Accountable Care Organization Participation and Cardiovascular Care Quality

Importance: The Medicare Shared Savings Program (MSSP) was introduced in 2012 to improve care quality and lower costs to Medicare. Under this program, accountable care organizations (ACOs) assumed responsibility for costs and care quality for a group of Medicare beneficiaries. Objective: To compare changes in quality measures for patients at outpatient cardiology practices before and after their participation in a Medicare Shared Savings Program ACO. Design, Setting, and Participants: This pre-post cohort study comparing quality prior to and after ACO participation evaluated the MSSP at 83 ACO outpatient cardiology practices compared with 332 non-ACO-participating cardiology practices, adjusted for secular trends, using 15 performance measures in the National Cardiovascular Data Registry PINNACLE (Practice Innovation and Clinical Excellence) Registry from January 1, 2013, through March 31, 2019. Data analysis was performed from 2022 to 2025. Exposures: Outpatient cardiology practice participation in the MSSP, which allows ACOs to share in the savings if predetermined cost targets are met, with payments adjusted based on a quality performance score. Main Outcomes and Measures: Primary end points included 15 quality measures for coronary artery disease, heart failure, atrial fibrillation, and hypertension. Results: During the study period, 2390244 patients (1273615 [53.3%] female; mean [SD] age, 58.5 [17.7] years) were cared for by 83 ACO practices, and 5415880 patients (2810204 [51.9%] female; mean [SD] age, 61.5 [16.3] years) were cared for by 332 non-ACO practices. Outpatient cardiology practice participation in an MSSP ACO was not associated with differential changes in various performance measures for coronary artery disease, heart failure, atrial fibrillation, and hypertension. There were no differential changes in the odds of β-blocker prescription, blood pressure control, antiplatelet prescription, angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) prescription, low-density lipoprotein (LDL) profiles, or smoking cessation for coronary artery disease; left ventricular assessment, β-blocker prescription, ACEI or ARB prescription, or implantable cardioverter defibrillator use for heart failure; anticoagulation for atrial fibrillation; or blood pressure control for hypertension. Exploratory analyses extending follow-up to 24 months revealed an increase in β-blocker use for heart failure (adjusted odds ratio [aOR], 1.23; 95% CI, 1.02-1.49; P =.03) and a decline in LDL profiles less than 100 mg/dL (to convert to millimoles per liter, multiply by 0.0259; aOR, 0.71; 95% CI, 0.51-0.999; P =.049). Among a subset of traditional Medicare patients, there was an increase in implantable cardioverter defibrillator use by 12 months (aOR, 1.66; 95% CI, 1.12-2.45; P =.01) following ACO participation. Conclusions and Relevance: Participation in an MSSP ACO was not found to be associated with early improvement in quality measures at outpatient cardiology practices.