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- ↵∗Address for correspondence:
Dr. Nestor R. Gonzalez, Professor of Neurosurgery, Director Neurovascular Laboratory, Neuroendovascular Fellowship Program Director, Cedars-Sinai Medical Center, Advanced Health Sciences Pavilion, 127 South San Vicente Boulevard, 6th Floor, Suite A6600, Los Angeles, California 90048.
In this issue of the Journal, Alawieh et al. (1) present a retrospective review of patients undergoing endovascular treatment for acute ischemic stroke with stent retrievers or aspiration-based thrombectomy at 7 centers in the United States. Their primary goal was to evaluate the impact of procedure time on the clinical outcomes of the patients treated. Procedure time was defined as the time from groin puncture to first recanalization achieving a Thrombolysis In Cardiac Ischemia (TICI) score of 2b or more, or to the suspension of the procedure if TICI 2b was not obtained. The primary endpoint clinical outcome was defined as the 90-day modified Rankin score (mRS) recorded during a follow-up visit to a stroke neurologist at 90 days (±14 days) after stroke or by a telephone interview.
The study found a significant change in the proportion of functional outcomes after 30 minutes of procedure time, with a reduction of 40% on good outcomes (mRS 0 to 2). In addition, the authors observed a plateau in the proportions of good and bad outcomes after 60 min, at around a proportion of 70% risk of poor outcomes. They also report an exponential increase in the rate of complications and intracerebral hemorrhage with increasing procedure time, with a doubling of the proportion of complications after 26 min. Interestingly, although there was also a decline in the proportion of good outcomes as the number of thrombectomy attempts increased, the association followed a more linear pattern, without a specific deflection point. In the multivariate regression analysis, procedure time <30 min was significantly associated with good outcomes with an odds ratio of 1.55 (95% confidence interval: 1.14 to 2.09), an effect that was preserved after adjusting for first-pass effect, number of attempts, the presence of tandem occlusions, or the location of the occluded artery.
The effect of procedural time on patient outcomes has been shown previously by the authors (2,3), and the present study adds to the evidence underscoring the benefit of achieving timely recanalization of the hypoperfused territory after acute ischemic stroke. In the current study, there was also a clear association between the number of attempts and poor outcomes. The number of attempts and procedure time for the most part go hand-in-hand, and they are expected to have a high correlation. Nevertheless, in this study, although the procedure time had a steep fall in the rate of good outcomes after 30 min, the number of attempts kept more of a linear relation with the clinical results. In the multivariate analysis, neither the number of attempts parameter estimate or odds ratio was listed, but the authors clarified that procedure time remained a significant predictor even if the number of attempts was included as a variable, which is also expected because they are highly correlated.
The practical implication of evaluating procedure time or number of attempts is the identification of a moment or step in which proceeding with the endovascular intervention may not be beneficial for the patient. There is a tension between achieving the recanalization of the occluded vessel and the risk of producing complications by continuing the manipulations of the intracranial artery. Defining whether time or number of attempts is the factor that may turn the intervention into a complication is challenging. This issue is partially addressed by the authors in the subgroup analysis of patients with prolonged procedure time and few attempts. In this group, despite a prolonged procedure time beyond 30 min, a lower number of attempts was a predictor of good outcomes. In other words, procedure time, as defined in this study, includes 2 components: the time to achieve access to the intracranial occluded vessel and the time of manipulation of the vessel with retrieval or aspiration attempts. The authors very well point out that perhaps the critical metric should be “time to recanalization after access has been achieved,” at least ≤60 min from the groin puncture time.
In the present study, aspiration thrombectomy achieved faster recanalization times than stent retriever thrombectomy; however, this did not translate to better clinical outcomes than thrombectomy, with 90-day mRS 0 to 2 in 37% of aspiration cases compared with 38% of the stent retriever cases. In fact, the proportion of TICI 2b or better was comparable in the 2 groups, 89% for aspiration and 86% for the stent retrievers. These results emphasize that the most important predictor of clinical outcome in the treatment of acute ischemic stroke is a successful recanalization. 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 presented by Alawieh et al. (1) in this study, it seems reasonable to conclude that at 60 min, one should consider the futility of continuing the procedure. It is also apparent that the number of thrombectomy attempts is negatively associated with good outcomes. However, in terms of defining the futility of additional attempts, it is less clear that 3 attempts should be the limit. The data presented in Figure 2D suggest that at 5 attempts, the cumulative percentage of recanalizations with TICI 2b is close to 85%, whereas at 3 attempts, that percentage is 70%. Also, Figure 1D shows that at 5 attempts, 40% of cases had good outcomes at 90 days. 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.
The authors should be congratulated for this contribution to the understanding of the factors involved in the success of the current techniques used for the management of acute ischemic stroke. Further analysis of these valuable data will likely help to define the points of futility and assist in refining the application of endovascular thrombectomy.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
Dr. Gonzalez has reported that he has no relationships relevant to the contents of this paper to disclose.
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