Relationship between blood pressure and outcome changes over time in acute ischemic stroke

Objective To evaluate whether the relationship between systolic blood pressure (SBP) and stroke outcome varies during the acute stage of ischemic stroke as a function of the elapsed time after stroke onset. Methods Patients who were hospitalized due to ischemic stroke within 6 hours of onset were retrospectively analyzed. SBP data were collected at 8 time points (1, 2, 4, 8, 16, 24, 48, and 72 hours after onset). The primary functional outcome measure was a poor outcome, defined as a modified Rankin Scale score of >2 at 3 months after stroke. Linear and quadratic models were constructed at each time point to assess relationships between SBP and outcome. Results Of the 2,546 patients, 728 (28.6%) had a poor outcome. SBP, as either a linear or quadratic term, had a significant effect on functional outcome, except at 4 hours after onset. For the initial 2 hours after onset, SBP had nonlinear U-shaped relationships with functional outcome, and patients with SBP of approximately 165 mm Hg were the least likely to have a poor outcome. Quadratic models exhibited a significantly better model fit. For 8-24 hours postonset, SBP exhibited linear relationships with functional outcome. For 48-72 hours postonset, SBP exhibited a J-shaped relationship with functional outcome, and the predicted probability of poor outcome was the lowest in patients with SBP of approximately 125 mm Hg. These relationships were relatively consistent across various sensitivity analyses. Conclusion This study revealed that the relationship between SBP and functional outcome may depend on elapsed time from stroke onset.