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Operators considering multiple clot retrieval attempts in mechanical thrombectomy may need to take a step back, a retrospective study suggested.

With each additional attempt, there was a greater incidence of emboli moving to a new territory, reflecting potential clot fragmentation, and an accompanying increase in infarct growth, reported researchers led by Wagih Ben Hassen, MD, of Sainte-Anne Hospital and the University of Paris Descartes.

Infarct growth was in turn an independent predictor of worse functional outcome (modified Rankin Scale [mRS] score >2) at 3 months (adjusted OR 1.05 per 1-mL increase, 95% CI 1.02-1.07), the group noted in .

It was important that the study found more retrieval attempts to be associated with emboli in new territories and larger infarct growth independently of procedural time, commented Johanna Fifi, MD, of the Icahn School of Medicine at Mount Sinai in New York City, who was not involved in the study.

"The key take home for me is that in thrombectomy, your first attempt at retrieval should be optimized as much as possible -- the techniques for doing this are still under debate. The new standard for judging thrombectomy technical outcome [will] be the so-called 'first pass effect' -- what percentage of the time can you get the vessel open on the first attempt," she wrote in an email to 乌鸦传媒.

However, "caution is needed when using retrieval attempt metrics as prognostic predictors," the study authors noted, adding that 45% of patients still had a favorable outcome when successful recanalization was achieved after a third clot retrieval attempt.

"Successful recanalization, even after multiple attempts is still better than no recanalization," the group emphasized.

"Consequently, in our opinion, it is irrelevant to suggest some sort of 'three strikes law' for endovascular procedures in [acute ischemic stroke due to large vessel occlusion], and one should rather draw attention to the potential impact of multiple [clot retrieval attempts] and encourage operators to use the best technique available to achieve full recanalization with a minimal number of maneuvers," wrote Ben Hassen and colleagues.

Fifi said she agreed with the authors' recommendations against a limit to retrieval attempts. "Multiple randomized trials have shown the tremendous efficacy of thrombectomy for [emergent large vessel occlusion] stroke; and there is sufficient data to say that an open vessel is better than a closed one for the patients," she noted.

Seemant Chaturvedi, MD, of the University of Maryland School of Medicine in Baltimore, said that a "three strikes" rule is "reasonable in the majority of patients, but care must always be individualized."

"In younger patients with embolic-appearing occlusions, going beyond three attempts can at times be useful," he told 乌鸦传媒, noting that factors such as underlying high-grade intracranial stenosis or vasculopathy can lead to multiple retrieval attempts in thrombectomy.

Ben Hassen and colleagues based their study on two registries of stroke patients who underwent mechanical thrombectomy in 2o16-2019 at one of two French comprehensive stroke centers. The study included 419 patients who achieved successful recanalization (i.e., expanded Thrombolysis in Cerebral Infarction Scale scores 2b, 2c, or 3).

Successful recanalization was achieved after one clot retrieval attempt in 53.5% of patients, two attempts in 25.5%, three attempts in 11.7%, and four or more attempts in 9.3%.

The investigators acknowledged the potential for confounding in their retrospective study. Moreover, 12% of 90-day mRS scores were missing, they said.

"These findings highlight the need for a randomized trial to define the appropriate therapeutic strategy when a first clot retrieval attempt is unsuccessful," they concluded.

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