In the current study, we investigated if there were differences primarily in immediate reperfusion performance and side effects, and secondarily in post-procedural hemorrhagic complications and clinical outcomes, depending on the choice of the first-line devices between SR and CA in patients with ICAS-LVO. Based on the results of our retrospective analysis of a multicenter registry, we could cautiously mention that the use of SR may be safer and more effective for ICAS-LVO than CA as a first-line thrombectomy method in terms of immediate reperfusion success and immediate occurrence of iatrogenic dissection or rupture.
Recently, studies have reported comparisons of reperfusion performance or side effects of CA and SR when performing EVT in overall LVO patients. In the ASTER trial, the reperfusion success did not differ between CA and SR (mTICI score of 2b or 3, SR 67.7% vs. CA 63.0%) [3, 21]. More recently, the COMPASS trial showed that first-line CA treatment was not inferior to first-line SR treatment with respect to good outcomes (mRS 0-2, SR 50% vs. CA 52%;non-inferiority margin absolute difference 15%; pnon-inferiority=0.0014) [4]. The secondary angiographic outcomes did not significantly differ between groups but tended to be better in CA rather than in SR in terms of the median time to successful reperfusion (SR 33 min vs. CA 22 min, p = 0.019). These trials provide convincing evidence that CA may be used as an alternative to SR thrombectomy as first-line therapy in anterior circulation LVO-related acute ischemic stroke within 6 hours of symptoms onset. However, these trials were performed in the Western countries (France, USA, and Canada), where the most predominant cause of emergency LVOs was known to be embolic occlusion. Large artery atherosclerosis as the suspected cause of stroke accounted for around 7.9% in the ASTER trial [3], and 5.5% was reported in a retrospective study from France [22]. In contrast, ICAS as an underlying etiology of LVO is reported to be more frequent among the Asian populations (17.6% – 19.0% based on most relevant methodology) [9, 11]. Mechanical thrombectomy in a severe atherosclerotic arterial bed may have different performance and side effects because stenotic lesions can cause additional friction with devices [23]. It has been suggested that ICAS-LVO may require a different approach than embolic LVO [8, 9]. Therefore, we evaluated if there were differences between SR and CA in terms of performance and side effects after first-line thrombectomy.
In the current study, immediate reperfusion performance was better when SR was used as a first-line device in ICAS-LVO. Therefore, rescue treatment involving the use of other devices was more common in the CA group, and the overall number of techniques was also higher with the use of CA. These results are consistent with those of the ASTER trial, in which rescue treatment after fist-line strategy tended to be more frequent in the CA group (32.8%) than in SR group (23.8%) with marginal statistical significance (3), and in a previously reported observational comparative study (CA 45.2% vs. SR 13.5%) that showed statistical significance [24]. In the current study, as rescue techniques, the rates of tirofiban infusion, angioplasty, or stent insertion were similar between the two groups, whereas the switching rate from CA to SR was significantly higher in the CA group than that in the SR group. Although the successful reperfusion rate was higher in the SR group, there were no significant differences in rescue techniques such as tirofiban infusion, suggesting that ICAS-LVO tends to reocclusion and still requires additional treatment in many patients.
Among the immediate side effects, the frequency of iatrogenic dissection or rupture appeared to be prominent. Mechanical thrombectomy may cause vessel damage [25-28]. Several animal studies have shown occurrence of intima and medial damage after thrombectomy using SR or CA devices. Some of the vessel damage could be transient, but some could leave long-term damage [26]. Despite these natural characteristics of mechanical thrombectomy, the occurrence rate of iatrogenic dissection or rupture in both groups of the current study was higher than that that of recent trials reported in Western countries. In the ASTER trial, the frequency of arterial dissection was only 1.1% (SR group) to 2.6% (CA group) (3). More frequent vessel injury in our study might be caused by vessel stenosis. When outcomes were compared between ICAS- and embolic LVOs with Solitaire stent thrombectomy, the frequency of vessel injury using the same definition as the current study accounted for 13.5% vs. 3.7%, respectively [29]. In addition, immediate vessel injury was more frequent in the CA group than in SR group in the current study. In general, SR is expected to have more vessel injury than CA. However, ICAS can make the tip of CA catheter more difficult to face thrombus due to hurdle-like anatomy of stenotic lumens. A recent review article attributes this phenomenon to the possibility that the tip of aspiration catheter may not properly contact the in situ thrombi but may face the surface of ICAS [30].
Even though rescue treatments were more frequently used and procedural time was longer in the CA group than in SR group, final reperfusion success and 3-month good outcome did not differ. Taken together, SR can be considered more advantageous as a first-line device than CA for treatment of ICAS-LVO. However, despite this immediate advantage, there was no significant difference in the outcome following aggressive rescue treatment and device switching [31, 32].
Despite of the differences of immediate reperfusion performance and side effect, there was no difference in the final outcome. The difference in the outcome of the first-line treatment may be complemented by the rescue treatment, but the effect of post-procedure management cannot be denied. Because the purpose of this study is not related to this, we could not present relevant data, but the followings could be considered. While lowering blood pressure when reperfusion after embolic occlusion is recommended to prevent reperfusion injury, maintaining blood pressure slightly higher for remnant stenosis would be helpful to maintain cerebral perfusion pressure in patients with ICAS. In addition, as shown in SAMMPRIS trial, we should consider maintaining sufficient antithrombotic activity with dual antiplatelets at least the first 3 months and use of intensive statin in anticipation of regression of stenosis [33, 34]. Further studies are needed on the post-procedure management with ICAS patients.
This study has several limitations. First, this was a retrospective study; therefore, it is not free from selection bias. Second, patients who were enrolled early in the study period in the registry underwent treatment with outdated devices, such as the first-generation Penumbra that are not currently in use. Moreover, new CA devices have been commercialized recently, and further studies on their effects and safety are needed. To this point, we also compared the first-generation and subsequent Penumbra systems but there was no difference in terms of outcomes (data not shown). In addition, future research may be required as new techniques such as Solumbra or stent retriever assisted vacuum-locked extraction have been introduced. Third, while we tried our best to distinguish underlying ICAS from vessel injury after EVT, it might be difficult to distinguish them completely, which can lead to errors. Nevertheless, because these errors were applied to both groups equally, there would be no significant bias in comparing the results. Finally, in this study, the device was selected based on the practitioner's personal preference, and there could be a bias because this was not a randomized trial. Despite these limitations, our study may be helpful in selecting devices in patients who are predicted to have ICAS-LVO [13-15].