For no particularly good reason, blood pressure has traditionally been classified according to the height of the diastolic pressure, although the systolic pressure is probably more important in determining the level of risk. Someone whose diastolic pressure runs between 90 and 95 mm Hg may be regarded as having borderline hypertension, and when it's between 95 and 110 mm Hg it's moderate, and at any higher levels it's severe. The most dangerous type is called malignant hypertension, which is regarded as an acute emergency requiring immediate treatment in a hospital. Whatever the underlying cause, when the blood pressure reaches a certain level for a sufficient length of time it sets off a vicious cycle of damage to the heart, brain, and kidneys, resulting in further elevation of the pressure. Not surprisingly, if untreated, malignant hypertension can be rapidly fatal. Because more people are treated nowadays than before, malignant hypertension is not common, and is mainly seen in people who have not had access to medical care.
White coat (or office) hypertension is a term used to describe people whose blood pressure is only high in a doctor's office.
Systolic hypertension is mainly seen in people over the age of 65 and is characterized by a high systolic, but normal diastolic, pressure (a reading of 170/80 mm Hg would be typical). It's caused by an age-related loss of elasticity of the major arteries.
Labile hypertension is a commonly used but inappropriate term for describing people whose pressure is unusually labile or variable. In fact, just about everyone has labile blood pressure.