Introduction The rate of first-attempt recanalization (FAR) with the newer-generation thrombectomy devices, and more specifically with aspiration devices, is not well known. Moreover, the effect of FAR on outcomes after mechanical thrombectomy is not properly understood.
Objective To report the rate of FAR using a direct aspiration first pass technique (ADAPT), investigate the association between FAR and outcomes, and identify the predictors of FAR.
Methods The ADAPT database was used to identify a subgroup of patients in whom FAR was achieved. Baseline characteristics, procedural, and postprocedural variables were collected. Outcome measures included 90-day modified Rankin scale (mRS) score, mortality, and hemorrhagic complications. Multivariate logistic regression was used to identify FAR predictors.
Results A total of 524 patients was included of whom 178 (34.0%) achieved FAR. More patients in the FAR group than in the non-FAR group received IV tPA (46.6% vs 37.6%; p<0.05). For the functional outcome, higher proportions of patients in the FAR group achieved functional independence (mRS score 0–2; 53% vs 37%; p<0.05). Additionally, we observed lower mortality and hemorrhagic transformation rates in the FAR group than the non-FAR group. Independent predictors of FAR in the anterior circulation were pretreatment IV tPA, non-tandem occlusion, and use of larger reperfusion catheters (Penumbra, ACE 64–68). Independent predictors of FAR in the posterior circulation were diabetes, onset-to-groin time, and cardioembolic etiology.
Conclusion FAR was associated with better functional outcome and lower mortality rate. When ADAPT is used, a larger aspiration catheter and pretreatment IV tPA should be employed when indicated.
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Treatment of acute stroke has evolved remarkably in the past decade. Since the publication of the pivotal trials showing the efficacy of mechanical thrombectomy (MT),1–5 MT has become the standard of care for treatment of acute stroke.6 The recanalization rate improved with second-generation stent retrievers and approached >80%.3 7 However, functional independence is still achieved in only around 50% of patients.8 Multiple thrombectomy attempts and long procedure time have been linked to poor outcome after MT.9 The proportion of patients who achieve recanalization at the first attempt was not routinely reported in thrombectomy trials and is not well known.1–3
In this study, we aimed to report the rate, predictors, and the outcome of first-attempt recanalization (FAR) using a direct aspiration first-pass technique (ADAPT).
We interrogated our prospectively collected ADAPT database to identify a subgroup of patients in whom FAR had been achieved. The database includes all patients who presented with ischemic stroke due to large vessel occlusion and were treated with MT using ADAPT between November 1, 2013 and January 1, 2018. The study was approved by the institutional review board at the Medical University of South Carolina.
ADAPT has been described in previous reports.10 11 Briefly, a Neuron 088 Max (Penumbra, Oakland, California, USA) is advanced as far safely as possible into the internal carotid artery for anterior circulation thrombi and to the largest caliber vertebral artery in the posterior circulation thrombi. The largest caliber aspiration catheter that the vessel can safely accommodate is selected for each case. Penumbra ACE 64 and 68 aspiration catheters were first used in July 2015. The reperfusion catheter is then advanced to the level of the thrombus over a microcatheter (3 Max reperfusion catheter, Penumbra Inc) and microwire (0.016 inch). Aspiration is then applied using an aspiration pump that is part of the Penumbra system. Engagement of the thrombus is confirmed by lack of blood return in the aspiration tubing under aspiration. Once aspiration catheter engagement is confirmed, the catheter is first advanced to ensure engagement with thrombus then slowly withdrawn while maintaining aspiration. If aspiration fails to recanalize the vessel, the catheter is advanced back to the thrombus as described above, and repeat aspiration is attempted. If recanalization fails with the aspiration catheter, a stent retriever is used (‘Solumbra’ technique).
Preprocedural variables included demographics, comorbidities, initial stroke severity, time from onset to groin, pretreatment IV tissue plasminogen activator (tPA), location of occlusion, and admission Alberta Stroke Program Early CT Score (ASPECTS). Initial stroke severity was assessed by the National Institutes of Health Stroke Scale score, which was documented by the stroke neurologist or senior neurology resident on admission. Admission non-contrasted and contrasted CT scans were reviewed by an independent neuroradiologist to record ASPECTS and location of the occlusion.
