Systolic vs. diastolic hypertension
Two numbers are recorded when taking blood pressure: the systolic pressure and the diastolic pressure. (The "top" number "bottom" number, respectively, in the following expression: 140/90.) The reason two numbers are necessary is that the pressure within blood vessels is not static - it changes dynamically each time the heart beats. While the heart is actually beating, blood is forced out of the heart and into the blood vessels. This instantaneously increases the pressure within the vessels. In between heart beats, the pressure within the blood vessels becomes lower.The blood pressure recorded while the heart muscle is contracting is the systolic pressure. The blood pressure recorded in between heart muscle contractions is the diastolic pressure. Both numbers are important, and when a person has hypertension, the elevated blood pressure can be seen with the systolic pressure (systolic hypertension,) with the diastolic pressure (diastolic hypertension,) or both. A "normal" systolic pressure is less than 140 mm Hg. A "normal" diastolic pressure is less than 90 mm Hg.
Most people below the age of 65 or 70 who have hypertension have elevations of the diastolic pressure. While these people also most often have elevation in the systolic pressure, it is felt that the chronic elevations in their diastolic pressures is the real problem - that is, the elevation in diastolic pressure is what eventually causes damage to the heart, brain and kidneys. In these individuals, reducing the diastolic pressure is the primary goal of therapy. Satisfactory therapy for these patients is generally regarded as reducing their diastolic pressures to less than 90. A secondary goal is to reduce their systolic pressure to less than 140, but the primary concern is the diastolic pressure.
In recent years, it has been recognized that elderly patients will often develop a form of isolated systolic hypertension. Their systolic pressure becomes elevated as they age (because blood vessels become "stiff" with age,) but their diastolic pressures remain within the normal range. Elderly patients with isolated systolic hypertension have an increased incidence of stroke, so they also require treatment. Here, reducing the systolic pressure is the primary goal of therapy. The goal of therapy has generally been to reduce their systolic pressure to 140 or less, while paying little attention to their already-normal diastolic pressure.
New observations about the "traditional" treatment goals
Recent clinical trials have called these treatment goals into question. Doctors who are pursuing these traditional goals may be overtreating some patients, and undertreating others. Observations that lead to this conclusion include:- For patients who are otherwise healthy, the therapeutic goal of 140/90 seems adequate. But for people with certain underlying medical problems - chiefly diabetes or kidney disease - 140/90 is still too high. These individuals continue to suffer the consequences of hypertension unless their blood pressure is reduced below the traditional target value of 140/90.
- In treating elderly patients with isolated systolic hypertension, the diastolic pressure (which is normal to begin with) is also most often reduced. It turns out that if the diastolic pressures in these elderly patients is reduced too much (below 65 - 70,) the risk of stroke increases.
New recommended treatment goals
1) For people with typical diastolic hypertension who are not at high risk, the traditional goal of reducing the blood pressure to less than 140/90 appears adequate.2) For elderly people with isolated systolic hypertension, caution should be taken to avoid reducing the diastolic pressure to less than 65 - 70. Less than optimal lowering of the systolic pressure should be accepted in order to avoid reducing the diastolic pressure too far.
3) For certain "high-risk" patients with diastolic hypertension, more aggressive therapy to reduce the diastolic pressure to 80 or less should be considered. These include:
- Those with diabetes. Reducing the blood pressure to 130/80 or less reduces the risk of cardiac disease.
- Those with renal insufficiency (kidney disease.) Reducing the blood pressure to 125/75 or less appears to slow the progression of kidney disease.
- Black patients. For reasons not well understood, African American patients continue to have high risk for hypertensive complications unless their diastolic blood pressure is reduced to below 85.
