Background and Purpose: The best approach to select patients for reperfusion therapy in acute ischemic stroke remains to be established. Different methodologies have been proposed using different clinical, vascular, and parenchymal imaging parameters. Our aim is to compare Perfusion-imaging Mismatch (PIM) and Clinical-Core Mismatch (CCM) patient selection and assess their ability to predict outcomes.
Methods: We reviewed our prospectively collected endovascular database at a tertiary care academic institution for patients with acute anterior circulation strokes, adequate CT perfusion imaging maps and a National Institute of health Stroke Scale (NIHSS) ≥10 from September 2010 to March 2015. Patients were categorized according to the PIM and CCM definitions. PIM was defined as follows: Core Lesion ≤50cc; Tmax >10sec <100cc; Mismatch (Tmax> 6s lesion - core lesion) ≥15cc and ratio >1.8. CCM was defined as: NIHSS ≥ 10 and core infarct <31 cc (and age < 80) or NIHSS ≥ 20 and core infarct <51 cc (and age < 80) or NIHSS ≥ 10 and core infarct <21 cc (and age ≥ 80). The ability of PIM and CCM to predict good outcomes (modified Rankin scale 0-2) was evaluated using the area under the receiver operating characteristic curves (AUC), Akaike information criterion (AIC) and Bayesian information criterion (BIC).
Results: A total of 368 patients qualified for the study. PIM had a lower number of qualifying patients compared to CCM (n=231, 62.8% vs n=303, 82.3%). The two groups were statistically different (p<0.001) with the following disagreement: 12 PIM+/CCM- and 84 PIM-/CCM+. There were no differences in good outcomes between PIM+ and PIM- patients (52% vs 48%, p=0.5). CCM+ patients had higher rates of good outcomes than CCM- (53% vs. 35%, p=0.015). There were no differences between PIM and CCM in predicting good outcomes as assessed by the AUC, AIC and BIC (0.82, 323.64 and 330.61 vs 0.82, 323.56 and 330.53 respectively)
Conclusion: We were unable to demonstrate a difference between the PIM and CCM in predicting clinical outcomes. However, PIM seems to unjustifiably disqualify a significant proportion of patients that still benefit from reperfusion. In contrast with CCM, PIM does not seem to be a good discriminator of good outcomes. Future prospective studies are warranted.