Blood pressure paradox in patients with non-ST-segment elevation acute coronary syndromes: results from 139,194 patients in the Can Rapid risk stratification of Unstable angina patients Suppress ADverse outcomes with Early implementation of the American College of Cardiology/American Heart Association Guidelines (CRUSADE) quality improvement initiative.

BACKGROUND: The relationship between systolic blood pressure (BP) and the risk of cardiovascular events is complex. In patients with chronic coronary artery disease, a J-shaped relationship has been shown, such that there is an increased risk of events both at high and low BP. The current coronary artery disease risk prediction models, however, considers a linear relationship between presenting BP and outcomes in patients presenting with acute coronary syndromes.

METHODS: We evaluated 139,194 patients with non-ST-segment elevation acute coronary syndromes in the Can Rapid risk stratification of Unstable anigina patients Suppress ADverse outcomes with Early implementation of the ACC/AHA guidelines (CRUSADE) quality improvement initiative. The presenting systolic BP was summarized as 10-unit increments. Primary outcome was a composite of in-hospital events all-cause mortality, reinfarction, and stroke. Secondary outcomes were each of these outcomes considered separately.

RESULTS: From the cohort of 139,194 patients, 9,566 (6.87%) patients had a primary outcome (death/reinfarction or stroke) of which 5,910 (4.25%) patients died, 3,724 (2.68%) patients had reinfarction, and 1,079 (0.78%) patients had a stroke during hospitalization. There was an inverse association between presenting systolic BP and the risk of primary outcome, all-cause mortality, and reinfarction such that there was an exponential increase in the risk with lower presenting systolic BP even after controlling for baseline variables. However, there was no clear relationship between stroke and lower presenting systolic BP.

CONCLUSIONS: In contrast to longitudinal impacts, there is a BP paradox on acute outcomes such that a lower presenting BP is associated with increased risk of in-hospital cardiovascular events. These associations should be considered in acute coronary syndrome prognostic models.