Article Text
PDF
Abstract
Background A direct aspiration first pass technique (ADAPT) is an efficient, safe, cost-effective, and fast thrombectomy technique.
Objective To evaluate anatomical and clot characteristics associated with success of the aspiration component as part of ADAPT.
Methods 106 cases of acute carotid-T, basilar, and middle cerebral artery occlusion undergoing endovascular treatment with ADAPT were retrospectively assessed for successful catheter-clot contact and successful primary aspiration, defined as a Thrombolysis in Cerebral Infarction score ≥2b after primary aspiration with 5F or 6F aspiration catheters. Patient age, National Institutes of Health Stroke Scale (NIHSS) score, time from symptom onset to groin puncture, time from groin puncture to revascularization, aortic arch type, access vessel tortuosity, vessel diameter at the proximal end of the thrombus, catheter-to-vessel ratio (CVR), clot density, length, and perviousness were determined.
Results Successful clot contact with the aspiration catheter was achieved in 76 cases (72%); these patients were younger (67.7±15.2 vs 73.7±11.4 years; p=0.05) and had less tortuous access vessels (1 vs 2 reverse curves; p=0.004) than those in whom clot contact failed. Successful primary aspiration occurred in 36 of these cases (47%) and was associated with significantly smaller vessel diameter at the proximal thrombus end (2.5±0.7 mm vs 3.1±1.3 mm; p=0.01) and higher CVR (CVR outer diameter: 0.85±0.2 vs 0.68±0.2; p=0.01 and CVR inner diameter: 0.72±0.2 vs 0.58±0.2; p<0.001). No significant differences were seen in aortic arch type, radiographic clot features, and NIHSS score.
Conclusion With ADAPT, patient age and vessel tortuosity affect the ability to deliver the aspiration catheter and achieve clot contact, whereas vessel diameter and CVR at the aspiration site seem to affect the effectiveness of clot aspiration. Strategies aimed at improving catheter deliverability and increasing CVR may increase the efficacy of ADAPT.
- intervention
- stroke
- thrombectomy
- technique
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information.
Statistics from Altmetric.com
Introduction
Endovascular treatment confers a significant clinical benefit over standard medical treatment in large vessel occlusion stroke.1–4 Rapid and successful recanalization leads to a better clinical outcome and decreased disability.5 Thrombectomy with a stent retriever is considered the standard technique by many authors, but other means of extracting a clot from intracranial vessels have been applied. A direct aspiration first pass technique (ADAPT) describes a technique with primary clot aspiration with a large-bore catheter (primary aspiration/aspiration component) and a possibility to expand the treatment with further devices (such as a stent retriever), using the aspirational catheter as a conduit to their introduction into the vessel system.6 ADAPT has been found to be an efficient, safe, cost-effective, and fast thrombectomy technique, leading to adequate revascularization (Thrombolysis in Cerebral Infarction (TICI) ≥2b) in up to 91.2% of cases.7–9 Results from the randomized COMPASS trial further suggest that ADAPT can be considered as a first-line approach for thrombectomy.10 Similar efficacy has also been shown in a recent meta-analysis of 9127 patients by Primiani et al, which also suggested a higher revascularization rate in the aspiration group than in the primary stent retriever group (89% vs 80%, p<0.0001).11
With the apparent overall equipoise between the two techniques, it would be beneficial to identify markers conferring an increased success rate with either technique in order to better tailor the treatment strategy to individual patients and, possibly, improve overall procedural efficacy. Previous authors identified isolated middle cerebral artery occlusion, shorter time from symptom onset to clot contact, IV thrombolysis, and younger age as possible predictors of aspiration success12–14; however, data on anatomic and clot characteristics predicting successful stroke treatment are limited.15–17 The purpose of this study is to assess the influence of imaging features of the vascular tree and the occluding thrombus associated with success of the aspiration component as part of the ADAPT technique. We hypothesize that properties of the clot, vessel anatomy, and the size of aspiration catheters influence the revascularization rate after first-line aspiration.
Methods
This was a retrospective, single-center analysis of consecutive patients with acute large vessel occlusion stroke treated with ADAPT.
Patient selection
Patients undergoing endovascular recanalization at our university hospital between June 2015 and September 2017 were included. Data were retrospectively extracted from an institutional review board-approved database; the need for written informed consent was waived. Procedural data acquisition was performed by treating neuroradiologists and entered in a standardized form immediately after the endovascular therapy procedure.
From this database, patients meeting the following inclusion criteria were selected: (1) acute ischemic stroke due to a large vessel occlusion in the anterior and posterior circulation, (2) age>18 years, (3) endovascular mechanical recanalization was performed using ADAPT, as documented by any attempt to primarily advance an aspiration catheter to the occlusion site. Patients were excluded if imaging datasets were incomplete prohibiting vascular or clot analysis or severe motion artifacts.
