In the 6–24 hour window, thrombectomy is indicated based on which criteria?

• A. Only within 6 hours
• B. Only if large infarct core
• C. Only with IV tPA contraindicated
• D. Based on perfusion mismatch or DAWN/DEFUSE-3 criteria

Answer: (D)

In the 6–24 hour window, deciding on thrombectomy relies on tissue viability rather than time alone. The essential idea is to find a region of brain that is already damaged (the core) but has a surrounding area that is still at risk but salvageable (the penumbra). If there’s a favorable mismatch showing substantial salvageable tissue, reperfusion can still yield meaningful benefit.

Trials like DAWN and DEFUSE-3 formalized this approach. They demonstrated that patients with a meaningful clinical-imaging mismatch or perfusion mismatch—where the core is small enough and there is a sizable penumbra—can benefit from thrombectomy up to 24 hours after onset. In practice, this means using perfusion imaging (CT or MR) to estimate the infarct core and the at-risk tissue, or applying the DAWN criteria that combine clinical factors with imaging to identify patients who still have salvageable tissue.

So, the best way to decide in this extended window is to look for that mismatch and proceed if the imaging and clinical profile indicate salvageable tissue, rather than relying on time alone. Large infarct cores or absence of a mismatch would argue against thrombectomy, whereas a favorable mismatch supports proceeding, even if IV tPA has already been given or is contraindicated.