Sex Differences in Access to Coronary Revascularization after Cardiac Catheterization: Importance of Detailed Clinical Data

BACKGROUND: Although some studies suggest that access to cardiac procedures may differ by sex, others have found no evidence of gender bias in cardiac care. OBJECTIVE: To study rates of percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) surgery in men and women after cardiac catheterization. DESIGN: Cohort study with prospective data collection. SETTING: Alberta, Canada. PATIENTS: Persons undergoing cardiac catheterization between 1 January 1995 and 31 December 1998 (n = 21 816). MEASUREMENTS: The occurrence of revascularization procedures (PCI or CABG) in the year after cardiac catheterization was measured. Unadjusted revascularization rates, partially adjusted rates (adjusted for clinical variables available in most databases, including administrative databases), and fully adjusted rates (additionally adjusted for extent of coronary artery disease and ejection fraction) were also evaluated. RESULTS: The unadjusted relative risk was 0.67 (95% CI, 0.65 to 0.71) for the end point of any revascularization in women relative to men. The relative risk increased to 0.69 (CI, 0.66 to 0.72) with partial adjustment and to 0.98 (CI, 0.94 to 1.03) with full adjustment, indicating equivalent access to revascularization for men and women. For PCI, the corresponding relative risks were 0.77 (CI, 0.73 to 0.82), 0.84 (CI, 0.80 to 0.89), and 1.02 (CI, 0.96 to 1.08). For CABG surgery, the relative risks were 0.54 (CI, 0.51 to 0.58), 0.51 (CI, 0.48 to 0.55), and 0.93 (CI, 0.87 to 1.01). CONCLUSIONS: In Alberta, Canada, clinical variables fully explain sex differences in rates of revascularization after cardiac catheterization, and misleading conclusions would arise without full adjustment for clinical differences between men and women. Extreme caution is needed in interpreting reports on access to care that use sparsely detailed clinical data sources.