Validation of a Novel Magnetic Resonance Imaging Biomarker of Infarct Severity to Predict Functional Outcome After Endovascular Thrombectomy.

Abstract

Endovascular thrombectomy (EVT) dramatically improves clinical outcomes, but the final infarct volume (FIV) on magnetic resonance imaging only accounts for a minority of the treatment effect. An imaging biomarker that more strongly correlates with post-EVT functional outcome would be helpful for clinical prognosis and serve as a surrogate outcome measure in trials of EVT-adjuvant therapies. Here, we aimed to validate a novel magnetic resonance imaging-based metric, infarct density, which leverages post-EVT apparent diffusion coefficient as a marker of infarct severity. A retrospective cohort was derived from a single-center prospective EVT registry. Consecutive patients treated with EVT for anterior circulation large vessel occlusion were included from 2018 to 2019 who achieved successful reperfusion (modified Thrombolysis in Cerebral Infarction ≥2b). Magnetic resonance imaging was performed 12 to 48 hours post-EVT and processed via RAPID to quantify FIV using the apparent diffusion coefficient <620 threshold. Lesion volume was also collected using an apparent diffusion coefficient <470 threshold, and infarct density was calculated as: (volume <470/volume <620)×100%. Good outcome was defined as ≤2 on the 90-day modified Rankin Scale. Multivariable logistic regression models quantified the association between clinical/imaging variables and outcome. Receiver operating characteristic analysis quantified model classification performance. Of 319 patients treated with EVT, 272 met inclusion criteria. The mean age was 69±13 years, 41% were female, and 62% achieved a good outcome. After adjusting for clinical and radiographic factors, FIV (adjusted odds ratio, 0.99 per 1 mL [95% CI, 0.98-1.00]; <i>P</i>=0.03) and infarct density (adjusted odds ratio, 0.95 per 1% [95% CI, 0.94-0.97]; <i>P</i><0.001) were both independently inversely associated with good outcome. The final model incorporating both FIV and infarct density achieved excellent classification performance (area under the curve, 0.87 [95% CI, 0.83-0.91]). Removing infarct density from the model diminished its performance (area under the curve, 0.83 [95% CI, 0.78-0.88]; <i>P</i>=0.01). Apparent diffusion coefficient-based infarct density after EVT is independently associated with long-term outcome and provides greater prognostic information than FIV alone. Post-EVT infarct density may be useful in clinical care and as a surrogate outcome measure in trials of EVT-adjuvant therapies.