Procedural variables included time from onset to recanalization (TOR), recanalization status, number of attempts, and intraprocedural complications. Recanalization status was assessed using modified Thrombolysis in Cerebral Infarction (mTICI) score. mTICI ≥2b was considered as a successful recanalization. For this study a TICI of 2c or 3 was considered a complete recanalization. FAR was defined as successful recanalization at the first attempt.
Outcome measures included a 90-day modified Rankin scale (mRS) score, and hemorrhagic complications. The mRS score was assessed at 90 days (±12 days) either by face-to-face interview with an experienced nurse practitioner or through a telephone interview. Hemorrhagic complications were assessed on follow-up CT scans within 72 hours after MT. Hemorrhagic complications were divided, based on European Cooperative Acute Stroke Study (ECASS) radiological criteria, into hemorrhagic infarctions, and parenchymal hemorrhage (PH).12
Baseline characteristics and outcome measures were compared using a univariate comparison and descriptive statistics. Variables were compared using a non-parametric t-test (Mann-Whitney) for non-continuous variables or with failed normality, Student’s t-test for continuous variables, and a X2 test for categorical variables. A multivariate logistic regression was used to identify FAR predictors in the anterior and posterior circulation. Analysis was performed using SPSS V.24 (IBM Corporation, New York, USA).
A total of 524 patients were included in the final analysis. Less than 1% of patients were excluded due to insufficient data. FAR was achieved in 33.9% of patients.
Comparison of first-pass and non-first pass groups
Table 1 summarizes the difference in preprocedural and procedural variables between the FAR group and the rest of our study cohort. No significant differences in demographics and comorbidities were found between the two groups. More patients in the FAR group received IV tPA (46.6% vs 37.6%; p<0.05) and TOR was shorter in the FAR group (16.5±14.3 vs 34.2±24.5 min; p<0.001).The FAR group had a better functional outcome (mRS score, median (IQR); 2 (3) vs 4 (3); p<0.001). Similarly, more patients in the FAR group achieved functional independence (53.4% vs 37%; p<0.05). The rate of hemorrhagic complications was lower in the FAR group (29.2% vs 40.2%; p<0.05), but there was no difference in the rate of PH2 between the two groups. On multivariate logistic regression controlling for variables studied at univariate level, FAR was a significant and independent predictor of good outcome (mRS 0–2) (OR=1.92, 95% CI 1.18 to 3.12, p=0.008).
Predictors of FAR
To investigate predictors of FAR, we divided patients into two groups based on location of the occlusion (anterior circulation vs posterior circulation).
In multivariate analysis, IV tPA (OR=1.62; 95% CI 1.06 to 2.46), tandem ICA occlusion (OR=0.18; 95% CI 0.04 to 0.78), and the use of larger aspiration catheters (OR=2.33; 95% CI 1.16 to 4.68) were predictors of FAR in the anterior circulation group (table 2). Multivariate analysis of predictors of FAR in the posterior circulation group identified diabetes (OR=16.76; 95% CI 3.08 to 71.66), onset-to-groin time (OR=0.99; 95% CI 0.998 to 0.999), and cardioembolic etiology (OR=0.17; 95% CI 0.03 to 0.88) as predictors of FAR (table 2).
To investigate the association between operator experience and FAR, we used ’year' as a surrogate for operator experience. The median year was 2016 (IQR 2) in the FAR group and 2015 (IQR 3) in the non-FAR group (p<0.05). However, year was not a significant predictor of FAR in the multivariate analysis.
Comparison of the FAR group and the group of patients who achieved successful and complete recanalization with more than one attempt
First, we compared the FAR group with patients who achieved successful recanalization (mTICI ≥2b) with more than one aspiration attempt. Baseline characteristics and comorbidities did not differ between the two groups . TOR was shorter in the FAR group (16.5±14.3 vs 33.4±24; p<0.01). More patients in the FAR group achieved functional independence (53% vs 40%; p<0.05) Figure 1. Similarly, the mortality rate was lower in the FAR group (12% vs 22%; p<0.01). (table 3)
Second, we compared patients who achieved complete recanalization (mTICI ≥2c) after the first pass with those who achieved complete recanalization with more than one pass. The former group had lower rate of PH2 (1% vs 5%; p<0.05) and mortality (12% vs 22%; p<0.01). Functional independence was achieved in more patients in the first attempt group, but the difference was not statistically significant (53% vs 44%; p=0.08)
In this study, FAR was achieved in 33.9% of patients treated with ADAPT, which is similar to the result reported with a stent retriever (~37%).13
Patients with FAR had a better functional outcome and lower mortality rate than patients who achieved successful recanalization (TICI ≥2b) with more than one attempt. Our results parallel those of a previous study comparing successful recanalization with first attempt to successful recanalization with more than one attempt.13
When we included only patients with complete recanalization (TICI ≥2c), there was a trend towards a better functional outcome in the FAR group, but the difference did not reach statistical significance. The lack of statistical difference is probably related to the small sample size.
