Implementation of a pilot accountable care organization payment model and the use of discretionary and nondiscretionary cardiovascular care

Background: Accountable care organizations (ACOs) seek to reduce growth in healthcare spending while ensuring high-quality care. We hypothesized that accountable care organization implementation would selectively limit the use of discretionary cardiovascular care (defined as care occurring in the absence of indications such as myocardial infarction or stroke), while maintaining high-quality care, such as nondiscretionary cardiovascular imaging and procedures.

Methods and results: The intervention group was composed of fee-for-service Medicare patients (n=819 779) from 10 groups participating in a Medicare pilot accountable care organization, the Physician Group Practice Demonstration (PGPD). Matched controls were patients (n=934 621) from nonparticipating groups in the same regions. We compared use of cardiovascular care before (2002-2004) and after (2005-2009) PGPD implementation, studying both discretionary and nondiscretionary carotid and coronary imaging and procedures. Our main outcome measure was the difference in the proportion of patients treated with imaging and procedures among patients of PGPD practices compared with patients in control practices, before and after PGPD implementation (difference-in-difference). For discretionary imaging, the difference-in-difference between PGPD practices and controls was not statistically significant for discretionary carotid imaging (0.17%; 95% confidence interval, -0.51% to 0.85%; P=0.595) or discretionary coronary imaging (-0.19%; 95% confidence interval, -0.73% to 0.35%; P=0.468). Similarly, the difference-in-difference was also minimal for discretionary carotid revascularization (0.003%; 95% confidence interval, -0.008% to 0.002%; P=0.705) and coronary revascularization (-0.02%; 95% confidence interval, -0.11% to 0.07%; P=0.06). The difference-in-difference associated with PGPD implementation was also essentially 0 for nondiscretionary cardiovascular imaging or procedures.

Conclusion: Implementation of a pilot accountable care organization did not limit the use of discretionary or nondiscretionary cardiovascular care in 10 large health systems.