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Table 4 Cox proportional hazard model for cumulative all-cause mortality after thoracic aorta replacement surgery

From: Association between institutional case volume and mortality following thoracic aorta replacement: a nationwide Korean cohort study

  Univariable model Multivariable model
HR (95% CI) P HR (95% CI) P
Case volume strata
 High volume (> 60 cases/year) Reference   Reference  
 Low & medium volume (≤60 cases/year)a 1.53 (1.37–1.70) < 0.001 1.55 (1.38–1.74) < 0.001
Age
 ≤ 49 Reference   Reference  
 50–59 1.23 (0.98–1.53) 0.070 1.27 (1.02–1.58) 0.036
 60–69 1.80 (1.49–2.18) < 0.001 1.87 (1.54–2.28) < 0.001
 70–79 3.08 (2.58–3.67) < 0.001 3.24 (2.67–3.93) < 0.001
 ≥ 80 4.22 (3.39–5.25) < 0.001 4.70 (3.73–5.93) < 0.001
Female 0.97 (0.88–1.08) 0.621 0.73 (0.65–0.82) < 0.001
Extracardiac arteriopathy 1.43 (1.24–1.65) < 0.001 1.15 (1.00–1.33) 0.058
Renal impairment 3.02 (2.23–4.09) < 0.001 1.89 (1.39–2.58) < 0.001
Chronic lung disease 1.34 (1.20–1.49) < 0.001 1.02 (0.91–1.14) 0.701
Hypertension 1.29 (1.16–1.44) < 0.001 0.94 (0.83–1.06) 0.320
Hyperlipidemia 1.25 (1.11–1.41) < 0.001 1.01 (0.89–1.15) 0.896
Diabetes 1.49 (1.25–1.76) < 0.001 1.07 (0.90–1.28) 0.448
Angina pectoris 1.23 (1.09–1.39) 0.001 0.99 (0.87–1.13) 0.852
Recent MI 1.43 (1.02–2.01) 0.040 1.22 (0.86–1.73) 0.269
History of PCI 1.94 (1.28–2.93) 0.002 1.05 (0.68–1.61) 0.829
Congestive heart failure 1.44 (1.22–1.70) < 0.001 1.17 (0.98–1.40) 0.081
Emergent surgery 1.35 (1.07–1.71) 0.012 1.37 (1.07–1.75) 0.012
Atrial fibrillation 1.45 (1.17–1.81) 0.001 1.17 (0.93–1.46) 0.178
Perioperative RBC Transfusion
 0–1 units Reference   Reference  
 2–3 units 2.32 (1.56–3.44) < 0.001 1.80 (1.21–2.67) 0.004
 4–5 units 3.76 (2.52–5.59) < 0.001 2.74 (1.83–4.08) < 0.001
 6- units 9.02 (6.09–13.37) < 0.001 5.95 (4.00–8.85) < 0.001
Surgery site
 Ascending aorta Reference   Reference  
 Aortic arch 1.72 (1.41–2.09) < 0.001 1.46 (1.20–1.79) < 0.001
 Descending thoracic aorta 1.10 (0.95–1.27) 0.193 1.25 (1.06–1.46) 0.006
 Combined 1.02 (0.90–1.16) 0.760 1.08 (0.94–1.23) 0.287
  1. CI Confidence interval, HR Hazard ratio, MI Myocardial infarction, PCI Percutaneous coronary intervention, RBC Red blood cell
  2. aLow- and medium-volume groups were merged into one group prior to the multivariable analysis to meet the proportional hazard assumption
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