Acute Myocardial Infarction Cohorts Defined by International Classification of Diseases, Tenth Revision Versus Diagnosis-Related Groups

Circulation: Cardiovascular Quality and Outcomes, Ahead of Print.
Background:Among Medicare value-based payment programs for acute myocardial infarction (AMI), the Hospital Readmissions Reduction Program usesInternational Classification of Diseases, Tenth Revision(ICD-10) codes to identify the program denominator, while the Bundled Payments for Care Improvement Advanced program uses diagnosis-related groups (DRGs). The extent to which these programs target similar patients, whether they target the intended population (type 1 myocardial infarction), and whether outcomes are comparable between cohorts is not known.Methods:In a retrospective study of 2176 patients hospitalized in an integrated health system, a cohort of patients assigned a principalICD-10diagnosis of AMI and a cohort of patients assigned an AMI DRG were compared according to patient-level agreement and outcomes such as mortality and readmission.Results:One thousand nine hundred thirty-five patients were included in theICD-10cohort compared with 662 patients in the DRG cohort. Only 421 patients were included in both AMI cohorts (19.3% agreement). DRG cohort patients were older (70 versus 65 years,P<0.001), more often female (48% versus 30%,P<0.001), and had higher rates of heart failure (52% versus 33%,P<0.001) and kidney disease (42% versus 25%,P<0.001). Comparing outcomes, the DRG cohort had significantly higher unadjusted rates of 30-day mortality (6.6% versus 2.5%,P<0.001), 1-year mortality (21% versus 8%,P<0.001), and 90-day readmission (26% versus 19%,P=0.006) than theICD-10cohort. Two observations help explain these differences: 61% ofICD-10cohort patients were assigned procedural DRGs for revascularization instead of an AMI DRG, and type 1 myocardial infarction patients made up a smaller proportion of the DRG cohort (34%) than theICD-10cohort (78%).Conclusions:The method used to identify denominators for value-based payment programs has important implications for the patient characteristics and outcomes of the populations. As national and local quality initiatives mature, an emphasis onICD-10codes to define AMI cohorts would better represent type 1 myocardial infarction patients.



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