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Endovascular treatment (EVT) was associated with better outcomes for some stroke patients even if they presented more than 16 hours since last known well, according to a retrospective study.

Among 150 such patients with emergent large vessel occlusion (LVO), EVT was associated with more than 11-fold greater odds of functional independence as reflected in a modified Rankin Scale (mRS) score of 0-2 compared with medical therapy alone (54% vs 33% at 90 days).

Favorable 90-day mRS score shift was also more common with EVT (common adjusted OR 5.17, 95% CI 1.80-15.62), reported a group led by Beom Joon Kim, MD, PhD, of Seoul National University Bundang Hospital, in a study .

EVT was associated with a favorable mRS score shift (common adjusted OR 10.54, 95% CI 2.18-59.34) even in the 109 patients who presented more than 24 hours from time last known well. This subgroup did not show significantly better odds of achieving mRS 0-2 compared with matched controls, though.

Thus, the study provides more evidence for "tenacious tissues resisting ischemic injury" beyond 16 hours from the time last known well and the possibility of salvageable tissue in "slow progressors," according to Kim and colleagues.

Roughly a third of the cohort fit imaging criteria of the three major EVT trials -- (n=50), (n=58), and (n=57) -- and 16% ultimately received EVT.

"Although the absolute number of additional candidates for EVT in the very late period is small, approximately one-third of the patients with LVO presenting 16 hours or more from the time LKW [last known well] may benefit from the recanalization," the investigators suggested.

"A consensus has not been reached on the best imaging criteria to identify treatable tissues in clinical practice. The image criteria for the DEFUSE 3 trial may have the potential to determine the treatment response based our subgroup analyses, which requires further study," they continued.

DEFUSE 3 imaging criteria included an initial infarct volume (ischemic core) of less than 70 mL, a ratio of volume of ischemic tissue-to-initial infarct volume of 1.8 or more, and an absolute penumbra volume of 15 mL or more.

In 2018, American Heart Association/American Stroke Association guidelines expanded the treatment window for EVT out to 24 hours after patient was last known well following the publication of DAWN and DEFUSE 3.

One downside to EVT in the present study was the increased risk of type 2 parenchymal hemorrhage (13% vs 3%, adjusted OR 4.06, 95% CI 0.63-26.30). Symptomatic hemorrhage (with an increase in the NIH Stroke Scale score of 4 points or more) occurred in two patients, both of whom had received EVT.

Patients included in the study arrived at Kim's institution at a median 43.5 hours since last known well.

The case-control study relied on a single hospital's stroke registry to retrospectively identify stroke patients who had been admitted in 2012-2018. Eligible individuals were those who had an acute ischemic stroke with internal carotid artery or middle cerebral artery occlusion, had a baseline NIH Stroke Scale score of 6 or more, and arrived 16 hours or more from time last known well.

The 150 study participants were 54% men, with an average age of 70.1 years. They presented with a median NIH Stroke Scale score of 12, median ischemic core volume of 11.5 mL, median penumbra volume (of >6 sec lesions) of 55.0 mL, and a median mismatch ratio of 4.0.

Propensity score matching was performed 1:2 to adjust for baseline imbalances between EVT and medical management groups. Those baseline differences included the EVT group being numerically more likely to have had unwitnessed stroke onset and shorter time from last known well to presentation.

Follow-up images were taken a median of 93 hours after arrival to assess patients' final infarct and presence of hemorrhagic transformation.

"EVT in our study showed a modest benefit in saving tissues with perfusion delay but failed to reverse baseline ischemic cores. This finding delineates the role of EVT in the very late time period to save the penumbral tissues, but [not] in the so-called DWI [diffusion-weighted image] reversal phenomenon," according to Kim and colleagues.

Limitations of the study included the possibility of confounding despite efforts of statistical adjustment and the inclusion of highly selected cases. What's more, EVT techniques and devices might have changed drastically since the beginning of the study period.

"Future randomized clinical trials are warranted to address the effectiveness of EVT and to determine the best imaging features for determining treatment responses," study authors wrote.

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