Blood pressure variability and outcome in acute ischemic and hemorrhagic stroke: a post hoc analysis of the HeadPoST study

The Head Positioning in Acute Stroke Trial (HeadPoST) is a pragmatic, international, cluster crossover randomized trial of 11,093 patients with acute stroke assigned to a lying-flat (0 degrees) or sitting-up (head elevated 30 degrees) position. This post hoc analysis aimed to determine the association between blood pressure variability (BPV) and outcomes for patients from a wide range of international clinical settings and how the association was modified by randomized head position. BPV was defined according to the standard criteria, with the key parameter considered the coefficient of variation (CV) of systolic BP (SBP) over 24 h. Outcome was ordinal 90-day Modified Rankin Scale (mRS) score. The association was analyzed by ordinal, logistic regression, hierarchical, mixed models with fixed intervention (lying flat vs. sitting up), and fixed period, random cluster, and random cluster-period, effects. Nine thousand one hundred and fifty six (8324 acute ischemic stroke and 817 intracerebral hemorrhage; mean age 68.1 years; 39.2% women) were included in the analysis. CV of SBP had a significant linear association with unfavorable shift of mRS at 90 days (adjusted odds ratio 1.06, 95% confidence interval 1.02-1.11; P = 0.01). There was no heterogeneity of the association by randomized head positioning. In addition, CV of diastolic BP (DBP) (1.08, 1.03-1.12; P = 0.001) over 24 h post stroke was significantly associated with 3-month poor outcome. The association was more apparent in sitting-up position (1.12, 1.06-1.19) compared with lying-flat position (1.03, 0.98-1.09) (P interaction = 0.005). BPV was associated with adverse stroke outcome, and the magnitude of the association was greater with sitting-up head positioning in terms of DBP variability.