Successful reperfusion for better outcomes in medium vessel occlusion: Penumbral salvage versus infarct volume reduction

Background: The benefits of endovascular thrombectomy (EVT) over medical treatment for medium vessel occlusion (MeVO) remain uncertain. Understanding how vascular reperfusion leads to favorable outcomes is crucial. This study examines whether penumbra salvage and infarct volume reduction quantify EVT benefits in MeVO patients and assesses their impact on clinical improvement post-reperfusion. Methods: We conducted a multicenter, observational study analyzing MeVO patients who underwent thrombectomy and received multimodal CT imaging from January 2020 to June 2024. EVT efficacy was evaluated by measuring follow-up infarct volume (FIV) on CT scans 24–48 h post-procedure and calculating the penumbra salvage index (PSI). PSI is the ratio of salvaged tissue volume (difference between baseline delay time (DT) >3 s volume and FIV) to baseline DT >3 s volume. Mediation analysis assessed PSI and FIV’s contributions to successful reperfusion and functional outcomes. Results: Of 338 patients, 241 (72%) achieved successful reperfusion. Median FIV was 21 mL (IQR 12–32 mL), and median PSI was 0.68 (IQR 0.50–0.82). Successful reperfusion was linked to a 0.10 increase in PSI (95% CI: 0.05–0.15, p < 0.001) and a 4.36 mL reduction in FIV (95% CI: 1.31–7.20, p = 0.005). Successful reperfusion predicted improved outcomes, with an adjusted odds ratio (aOR) of 1.92 (95% CI: 1.08–3.47, p = 0.020) for excellent outcomes (modified Rankin Scale (mRS) score 0–1) and an aOR of 1.70 (95% CI: 1.01–2.89, p = 0.024) for functional independence (mRS score 0–2). PSI and FIV accounted for 44% and 16%, respectively, of the effect of reperfusion on excellent outcomes. Conclusions: In acute MeVO patients, penumbra salvage significantly mediates the beneficial relationship between reperfusion and excellent clinical outcomes, more so than infarct volume reduction.