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 angiography 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, reinfarction, or rehospitalization) over a follow-up period of one to four years in 6851 patients hospitalized with acute myocardial infarction at 16 Kaiser Permanente hospitals from 1990 through 1992. The percentage of patients who underwent angiography within three months after infarction ranged from 30 to 77 percent. We selected a subcohort of 1109 patients from three hospitals with higher rates of angiography and 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 established 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 disease events (P<0.001) among the 16 hospitals after adjustment for age, sex, race, coexisting conditions, and the location of the infarction (subendocardial vs. transmural). In the subcohort, 440 patients met criteria indicating that angiography was necessary and 669 did not. Among the former, patients treated at hospitals with higher rates of angiography 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 treated at hospitals with higher angiography rates were smaller (hazard ratios, 0.85 to 0.90 for death and any heart disease event, respectively).


CONCLUSIONS
During the one to four years after myocardial infarction, patients treated at hospitals with higher rates of angiography had 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.
Selby
J V
JV
Division of Research, Kaiser Permanente Medical Care Program (Northern California Region), Oakland, CA 94611, USA.
Fireman
B H
BH
Lundstrom
R J
RJ
Swain
B E
BE
Truman
A F
AF
Wong
C C
CC
Froelicher
E S
ES
Barron
H V
HV
Hlatky
M A
MA
D000368:Aged; D002140:California; D015331:Cohort Studies; D017023:Coronary Angiography / Q000706:statistics & numerical data*; D005260:Female; D006331:Heart Diseases / Q000401:mortality*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging*; D017063:Outcome Assessment, Health Care; D012044:Regression Analysis; D012189:Retrospective Studies; D012306:Risk