Retrograde Angiography to Detect Dropped Thrombus in Mechanical Thrombectomy

Abstract

Objective: The risk of embolization to distal territory or to new territory in mechanical thrombectomy remains a major issue despite advancements in technological device. This condition can be caused by a large and firm dropped thrombus without passing through a guiding catheter during stent retriever or aspiration catheter withdrawal. This report introduced a novel technique referred to as retrograde angiography to detect dropped thrombus.

Methods: The retrograde angiography to detect dropped thrombus technique is a kind of retrograde angiography that consists of a contrast medium injection via a distal microcatheter and aspiration through an inflated balloon-guiding catheter. This method was used to detect dropped thrombus at the balloon-guiding catheter tip when back flow was blocked from the balloon-guiding catheter after stent retriever or aspiration catheter withdrawal. We retrospectively reviewed four consecutive patients who underwent the retrograde angiography to detect dropped thrombus technique during mechanical thrombectomy for acute ischemic stroke due to large vessel occlusion in the anterior circulation between January 2018 and January 2021.

Results: Three of four patients had dropped thrombus, which was diagnosed with the technique and retrieved completely with subsequent procedures while maintaining the balloon-guiding catheter inflated. None of the patients experienced embolization to distal territory/embolization to new territory, and a successful reperfusion was achieved in all four cases.

Conclusions: The retrograde angiography to detect dropped thrombus is a technique to detect a dropped thrombus at the balloon-guiding catheter tip and allows us to retrieve it with subsequent mechanical thrombectomy procedures while maintaining the balloon-guiding catheter inflated and it may be useful for reducing the risk of embolization to distal territory/embolization to new territory.

Keywords: Endovascular procedures; ischemic stroke; thrombectomy.

Figure 1.

Schema of mechanical thrombectomy and the subsequent retrograde angiography to detect dropped thrombus (RAD²) technique. (A) Stent retriever (SR) and aspiration catheter (AC) withdrawal are started while sucking from the AC and inflated balloon guiding catheter (BGC) with aspiration pump and a 20mL syringe, respectively. Then, the SR and AC are removed with holding the state while confirming little back flow from the AC. (B) When the back flow via the BGC is still poor after SR or AC withdrawal, manual aspiration (MA) is performed to remove small dropped thrombi while the BGC is inflated. (C) If back flow is still poor via the BGC, a microcatheter (MC) is deployed proximal to the petrous segment of the internal carotid artery. Then, antegrade angiography via the MC is performed to validate whether recanalization of the occlusion site is achieved while maintaining the proximal side of the BGC open and the balloon inflated. (D) This schema is a main component of the RAD2 technique. MA through the BGC with a 20 mL syringe is subsequently started with the additional administration of a contrast medium via the MC, and a dropped thrombus can be identified at the BGC tip via the retrograde angiography.

Figure 2.

Digital subtraction angiograms in case 2 in Table 1. (A) Right common carotid angiography via a balloon guiding catheter (BGC) reveals the right cervical internal carotid artery (ICA) occlusion. (B) Right internal carotid angiography via a microcatheter (MC) to confirm the extent of occlusion reveals patency of the intracranial ICA before mechanical thrombectomy. (C) Antegrade angiography via a MC distal to the right cervical ICA stenosis after percutaneous transluminal angioplasty reveals an occlusion of C5 segment of the ICA and subsequent retrograde angiography reveals no dropped thrombus at the BGC tip or the stenosis.

Figure 3.

Interventional radiologic therapy images of a representative case (case 3 in Table 1). (A) Diffusion-weighted magnetic resonance imaging on admission shows high-intensity areas in the left frontal and temporal lobes. (B) Magnetic resonance angiography shows the occlusion of the right internal carotid artery (ICA). (C) Right common carotid angiography (lateral image) via a balloon-guiding catheter (BGC) reveals the right cervical ICA occlusion before mechanical thrombectomy. (D) Antegrade angiography (lateral image) via a microcatheter deployed at the C5 segment of the right ICA reveals no intracranial large vessel occlusion after mechanical thrombectomy. (E) Filling defects (arrowhead) indicating a dropped thrombus is detected at the BGC tip in the subsequent retrograde angiography (lateral image) via the microcatheter while aspirating from the inflated BGC with a 20 mL syringe (RAD² technique). (F) Filling defects (arrowhead) indicating a dropped thrombus in Figure 2(E) is magnified. (G) Right internal carotid angiography (lateral image) shows the disappearance of the filling defects after crushing the thrombus with a J-shaped guidewire and removing the fragmented thrombi by manual aspiration through the BGC. (H) The tip of the BGC in Figure 2(G) is magnified. (I) Final right internal carotid angiography (lateral image) shows successful reperfusion (modified Thrombolysis In Cerebral Infarction grade 2b).

Figure 4.

Schema of the mechanisms of embolus formation during mechanical thrombectomy with a stent retriever (SR). (A) Water-hammer effects of the blood flow shearing off parts of the thrombus. (B) Crossing clots especially with a larger microcatheter (MC). (C) Crushing clots by struts of the SR. (D) Thrombus fragmentation by friction between the vessel wall and the thrombus while withdrawing it. (E) A temporary loss of apposition between the SR and the thrombus while withdrawing them into a large vessel from a smaller one. (F) Shearing off the thrombus by the sides of the balloon-guiding catheter (BGC) with a smaller lumen into which the thrombus is pulled.