Background Recent studies suggest that the proven benefits of endovascular thrombectomy (EVT) for the treatment of large vessel occlusion (LVO) strokes are transferable to more peripheral distal vessel occlusion (DVO) strokes under certain circumstances. Safely accessing and extracting these thrombi however remains challenging, particularly in more tortuous peripheral arteries. For such cases we have utilized the dual suction Headway27 microcatheter thrombectomy, or micro-ADAPT, technique with the aim of reducing potential trauma associated with negotiating stent retrievers or large bore aspiration catheters into the peripheral intracranial vasculature. We present our experience utilizing the micro-ADAPT in the treatment of DVO strokes. We describe our technique as well as present angiographic and clinical outcomes.
Methods A retrospective review of our institution’s prospectively collected EVT registry for the 12 months spanning July 2017 to June 2018 was undertaken. Data on all cases of micro-ADAPT EVT were collected and analyzed.
Results Micro-ADAPT EVT was performed 14 times over the study period, with a recanalization rate of 79%. DVO strokes in multiple locations were treated, including the A3, M3, P3, and superior cerebellar artery. In cases where an LVO stroke was also present, the mean duration between primary LVO recanalization and secondary DVO micro-ADAPT recanalization was 15.5 min. No complications relating to the micro-ADAPT technique were recorded. No infarcts were present in the territory of the recanalized DVO stroke on day 1 CT in successful micro-ADAPT cases
Conclusions In the setting of challenging peripheral DVO strokes, the micro-ADAPT technique appears to be a fast and effective technique with a low complication rate.
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Since publication of the landmark randomized controlled trials proffering conclusive evidence for the benefit of endovascular thrombectomy (EVT) in the treatment of emergent large vessel occlusion (LVO) stroke,1–4 attention has shifted to the potential benefits of offering EVT to a wider cohort of patients. Late window trials have extended the potential timeframe for EVT in certain patients up to 24 hours5 6 and recent studies have provided evidence for the efficacy of EVT in distal vessel occlusion (DVO) strokes beyond the well studied M1 division.7–10 Whether these DVO strokes occur as the primary intracranial occlusion or as a secondary occlusion on a background of a more proximal LVO thrombus, recent evidence suggests that endovascular treatment of DVO strokes is both viable and beneficial in certain circumstances. The challenge associated with accessing and extracting these more distal thrombi may however be significant; tortuous arterial anatomy and small vessel size may prohibit the use of stent retrievers and medium to large bore aspiration catheters due to an inability to navigate these distal vessels and concerns over arterial trauma.
In an attempt to gain access to challenging DVO strokes while minimizing the risk of arterial injury, we have developed the ‘micro-ADAPT’ technique of dual suction Headway27 microcatheter thrombectomy. Here we describe our technique and provide radiological and clinical outcomes for patients treated with this technique at our institution over a 12 month period.
A retrospective review of our institution’s prospectively collected EVT registry was undertaken and all patients treated with the micro-ADAPT thrombectomy technique within the 12 months spanning July 2017 to June 2018 were included for analysis.
Pretreatment patient data collected included the following: National Institutes of Health Stroke Scale (NIHSS) score, Alberta Stroke Program Early CT Score (ASPECTS), location of DVO stroke and/or LVO stroke, and whether intravenous thrombolysis (iv tissue plasminogen activator (tPA)) had been administered. Intraprocedural data collected included whether the micro-ADAPT technique successfully extracted the DVO thrombus, the number of micro-ADAPT passes required to extract the thrombus, and the time metrics of LVO and DVO EVT. Two modified Treatment in Cerebral Ischemia (mTICI) scores were documented. The DVO mTICI defined reperfusion success solely in the DVO territory in which micro-ADAPT was utilized, with a scoring system (1, 2A, 2B, 2C, and 3) identical to the standard mTICI. The overall mTICI was also documented, which defined overall reperfusion success in patients with both proximal LVO and DVO strokes. Post-treatment data collected included complications related to the micro-ADAPT technique, including symptomatic or asymptomatic intracranial hemorrhage, day 1 ASPECTS score, whether an infarct occurred in the DVO territory of micro-ADAPT treatment, and 90 day modified Rankin Score (mRS) score.
