When five or more attempts with a stent-retriever are needed, functional outcomes are no better than with no recanalization, researchers found.


In patients with large vessel occlusion (LVO) stroke, the number of pass attempts with a stent-retriever should be limited to four, with a puncture-to-recanalization time within 125 minutes since more than that is unlikely to increase the odds of a favorable functional outcome and could subject patients to increased risks without providing any benefits, according to data published online August 27, 2018, ahead of print in Stroke.


Commenting on the study for Neurovascular Exchange, Perry P. Ng, MD (CHPG Neurosciences and Spine, Lakewood, CO), pointed out that while thrombectomy achieves recanalization in about 80% of patients with LVO stroke, “there is currently no consensus as to the number of thrombectomy passes after which the procedure should be aborted or a different technique tried” in the remaining 20%.


“Additional thrombectomy passes increase procedure time, radiation exposure to the patient and interventional team members, procedural risk, etc,” he noted. “So, there is a need for establishing a cut-off at which time the operator should consider alternative techniques or aborting the procedure.”


In an email to NVX, authors Jang-Hyun Baek, MD (National Medical Center, Seoul, Korea), and Byung Moon Kim, MD, PhD (Yonsei University College of Medicine and Severance Hospital, Seoul, Korea), explained that deciding when to change strategy is crucially important “because rapid recanalization is as critical as recanalization itself. If we can predict that the current endovascular modality is not effective anymore, we can rapidly introduce other endovascular modalities to get a successful recanalization.”


The investigators conducted a retrospective review of 467 patients who were treated at one of 16 stroke centers with a stent-retriever as the first endovascular modality for intracranial large artery occlusion in the anterior circulation. They then evaluated the relationship between the number of passes and functional outcome.


Overall, successful recanalization, defined as mTICI 2b/3, was achieved using a stent-retriever alone in 82.2% of patients. Recanalization rates dropped as the number of passes increased. Among patients who underwent five or more passes, the rate of successful recanalization was only 5.5%.


Multivariate analysis revealed that functional outcomes were better among patients who underwent one to four passes, compared with those who did not achieve successful recanalization. On the other hand, for patients treated with five or more passes, functional outcomes were no better than for those who did not achieve recanalization.


Odds of Favorable Outcome, Compared with Patients with No Recanalization


OR (95% CI)

P Value

One Pass

8.06 (3.69-17.6)

≤ 0.001

Two Passes

7.78 (3.37-18.0)

≤ 0.001

Three Passes

6.10 (2.31-16.1)

≤ 0.001

Four Passes

6.57 (2.11-20.4)

≤ 0.001

Five Passes

1.70 (0.42-6.90)


Six Passes or More

0.33 (0.02-5.70)



Currently, said Ng, the decision as to when to abort a thrombectomy procedure rests with the operator and, given a lack of clear guidelines, can depend on a multitude of factors, including patient age, morbidity status, and degree of ability to remain still, access difficulty, procedure time, and time since stroke onset.


The study provides some additional guidance on this issue. “If an occlusion is destined to be recanalized by the stent retriever, most of [the time] (94.5%), recanalization could be achieved within 4 passes,” the authors told Neurovascular Exchange. Once the number of passes reaches four to five, they added, “one might as well consider introducing alternative endovascular modalities for better recanalization.”


Procedure Time Also Important


Ng interpreted the data similarly. “The authors recommend that recanalization with stent retriever thrombectomy be achieved within four passes or a groin-puncture to recanalization time of 125 minutes,” he says. “After four passes, a non-stent retriever strategy or aborting the procedure should be considered.” He noted that the cutoff values were further decreased in patients with ASPECTS ≤ 7 to three stent retriever passes and puncture to recanalization time of 60 minutes.


The duration of the procedure is as important as the number of passes, indicate the authors. In fact, they suggest that number of passes may simply act as a surrogate for procedure time.


While the retrospective nature of the study and other limitations are barriers to generalization, noted Ng, “the findings do support the existence of a cutoff limit for time and number of passes after which the success rate of additional attempts are unlikely to achieve recanalization. Every operator should bear this in mind and reassess each stroke case as additional passes are needed in an attempt to find a balance between the risk versus benefit of continuing.”


The authors acknowledge the limits of the study’s generalizability. “We tried very hard to minimize the bias and secure the generalizability,” they noted. “However, one should be cautious when applying the specific breaking points to their cases.”




Baek JH, Kim BM, Heo JH, et al. Number of stent retriever passes associated with futile recanalization in acute stroke. Stroke. 2018;Epub ahead of print.



Kim, Baek, and Ng report no relevant conflicts of interest.