LARGE CT PERFUSION–DEFINED MISMATCH PREDICTS EARLY IMPROVEMENT AFTER IV THROMBOLYSIS IN ACUTE ISCHAEMIC STROKE

Background An arbitrary perfusion imaging “mismatch” ratio (total perfusion defect : irreversibly damaged “core” volumes) of >1.2 has been widely utilised in research to select patients for reperfusion therapies in acute ischaemic stroke. MRI studies suggest that a higher ratio may define a greater differential treatment response. We evaluated whether CTP mismatch ratio provided additional prognostic information compared to clinical examination and appearances on non–contrast CT (NCCT). Methods Patients recruited to two sub–6 hour prospective observational studies of ischaemic stroke who received intravenous thrombolysis (rtPA) and who had a deficit on acute CTP imaging were included for analysis. CTp measured perfusion deficit was defined by delay time >2s, and core defined by delay time >2s plus relative cerebral blood flow 1 predictor where multiple predictors were significant on regression. Analysis was repeated for the subset of subjects who recanalised. Results 61 subjects were included: median admission NIHSS=13, median onset–to–CT time=160 minutes. Twenty subjects had confirmed recanalisation on 24–72h CT angiography. No predictor was significantly associated with major neurological improvement, with CTP mismatch performing best (p=0.078). On expansion of this outcome to include subjects with a 24 hour NIHSS score of ≤2 or 8 or more points improvement, only CTP mismatch ratio was a significant predictor (Optimal cut point: >3.4; Positive Predictive Value [PPV]: 45; Negative Predictive Value [NPV]: 8