Worse Outcomes With Longer Stroke Thrombectomy Procedure Times

February 26, 2019

Longer thrombectomy procedure times are associated with worse outcomes in acute ischemic stroke patients, a new study shows.

"Procedure times exceeding 30 to 60 min or more than 3 aspiration attempts is associated with unfavorable outcomes, including higher rates of postprocedural intracerebral hemorrhage and other complications," the authors report.

"Exceeding 60 minutes of procedure time or 3 aspiration attempts should trigger a careful assessment of the futility and risks of continuing the procedure," they conclude.

The study also showed that the impact of procedure time was specifically related to the time spent undergoing thrombectomy after establishment of intracranial access, rather than the entire procedure time.

The study was published online February 25 and appears in the March 5 issue of the Journal of the American College of Cardiology.

The researchers, led by Ali Alawieh, PhD, Medical University of South Carolina, Charleston, note that in recent years, mechanical thrombectomy has been proven to be a viable treatment strategy for patients with acute ischemic stroke, with treatment windows extended to 24 hours.

"With the advent of newer techniques and devices, as well as inclusion of more patients, there is a need for optimizing patient selection and delineating the limits of interventions, so that patients who will achieve the most benefit can undergo the appropriate treatment with the least possible exposure to harm," they write.

They conducted a large, multicenter, retrospective review of modern mechanical thrombectomy techniques with the goal of defining the impact of procedural variables, procedure time, and number of attempts on the success of treatment, functional outcomes, and risks for complications and hemorrhage.

They analyzed data on 1359 patients who underwent endovascular thrombectomy with a stent retriever or direct aspiration at seven US centers from 2013 to 2018. Multivariate analyses were used to assess the impact of procedure time on 90-day modified Rankin score (mRS), successful recanalization, postprocedural symptomatic hemorrhage (sICH), and complications.

Results showed a 40% reduction in the likelihood of good functional outcomes (mRS, 0 to 2) when procedure time extended beyond 30 min (P < .01).

Rates of sICH and complications increased exponentially with procedure time. The cumulative rate of successful recanalization and good outcomes plateaued after 60 min of procedure time.

In addition to procedure time, the number of attempts was also important. In patients with procedure time longer than 30 min, fewer attempts were predictive of the success of thrombectomy and good outcomes (P < .01).

The authors note that each thrombectomy pass represents an independent interaction with the vessel with a finite complication rate, so that multiple attempts cumulatively add to the risk profile.

"Importantly, the number of attempts demonstrated a linear [inverse] association with rates of good outcome and increased risk of hemorrhage," they report.

Aspiration vs Stent Retriever

Successful recanalization was achieved faster with the direct aspiration at first pass technique than with a stent retriever, but the direct aspiration technique was more sensitive to procedure time than use of a stent retriever, with a higher likelihood of good outcome at 90 days with procedure times of less than 30 min.

The likelihood of a good functional outcome dropped significantly and then plateaued beyond 30 min in patients who underwent aspiration first.

In contrast, although there was a drop-off at 60 min for patients who underwent thrombectomy with a stent retriever, these patients achieved comparable rates of recanalization and good outcomes at slower rates.

"This again highlights the idea that the time to gain access to the occlusion may not be as critical as the amount of time spent attempting recanalization once access is achieved. Performance of aspiration-based thrombectomy is associated with faster intracranial access times than use of a SR [stent retriever] thrombectomy, which could explain why the aspiration cohort was more sensitive to procedure times <30 minutes," the researchers write.

The investigators also found that posterior stroke was more sensitive to procedure time than anterior stroke.

They note that there could be a subgroup of occlusions that are relatively easy to recanalize but have challenging proximal anatomy. In such cases, gaining access to the level of occlusion can consume valuable time.

They suggest that the subgroup of patients with longer procedure times (between 30 and 60 min) and fewer attempts at thrombectomy (zero to two attempts) most likely represent this group. For these patients, intracranial access proved time consuming, but the actual thrombectomy was straightforward and was associated with a higher likelihood of a good outcome. "Thus, the more salient time metric might be the time to recanalization once access is achieved."

They point out that there is mounting evidence that patients with posterior circulation occlusions derive similar benefits from thrombectomy as those with large-vessel occlusions of the anterior circulation.

They report that in this study, although the procedure time for a posterior fossa mechanical thrombectomy was longer, the impact of rapid recanalization on rates of favorable outcomes in these cases was much higher than for anterior circulation (odds ratio [OR] of 5.61 for an mRS of 0 to 2 at 90 days in posterior circulation mechanical thrombectomy vs OR of 1.72 for anterior circulation thrombectomy).

"This suggests that posterior circulation occlusions, although they can be more challenging, are also more time sensitive," the investigators write.

They conclude, "Future studies should gather data on the relationship between specific thrombectomy devices and techniques and the success of recanalization procedures for patients with acute ischemic stroke."

In an accompanying editorial, Nestor K. Gonzalez, MD, Cedars-Sinai Medical Center, Los Angeles, California, notes that when performing thrombectomy, there is tension between achieving recanalization of the occluded vessel and the risk of producing complications by continuing the manipulation of the intracranial artery.

He agrees that, with regard to considering the futility of continuing, the current study suggests the critical metric should be "time to recanalization after access has been achieved."

Gonzalez points out that although aspiration achieved faster recanalization than stent retriever thrombectomy in this study, final rates of recanalization were comparable in the two groups, as were the rates of good outcomes.

"These results emphasize that the most important predictor of clinical outcome in the treatment of acute ischemic stroke is a successful recanalization," he writes. "So, the pertinent question to determine when to stop a thrombectomy intervention is when or after how many attempts a successful recanalization is unlikely."

On the basis of the results of this study, "it seems reasonable to conclude that at 60 min, one should consider the futility of continuing the procedure," he states.

Although the number of thrombectomy attempts is negatively associated with good outcomes, Gonzalez says it is less clear that three attempts should be the limit when considering the futility of continuing.

He points out that the cumulative percentage of recanalizations was close to 85% at five attempts, whereas at three attempts, that percentage was 70%.

"Given that recanalization success is the most important predictor of outcome, these data suggest that the rate of complications produced by 2 additional manipulations of the artery would not overcome a potential 15% increase in obtaining recanalization, and that in challenging cases, >3 attempts of thrombectomy might still be beneficial," he adds.

The authors' disclosures of relevant financial relationships are listed in the original article. Alawieh and Gonzalez have disclosed no such financial relationships.

J Am Coll Cardiol. Published online February 25, 2019. Abstract, Editorial

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