Although the field of hypertension can now be regarded as a mature science, we still have difficulty understanding the core metric of this discipline: blood pressure.
There are two main sources of information on this topic: epidemiologic studies that have linked BP levels to cardiovascular outcomes; and clinical trials that have studied the effects of BP reductions on prevention of cardiovascular, stroke and renal event rates.
Epidemiologic reports from such sources as Framingham and the Prospective Studies Collaboration suggest a direct relationship between BP and major coronary and stroke events down as low as a systolic BP of 115 mmHg. Even BP levels that are “usual” by conventional standards are associated with higher event rates than “optimal” levels. Clinical trials tell a different story. Early trials demonstrated that reducing SBPs from above to below 160 mmHg reduced cardiovascular events. But we have no direct evidence from primary endpoints in RCTs that achieving below 140 mmHg provides further benefits, though secondary analyses are supportive. In ACCORD reduction of SBP below 120, as compared with below 140 mmHg, decreased stroke but not coronary or fatal events. Secondary analyses from hypertension trials like VALUE and ACCOMPLISH confirm stroke benefits with low BPs but raise concern about other cardiovascular endpoints.
It seems that 140 mmHg is a reasonable target for treatment. In young patients, and possibly with innovative therapies, lower targets could be beneficial.
© 2012 Lippincott Williams & Wilkins, Inc.