J Korean Med Sci.  2022 Sep;37(36):e270. 10.3346/jkms.2022.37.e270.

Annual Case Volume and One-Year Mortality for Endovascular Treatment in Acute Ischemic Stroke

  • 1Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea
  • 2Department of Neurology, Korea University Guro Hospital, Seoul, Korea
  • 3Department of Neurology, Inje University Ilsan Paik Hospital, Goyang, Korea
  • 4Department of Neurology, Uijeongbu Eulji Medical Center, Eulji University, Uijeongbu, Korea
  • 5Department of Neurology, Soonchunhyang University Hospital, Soonchunhyang University College of Medicine, Seoul, Korea
  • 6Department of Neurology, Dong-A University Hospital, Dong-A University College of Medicine, Busan, Korea
  • 7Clinical Research Center, Asan Institute for Life Sciences, Asan Medical Center, Seoul, Korea
  • 8Department of Biostatistics, Korea University College of Medicine, Seoul, Korea
  • 9Health Insurance Review and Assessment Service, Wonju, Korea
  • 10Department of Neurology, Gyeonggi Provincial Medical Center Icheon Hospital, Icheon, Korea
  • 11Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, Illinois.


The association between endovascular treatment (EVT) case volume per hospital and clinical outcomes has been reported, but the exact volume threshold has not been determined. This study aimed to examine the case volume threshold in this context.
National audit data on the quality of acute stroke care in patients admitted via emergency department, within 7 days of onset, in hospitals that treated ≥ 10 stroke cases during the audit period were analyzed. Ischemic stroke cases treated with EVT during the last three audits (2013, 2014, and 2016) were selected for the analysis. Annual EVT case volume per hospital was estimated and analyzed as a continuous and a categorical variable (in quartiles). The primary outcome measure was 1-year mortality as a surrogate of 3-month functional outcome. As post-hoc sensitivity analysis, replication of the study results was examined using the 2018 audit data.
We analyzed 1,746 ischemic stroke cases treated with EVT in 120 acute care hospitals. The median annual EVT case volume was 12.0 cases per hospital, and mortality rates at 1 month, 3 months, and 1 year were 12.7%, 16.6%, and 23.3%, respectively. Q3 and Q4 had 33% lower odds of 1-year mortality than Q1. Adjustments were made for predetermined confounders. Annual EVT case volume cut-off value for 1-year mortality was 15 cases per year (P < 0.02). The same cut-off value was replicated in the sensitivity analysis.
Annual EVT case volume was associated with 1-year mortality. The volume threshold per hospital was 15 cases per year.


Endovascular Treatment; Acute Stroke; Clinical Outcomes; Volume Threshold


  • Fig. 1 Distribution of annual EVT case volume among 120 hospitals.EVT = endovascular treatment.

  • Fig. 2 Predicted probabilities of non-linear effects of annual EVT case volume. Predicted probabilities of non-linear effects of annual EVT case volume on unadjusted and adjusted 1-month (A, P = 0.020 [P < 0.001 for overall effect]; B, P = 0.152 [P < 0.001 for overall effect]), 3-month (C, P = 0.008 [P < 0.001 for overall effect]; D, P = 0.081 [P < 0.001 for overall effect]), and 1-year mortality (E, P < 0.001 [P < 0.001 for overall effect]; F, P = 0.021 [P = 0.006 for overall effect]). Adjusted for age, sex, NIHSS score, and onset-to-door time (min).EVT = endovascular treatment, NIHSS = National Institute of Health Stroke Scale.

  • Fig. 3 Predicted probabilities of linear effect of annual EVT case volume. Predicted probabilities of linear effect of annual EVT case volume on unadjusted and adjusted 1-month (A, P < 0.001; B, P < 0.001), 3-month (C, P < 0.001, D, P < 0.001), and 1-year mortality (E, P = 0.102; F, P = 0.041). Adjusted for age, sex, NIHSS score, and onset-to-door time (min).EVT = endovascular treatment, NIHSS = National Institute of Health Stroke Scale.


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