Area socioeconomic status and mortality after coronary artery bypass graft surgery: the role of hospital volume

Am Heart J. 2007 Aug;154(2):385-90. doi: 10.1016/j.ahj.2007.04.052.


Background: Individuals of low socioeconomic status (SES) have reduced access to coronary artery bypass graft surgery (CABG). It is unknown if low-SES CABG patients have reduced access to hospitals with better outcomes.

Methods: We conducted a retrospective cohort analysis of the California CABG Mortality Reporting Program, consisting of individuals with zip code information who underwent CABG at participating hospitals in 1999-2000 (n = 18,961). Primary outcome measures were inhospital mortality after CABG; primary independent variables of interest were area-level SES, clinical risk factors, and hospital volume. We used 2-level hierarchical random-effects logit models to estimate the relationship between explanatory variables and inhospital mortality.

Results: Within high-volume hospitals, patients of low-SES areas had greater mortality than those of mid- and high-SES areas (2.5% vs 1.5% vs 1.8%, P = .024). However, there was no relationship between SES and mortality in lower-volume hospitals. Contrary to expectations, individuals of high-SES areas (42%) underwent surgery at low-volume hospitals more often than patients of low-SES areas (28%, P < .001), although mortality at low-volume hospitals was greater than that at high-volume facilities (P < .001). Discrepancies were not explained by distance traveled.

Conclusions: Mortality after CABG is modified by both SES and hospital volume. Within high-volume hospitals, patients of low-SES areas fared worse than patients of higher-SES areas. Patients of high SES tended to have CABG surgery at low-volume hospitals where mortality was greater and therefore had higher mortality than expected.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • California / epidemiology
  • Coronary Artery Bypass / mortality*
  • Coronary Artery Bypass / statistics & numerical data
  • Female
  • Hospital Mortality
  • Hospitals / statistics & numerical data*
  • Humans
  • Male
  • Middle Aged
  • Retrospective Studies
  • Social Class*