ICAD resolution & complex posterior circulation case

Endovascular treatments for intracranial athersclerosis and tandem occlusions in posterior circulation

Endovascular treatment of acute large vessel occlusion (LVO) secondary to intracranial atherosclerosisespecially in the posterior circulation remains challenging, with no standardized strategy. A critical decision is whether to perform emergency stenting concurrently. The ANGEL-REBOOT trial, which included 348 patients with acute LVO within 24 hours of symptom onset (approximately 95% of whom had ICAD-related LVO), demonstrated no significant differences in 90-day mRS or mortality between the bailout angioplasty group and the standard treatment group. However, the bailout angioplasty group exhibited higher risks of symptomatic intracranial hemorrhage, PH-2 type hematoma, and procedural arterial dissection. The ongoing PISTAR trial and its pooled analysis with ANGEL-REBOOT are anticipated to provide new insights to this inconclusive question. The PISTAR study includes not only refractory occlusions but also patients with early reocclusion after at least one thrombectomy attempt or those with severe intracranial stenosis, offering alternative timing to switch to a salvage angioplasty strategy. The Neuroform Atlas stent, which might be associated with a lower risk of complications in emergency stenting, and the procedural approach is more standardized.

Subsequent to the ANGEL-REBOOT study, three registry cohort studies limited to acute vertebrobasilar occlusion (PC-SEARCH, PERSIST, and SAINT) suggested that for patients with failed thrombectomy, salvage stenting were associated with better neurological outcomes and lower mortality without increasing the risk of symptomatic intracranial hemorrhage. The 2024 European Stroke Organisation and European Society for Minimally Invasive Neurological Therapy guidelines, recommend salvage angioplasty for patients with thrombectomy failure, based on expert consensus. Additionally, the RESCUE-ICAS registry study indicated that even patients with successful recanalization but residual stenosis of more than 50%, presumed to be of ICAD etiology, could achieve better functional outcomes with emergency stenting without increased risk of symptomatic intracranial hemorrhage. Thus, these studies collectively suggest that the equipoise of emergency intracranial angioplasty is acceptable, particularly for posterior circulation occlusions.

Tandem occlusions in the posterior circulation, accounting for approximately 25% of acute basilar artery occlusions, are often caused by acute occlusion of the dominant vertebral artery. Compared with the anterior circulation, they are associated with poorer prognosis and higher mortality. Rapid access establishment is crucial. There are typically two routes: the "dirty" route, which involves accessing through the affected vertebral artery using a semi-antegrade method to prioritize treatment of the distal occluded vessel; and the "clean" route, which accesses through the contralateral vertebral artery to more rapidly reach the intracranial vessels, treating only the distal occlusion, although there is a risk of re-embolization from the contralateral occluded stump. Etiologically, these occlusions are mostly due to atherosclerosis, with acute or chronic occlusion on the basis of stenosis of the vertebral artery orifice, with thrombi distal to the extracranial occlusion site as vertebral artery stump syndrome (VASS). The V2/3 segments of the vertebral artery often have antegrade blood flow from muscular branch anastomoses for distal embolic. Intracranial occlusions not at the basilar artery apex usually indicate the presence of tandem stenosis.

The use of embolic protection devices such as BGC and filters is not always feasible in the posterior circulation. When accessing through the "dirty" route for thrombectomy, blood flow control to prevent secondary embolism from the stump can be achieved using BAT techniques with small balloons shuttling the guide catheter or intermediate catheter to pass through the extracranial and intracranial occlusion. For intracranial occlusions, it is essential to first determine whether the location is prone to ICAD and the surrounding thrombus burden. For locations with rich perforators, such as the basilar artery trunk, first-line SWIM technique can be used to expose the lesion and debulk the thrombus. For stenotic occlusions in the V4 segment of the vertebral artery with high thrombus burden distally, the BASIS technique is preferred. For salvage angioplasty in areas with rich perforating arteries, suboptimal balloon angioplasty alone or together with self-expanding stents may be considered over balloon-mounted stents to reduce perioperative complication risks. In terms of compatibility, in addition to ACHEVA devices, stent retrievers such as Trevo Baby 3.0 mm stent and JRecan 2.5 mmcan also be retrieved using the Maverick balloon. After recanalization, extracranial vertebral artery angioplasty is often required to prevent stump reocclusion and re-embolization. It should be noted that most coronary/peripheral balloons and vertebral artery balloon-expandable stents are only compatible with intermediate catheters up to 115 cm in length. When chronic occlusion of the vertebral artery orifice is difficult to cross, unconventional approaches such as retrograde access through cervical collateral anastomoses or direct puncture of the vertebral artery at the skull base level may be considered.

Reference

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