Blood Pressure Variability: Its Definition, Measurement, and Prognostic Significance in Acute Stroke

Background: How best to manage elevated blood pressure (BP) in the acute stroke period remains unclear. Blood pressure variability (BPV), that is variability in BP over a period of time, may predict outcome in acute stroke, and could explain the ongoing uncertainty surrounding acute stroke BP management. Moreover, it presents a potentially modifiable therapeutic target. Evidence of the effect of BPV on outcome following stroke is scarce, and how best to measure or define BPV in acute stroke is unknown. Objectives: This thesis aimed to determine the prognostic significance of BPV in acute stroke, and to investigate how best to measure and define BPV in the immediate post-stroke period. Methods: The following studies were undertaken: a systematic review and meta‐analysis of observational studies to assess the effect of BPV on outcome in acute stroke; a feasibility study to assess the ability of a novel BP measurement device to capture very‐short‐term BPV; post‐hoc analyses of three acute stroke randomised controlled trials to assess the effect of BPV on outcome using individual patient data; a prospective observational study to measure acute stroke BPV using a variety of measurement techniques. Results: This thesis has demonstrated that greater BPV is associated with poor outcome in acute stroke. However, the presence and strength of this relationship is influenced by a number of factors including: frequency, timing, and nature of BP measurements; time from stroke onset; BPV parameters; use of thrombolytic therapy; and the timing of outcome measures. For the first time in acute stroke, the observational study describes and compares beat‐to‐beat, casual cuff, and ambulatory BP monitoring (ABPM) derived BPV, showing that it is feasible and acceptable to patients to measure BPV using casual cuff and beat‐to‐beat measurements, and reports significant associations between beat‐to‐beat and casual cuff BPV parameters and outcome.