Peggy Nguyen, MD 

Borst J, Berkhemer OA, Roos YBWEM, van Bavel E, van Zwam WH, van Oostenbrugge RJ, et al. Value of Computed Tomographic Perfusion–Based Patient Selection for Intra-Arterial Acute Ischemic Stroke Treatment. Stroke. 2015 

The current treatment of acute ischemic stroke is largely dependent on the timing of presentation from ictus; that is, thrombolytics up to 4.5 hours and thrombectomy up to 6 hours from onset, but many patients continue to present outside of the window for intervention. The use of advanced imaging modalities for markers to stratify patients who may benefit is an area of enormous interest. Here, the authors looked at a subset of 175 patients in the MR CLEAN study who underwent CT perfusion with the goal of evaluating the relationship between CTP deprived parameters and functional outcome, investigating whether the efficacy of intraarterial treatment (IAT) on outcome was modified by the CTP derived parameters, and investigating the effect of CTP mismatch selection on the efficacy of IAT.
The authors did find a significant association between both CTP-derived ischemic core volume and percentage ischemic core and functional outcome, but not penumbra volume, indicative of a poorer functional outcome with larger ischemic core. However, there was no interaction between CTP derived parameters (ischemic core volume, penumbra volume, and percentage ischemic core) and treatment effect, indicating that the efficacy of IAT was independent of CTP parameters.

CTP mismatch, defined per criterion used in EXTEND-IA as an ischemic core < 70 mL and a penumbra of at least 10 mL and 20% larger than the ischemic core, was present in 102/175 patients. Patients with mismatch present were more likely to have a higher NIHSS and presence of an ICA terminus occlusion. There was no significant interaction between mismatch and treatment effect on the mRS scale endpoint nor on the dichotomized endpoints of mRS. Patients with a large ischemic core > 70 mL experienced higher mortality than those with smaller ischemic cores. All patients, despite the volume of ischemic core, had a shift towards better outcome after IAT compared to usual care alone.

This study confirms the benefit of IAT for acute ischemic stroke, even in those with a large CTP ischemic core, shows that larger ischemic core volumes are associated with worse functional outcomes, but found no interaction between treatment effect and CTP core volume nor other CTP derived parameters. The authors point out that CTP appears useful for predicting functional outcome, but cannot reliably identify patients who will not benefit from IAT. Further studies are needed.