Misclassification of Myocardial Injury As Myocardial Infarction: Implications for Assessing Outcomes in Value-Based Programs

Importance: Similar to other patients with acute myocardial infarction, patients with type 2 myocardial infarction (T2MI) are included in several value-based programs, including the Hospital Readmissions Reduction Program and the Hospital Value-Based Purchasing Program. To our knowledge, whether nonischemic myocardial injury is being misclassified as T2MI is unknown and may have implications for these programs.

Objective: To determine whether patients with nonischemic myocardial injury are being miscoded as having T2MI and if this has implications for 30-day readmission and mortality rates.

Design, Settings, And Participants: Using the new International Statistical Classification of Diseases and Related Health Problems, Tenth Revision code, we identified patients who were coded as having T2MI between October 2017 and May 2018 at Massachusetts General Hospital. Strict adjudication using the fourth universal definition of MI was then applied.

Main Outcome And Measures: Clinical adjudication of T2MI and 30-day readmission and mortality rates as a function of T2MI or nonischemic myocardial injury.

Results: Of 633 patients, 369 (58.3%) were men and 514 (81.2%) were white. After strict adjudication, 359 (56.7%) had T2MI, 265 (41.9%) had myocardial injury, 6 (0.9%) had type 1 MI, and 3 (0.5%) had unstable angina. Patients with T2MI had a higher prevalence of cardiovascular comorbidities than those with myocardial injury. Patients with T2MI and myocardial injury had high in-hospital mortality rates (10.6% and 8.7%, respectively; P = .50). Of those discharged alive (563 [88.9%]), 30-day readmission rates (22.7% vs 21.1%; P = .68) and mortality rates (4.4% vs 7.4%; P = .14) were comparable among patients with T2MI and myocardial injury.

Conclusions And Relevance: A substantial percentage of patients coded as having T2MI actually have myocardial injury. Both conditions have high 30-day readmission and mortality rates. Including patients with high-risk myocardial injury may have substantial implications for value-based programs.