The cervical internal carotid artery was accessed utilizing a Neuron Max 088 catheter with Neuron Select 6 F inner catheter (Penumbra, Alameda, California, USA) through a 9 F common femoral artery sheath. When present, the primary, proximal LVO stroke was accessed utilizing a 0.055 inch or 0.070 inch Sofia or Sofia Plus 125 cm intermediate catheter and Headway27 microcatheter (Microvention Terumo, Tustin, California, USA) over an 0.014 inch microwire of the neurointerventionist’s choice. The recanalization technique of the proximal LVO thrombus varied depending on the case, with stent retrievers and ADAPT both utilized. Once the proximal LVO stroke was recanalized, or in cases where no LVO stroke was present, the DVO stroke was accessed utilizing a 0.055 inch 125 cm Sofia intermediate catheter and a Headway27 microcatheter over a 0.014 inch microwire. Without crossing the thrombus, the Headway27 microcatheter was advanced, its proximal margin over the microwire. The Sofia intermediate catheter was then advanced over the Headway27 and positioned as close to the thrombus as possible, to minimize the risk of emboli into new territories.
Engaging the thrombus
Following removal of the microwire, mechanical suction was applied through the Headway27 via the Penumbra Pump MAX (Penumbra) over a period of 3 min. If blood flowed back into the pump, the microcatheter was advanced further into the thrombus until flow arrest was achieved, indicating thrombus engagement. Intermittent staccato movement of blood and saline in the pump tubing without free flow appeared to strongly suggest engagement and partial ingestion of thrombus in the microcatheter tip. During this time, two 60 mL Vaclok syringes (Merit Medical, South Jordan, Utah, USA) were connected to a three-way tap and extension tubing purged with saline. The ‘off’ position was turned towards the extension tube and the two syringes placed into suction creating a 120 mL ‘double Vaclok syringe’. This device was then connected to the rotating hemostatic valve port of the intermediate catheter.
Retrieving the thrombus
The ‘off’ position of the three-way tap was then turned towards one of the Vaclok syringes producing suction on the intermediate catheter with the aim of achieving reversal of flow in the vessel proximal to the thrombus. Gentle, slow traction was then applied to the microcatheter without disconnecting the pump suction. If the intermediate catheter rides distally towards the thrombus, it is allowed to do so. Care was taken not to place sudden traction on the Headway27 as this may break the suction seal between the thrombus and the microcatheter tip, and also not to over loosen the rotating hemostatic valve holding the microcatheter. If the first Vaclok syringe fills with blood during microcatheter withdrawal, the three-way tap is turned with the ‘off’ position towards the full syringe, allowing suction from the second syringe.
As the tip of the microcatheter approaches the tip of the intermediate catheter, the operator then makes a decision whether to retrieve the microcatheter and thrombus fully through the intermediate catheter, leaving it in the intracranial circulation and applying suction to the intermediate catheter after, or ‘corking’ a larger thrombus at the intermediate catheter tip and retrieving both through the guide catheter, applying suction to the guide catheter after both intermediate and microcatheters have been removed concurrently. The retrieval process is then complete and check angiography can be performed.
A total of 251 EVTs were performed at our institution between July 2017 and July 2018; during this time period, the micro-ADAPT thrombectomy technique was used in 14 DVO strokes in 12 patients, 11 times in the anterior circulation and 3 times in the posterior circulation (table 1).
Successful extraction of the DVO thrombus utilizing the micro-ADAPT technique was achieved in 79% (11/14) of cases with a first pass recanalization rate of 71% (10/14). DVO territory reperfusion was complete in all cases of successful micro-ADAPT thrombus extraction (91% DVO mTICI 3 and 9% DVO mTICI 2C) with no distal embolic events related to the micro-ADAPT technique.
Seventy-nine per cent (11/14) of the DVO strokes were secondary intracranial occlusions on a background of a more proximal primary LVO stroke. In this group, the DVO stroke was in the same arterial territory as the LVO stroke in 72% (8/11) and in a different arterial territory in 28% (2/11). The mean duration between primary LVO recanalization and secondary DVO micro-ADAPT recanalization was 15.5 min (range 9–21 min). In 21% (3/14) of cases, the DVO stroke was the primary intracranial occlusion with no proximal LVO stroke present, and the micro-ADAPT technique was used as the firstline treatment; of these cases 66% (2/3) were successfully recanalized. Only 8% (1/14) of patients received iv tPA prior to micro-ADAPT thrombectomy, most commonly due to late presentation/unknown time of onset and active anticoagulation.
