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Alter DA, Naylor CD, Austin PC, Tu JV. Long-term MI Outcomes at Hospitals With or Without On-site Revascularization. JAMA. 2001;285(16):2101–2108. doi:10.1001/jama.285.16.2101
Author Affiliations: Institute for Clinical Evaluative Sciences (Drs Alter, Naylor, Austin, and Tu); Divisions of Cardiology, Schulich Heart Center (Dr Alter), and General Internal Medicine (Dr Tu), Sunnybrook and Women's College Health Science Center; and University of Toronto Clinical Epidemiology and Health Care Research Program (Drs Naylor and Tu), Department of Public Health Sciences (Drs Austin, Tu, and Naylor), and Dean's Office (Dr Naylor), Universtiy of Toronto, Toronto, Ontario.
Context Many studies have found that patients with acute myocardial infarction
(AMI) who are admitted to hospitals with on-site revascularization facilities
have higher rates of invasive cardiac procedures and better outcomes than
patients in hospitals without such facilities. Whether such differences are
due to invasive procedure rates alone or to other patient, physician, and
hospital characteristics is unknown.
Objective To determine whether invasive procedural rate variations alone account
for outcome differences in patients with AMI admitted to hospitals with or
without on-site revascularization facilities.
Design Retrospective, observational cohort study using linked population-based
administrative data from a universal health insurance system.
Setting One hundred ninety acute care hospitals in Ontario, 9 of which offered
Patients A total of 25 697 patients hospitalized with AMI between April
1, 1992, and December 31, 1993, of whom 2832 (11%) were in invasive hospitals.
Main Outcome Measures Mortality, recurrent cardiac hospitalizations, and emergency department
visits in the 5 years following the index admission, adjusted for patient
age, sex, socioeconomic status, illness severity, and index revascularization
procedures; attending physician specialty; and hospital volume, teaching status,
and geographical proximity to invasive-procedure centers and compared by hospital
Results Patients admitted to invasive-procedure hospitals were much more likely
to undergo revascularization (11.4% vs 3.2% at other hospitals; P<.001). However, many other clinical and process-related factors
differed between the 2 groups. Although mortality rates were similar between
the 2 institution types, the nonfatal composite 5-year event rate (ie, recurrent
cardiac hospitalization and emergency department visits) was lower for patients
initially admitted to invasive-procedure hospitals (71.3% vs 80.4%; unadjusted
odds ratio [OR], 0.65; 95% confidence interval [CI], 0.52-0.82; P<.001). This advantage persisted after adjustment for sociodemographic
and clinical factors and procedure utilization (adjusted OR, 0.68; 95% CI,
0.53-0.89; P<.001). However, the nonfatal outcome
advantages of invasive-procedure hospitals were explained by their teaching
status (adjusted OR, 0.98; 95% CI, 0.73-1.30; P =
Conclusions In this sample of patients admitted with AMI, the differing outcomes
of apparently similar patients treated in 2 different practice settings were
explained by multiple competing factors. Researchers conducting observational
studies should be cautious about attributing patient outcome differences to
any single factor.
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