Abstract Body: Introduction: Endovascular thrombectomy (EVT) dramatically improves clinical outcomes, but the reduction in final infarct volume only accounts for a minority of the treatment effect. There is a need for surrogate imaging biomarkers that more strongly associate with functional outcome, to refine prognostication and facilitate development of EVT-adjuvant neuroprotective therapies. Our group recently developed a straightforward ADC-based metric of post-EVT infarct density (i.e. a measure of infarct severity). We aimed to validate this novel metric in a multicenter study of EVT patients.
Methods: A retrospective cohort included consecutive patients with anterior circulation LVO who underwent EVT at two stroke centers. MRI was performed 12–48 hours post-EVT. Good functional outcome was defined as a 90-day modified Rankin Scale score ≤2. MR imaging was processed via RAPID, and final infarct volume was based on the standard ADC <620 threshold. Lesion volume was also assessed using ADC <470, and infarct density was calculated as the percentage of final infarct volume with ADC <470 (Figure 1). Multivariate logistic regression quantified the associations between clinical/imaging variables and functional outcome. Model performance was quantified by ROC analysis and compared to a model consisting solely of clinical variables and a model consisting of clinical variables and infarct volume.
Results: Of 312 patients, 284 (92%) achieved successful recanalization (mTICI ≥2b), and 54% achieved a good outcome. The mean age was 69 years (+/- 14); 41% were female. The mean final infarct volume was 50mL (+/- 73). Infarct density was significantly lower in patients with a good outcome (8.3% vs 30.3%, p<0.0001). Table 1 reports the univariate and multivariate analyses. Infarct density was robustly associated with outcome after adjustment for other significant factors including infarct volume (aOR: 0.954 per 1% increase in infarct density). Figure 2 compares the AUC of the three prespecified models, and the best classification was achieved by including infarct density (AUC 0.87; 95%CI: 0.83-0.91).
Conclusion: Infarct density after EVT is independently associated with long term clinical outcome and provides greater prognostic value than final infarct volume alone. Derived from routinely acquired MRI, infarct density is a potentially useful and easily calculable surrogate outcome measure that can be used in clinical trials of EVT-adjuvant therapies.