Repeated clot retrieval attempts are associated with an increased rate of emboli to new territory (ENT) and greater infarct growth—resulting in poorer functional outcomes in acute ischaemic stroke patients even after successful recanalisation has been achieved. These findings are based on data from two pooled, multicentric prospective patient registries and are published in Neurology, the medical journal of the American Academy of Neurology (AAN).
“Among successfully recanalised patients, clot retrieval at the first clot retrieval attempt significantly reduced infarct growth and improved functional outcome,” Wagih Ben Hassen (Department of Neuroradiology, University of Paris, Paris, France) and colleagues write in their report. “Each additional retrieval attempt was correlated with a higher rate of ENT and a greater increase in infarct growth volume, reducing the odds of favourable functional outcome. These findings highlight the need for a randomised trial to define the appropriate therapeutic strategy when a first clot retrieval attempt is unsuccessful.”
Despite successful recanalisation via endovascular therapy (EVT) being achieved more than 80% of the time in patients with acute ischaemic stroke caused by large vessel occlusion, less than half of these patients have achieved favourable three-month outcomes in previous studies, according to Ben Hassen et al. And, while the number of clot retrieval attempts has “recently been identified as a marker of clinical outcome” in this area—independent of final recanalisation success— the detrimental effect of repeated clot retrieval on functional outcome “is not straightforward, and has not yet been explained”, leading the France-based research team to attempt to “elucidate the link between the number of clot retrieval attempts and the functional outcome in a successfully recanalised population”.
For this, they extracted data from two prospective registries, including consecutive acute ischaemic stroke-large vessel occlusion (AIS-LVO) patients treated with mechanical thrombectomy between January 2016 and 2019 at two large, comprehensive stroke centres in Lille and Paris. Anterior circulation AIS-LVO patients with a known onset of symptoms treated with EVT, and with pretreatment and 24-hour post-treatment diffusion-weighted imaging (DWI) achieving successful recanalisation—defined as expanded Thrombolysis in Cerebral Infarction Scale (eTICI) scores of 2b, 2c, or 3—were included.
Among 902 anterior circulation stroke patients with known symptom onset treated via mechanical thrombectomy across the two registries, 502 patients (56.1% women; mean age 68±15 years) were eligible. A total of 419 patients achieving successful recanalisation were included—with recanalisation being obtained after one clot retrieval attempt in 224 patients (53.5%), after two attempts in 107 patients (25.5%), three attempts in 49 patients (11.7%), and four or more attempts in 39 patients (9.3%). In the subsequent analysis, associations between the number of clot retrieval attempts, and ENT, infarct growth and three-month outcomes, were assessed, the authors report.
Occurrence of ENT was “highly correlated” with an increasing number of clot retrieval attempts, they add, stating that there were 23 cases of ENT in the whole study population (5.5%), with two cases in the one clot retrieval attempt group (1%), three in the two clot retrieval attempts group (2.8%), seven in the three clot retrieval attempts group (14.3%), and 11 in the four-or-more clot retrieval attempts group (28.2%). The one clot retrieval attempt group also had the lowest infarct growth volume and the lowest rates of ENT. Infarct growth increased linearly with the number of clot retrieval attempts in the study, Ben Hassen et al add.
In terms of functional outcomes, symptomatic intracranial haemorrhage (sICH) rates increased with the number of clot retrieval attempts. The group of one retrieval attempt experienced the lowest rate of sICH (5.8%) compared to 8.4%, 6.1% and 10% in the two, three, and four-or-more clot retrieval attempt groups, respectively. In addition, favourable functional outcome decreased with each additional clot retrieval attempt in the successfully recanalised population, the authors report, and the one clot retrieval attempt group had the highest rate of favourable outcome of any group. Infarct growth was also found to be an independent negative predictor of favourable outcome in binary logistic regression analysis.
According to Ben Hassen et al, recent studies have linked the detrimental effect of repeated clot retrieval attempts on functional outcome to the “drastic decrease” in successful recanalisation rates after each additional attempt. However, they assert that, in their study, patients with a similar baseline infarct volume who achieved successful recanalisation were included to better identify an independent effect of repeated thrombectomy attempts—and they ultimately found that repeated thrombectomy manoeuvres led to an increased rate of ENT, correlated to “substantial” infarct growth.
The authors add that time from symptom onset to successful recanalisation and procedure duration are also “prominent factors” for infarct evaluation, and, while both increased with the number of clot retrieval attempts, this link between retrieval attempts, infarct growth volume, and outcome, persisted even after adjusting for these durations, “underlining a potential independent effect of the number of clot retrieval attempts”.
“Achieving successful recanalisation with the fewest clot retrieval attempts, ideally with a single pass, appears to be a new goal, redefining procedural ‘success’ in stroke endovascular
therapy and underlining the need to develop a new generation of devices designed to increase the rate of complete revascularisation at the first attempt,” Ben Hassen and colleagues claim. “However, caution is needed when using retrieval attempt metrics as prognostic predictors. Hence, in the present cohort, when eTICI 2b, 2c, or 3 recanalisation was obtained after a third attempt, 45% of patients still had a favourable outcome.
“Successful recanalisation—even after multiple attempts—is still better than no recanalisation. Consequently, in our opinion, it is irrelevant to suggest some sort of ‘three strikes law’ for endovascular procedures in AIS-LVO [patients], and one should instead draw attention to the potential impact of multiple clot retrieval attempts and encourage operators to use the best technique available to achieve full recanalisation with a minimal number of manoeuvres.”