Tolga D. Dittrich, MD

Lopez-Rivera V, Abdelkhaleq R, Yamal J-M, Singh N, Savitz SI, Czap AL, Alderazi Y, Chen PR, Grotta JC, Blackburn S, et al. Impact of Initial Imaging Protocol on Likelihood of Endovascular Stroke Therapy. Stroke. 2020;51:3055-3063.

Endovascular therapies (EVT) are a cornerstone of acute ischemic stroke therapy. CT- based perfusion imaging (CT-P), in addition to native CT and CT angiography, has become established in many clinics for the identification of patients with large vessel occlusions (LVO) who are eligible for EVT. But how does the choice of initial imaging protocol affect the probability of conducting EVT in patients with LVO?

A recent retrospective cohort study with four stroke centers has addressed this question. All four centers routinely performed native CT and CT angiography as part of the initial radiological assessment. The capacity to perform CT-P and EVT was present at all centers at all times. One participating center routinely performed additional CT-P with a high rate of usage (CTP-H), whereas the other three centers performed CT-P at a lower rate of usage (CTP-L) only at clinical discretion.

Of the total 715 patients included with acute ischemic stroke due to LVO, 403 (56%) presented at the CTP-H, and 312 (44%) at CTP-L centers. As expected, CT-P performance was higher at the CTP-H center than at the CTP-L centers (72% versus 18%, P<0.01). The initial radiological assessment in both CTP-H and CTP-L centers was independent of the time of presentation after symptom onset. The probability of performing EVT was higher in the CTP-L centers without resulting in a worse outcome or increased bleeding rate.

In the acute setting (i.e., patients presenting within 6 hours after symptom onset), the additional benefit of perfusion imaging in cases with angiographically proven LVO seems less evident as there is a lack of convincing arguments for not performing EVT in these scenarios. Conversely, we know from DAWN and DEFUSE-3 that perfusion imaging in patients presenting late (i.e., 6-24 hours after symptom onset) is a helpful instrument to identify those with large penumbra who may qualify for EVT.

Ultimately, the important and yet not conclusively answered question arising in the context of this study is, in what time frame the performance of CT perfusion imaging can influence the decision for or against EVT in such a way that the functional outcome of patients with LVO is positively influenced.