Assessing the Clinical Relevance of Blood Pressure Measures in Spontaneous Intracerebral Hemorrhage: A Post Hoc Analysis of ATACH-2.

backgroundRecent American Heart Association guidelines have relied on post hoc subgroup analyses to identify summary blood pressure measures for targets in early management of acute intracerebral hemorrhage. To our knowledge, measurement error has not been considered when determining the impact of these summary measures. Our objective was to determine whether statistically significant differences in three systolic blood pressure (SBP) measures (achieved SBP, SBP variability, and magnitude of SBP reduction) in patients with intracerebral hemorrhage from the antihypertensive treatment of acute cerebral hemorrhage II (ATACH-2) randomized clinical trial are clinically meaningful by comparing them to a minimally detectable difference (MDD) of 10 mm Hg.

methodsWe performed a post hoc analysis of individual patient data from the ATACH-2 randomized clinical trial, evaluating the differences in achieved SBP, SBP variability, and magnitude of SBP reduction between patients with favorable (modified Rankin scale score 0-3) and unfavorable (modified Rankin scale score 4-6) outcomes. We used the empirical cumulative distribution functions and Kolmogorov-Smirnov tests to compare distributions, and we considered differences clinically meaningful if they exceeded the MDD of 10 mm Hg. We also performed a propensity score matched analysis to understand the nature of the association between these measures and outcomes.

resultsAlthough SBP variability in the first 24 h differed statistically between outcome groups, the mean difference (95% confidence interval) did not exceed the MDD threshold. Achieved SBP and magnitude of SBP reduction showed no significant differences between groups. In the propensity score matched analysis, there were no statistical differences between any blood pressure measurements and outcomes.

conclusionsOur findings suggest that although there are statistically significant differences in SBP variability between patients with good and poor outcomes in ATACH-2, these differences do not meet the threshold for clinical relevance because they were within the range of measurement noise. The propensity score matched analysis suggested that the association between summary blood pressure measurements and outcomes is not robust to analytical method. These findings emphasize the need for caution in interpreting post hoc findings for clinical decision-making.