Experimental Analysis of Intra-luminal Pressure by Contrast Injection during Mechanical Thrombectomy: Simulation of Rupture Risk of Hidden Cerebral Aneurysm in Tandem Occlusion with Blind Alley.

Mechanical thrombectomy using a retrograde approach is performed for tandem occlusion of the internal carotid artery (ICA). In our patient, a guiding catheter was easily passed by the stenosed lesion despite severe stenosis at the ICA origin. Therefore, we aimed to recanalize the occlusion of the terminal ICA without angioplasty for the stenosed lesion. When contrast was injected, a massive extravasation of contrast from the C2 portion of the ICA was observed. It was speculated that the bleeding was caused by rupture of an aneurysm at that site due to increased intra-arterial pressure caused by the contrast injection to a blind alley, which was created by a wedged guiding catheter at severe stenosis at the ICA origin and the occlusion of the terminal ICA. Our simulation experiment using a silicon vascular model in this situation demonstrated that the elevation of intra-arterial pressure in such blind alley reached over 50, 100, and 200 mmHg by injection of contrast from a microcatheter, a 4-Fr inner catheter, and a 9-Fr balloon-guiding catheter, respectively. When a retrograde approach is planned for tandem occlusion of the ICA, even when the proximal lesion is easily passed, prior angioplasty for the proximal lesion should be considered to avoid wedging by catheter.