The higher rate of hemorrhage observed in patients with more than one attempt is likely to be multifactorial. Multiple attempts reflect longer procedure times, which have been linked to higher complication rates.14–16 This could reflect repeated traumatic shearing of the lenticulostriates—for example, from repeated thrombectomy attempts. This is less likely to be a factor with direct aspiration than with stent retrievers, which anecdotally have been associated with more shearing forces and vascular injury.17 In addition, longer procedure times may predispose to higher rates of progression to infarction, especially of a deep-seated core with more compromised end perfusion, which could lead to higher rates of hemorrhage from hemorrhagic conversion of core infarcts.18 19
ADAPT has been used exclusively at our institution since 2013. The FAR rate improved from 26% in 2013 to 37.7% in 2017 (supplementary figures e1, e2). This improvement could be attributed to the increased experience of our neurointerventionalists and the use of more advanced aspiration catheters.20 In our study, year (which was used as a surrogate for operator experience) was not a predictor for FAR. However, it should be noted that a significant portion of thrombectomy procedures were performed by fellows in training with attending supervision, which might explain the lack of association between year and FAR.
Clot composition is an important predictor of successful recanalization. Previous studies have shown that thrombi from a cardioembolic source have a higher percentage of white blood cells and fibrin component and are associated with less recanalization.21–23 In our study, cardioembolic etiology was inversely associated with FAR in the posterior circulation group, but not in the anterior circulation.
Our study, together with previous studies, support an association between multiple attempts and poor outcome after successful recanalization.9 13 However, it should be emphasised that our findings do not prove a causation as it is unknown if the worse outcome resulted from multiple attempts or from the underlying etiology that required multiple attempts.14–16
Recanalization success depends on location of the occlusion, vascular anatomy, clot characteristics, and the underlying etiology.24–27 Tandem occlusion, underlying atherosclerosis, and long clot have been shown to be predictors of unsuccessful recanalization.9 25 27 On the other hand, IV tPA and a shorter time from onset to groin were associated with successful recanalization.26 28
In our study, the presence of tandem occlusions, pretreatment with IV tPA and use of large aspiration catheters were independent predictors of FAR. Our results add to the growing evidence that pretreatment with tPA improves recanalization with MT andshould not be delayed in eligible patients.28–30 It should not be surprising that use of ACE 64 and 68 aspiration catheters was associated with FAR. ACE 64 and 68 are the largest reperfusion catheters available to date and provide larger inner lumen and more aspiration power than any other aspiration catheters.20
Our study has a number of limitations. First, it is a retrospective design, which has methodical shortcomings. Second, the final mTICI score was reported by the operators, and there was no central review, which raises concern that the rate of successful recanalization might have been overestimated. Third, our study included only patients treated with ADAPT, and our results may not apply to patients treated with stent retrievers. Finally, previous studies have shown that clot characteristics can predict recanalization success.21–23 31 However, our attempt to collect data on clot characteristics was faced with missing CT angiograms for patients who had undergone CT angiography at Spoke hospitals before transfer to our institution.
Recanalization with first aspiration attempt was associated with better functional outcome, lower mortality, and hemorrhagic transformation rate. tPA and larger aspiration catheters should be used when indicated.
Contributors All authors have provided a substantial contribution to the conception and design of the studies and/or the acquisition and/or the analysis of the data and/or the interpretation of the data. They have drafted the work or revised it for significant intellectual content and approved the final version of the manuscript. They agree to be accountable for all aspects of the work, including its accuracy and integrity.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests AS: consulting-Penumbra, Minnetronix, Cerenovus. AT: consulting-Codman, Penumbra, Microvention, Blockade, Pulsar Vascular, Medtronic, Siemens; research grants- Codman, Penumbra, Microvention, Pulsar Vascular, Medtronic Stock- Pulsar Vascular, Blockade. The remaining authors report no disclosure.
Patient consent Not required.
Ethics approval Medical University of South Carolina institutional review board.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Additional data from this project can be acquired by contacting the corresponding author.
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