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Does physician specialty affect the survival of elderly patients with myocardial infarction?
C D Frances1, M G Shlipak, H Noguchi
1Department of Medicine, University of California, San Francisco, USA.
Insights
Treatment by a cardiologist for elderly patients with acute myocardial infarction (AMI) showed significant differences in care but no significant reduction in one-year mortality. Advanced statistical methods confirmed no incremental mortality benefit from cardiologist care.
Area of Science:
- Cardiology
- Geriatric Medicine
- Health Services Research
Background:
- Elderly patients with acute myocardial infarction (AMI) represent a vulnerable population with complex healthcare needs.
- The impact of specialist care, specifically by cardiologists, on mortality outcomes in this demographic requires rigorous investigation.
- Existing studies may be limited by confounding factors, necessitating advanced statistical approaches to isolate treatment effects.
Purpose of the Study:
- To evaluate the effect of cardiologist treatment on mortality in elderly patients experiencing AMI.
- To account for measured and unmeasured confounding variables using risk-adjustment and instrumental variable (IV) methods.
- To compare outcomes based on whether patients were admitted by a cardiologist.
Main Methods:
- Retrospective cohort study utilizing medical chart and administrative hospital/death records for 161,558 elderly patients with AMI.
- Comparison of least squares (LS) multivariate regression with IV methods to adjust for unmeasured patient characteristics.
- Primary outcomes: 30-day and one-year mortality. Secondary outcomes: medication use and revascularization procedures.
Main Results:
- Patients admitted by cardiologists had less severe AMIs and fewer comorbidities.
- Initial analysis showed a 10% lower one-year mortality for cardiologist-admitted patients; LS regression adjusted this to 2%.
- IV analysis revealed a statistically insignificant association between cardiologist admission and one-year mortality (RR 0.96).
Conclusions:
- Despite observed treatment differences, including higher rates of revascularization and certain medications, no significant incremental mortality benefit was found for elderly AMI patients treated by cardiologists.
- Advanced statistical methods, particularly IV, suggest that unmeasured factors may explain the initial observed survival advantage.
- The findings highlight the importance of controlling for unmeasured confounding in observational studies of healthcare interventions.
Objective:
To determine the effect of treatment by a cardiologist on mortality of elderly patients with acute myocardial infarction (AMI, heart attack), accounting for both measured confounding using risk-adjustment techniques and residual unmeasured confounding with instrumental variables (IV) methods.
Data Sources/Study Setting:
Medical chart data and longitudinal administrative hospital records and death records were obtained for 161,558 patients aged > or =65 admitted to a nonfederal acute care hospital with AMI from April 1994 to July 1995. Our principal measure of significant cardiologist treatment was whether a patient was admitted by a cardiologist. We use supplemental data to explore whether our analysis would differ substantially using alternative definitions of significant cardiologist treatment.
Study Design:
This retrospective cohort study compared results using least squares (LS) multivariate regression with results from IV methods that accounted for additional unmeasured patient characteristics. Primary outcomes were 30-day and one-year mortality, and secondary outcomes included treatment with medications and revascularization procedures.
Data Collection/Extraction Methods:
Medical charts for the initial hospital stay of each AMI patient underwent a comprehensive abstraction, including dates of hospitalization, admitting physician, demographic characteristics, comorbid conditions, severity of clinical presentation, electrocardiographic and other diagnostic test results, contraindications to therapy, and treatments before and after AMI.
Principal Findings:
Patients admitted by cardiologists had fewer comorbid conditions and less severe AMIs. These patients had a 10 percent (95 percent CI: 9.5-10.8 percent) lower absolute mortality rate at one year. After multivariate adjustment with LS regression, the adjusted mortality difference was 2 percent (95 percent CI: 1.4-2.6 percent). Using IV methods to provide additional adjustment for unmeasured differences in risk, we found an even smaller, statistically insignificant association between physician specialty and one-year mortality, relative risk (RR) 0.96 (0.88-1.04). Patients admitted by a cardiologist were also significantly more likely to have a cardiologist consultation within the first day of admission and during the initial hospital stay, and also had a significantly larger share of their physician bills for inpatient treatment from cardiologists. IV analysis of treatments showed that patients treated by cardiologists were more likely to undergo revascularization procedures and to receive thrombolytic therapy, aspirin, and calcium channel-blockers, but less likely to receive beta-blockers.
Conclusions:
In a large population of elderly patients with AMI, we found significant treatment differences but no significant incremental mortality benefit associated with treatment by cardiologists.