Abstract WP129: The Heat Grading Scale as a Neurovascular Remodeling Based Score in Aneurysms Treated With Flow Diversion

Abstract

Objective: To apply principles of neurovascular remodeling in the classification of flow diverted aneurysms to predict outcomes using the HEAT (Hemodynamics, Endothelialization and Aneurysmal Thrombosis) grading scale. Introduction: The goal of flow diversion is to exclude an aneurysm from circulation through endothelialization of the aneurysmal neck and hemodynamic induction of aneurysmal thrombosis. Current grading scales do not include the above parameters to evaluate aneurysms after flow diversion. Methods: Reconstructions using 360° virtual reality (VR) models based on volumetric digital subtraction angiography (DSA) scans of unruptured, wide-neck intracranial aneurysms treated with Pipeline™ from March 2010 to May 2018 at our comprehensive stroke center were built using Surgical Theatre ® . The HEAT grading scale was used to generate a 0 to 15-point score that evaluated residual filling (none 0%, entry remnant <5%, subtotal 5-95%, total >95%), stasis phase (persistent contrast at venous phase, clearance before venous phase, arterial clearance before capillary phase), endoleak (absence, presence), free-hanging edge (absent, present without thrombus, present with thrombus), in-stent stenosis (0-29% minimal, 30-49% mild, 50-69% moderate, 70-94% severe, 95-99% critical), and branch filling (complete, partial TICI 2b >50%, partial TICI 2a <50%, insufficient). Each case was assigned a HEAT score by four neurointerventionalists using DSA, CT angiography (CTA), and the VR model. Results: Fifty out of 86 Pipeline™ cases had 3D rotational DSA and met technical standards required to build the VR model. Clinical adverse events including central retinal artery occlusion, middle cerebral artery syndrome, and amaurosis fugax were positively associated with HEAT score (n=3, p=<0.001) as were subclinical adverse events including endoleak (n=2) and free-hanging edge with thrombus (n=2) (p=<0.001). Interrater variability was high (k=0.8). Conclusion: The HEAT grading scale is sensitive, reproducible, and associated with clinical outcome. Larger prospective studies are warranted to validate our results.