The Growth Rate of Early DWI Lesions is Highly Variable and Associated with Penumbral Salvage and Clinical Outcomes following Endovascular Reperfusion

Background The degree of variability in the rate of early diffusion-weighted imaging expansion in acute stroke has not been well characterized. Aim We hypothesized that patients with slowly expanding diffusion-weighted imaging lesions would have more penumbral salvage and better clinical outcomes following endovascular reperfusion than patients with rapidly expanding diffusion-weighted imaging lesions. Methods In the first part of this substudy of DEFUSE 2, growth curves were constructed for patients with >90% reperfusion and <10% reperfusion. Next, the initial growth rate was determined in all patients with a clearly established time of symptom onset, assuming a lesion volume of 0 ml just prior to symptom onset. Patients who achieved reperfusion (>50% reduction in perfusion-weighted imaging after endovascular therapy) were categorized into tertiles according to their initial diffusion-weighted imaging growth rates. For each tertile, penumbral salvage [comparison of final volume to the volume of perfusion-weighted imaging (Tmax > 6 s)/diffusion-weighted imaging mismatch prior to endovascular therapy], favorable clinical response (National Institutes of Health Stroke Scale improvement of ≥8 points or 0–1 at 30 days), and good functional outcome (90-day modified Rankin score of ≤2) were calculated. A multivariate model assessed whether infarct growth rates were an independent predictor of clinical outcomes. Results Sixty-five patients were eligible for this study; the median initial growth rate was 3·1 ml/h (interquartile range 0·7–10·7). Target mismatch patients (n = 42) had initial growth rates that were significantly slower than the growth rates in malignant profile (n = 9 patients, P < 0·001). In patients who achieved reperfusion (n = 38), slower early diffusion-weighted imaging growth rates were associated with better clinical outcomes (P < 0·05) and a trend toward more penumbral salvage (n = 31, P = 0·103). A multivariate model demonstrated that initial diffusion-weighted imaging growth rate was an independent predictor of achieving a 90-day modified Rankin score of ≤2. Conclusions The growth rate of early diffusion-weighted imaging lesions in acute stroke patients is highly variable; malignant profile patients have higher growth rates than patients with target mismatch. A slower rate of early diffusion-weighted imaging growth is associated with a greater degree of penumbral salvage and improved clinical outcomes following endovascular reperfusion.