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Table 1 Patient characteristics across hospital volume groups

From: Volume-based referral for cardiovascular procedures in the United States: a cross-sectional regression analysis

Characteristics Hospital CABG Volume   Hospital PCI Volume  
  Overall Low (<450) High (≥450) P Overall Low (<400) High (≥400) P
% of patients (weighted) 100.0 38.4 61.6 - 100.0 14.0 86.0 -
% of hospital year groups* 100.0 69.8 30.2 - 100.0 45.1 54.9 -
Mean age, (SD) years 66.0 (0.07) 65.9 (0.08) 66.1 (0.11) 0.12 64.2 (0.08) 63.7 (0.12) 64.2 (0.09) <0.001
Age     0.11     <0.001
   Less than 65 41.1 41.7 40.7   48.7 50.7 48.3  
   65–74 years 34.5 34.2 34.7   28.8 27.6 29.0  
   75 years of age and older 24.4 24.1 24.6   22.5 21.7 22.6  
Male 69.5 69.4 69.5 0.90 65.5 64.4 65.7 <0.001
Race     0.014     0.016
   White 64.2 59.2 67.3   63.3 56.7 64.4  
   Black 3.8 3.8 3.9   4.5 5.1 4.4  
   Other 7.5 9.5 6.2   7.3 10.1 6.9  
   Race not reported/missing 24.5 27.6 22.6   24.9 28.1 24.4  
Primary payer     <0.001     <0.001
   Medicare 53.8 51.9 55.0   49.0 45.7 49.5  
   Medicaid 4.0 4.7 3.5   4.0 5.3 3.8  
   Private 37.3 37.4 37.3   41.2 40.6 41.4  
   Other/missing 4.9 6.0 4.2   5.8 8.4 5.4  
Diabetes 29.5 29.8 29.3 0.14 24.9 25.4 24.8 0.12
Hypertension 58.6 58.0 58.9 0.098 54.1 53.0 54.3 0.022
COPD 17.3 17.5 17.2 0.37 11.2 11.9 11.0 0.002
Congestive heart failure 17.6 17.5 17.7 0.64 9.9 10.7 9.8 <0.001
Peripheral vascular disease 7.6 7.5 7.6 0.55 5.6 5.4 5.6 0.43
Renal disease 6.0 5.8 6.1 0.11 2.6 2.9 2.5 <0.001
Coronary disease     <0.001     <0.001
   MI as primary diagnosis 20.3 20.1 20.4   31.0 37.6 29.9  
   MI as secondary diagnosis 5.7 6.3 5.3   4.5 5.0 4.4  
   Other coronary artery disease 65.6 65.5 65.7   60.2 53.1 61.4  
   No coronary disease 8.4 8.1 8.6   4.3 4.3 4.3  
Admission type     <0.001     <0.001
   Emergency 23.7 23.8 23.6   31.9 36.9 31.1  
   Urgent 25.2 22.1 27.1   26.1 23.6 26.5  
   Elective 41.5 38.6 43.4   32.3 21.5 34.1  
   Other/missing 9.6 15.6 5.9   9.6 18.1 8.2  
Arrived by inter-hospital transfer     <0.001     <0.001
   Yes 18.0 11.5 22.0   18.2 9.0 19.7  
   No 78.8 85.4 74.7   78.4 88.4 76.8  
   Unknown 3.2 3.2 3.3   3.4 2.7 3.6  
Year     0.59     0.17
   1998 25.4 26.0 25.1   22.0 25.6 21.4  
   1999 23.7 21.5 25.1   22.2 24.2 21.9  
   2000 25.5 25.2 25.7   26.0 25.6 26.1  
   2001 25.3 27.4 24.0   29.8 24.6 30.6  
Procedure-specific variables         
   Same admission PCI 2.8 3.3 2.4 <0.001 - - - -
   Concomitant valve procedure 10.6 9.5 11.3 <0.001 - - - -
   Internal mammary artery graft 16.8 13.4 18.8 <0.001 - - - -
   Multivessel PCI - - - - 14.5 14.8 12.6 <0.001
  1. Unless noted otherwise, findings are expressed as percentages
  2. Percentages may not sum to 100 due to rounding
  3. * Hospital year groups refer to the number of hospitals that contributed data in each year of the NIS. A hospital participating in the NIS over the 3 year period would be considered to have contributed 3 hospital year groups to the analysis.