P-004 Publishing Title: Incidence of Large Vessel Occlusions Amongst All Hospital Discharges for Acute Ischemic Stroke – Estimating a Thrombectomy Eligible Population

BackgroundEndovascular therapy has been endorsed for emergent large vessel occlusions (ELVO). However the incidence of ELVO is ill defined and speculative. A methodical estimate of these patients is important for developing systems of care, resource allocation and market projections.ObjectiveTo determine the national burden of ELVO by extrapolating these rates from a tertiary rural health system that captures over 85% of all ischemic strokes within its large rural catchment area to the national inpatient sample (NIS) database.MethodologyAll hospital discharges with a primary or secondary diagnosis of AIS (ICD-9 433.xx, 434.xx, 435.xx) over a 3 year period in a rural tertiary health system in the “stroke-belt” were evaluated for ELVO (ICA-T, MCA, BA) based on admission CT or MR angiography. For anterior circulation strokes, an ASPECTS ≥6 was considered favorable for thrombectomy. The same ICD-9 codes were utilized to query the NIS-database to determine all AIS hospital discharges nationally and the ELVO rates were estimated based on the results from our catchment population.ResultsThere were 2757 AIS hospital discharges over a 3 year period (March 2012 to March 2015) based on the selected ICD-9 codes. An ELVO was present in 324 (11.8%) of these patients. Out of these, M1-occlusion was present in 232 (71.6%), ICA-T in 37 (11.4%) and BA in 55 (17%) patients. The majority of ELVO patients (n = 174, 53.7%) presented within 6 hours of last seen normal (LSN). Of the remaining 150 (46.3%) patients: 45 (13.6%) presented at 6–12 hours, 60 (18.5%) at 12–24 hours and 27 (8.3%) at greater than 24 hours of LSN. There were 19 (5.9%) patients with unknown LSN. For anterior circulation (n = 269, 83%) an ASPECTS ≥6 was observed in 118 of 150 (78.7%) patient presenting within 6 hours of LSN and in 66 of 1119 (55.5%) patients presenting after 6 hours of LSN (p < 0.0001). The same ICD-9 codes for the NIS-database returned 1,135,030 AIS discharges nationally for 2013. Applying the statistics from our population to the NIS-database yields 133,388 large vessel strokes nationally (95,512 M1, 15,233 ICA-T and 22,643 BA). Of these, 71,634 patients are estimated to present within 6 hours and 61,754 after 6 hours of LSN. There could be 48,579 patients within 6 hours and 27,172 patients after 6 hours with an ASPECTS ≥6 resulting in a total of 75,751 potential thrombectomy eligible patients in the anterior circulation.ConclusionAlmost 12% of the patients in our large rural sample of AIS