No complications relating to the micro-ADAPT technique were recorded in our patient cohort; specifically no symptomatic or asymptomatic intracranial hemorrhages occurred. No infarcts were present in the territory of the recanalized DVO on day 1 CT in cases where micro-ADAPT EVT was successful. In the nine patients in whom the micro-ADAPT technique was successfully utilized to recanalize a single DVO stroke, the mean 90 day mRS score was 1. In the two patients with attempted micro-ADAPT recanalization of more than one DVO stroke in whom success was achieved in one from two occlusions, the mean 90 day mRS score was 2.5. The final patient, in whom the micro-ADAPT technique was unsuccessful, was subsequently recanalized using a stent retriever with a 90 day mRS score of 4.
Recent studies suggest that the well described benefits of EVT in proximal LVO strokes of the anterior circulation are likely transferable to smaller DVO strokes under certain circumstances.7–10 Patients with a primary DVO stroke in an eloquent territory, with severe symptoms, as evidenced by a high NIHSS or are tPA ineligible, appear to derive benefit from DVO EVT.9 Patients with a recanalized primary LVO stroke who have one or more DVO strokes that were present prior to, or occurred secondary to, the primary LVO EVT may also benefit from pursuing these more distal thrombi, as evidenced by the improved clinical outcomes of patients with mTICI 3 reperfusions in comparison with poorer quality mTICI 2B reperfusions.11–13
While there is growing evidence that pursuing DVO strokes may be beneficial under certain circumstances, achieving safe complication free DVO recanalization is often challenging. Several studies have reported relatively higher rates of postprocedural hemorrhage following EVT for strokes beyond the M1 segment7 14 and that has been the experience at our institution. We feel that the higher rates of hemorrhage likely relate to the often prominent distortion of the local arterial architecture when negotiating stent retrievers or large bore aspiration catheters into the more peripheral intracranial arteries. We consequently began applying suction via the Headway27 microcatheter for peripheral DVO strokes and, with additional application of suction through the intermediate catheter, developed the micro-ADAPT technique described in this paper. In our early experience, we find it offers less traumatic access to peripheral DVO strokes, particularly those in which the arterial anatomy leading to the occlusion is tortuous.
The Headway27 microcatheter has already been successfully used during LVO EVT for intracranial access and deployment of stent retrievers15 and it is the primary choice of microcatheter for EVT among some members of our group. Its relatively small 2.6 F (0.86 mm) distal outer diameter and length of 156 cm also make it navigable through tortuous, small intracranial arteries to sites of DVO strokes. However, when used as a primary aspiration catheter, the 0.027 inch (0.69 mm) distal inner diameter of the Headway27 will naturally generate less suction at the clot interface than larger bore catheters designed specifically for aspiration thrombectomy given the direct correlation between suction force and area of catheter tip.16 In our micro-ADAPT technique, the lower suction force generated through the Headway27 is partially compensated for by placing the Sofia intermediate catheter as close to the thrombus as possible, reducing the distance the clot has to traverse to the intermediate catheter, and additionally applying suction at the intermediate catheter. In this way we are able to generate net flow reversal in the affected distal vessel; as well as reducing the risk of thrombus fragmentation during retrieval, it also allows us to apply a larger suction force to the thrombus via the larger diameter intermediate catheter at the earliest opportunity.
The efficacy of this dual suction micro-ADAPT technique is born out by the excellent results achieved in our small patient cohort, successfully extracting the DVO thrombus in 79% of cases, the majority (71%) after a single pass. These results compare favorably with those published for other DVO recanalization techniques, such as the 3MAX (Penumbra, Alameda, California, USA), a catheter designed specifically for primary aspiration thrombectomy in smaller intracranial arteries. The 3 MAX is significantly larger than the Headway27 (3MAX; 3.8 F distal outer diameter and 0.88 mm distal inner diameter) and while this means that greater suction force can be generated directly at the thrombus interface, recanalization rates using 3MAX and micro-ADAPT technique appear to be very similar. In a recent study by Altenbernd et al17 assessing the efficacy and safety of the 3MAX, mTICI 3 reperfusion was achieved in 70.7–82.8% of cases with a first pass recanalization rate of 79%. As previously discussed, we feel that the greater suction force that can be applied via larger distal aspiration microcatheters such as the 3 MAX can be offset by applying dual suction via a smaller distal microcatheter and an distally placed intermediate catheter as in our micro-ADAPT technique. The fact that no procedural intracranial hemorrhage (ICH) occurred in our micro-ADAPT cohort in comparison with asymptomatic ICH rates of 17.2% and symptomatic ICH rates of 3.4% in the 3MAX, possibly reflects the less traumatic nature of the micro-ADAPT technique using the smaller, more trackable Headway27 catheter. It is also important to note that the location of DVO strokes treated with micro-ADAPT in this study was more varied than those treated with the 3MAX in the study by Altenbernd et al.17 While the 3MAX was used for M2 and M3 occlusions only, the micro-ADAPT technique also successfully recanalized A3, P3, and superior cerebellar artery occlusions, locations in which access with the larger 3MAX catheter is likely to be more challenging and potentially more traumatic.
