Interhospital transfers among Medicare beneficiaries admitted for acute myocardial infarction at nonrevascularization hospitals

Abstract

Background: Patients with acute myocardial infarction (AMI) who are admitted to hospitals without coronary revascularization are frequently transferred to hospitals with this capability, yet we know little about the basis for how such revascularization hospitals are selected.

Methods and results: We examined interhospital transfer patterns in 71 336 AMI patients admitted to hospitals without revascularization capabilities in the 2006 Medicare claims using network analysis and regression models. A total of 31 607 (44.3%) AMI patients were transferred from 1684 nonrevascularization hospitals to 1104 revascularization hospitals. Median time to transfer was 2 days. Median transfer distance was 26.7 miles, with 96.1% within 100 miles. In 45.8% of cases, patients bypassed a closer hospital to go to a farther hospital that had a better 30-day risk standardized mortality rates. However, in 36.8% of cases, another revascularization hospital with lower 30-day risk-standardized mortality was actually closer to the original admitting nonrevascularization hospital than the observed transfer destination. Adjusted regression models demonstrated that shorter transfer distances were more common than transfers to the hospitals with lowest 30-day mortality rates. Simulations suggest that an optimized system that prioritized the transfer of AMI patients to a nearby hospital with the lowest 30-day mortality rate might produce clinically meaningful reductions in mortality.

Conclusions: More than 40% of AMI patients admitted to nonrevascularization hospitals are transferred to revascularization hospitals. Many patients are not directed to nearby hospitals with the lowest 30-day risk-standardized mortality, and this may represent an opportunity for improvement.

FIGURE 1. Transfers of AMI Patients from Non-Revascularization Hospitals

This map shows transfers of patients from non-revascularization hospitals (yellow) to revascularization hospitals (green). The thickness of the lines is proportional to the number of transfers between the hospitals. The diameter of the markers for revascularization hospitals is inversely proportional to their 30-day risk-standardized mortality, with hospitals with better outcomes having larger diameter.