Abstract 61: Limited Eligibility for Trials of Endovascular Therapy for Acute Ischemic Stroke in the US: A Population-Based Assessment
BACKGROUND: Definitive evidence of the effectiveness of mechanical embolectomy for acute ischemic strokes (AIS) is lacking. In light of the recently futile Interventional Management of Stroke (IMS) III Trial, several Phase III trials are underway or being designed to test combined IV/intra-arterial (IA) therapies in novel subgroups. With the concern that more trials are being undertaken than can be feasibly completed in a timely manner, we estimate the number of AIS patients eligible for IA trials in the US annually.
METHODS: We ascertained all AIS in 2005 seen in an ED among our 1.3 million Greater Cincinnati/Northern Kentucky (GCNK) population. Relevant data, including age, last known well (LKW) times, and NINDS/ECASS3 eligibility criteria for IV rtPA, were abstracted from patient charts. We assumed that patients <18 or >85 years, with NIHSS<8 or with prior disability (modified Rankin >2) would not be enrolled in IA trials. We also assumed that door to randomization would typically be 60 minutes and randomization to IA therapy would be 60 minutes; thus LKW needed to be <6 hours to initiate IA therapy at <8 hours (per FDA clearance). Regional IA-trial eligibility rates were then age/race/sex-adjusted to the 2010 US census data to estimate national rates.
RESULTS: In 2005,1842 AIS had ED encounters among GCNK residents, and 434 (24%) were NIHSS≥8. After overlapping exclusions of age (23%), baseline disability (46%), and time (38% >6 hrs, 20% undocumented), 86 AIS met potential eligibility for IA trials. Among these, 77 (90%) arrived within 3.5 hours, including 57 IV rtPA-eligible. After adjustment, we estimate 410,000 AIS presentations to a US ED annually, and 16,663 (4.1%) eligible for IV/IA trials (19,500 for all IA trials).
CONCLUSIONS: Our estimate of 16,663 (4.1%) AIS that might qualify for IV/IA trials annually will be reduced dramatically by additional patient selection criteria (thrombus, core, higher NIHSS), availability/participation of recruiting centers, transport delays, and non-consent by subjects/surrogates; literature-based projections will be provided at the presentation. The stroke field will need to minimize trials, collaborate internationally, and/or pool trial data to complete a definitive, Phase III trial in a timely (5-year) manner.
- © 2012 by American Heart Association, Inc.