Hypoperfusion Intensity Ratio Predicts Successful Recanalization in M2 MCA Occlusion Stroke Treated with Thrombectomy

The role of endovascular thrombectomy for acute ischemic stroke due to M2 MCA occlusion remains uncertain, in part because angiographic recanalization rates are lower than those achieved in large-vessel occlusion. The hypoperfusion intensity ratio (HIR), a perfusion-derived marker of collateral physiology, has been associated with infarct evolution and outcomes, but its relationship with the technical success of thrombectomy in M2 occlusion is unknown.

In this retrospective, multinational study of the Multicenter Analysis of Primary Distal Medium Vessel Occlusions: Effect of Mechanical Thrombectomy (MAD-MT) Consortium registry, patients with M2 MCA occlusion who underwent EVT between September 2017 and July 2023 were included. Multivariable logistic regression analysis for successful EVT (mTICI 2b-3) was performed with HIR alongside demographic and stroke characteristics.

Among 111 patients with M2 MCA occlusion, 23 (21%) had unsuccessful EVT and 88 (79%) had successful EVT. HIR (0.50 [0.00-0.63] versus 0.20 [0.00-0.40], P = .007) and NIHSS score (15 [10-18] versus 10 [7-16], P = .05) were significantly lower in patients with mTICI 2b-3, along with a significantly higher ASPECTS (8 [6-10] versus 9 [8-10], P = .03). In the multivariable logistic regression analysis, higher HIR, representing impaired collateral circulation, was independently associated with lower odds of mTICI 2b-3 (OR per 0.1-unit increase, 0.80; 95% CI, 0.64-0.98; P = .038).

This retrospective study suggests that HIR may serve as a predictor of success in EVT and a potentially useful adjunct tool for decision-making in patients who have had MeVO stroke. However, the limited sample size and unmeasured confounders should be considered. These findings underscore the role that perfusion imaging-based quantitative collateral assessments can play in prognosis for these patients.