Abstract TP436: MyRIAD Mechanisms of Recurrent Stroke in Intracranial Atherosclerotic Disease

Abstract

Background: The NINDS-funded Mechanisms of Early Recurrence in Intracranial Atherosclerotic Disease (MyRIAD) study used a battery of MRI and TCD techniques to discern key pathophysiology leading to a relatively high rate of recurrent stroke. Our study objectives aimed to relate imaging abnormalities of limited arterial blood flow, distal tissue perfusion and artery-to-artery emboli with new infarcts on 6-8 week MRI. Methods: MyRIAD is a prospective, multicenter, observational study of patients with recent (<21 days) ischemic stroke or TIA due to 50-99% ICAD. Quantitative MRA (QMRA), perfusion MRI and TCD vasomotor reactivity (VMR) with emboli detection (ED) were acquired at enrollment. Central adjudication of each imaging modality, clinical events and 6-8 week MRI were independently ascertained. Results: MyRIAD enrolled 105 (mean age 63.7 years, SD 11.8 years; 43% women) patients. Primary outcomes of recurrent stroke in the territory occurred in 9/105 (9%) with secondary outcomes of territorial TIA in 7/105 (7%) and new infarcts on 6-8 week MRI in 22/87 (25%). The limited number of clinical stroke and TIA endpoints precluded definitive analysis of mechanism. Pre-specified Tmax>4s 10 cc lesions on perfusion MRI were noted in 40/92 (43%) but did not predict new infarcts at 6-8 week MRI. New infarcts were noted in 12/44 (27%) of those with Tmax>4s 5 cc lesions at baseline compared to 3/26 (12%) when absent. Abnormal volume flow ratio (VFR) on QMRA was noted in 25/98 (26%), abnormal TCD VMR in 25/76 (33%) and ED in 30/74 (41%). Other pre-specified analyses revealed both abnormal VMR and ED in 21/77 (27%) and both abnormal Tmax>4s perfusion and VFR in 16/99 (16%). Two or more imaging abnormalities were noted at baseline in 49/105 (47%) and stenosis ≥ 70% in 76/91 (84%). New infarcts on 6-8 week MRI were more frequent with ≥ 2 abnormalities (33 vs 18%, p=0.1) and ≥ 70% stenosis (29 vs 7%, p=0.2). Conclusions: Early, recurrent infarction on MRI is common in ICAD. Imaging abnormalities of limited arterial blood flow or distal tissue perfusion and artery-to-artery emboli are frequent and the presence of multiple abnormalities may increase risk. Larger ICAD studies are needed to link routinely acquired imaging with covert infarcts and cognitive impairment.