Influence of transfer-in rates on quality of care and outcomes at receiving hospitals in patients with non-ST-segment elevation myocardial infarction

Background: Patients with non-ST-segment elevation myocardial infarction (NSTEMI) are frequently transferred to tertiary hospitals for angiography and/or revascularization from hospitals lacking such capabilities. Given that patients who undergo invasive cardiac procedures are younger and have fewer comorbidities compared with those managed medically, the relative proportion of transfer-in patients at tertiary hospitals may influence comparisons of quality and guidelines adherence. Methods: We evaluated 142,092 NSTEMI patients treated at 396 revascularization-capable sites in the CRUSADE National Quality Improvement Initiative from 2001 to 2006. Transfer-in patients were included if they arrived at the receiving hospital after their first presentation to a different hospital. Hospitals were categorized into tertiles based upon their transfer-in rates (low, intermediate, and high) and adherence to practice guidelines recommendations for NSTEMI. In-hospital clinical outcomes were compared across hospital tertiles. Results: Acute and discharge composite guidelines adherence scores improved at hospitals with an increasing proportion of transfer-in patients, both for transferred as well as for directly admitted patients. These better adherence scores were inversely associated with overall mortality, with the lowest mortality observed in patients at hospitals with the highest transfer-in rates. However, once adjusted for baseline confounders, the mortality rates for patients in the hospitals in the highest transfer-in tertile did not differ significantly compared with the sites in the lowest transfer-in tertile (odds ratio 1.02, 95% CI 0.90-1.16). Conclusions: Our findings show that the proportion of NSTEMI patients transferred into revascularization-capable hospitals varies significantly. Hospitals with a higher proportion of transfer-in patients tend to provide higher overall quality of NSTE acute coronary syndrome care; they also have lower overall in-hospital mortality, which may, in part, be related to the lower-risk baseline characteristics of patients at these hospitals.