NEW YORK (Reuters Health) – In high-risk post-acute coronary syndrome (ACS) patients, a J- or U-shaped association exists between blood pressure and the risk of future cardiovascular events, with an “exponential increase in event rates at high and low BP values,” according to a post hoc analysis from a large prospective randomized study.

The lowest event rates were seen in the BP range of roughly 130 to 140 over 80 to 90 mm Hg, whereas the curve was relatively flat for systolic BP of 110 to 130 mm Hg and diastolic BP of 70 to 90 mm Hg.

This suggests that the paradigm of “lower is better” in cardiovascular medicine is not applicable to BP control beyond a certain target, and that “too low” of a pressure (especially < 110/70 mm Hg) may be dangerous,” the study team notes in the November 23 issue of Circulation. “Aggressive BP control” has been advocated in patients with ACS, but few data exist in this population relative to cardiovascular outcomes, Dr. Christopher P. Cannon from Brigham and Women’s Hospital, Boston and colleagues point out in their report. To investigate, they analyzed 4,162 patients enrolled in the PROVE IT-TIMI 22 (Pravastatin or Atorvastatin Evaluation and Infection Therapy – Thrombolysis in Myocardial Infarction 22) study. In the study, patients who had been hospitalized for an ACS within the preceding 10 days were randomly assigned to receive 40 mg/d of pravastatin or 80 mg/d of atorvastatin and were followed up for 18 to 36 months. The primary outcome was a composite of death due to any cause, myocardial infarction (MI), unstable angina requiring rehospitalization, revascularization after 30 days, and stroke. The secondary outcome was a composite of death due to heart disease, nonfatal MI, or revascularization. As mentioned, the relationship between systolic and diastolic BP followed a J- or U-shaped curve association with primary, secondary, and individual outcomes, with increased event rates at both low and high BP values. This was true in both unadjusted and fully adjusted analyses. “The degree of statin therapy did not mitigate the J- or U-shaped curve phenomenon,” they note, nor did adjustment for baseline C-reactive protein and average levels of LDL-cholesterol on treatment. In a nonlinear Cox proportional hazards model, the incidence of the primary outcome was lowest at a nadir of 136/85 mm Hg (range 130 to 140 mm Hg systolic and 80 to 90 mm Hg diastolic). The curve was relatively flat for systolic pressures of 110 to 130 mm Hg and diastolic pressures of 70 to 90 mm Hg, they report. Dr. Cannon and colleagues say these findings “provide support for the Seventh Report of the Joint National Committee’s guideline recognition of a possible increased risk when diastolic pressures are lowered to < 60 mm Hg.” “Our findings are consistent,” they add, “with recent studies in stable patients but extend the observation to high-risk post-acute coronary syndrome patients. As such, this study helps provide evidence that clinicians treating hypertension should aim for a systolic BP < 140 mm Hg but not < 110 mm Hg.”