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Reperfusion success after mechanical thrombectomy for a large vessel occlusion dimmed with every passing hour from stroke endovascular center arrival to groin puncture, according to the HERMES group.

The odds dropped the longer to groin puncture from admission (OR 0.78 per hour, 95% CI 0.64-0.95) or first imaging (OR 0.74 per hour, 95% CI 0.59-0.93), according to Romain Bourcier, MD, PhD, of the University Hospital of Nantes, France, and collaborators.

Their meta-analysis of pooled patient-level data from the thrombectomy arms of seven randomized trials (n=728) was published online in .

"Our results could be confusing compared with the results of the late time studies [DAWN and DEFUSE 3]. Importantly, even if the reperfusion rate declines as time elapses, patients recanalized in later times continue to have better clinical outcome compared with those without reperfusion," the investigators emphasized.

In 2018, based on DAWN and DEFUSE 3 data showing benefits to late thrombectomy, U.S. guidelines expanded the window for endovascular stroke therapy from 6 hours to 24 hours after the patient was last known to be well.

"The bottom line is that time is brain -- still. All the publicity around longer time windows may have sent the wrong message to the troops out there. Yes, we can treat some patients late and get success. But for the majority of patients, early is better, and the best chance for success is with early, timely intervention," commented Patrick Lyden, MD, of Cedars-Sinai Medical Center in Los Angeles, who was not part of the research group.

Cutting down modifiable in-hospital delays is still crucial, the investigators said, though they said they couldn't tell from their data if it was best to start by optimizing patient transfer, imaging, or procedural factors.

The HERMES participants included in the meta-analysis were patients with M1/M2 or intracranial carotid artery occlusions. The group was age 65.4 years on average and 47.4% women. Successful reperfusion was defined as an adjusted mTICI score of 2b/3 at the end of thrombectomy.

"While the probability of successful reperfusion decreased in our study with all intervals, the association was much more pronounced when arrival at the emergency department or imaging to groin puncture were considered compared with onset to groin puncture," Bourcier's group noted.

In fact, the study population showed no relationship between time from stroke onset to arterial access and successful reperfusion. The authors said this was "possibly because several of the trials used imaging selection criteria to choose patients (thereby selecting those more likely to be slow progressors), and one trial examined an extended 12-hour eligibility window from stroke onset."

They acknowledged that the trials they pooled differed in study entry criteria and imaging modalities used. Moreover, they lacked any information on thrombectomy procedural details, such as device selection.

“Patients with favorable imaging profiles had very good reperfusion rates in DEFUSE 3 and DAWN indicating that extended time is not a barrier to high repulsion rates in well-selected patients,” according to Gregory Albers, MD, of California’s Stanford University. “Of course, sooner is always better, but when the patient does not arrive early we need imaging to determine if they are still a good candidate for thrombectomy.”

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