Abstract
BACKGROUND: Cardiologists are increasingly moving from independent practice to direct employment by hospitals. Hospital employment has the potential to improve care coordination and delivery, but little is known about its effect on care quality and outcomes. OBJECTIVES: In this study, we sought to assess the association between hospital employment of cardiologists and patient outcomes, care quality, and utilization among patients hospitalized with incident acute myocardial infarction (AMI) or heart failure (HF). METHODS: We used a sample of Medicare fee-for-service beneficiaries hospitalized with incident AMI or HF from 2008 to 2019. We identified the accountable cardiologists that cared for these patients and determined their employment status by means of tax identification numbers. We used difference-in-differences methods to compare clinical outcomes, quality measures, and utilization for patients treated by hospital-employed cardiologists after switching from independent to hospital-employed practice, to outcomes for patients treated by cardiologists who remained independent. Models were adjusted for time trends and patient, hospital, and cardiologist characteristics. Patient outcomes were in-hospital mortality, 30-day mortality, and 30-day readmission. Quality measures were receipt of: 1) a guideline-recommended test to assess cardiac function; and 2) a 30-day follow-up clinic visit. Utilization measures were length of stay and, for AMI patients, the proportion receiving coronary revascularization. RESULTS: The proportion of U.S. cardiologists employed by hospitals increased from 26% in 2008 to 63% in 2019. We identified 186,052 AMI and 259,849 HF patients cared for by cardiologists who switched to hospital employment and 168,052 AMI and 245,769 HF patients cared for by independent cardiologists. Patient characteristics were similar (mean age 80.8 years; 47% men). We found no significant differences in outcomes (eg, adjusted difference in 30-day mortality 0.03% [95% CI: -0.39% to 0.45%] for AMI patients and -0.05% [95% CI: -0.37% to 0.27%] for HF patients); no differences in most quality metrics except a small increase in the proportion of HF patients with 30-day follow-up (adjusted difference: 1.04%; 95% CI: 0.46%-1.62%); and no differences in utilization between patients treated by hospital-employed cardiologists (postswitch) vs independent cardiologists. CONCLUSIONS: Among U.S. cardiologists, there has been a large shift from independent practice to direct employment by hospitals. We found minimal evidence that cardiologist employment by hospitals improves care quality or outcomes.