Data assessed included patients’ age, admission National Institutes of Health Stroke Scale (NIHSS) score, modified Rankin Scale score before admission, time between symptom onset/last seen well, groin puncture and flow restoration, administration of intravenous thrombolysis, and periprocedural complications. The size of aspiration catheters employed was retrieved from the operative reports. In all cases aspiration was performed manually with a syringe. Study protocols were conducted in compliance with the Declaration of Helsinki and in accordance with ethical guidelines.
Radiographic data acquisition and analysis
Primary aspiration success (PAS) was evaluated on the procedural angiograms by an interventional neuroradiologist (with 5 years' experience of performing thrombectomy). Contact between the aspiration catheter and the clot before the primary aspiration attempt was assessed, and the data were grouped into successful catheter-clot contact (SCC) and failed catheter-clot contact (FCC). First-pass TICI score after primary aspiration was further evaluated. PAS was defined as TICI 2b or 3 after one or two aspiration attempts. No PAS was defined as TICI 0-2a after at least one performed aspiration maneuver.
Preintervention non-contrast cranial CT and CT angiography (CTA) were assessed for clot characteristics and vascular anatomy by a senior resident (with 4 years' experience in diagnostic radiology, including 2 years in neuroradiology). Clot density was evaluated on the non-contrast cranial CT scan using circular regions of interest in the proximal, middle, and distal third of the hyperdense vessel sign and calculating the mean value (figure 1A). In cases with poor visualization of a hyperdense vessel sign, the corresponding CTA filling defect was used to direct the measurement on the non-contrast CT. For assessment of the clot length, the filling defect on coronal and axial CTA maximum intensity projections was measured using one or more straight lines; the longest obtained total length was recorded (figure 1B). In cases of insufficient evaluation due to poor collateral flow, the dense vessel sign or blooming artifact on susceptibility-weighted or T2*-weighted gradient-echo MR images was measured accordingly.18 Clot perviousness, defined as the clot’s increase in attenuation on the CTA compared with non-contrast CT, was measured by placing circular regions of interest in near-identical location on the proximal CTA filling defect (figure 1C) and calculating the increase in mean Hounsfield units (HU).
Radiographic data acquisition on non-contrast cranial CT and CT angiography (CTA). (A) Clot density with Hounsfield unit measurements of a proximal, middle, and distal third of a thrombus using the dense vessel sign on the native CT scan. (B) Definition of the clot length and vessel diameter at the proximal clot end on the axial CTA scan. (C) Measurement of the clot perviousness on the axial CTA scan.
Vascular anatomy was assessed on CTA. If the CTA data were not obtained or were insufficient for the estimation (eg, only intracranial CTA performed) the digital subtraction angiographic or contrast-enhanced MR angiographic data were used in addition. The number of reverse curves along the vascular tree from the aortic arch to the occlusion site were counted as a simplified measure of vascular tortuosity.19 The vessel diameter directly proximal to the occluding clot was measured on axial CTA maximum intensity projections (figure 1B). From this, the catheter-to-vessel ratio (CVR) was calculated by dividing the nominal inner (CVR-ID), as well as the outer diameter (CVR-OD) of the employed aspiration catheter and the vessel diameter.
Statistical analysis
Baseline variables are described using standard descriptive statistics with MedCalc Statistical Software version 12.7.0.0 (MedCalc Software bvba, Ostend, Belgium). Patients were grouped according to SCC and PAS. Baseline variables, clot, and vascular characteristics were compared between groups using appropriate parametric and non-parametric test for continuous and categorical variables.
Results
Navigation to the occlusion site
Among a total of 293 patients identified, 106 met the inclusion criteria and were included in the analysis. SCC was seen in 76 cases (72%). Baseline variables, vascular and clot characteristics according to clot contact status are summarized in table 1. Patients with SCC were younger (67.7±15.2 vs 73.7±11.4 years - p=0.05) and had less vessel tortuosity (median 1 vs 2 reverse curves; p=0.004).
Results in all patients according to achieved clot contact.
Primary aspiration success
PAS was seen in 36 out of the 76 cases with SCC (47%) and in only one case with FCC (3%). Table 2 summarizes the tested variables according to PAS status. While clot characteristics were similar for patients with PAS and no PAS, vessel diameter at the occlusion site was lower in patients with PAS (2.5±0.7 mm vs 3.1±1.3 mm; p=0.01) and CVR-ID and CVR-OD were higher (0.72±0.2 vs 0.58±0.2; p<0.001 and 0.85±0.2 vs 0.68±0.2; p=0.01, respectively). In addition, time from symptom onset to groin puncture was longer in patients with PAS (264.7±126 min vs 197.7±75 min; p=0.04), but the time from groin puncture to recanalization was significantly shorter (24.0±13 min vs 62.2±36 min; p<0.001).
