VARIATION AMONG HOSPITALS IN CORONARY-ANGIOGRAPHY PRACTICES AND OUTCOMES AFTER MYOCARDIAL-INFARCTION IN A LARGE HEALTH MAINTENANCE ORGANIZATION

Background Wide geographic variation in the use of coronary angiograph y after myocardial infarction has been documented internationally and within the United States. An associated variation in clinical outcomes has not been consistently demonstrated. Methods We assessed the risk of death from heart disease and of any heart disease event (death, rei nfarction, or rehospitalization) over a follow-up period of one to fou r years in 6851 patients hospitalized with acute myocardial infarction at 16 Kaiser Permanente hospitals from 1990 through 1992. The percent age age of patients who underwent angiography within three months afte r infarction ranged from 30 to 77 percent. We selected a subcohort of 1109 patients from three hospitals with higher rates of angiography an d four with lower rates for a record review to assess the severity of infarction, the number of coexisting conditions, treatments received, and the appropriateness and necessity of angiography, using establishe d criteria. Results The rates of angiography were inversely related to the risk of death from heart disease (P=0.03) and the risk of heart d isease events (P<0.001) among the 16 hospitals after adjustment for ag e, sex, race, coexisting conditions, and the location of the infarctio n (subendocardial vs. transmural). In the subcohort 440 patients met c riteria indicating that angiography was necessary and 669 did not. Amo ng the former, patients treated at hospitals with higher rates of angi ography had a lower risk of death and of any heart disease event than those treated at hospitals with lower rates (hazard ratios, 0.67 and 0 .72, respectively). Among the latter, the apparent benefits of being t reated at hospitals with higher angiography rates were smaller (hazard ratios, 0.85 to 0.90 for death and any heart disease event, respectiv ely). Conclusions During the one to four years after myocardial infarc tion, patients treated at hospitals with higher rates of angiography h ad more favorable outcomes than those treated at hospitals with lower rates. This association was stronger among patients for whom published criteria indicated that angiography was necessary.