The effect of increases in HMO penetration and changes in payer mix on in-hospital mortality and treatment patterns for acute myocardial infarction.
OBJECTIVE
To determine whether changes in health maintenance organization (HMO) penetration or payer mix affected in-hospital mortality and treatment patterns of patients with acute myocardial infarction (AMI).


METHODS
Observational study using patient-level logistic regression analysis and hospital and year fixed effects of data from the Agency for Healthcare Research and Quality's Healthcare Cost and Utilization Project Nationwide Inpatient Sample, a geographically diverse sample of 20% of the hospitalized patients in the United States.


METHODS
Discharges of patients (n = 340,064) with a primary diagnosis of acute myocardial infarction who were treated in general medical or surgical hospitals that contributed at least 2 years of data to the HealthCare Cost and Utilization Project Nationwide Inpatient Sample from 1989 to 1996. In-hospital mortality and rates of cardiac catheterization, angioplasty, or coronary artery bypass grafting for Medicare patients or non-Medicare patients were the main outcome measures.


RESULTS
Among Medicare patients, increases in HMO penetration were associated with reduced odds of receiving cardiac catheterization, angioplasty, or coronary artery bypass grafting of 3% to 16%, but were not associated with any change in mortality risk. Increases in the number of HMOs within a metropolitan statistical area, our measure of HMO competition, were associated with small but significant increases in the odds of cardiac catheterization and angioplasty of about 2%. There was no pattern of changes in cardiac procedure rates or in-hospital mortality among non-Medicare patients.


CONCLUSIONS
Increases in HMO penetration reduced cardiac procedure rates by statistically significant but small amounts among Medicare patients with AMI, without affecting mortality rates.
Center for Health Equity Research and Promotion, Philadelphia Veterans Hospital, and Department of Medicine, School of Medicine, University of Pennsylvania, Philadelphia 19104-6021, USA. volpp70@mail.med.upenn.edu
Kevin G M
KG
Volpp
Edward
E
Buckley
D000368:Aged; D005260:Female; D006279:Health Maintenance Organizations; D006302:Health Services Research; D017052:Hospital Mortality / Q000639:trends*; D006801:Humans; D019458:Insurance Coverage / Q000706:statistics & numerical data; D008297:Male; D006278:Medicare; D009203:Myocardial Infarction / Q000401:mortality* / Q000601:surgery; D010818:Practice Patterns, Physicians'; D012044:Regression Analysis; D020379:Risk Adjustment; D014481:United States / Q000453:epidemiology