In a managed care setting, are there sex differences in the use of coronary angiography after acute myocardial infarction?

OBJECTIVES: The goal of this study was to examine sex differences in the use of coronary angiography after acute myocardial infarction in managed care facilities by using the American College of Cardiology/American Heart Association (ACC/AHA) practice guidelines (which incorporate clinical information on infarct complications, severity of illness, and comorbidity).
BACKGROUND: Although sex differences in the use of coronary angiography after acute myocardial infarction have been previously explored, the effects of indications for coronary angiography and common health insurance coverage on the sex and coronary angiography use relation have not been previously examined.
METHODS: This historical prospective study analyzed data collected from a random sample of 1133 patients (377 women, 756 men) from among 2740 patients hospitalized with validated acute myocardial infarction between Jan. 1, 1990, and Dec. 31, 1992, from seven of 16 Northern California Kaiser Facilities (three with high procedure rates for coronary angiography, four with low rates relative to the average region-wide utilization rate). In accordance with the guidelines, use of coronary angiography was determined for the in-hospital and "0 to 8 weeks" postdischarge periods. Patients were assigned time specific ACC/AHA classes for coronary angiography indications (I = highly indicated, IIA = probably indicated, IIB = not harmful, III = not indicated). The independent impact of ACC/AHA class, age, race, and facility on the sex and use of coronary angiography relation was examined by the Cox proportional hazard model.
RESULTS: Accounting only for ACC/AHA class, fewer women underwent coronary angiography compared with men among the "highly indicated" class I patients during the in-hospital period (43% vs 35%; p < 0.05), but not after discharge. Use of coronary angiography between the sexes was not statistically different among classes IIA, IIB, and III for both periods. After adjusting for differences in age, race, facility, and ACC/AHA class, we found no sex difference in in-hospital use of coronary angiography (hazard ratio (HR) = 1.02; 95% confidence interval [CI], 0.82 to 1.26), but among those discharged without receiving coronary angiography, women probably received fewer angiograms than did men (HR = 0.61; 95% CI, 0.37 to 1.00). For both periods, no significant sex difference in use of coronary angiography was found within ACC/AHA classes after adjustments.
CONCLUSION: In a setting where health insurance is prepaid and after controlling for ACC/AHA classification for coronary angiography indications, age, race, and facility, use of coronary angiography after myocardial infarction was similar among men and women during hospitalization, but was lower among women after discharge. Likely explanations for these differences in use of coronary angiography may include effects of physician judgment, patient decision, other social factors, or clinical information not captured in the practice guidelines.