Jay Shah, MD
Albers GW, Goyal M, Jahan R, Bonafe A, Diener HC, Levy EI, et al. Relationships Between Imaging Assessments and Outcomes in Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke. Stroke. 2015
Patients with target mismatch (TMM) have relatively small ischemic core with substantially larger region of critical hypoperfusion and have strong association between early reperfusion and favorable clinical outcomes. SWIFT PRIME was a randomized trial evaluating treatment with intravenous tPA versus tPA plus endovascular therapy. Brain imaging was primarily accomplished by CT perfusion. The authors in this study evaluated relationships between baseline and follow-up imaging and clinical outcomes. Ischemic core and hypoperfusion volumes were calculated and patients were stratified as either TMM or malignant profile. Imaging, typically MRI, was obtained at 27 hours to calculate infarct volume.
196 patients were enrolled in SWIFT PRIME and 166 had baseline perfusion imaging. 141 patients had the TMM profile while 25 did not. There was a potent relationship between 27-hour infarct volumes and clinical outcomes. Expectedly, results demonstrated progressively larger infarcts with modified rankin scale increase. Patients with TMM profile had significantly higher rates of reperfusion, smaller infarct volumes, and higher rates of functional independence at 3 months in the intervention group. In the malignant group, functional independence rates were 10% lower compared to rates in TMM group.
Results indicate that patients with TMM profile have favorable response to endovascular therapy on both clinical and imaging outcomes. As endovascular therapy becomes readily available, judicious patient selection will be important. As this study suggests, CT perfusion can be utilized to select patients with the favorable TMM profile. However, a limitation to this approach could be the potential unavailability of performing perfusion imaging at all hours and may lead to delays in thrombolytic and/or endovascular therapy. Interestingly, timing was monitored in SWIFT PRIME and perfusion imaging did not delay time to femoral puncture. It is also important to note that due to the low number of patients with malignant profile, the study was not powered to assess this population. Therefore, it would be premature to conclude that this group has inadequate response to endovascular therapy. Further studies are required to appropriately assess this subgroup.