Using a “Tissue Clock” for Selection of Acute Stroke Thrombectomy Candidates

Endovascular thrombectomy (EVT) has been demonstrated to improve the outcome for select patients with large-vessel occlusion (LVO) who can be treated within 6 hours. Instead of using a rigid time window, a more physiologic approach is to use a “tissue-based clock.” In this paradigm, patients with small infarct cores and extensive areas of brain tissue at risk for infarction can be treated without the constraint of a rigid time window.

To evaluate the use of EVT in select patients with LVO and radiologic data suggesting a small infarct core and greater amount of tissue at risk (“radiologic mismatch”), researchers randomized 206 patients (mean age, 70) who were last known to be well 6 to 24 hours previously, including patients who woke up with stroke symptoms. Patients were assigned to thrombectomy plus standard supportive care or to supportive care alone. The primary endpoint of the manufacturer-sponsored trial was a modified Rankin Scale (mRS) score of 0 to 2 (indicating functional independence) at 90 days, or a utility-weighted Rankin score.

Participants had occlusion of the distal internal carotid or proximal middle cerebral artery and had severe strokes (median NIH stroke scale score, 17). Median time from the last known well point was 12.8 hours. The trial was stopped early when the superiority of EVT became evident (mRS score 0−2, 49% EVT group vs. 13% control group; mean utility-weighted mRS score, 5.5 EVT group vs. 3.4 control group). There was no difference in symptomatic brain hemorrhage (6% EVT vs. 3% control) or all-cause death at 90 days (19% EVT vs. 18% control).