Results according to PAS status in patients with clot contact (SCC)
Discussion
As mechanical recanalization has become a standard in stroke treatment, choosing the most time-efficient, safe, and at the same time, cost-effective recanalization strategy is of growing importance. Because the majority of evidence supporting mechanical recanalization is based on the use of stent retrievers,1–4 the role of ADAPT as an alternative option for vessel recanalization is less clearly defined.20 The present analysis aimed to identify potential markers of technical success of the aspiration component of ADAPT. Our findings support the hypothesis that with ADAPT, once clot contact is achieved, successful clot aspiration is promoted by a smaller vessel size and larger CVR (CVR-OD and CVR-ID). This finding can most likely be explained by the resulting increase in force acting on the clot with relatively larger inner catheter diameters.21 22 Several previous reports have suggested that large-bore aspiration catheters can effectively remove clots,23 24 but to our knowledge this is the first study assessing CVR on a patient level in ADAPT. Our findings support the idea that for a given occlusion type, choosing the largest available aspiration catheter that can be safely delivered might be a strategy to increase technical aspiration success.
In addition, we found that age and vessel tortuosity negatively affect the ability to achieve clot contact and thus may impede recanalization, as failure to reach the occlusion site is a relevant known cause for overall reperfusion failure.25 26 Regarding ADAPT, this implies that the ease of deliverability is an important aspect of aspiration catheter design. Interestingly, Mascitelli and colleagues previously also reported a decreased chance for aspiration success with ADAPT in older patients.13 A similar analysis by Blanc and colleagues identified isolated M1 segment occlusion and shorter time from symptom onset to clot contact as predictors of successful aspiration12 ; these observations were not reproduced in our sample. It is possible that these differences are related to study design, as we assessed aspiration success only in patients with documented clot contact; another reason could be the comparably small sample size in our study.
Against our hypothesis, we did not observe a significant relationship between clot characteristics, including length, density, and perviousness, and aspiration success. Previous reports have shown that clots richer in fibrin and thus more firm, cohesive, and less compliant, can be associated with failed mechanical recanalization, both using aspiration and stent-retrieving techniques.20 27 Previous studies on imaging identification of clot composition have suggested that increased CT density corresponds to erythrocyte-rich clots, which have been linked to an increased chance of reperfusion success.28 Based on our results, it appears that prediction of aspiration success based on CT imaging is challenging, at least with basic, clinically applicable measurement techniques. In this regard, a recent meta-analysis has suggested higher clot density as a potential marker of success for stent retriever-based clot extraction, whereas only an opposite tendency was found in the aspiration subgroup.29 Compared with previous authors, we also employed a simplified method to assess thrombus perviousness.30 However, our simplified method has the advantage of being directly applicable clinically, as the goal of our analysis was to identify markers that can help in making acute treatment decisions. Overall, studies with larger sample sizes, and possibly more detailed analysis of clot imaging appearance, are required to assess whether aspiration success can be predicted in this way.
Limitations
Our study results are derived from retrospective analysis, which has well-known limitations—most importantly, the potential for selection bias. In addition, decision on a certain recanalization technique was at the discretion of the operator, depending on his/her experience and skills, as well as personal preferences. This could have made the results unrepresentative for all patients where primary aspiration or use of large-bore catheters could be applicable. The sample size is limited, which is related to the detailed manual assessment of clot and vessel characteristics. As we tried to determine the utility of clinically applicable measurement techniques, particularly for clot characterization, the chosen techniques were less accurate than theoretically possible (eg, we did not employ image coregistration or clot segmentation techniques).
Conclusions
Patient age and access vessel tortuosity can affect the ability to deliver the aspiration catheter and achieve clot contact with ADAPT. Once clot contact is achieved, vessel diameter and CVR at the aspiration site seem to affect the effectiveness of clot aspiration. For physicians using ADAPT and for entities developing new aspiration catheters, strategies aimed at improving catheter deliverability and increasing CVR may increase the efficacy of ADAPT.
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information.
Ethics statements
Ethics approval
Study protocols were conducted in compliance with the Declaration of Helsinki and in accordance to ethical guidelines (Ethics Committee of the Hamburg Chamber of Physicians, Hamburg, Germany WF-035/18). Due to the retrospective nature of the data collection and analysis, the need for written informed consent was waived.
References
Footnotes
Contributors Conception/design of work – AMF, AAK. Data collection – AAK, AMF, HL, FF. Data analysis and interpretation – AAK, AMF, JHB, JF. Drafting the article – AAK, AM. Critical revision of the article – AAK, AMF, JHB, JF, FF, HL. Final approval of the version to be published – AAK, AMF, JF. Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved – AAK, AMF, JHB, JF, FF, HL.
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 JHB: personal fees as consultant for Microvention, Stryker, Cerenovus, Acandis and Medtronic outside the submitted work. JF: personal fees from Consultant for Microvention, Stryker, Cerenovus, Acandis, Penumbra and Medtronic outside the submitted work. He is a member of the executive board of the scientific societies DGNR and ESMINT.
Provenance and peer review Not commissioned; externally peer reviewed.