Use of Imaging to Select Patients for Late Window Endovascular Therapy

Gregory W. Albers, MD

Stroke. 2018;49(9):2256-2260.

MRI Findings in Persistent Occlusion

In patients with large artery occlusion who do not experience recanalization, the DWI lesion typically expands into much or all of the persistent T_max >6 seconds perfusion lesion.^[8–10] However, late window patients, who are selected based on having salvageable tissue, typically have good collaterals, and the final infarct volume may not be obtained for several days.^[13] Therefore, a follow-up scan at 24 hours will often underestimate infarct volume in patients who have a persistent occlusion.

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Table 1. Key Imaging-Based Inclusion Criterial for DEFUSE 3 and DAWN
	DEFUSE 3	DAWN
Ischemic core volume	≤70 mL	≤20 mL if age >80
		≤30 mL if age <80 and NIHSS 10–20
		≤50 mL if age <80 and NIHSS >20
Mismatch volume	≥15 mL and a mismatch ratio of ≥1.8	Not required
Vessel occlusion	M1 or ICA (cervical and intracranial)	M1 or ICA (intracranial and cervical if stent not anticipated to be required)

DAWN indicates Triage of Wake-up and Late Presenting Strokes Undergoing Neurointervention With Trevo); DEFUSE 3, Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3; ICA, internal carotid artery; M1, the first segment of the middle cerebral artery; and NIHSS, National Institutes of Health Stroke Scale.

Table 2. MRI Versus CTP in Early and Late Window Thrombectomy Studies
Study	N	90-d mRS 0–2	90-d mRS 0–2	Absolute
Study	N	Control (%)	Thrombectomy (%)	Benefit (%)
SWIFT PRIME*
MRI	34	33	63	30
CTP	139	40	60	20
DEFUSE 3†
MRI	49	19	61	42
CTP	133	16	39	23
DAWN
MRI	83	35‡		NA
CTP	123	29‡		NA

CTP indicates computed tomography perfusion; DAWN, Triage of Wake-up and Late Presenting Strokes Undergoing Neurointervention With Trevo; DEFUSE 3, Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3; MRI, magnetic resonance imaging; mRS, modified Rankin Scale; and SWIFT PRIME, Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment for Acute Ischemic Stroke.
*SWIFT PRIME was an early window (<6 hours) study.
†CTP and MRI groups had statistically significant treatment effects on the studies primary outcome.
‡DAWN reported pooled data for the thrombectomy and control arms for the MRI and CTP subgroups.