It is well established that controlling your blood pressure with blood-pressure lowering medications reduces risks of heart related events and death. It has been further demonstrated that lowering systolic blood pressure (SBP) as well diastolic blood pressure (DBP) means that you’ll benefit.
In the late 1970s, data revealed that while there is no level of SBP lowering that does not incrementally improve outcomes, such may not be the case for DBP. Subsequently, numerous analyses have been performed demonstrating that when lowered from high numbers above 90, diastolic blood pressure improvements decreased risks. But if DBP keeps getting lower, there is a higher risk of mortality and coronary events in those whose DBPs were lowered below 65-85 mm Hg.[3,4,5] Many of these analyses were, however, based on small numbers of cases.
Three explanations might explain this phenomenon.
- Diastolic hypotension is frequently noted in conditions such as cardiomyopathy or malignancy and some patients may simply have a more serious risk level overall.
- Another explanation is that low DBP is really a marker for widened pulse pressure, which is an indicator of increased arterial stiffness and atherosclerosis.
- Finally, some have suggested that diastolic hypotension reduces coronary filling pressures, thereby inducing endocardial ischemia.
In practice, diastolic hypotension by itself is a relatively uncommon complication of antihypertensive therapy. On the contrary, many patients are inadequately treated and have both SBP and DBP above the recommended targets.
One group where diastolic hypotension may complicate therapy is the elderly. In elderly persons, a common variant of hypertension is isolated systolic hypertension with a wide pulse pressure and normal or even low diastolic pressure. Although numerous studies, notably the Systolic Hypertension in the Elderly Program (SHEP), have demonstrated the considerable benefits of treating this form of hypertension, DBP lowering is an inevitable consequence of such treatment.
When the data from the SHEP trial was reanalyzed, a higher incidence of cardiovascular disease events in those patients with isolated systolic hypertension whose DBPs were lowered to less than 70 mm Hg. In those patients with DBP less than 55 mm Hg, the risk of cardiovascular events nearly doubled. There are some problems with these data because, again, the numbers of patients who achieved DBP <55 mm Hg were small and a careful reading of this study suggests that levels of 45 mm Hg were not harmful.
The authors of that research conclude that patients who achieve DBP levels of about 55-60 mm Hg deserve more careful monitoring and more aggressive treatment of other cardiovascular risk factors.
Based on these results we recommend treating patients with isolated systolic hypertension to lower SBP to <140 mm Hg, as recommended by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Caution should reign when DBP hovers around 56-60 mm Hg because (as far as we can currently tell) that is the point at which risk may approach benefit. As always, it remains prudent to offer such patients aggressive control of their other cardiovascular risk factors.