title: Intra-arterial Stroke Treatment prior to the Stent-Retriever Era: High Mortality and Lack of Volume-Outcome Association.
abstract: BACKGROUND
  Mechanical thrombectomy for acute large-vessel occlusive stroke is beneficial when performed with stent-retriever devices; however, little is known about real-world experience with intra-arterial treatment (IAT). We aimed to clarify how hospitals influence outcomes for Medicare thrombectomy patients to inform future delivery of effective mechanical thrombectomy treatment.
  
  
  METHODS
  This is a retrospective cohort study that includes a Medicare fee-for-service patient population. Patients with a primary stroke discharge (ICD-9-CM 433.x1, 434.x1, 436) were included; billing codes were used to identify patients receiving IAT, intravenous thrombolytics (IVT), or a combination of these treatments. Characteristics of treated patients were summarized using descriptive statistics; long-term mortality was summarized via Kaplan-Meier curves; and multilevel logistic regression models with random hospital-level intercept were built to determine hospital influence on outcome and whether a volume-outcome association existed.
  
  
  RESULTS
  A total of 4557 patients received IAT at 544 hospitals. The mean age of IAT patients was 76 years. IAT patients had longer hospital stay (9.7 versus 6.8 days), longer stay in the ICU (5.5 versus 3.3 days), and greater probability of intubation (36.7% versus 9.5%) compared with IVT patients. Ninety-day mortality was 46% IAT versus 26% IVT. Hospitals had little influence on outcomes (intraclass correlation coefficient, <.01). No association between procedural volume and outcomes was identified.
  
  
  CONCLUSIONS
  IAT for 2007-2010 was associated with higher patient mortality than recent and prior clinical trials. Treated Medicare patients were considerably older than clinical trial populations. Hospitals had little influence on mortality, and increased hospital volume was not associated with lower mortality. Future real-world experience should monitor these parameters as use of stent retrievers disseminates.
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan. Electronic address: adityap@med.umich.edu.
authors.forename: Aditya S
authors.initials: AS
authors.lastname: Pandey
authors.affiliation: Department of Emergency Medicine, University of Michigan, Ann Arbor, Michigan; Department of Neurology, University of Michigan, Ann Arbor, Michigan.
authors.forename: William J
authors.initials: WJ
authors.lastname: Meurer
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Neeraj
authors.initials: N
authors.lastname: Chaudhary
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Gemmete
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan.
authors.forename: B Gregory
authors.initials: BG
authors.lastname: Thompson
authors.affiliation: Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan; Department of Emergency Medicine, University of Michigan, Ann Arbor, Michigan; Department of Neurology, University of Michigan, Ann Arbor, Michigan.
authors.forename: Lewis B
authors.initials: LB
authors.lastname: Morgenstern
authors.affiliation: Department of Neurology, University of Michigan, Ann Arbor, Michigan.
authors.forename: James F
authors.initials: JF
authors.lastname: Burke
mesh_terms: D061605:Administration, Intravenous; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D057510:Endovascular Procedures / Q000009:adverse effects / Q000295:instrumentation* / Q000401:mortality; D005260:Female; D005343:Fibrinolytic Agents / Q000008:administration & dosage* / Q000009:adverse effects; D061847:Hospitals, High-Volume; D061846:Hospitals, Low-Volume; D006801:Humans; D053208:Kaplan-Meier Estimate; D007902:Length of Stay; D016015:Logistic Models; D008297:Male; D006278:Medicare; D015999:Multivariate Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D015607:Stents; D020521:Stroke / Q000175:diagnosis / Q000401:mortality / Q000628:therapy*; D017131:Thrombectomy / Q000009:adverse effects / Q000295:instrumentation* / Q000401:mortality; D015912:Thrombolytic Therapy / Q000009:adverse effects / Q000401:mortality; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States
chemical_list: D005343:Fibrinolytic Agents
keywords: Mechanical thrombectomy; endovascular stroke therapy; stent retrievers; surgical volume–outcome; volume–outcome relationships