Christopher Wilkins, MD
Al-Dasuqi K, Payabvash S, Torres-Flores GA, Strander SM, Nguyen CK, Peshwe KU, Kodali S, Silverman A, Malhotra A, Johnson MH, et al. Effects of Collateral Status on Infarct Distribution Following Endovascular Therapy in Large Vessel Occlusion Stroke. Stroke. 2020;51:e193–e202.
Endovascular therapy has become an invaluable tool in the treatment of acute ischemic stroke as it can provide significant improvement in the functional outcome of selected patients. Since its reception, studies have broadened the time window for endovascular therapy by using perfusion imaging during acute ischemic strokes to determine how much cerebral tissue is, or close to be, infarcted (i.e., the core) and comparing it to tissue which has reduced blood flow but is likely salvageable with reperfusion (i.e., the penumbra). The volume of the core, as well as ratio between core and penumbra, ultimately determines which patients are appropriate for endovascular therapy. Studies have shown that cerebral collateral circulation can be a major determinant of final infarct volume and can thus impact who would be deemed appropriate for thrombectomy. However, data on whether the status of collateral circulation impacts final clinical outcome in those undergoing thrombectomy remains discrepant.
In this retrospective study, Al-Dasuqi et al. investigated how collateral status impacts final infarct size, as well as functional outcomes, in those with successful and unsuccessful recanalization following endovascular therapy with either mechanical thrombectomy or intra-arterial thrombolytic drug delivery. The authors selected patients who: had evidence of large vessel occlusion on CTA in the ICA or MCA at the M1 or proximal M2 segment; underwent mechanical thrombectomy or intraarterial thrombolysis, with or without IV-tPA before intervention; had follow up MRI obtained within 24 hours to 7 days post endovascular treatment. The collateral status of patients was defined using a grading system designed by Miteff et al.1 There are 3 grades which include: “good,” where the entire MCA distal to the occluded segment reconstitutes with contrast; “moderate,” where some MCA branches distal to the occluded segment reconstituted in the sylvian fissure; and “poor,” where only distal superficial MCA branches reconstituted distal to the occlusion. Though many different grading systems for collateralization have been created, Al-Dasuqi et al. used the grading system by Miteff et al. because this grading system showed to be reliable in predicting favorable and poor outcomes in patients treated with IV-tPA while other collateral grading systems were of limited value. Successful recanalization was defined by mTICI score of 2b-3. A summation map of all infarct lesions detected on MRI was created to identify regions of infarct associated with mTICI scores and collateral grading. Early functional outcome was measured using the modified Rankin Scale (mRS) at discharge with a favorable outcome defined as mRS score of 0 to 2.