Modeling Perforator Occlusion After Flow Diversion.

Endoluminal flow diverters are increasingly used to treat cerebral aneurysms. Despite good aneurysm occlusion efficacy, delayed ischemic complications due to side branch or perforator occlusion remain a serious concern. However, the mechanisms leading to side branch occlusion are poorly understood. To investigate these mechanisms, a combination of animal and computational models was utilized. Flow diverters were deployed in four rabbit superior mesenteric artery (SMA) and studied with computational fluid dynamics (CFD) and a previously developed fibrin dynamics model. Subject-specific vascular models were reconstructed from 3D rotational angiography images and flow conditions were derived from Doppler ultrasound velocity measurements. Flow diverting devices were virtually deployed within the vascular models under guidance from angiography images. Coupled flow and fibrin production, transport, and adhesion simulations were carried out and the effects of fibrin accumulation at the origin of jailed side branches after flow diverter implantation were analyzed. The results of the computational models suggest significant fibrin accumulation across the struts of all flow diverting devices jailing side branches. Larger accumulation was observed at the more distal branches. However, minor flow alterations were produced which were not detectable in angiography sequences. These results were in agreement with experimental observations. On the other hand, fibrin accumulation alone did not explain complete side branch occlusions, which are likely the result of the interaction between initial fibrin accumulation and subsequent cell migration from the peripheral parent artery.