As far as we know, this is the first report about permanently implanting LVIS to deal with embolic refractory intracranial LVO. Refractory occlusions, which remained after several times of thrombectomy and angioplasty, happened in both two cases, and they both occurred at the paraclinoid segment of ICA. The leading cause of this phenomenon might be the tortuous shape of the paraclinoid segment made the embolus easier to be blocked at this segment. These blocks are usually hard clots, which are difficult to be pulled out. In both cases, LVIS implantation with post-stenting balloon dilation was used as the final therapy and mTICI 2b-3 grade recanalization was achieved finally, which improved the neurological scores and symptoms of the patients. These results primarily conveyed the feasibility of LVIS implantation in dealing with refractory intracranial LVO.
Permanent stent implantation with or without angioplasty is a preferable rescue therapy for unsuccessful recanalization. The efficacy of this technique has been generally accepted by practitioners, and it is performed more actively these years to deal with refractory LVO. Different types of stents, including Solitaire stent, Apollo stent, Enterprise stent, Wingspan stent, and Neuroform stent, have been implanted to deal with refractory occlusion [1,2,3, 6]. However, in the case of hard clot embolization, the remaining hard clots may protrude into these large-cell stents, which will increase the risk of re-stenosis and thrombosis.
Thus, to explore a novel effective strategy specifically for refractory LVO due to hard clot embolization, we creatively used LVIS, which is originally designed for treating intracranial aneurysms. In our cases, more than 3 times of thrombectomy and other techniques were used but failed, and an LVIS implantation with post-stenting angioplasty finally achieved recanalization. We supposed that if we used this technique in advance, the procedure time would be significantly reduced, which might improve the outcomes. According to our experience, we found that several characteristics might contribute to the ability of LVIS to deal with refractory LVO, especially to deal with occlusion that was induced by hard clot [4, 7]: 1) The higher metal coverage (23%) and small cell size (< 0.9 mm) can avoid the protrusion of the hard thrombus into the vessel after stenting and angioplasty. This feature is especially suitable for treating hard clot occlusion. 2) LVIS can be full-long visualized because of the double helical tantalum strands, which is important for judging whether the stent is fully and correctly expanded. 3) Due to the closed-cell design, re-sheathability of LVIS can be up to 90%, and post-dilation balloon can be easily managed through. Based on these experiences, larger-scale clinical research was needed to confirm the efficacy and safety of LVIS in treating refractory LVO due to hard clot embolization.
Several concerns remain in dealing with refractory LVO with LVIS. Firstly, the high metal coverage and small cell size design of LVIS may lead to high re-stenosis rate [8]. In our two cases, no acute in-stent re-occlusion occurred in-hospital after stent implantation with the combination of anti-platelet drugs. In some other studies, the in-stent stenosis rate in LVIS was comparable with other stents [9]. In fact, re-stenosis is a common complication after stent implantation which can be partially avoided by anti-platelet drugs. It deserves further investigation of whether LVIS will lead to a higher re-stenosis rate after being implanted in patients with LVO. Another concern about LVIS implantation is its radial force. Due to the braided design of LVIS, its radial force may be lower than its laser-cut counterparts [4]. However, in vitro tests showed that LVIS had a comparable radial force among LEO, Enterprise, and Neuroform stents, which indicated that LVIS also has a promising radial force especially when it is fully open and pushing aggressively during the deployment [10]. At present, there is lack of data about implanting LVIS to treat LVO, and further investigation is needed to settle these concerns.