In all EVT eligible cases, recanalization of the largest, most proximal arterial occlusion is clearly the priority, and in the majority of our cases the micro-ADAPT technique was used to pursue secondary DVO strokes in the setting of a more proximal primary LVO thrombus. Making the decision to pursue the DVO stroke in these patients was based on several factors, including whether tPA had been administered, the eloquence of and collateral supply to the affected territory, and its potential to provide collateral blood supply to adjacent arterial territories. For example, in one case (figure 1), following recanalization of a proximal M2 LVO stroke, secondary DVO strokes were identified in ipsilateral A3 and Rolandic M4 branches. The M4 occlusion was too distal to pursue and a successful micro-ADAPT recanalization of the more accessible A3 occlusion was performed in order to prevent a concomitant anterior cerebral artery infarct as well as maximizing collateral supply to the territory of the M4 occlusion. In a further case, a delayed presentation basilar trunk LVO stroke underwent successful proximal recanalization to reveal right-sided superior cerebellar artery (SCA) occlusion. Review of CT demonstrated early ischemic change in the contralateral left SCA territory and a decision was made to pursue the right SCA occlusion with the hope of minimizing the size of cerebellar infarction and consequent disability. In this case, the micro-ADAPT thrombectomy was technically successful with no infarct occurring in the right SCA territory, but unfortunately due to the delayed presentation the left SCA territory infarct progressed and extensive pontine infarcts occurred due to prolonged perforator occlusion.
While overall results using the micro-ADAPT technique have been excellent, cases in which the technique failed offer some insights into its limitations. In the one case the DVO stroke was in the small M2 division arising at a hyper-acute angle from the M1; here the Headway27 was negotiated to the clot interface but the Sofia intermediate catheter would not make the turn into the origin of the M2 meaning that when dual suction was applied, flow reversal in the M2 was suboptimal. Two attempts at Headway27 suction led to some fragmentation of the clot with only partial vessel recanalization. In another case the micro-ADAPT technique was used for a mid M2 thrombus which appeared to be nearly 1 cm in length on non-contrast CT. After one failed suction attempt the technique was abandoned as we felt that the clot was too large to be successfully captured by direct aspiration on the Headway27. In this case, without changing our equipment, the Headway27 was then negotiated past the thrombus allowing deployment of a stent retriever with successful vessel recanalization.
The major strengths of this study are the excellent clinical and radiological follow-up while its clear limitations are the retrospective nature and small number of patients involved. The patient cohort in whom the micro-ADAPT technique was used were prospectively selected at the time of presentation as those in whom the anatomical and radiological features suggested success and therefore bias exists regarding our high technical success rates. However, we feel that this careful patient selection should be practiced in real world scenarios meaning that although this technique is not generalizable to all DVO strokes it is a viable option in situations similar to those described in this study. Without larger randomized studies it is also difficult to know how significantly recanalization of the DVO stroke contributed to the good clinical outcomes in the group of patients in whom proximal LVO strokes were also recanalized. However, logic and recent studies12 18 suggest that, in the absence of complications, the improved mTICI reperfusion rates achieved by recanalizing both LVO and DVO strokes should lead to better outcomes in comparison with recanalization of the LVO stroke alone
The dual suction Headway27 microcatheter thrombectomy, or micro-ADAPT thrombectomy, appears to be a useful technique in the treatment of distal vessel occlusion strokes, particularly those in smaller, more tortuous arteries where navigation of stent retrievers or larger bore aspiration catheters is challenging and potentially traumatic. We believe that in this setting the micro-ADAPT technique offers fast, effective, and safe recanalization and is a valuable addition to the armory when dealing with the increasing burden of DVO strokes.
Contributors MCT is the principal investigator and performed the procedures, manuscript construction and editing, images, and video editing. TJP performed the procedures and edited the manuscript. AHYC is the senior author/investigator, and performed the procedures, manuscript construction, and editing.
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 None declared.
Patient consent Not required.
Ethics approval The study was approved by the Western Australian Health GEKO committee.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data are included in the published manuscript.
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