Hospitalizations and Outcomes of T1MI Observed Before and After the Introduction of MI Subtype Codes.

Background: International Classification of Disease (ICD)-10 coding of type 1 myocardial infarction (MI) is used for reimbursement, value-based programs, and clinical research.
Objectives: This study sought to determine whether the introduction of ICD-10 codes for type 2 and types 3-5 MI was associated with changes in hospitalizations for ICD-10 codes now attributed to type 1 MI.
Methods: Using the Nationwide Readmissions Database, we identified patients with ICD-10 codes now attributed to type 1 MI between January 2016 and December 2018. Patients were stratified according to the timing of their event in relation to the introduction of the type 2 and types 3-5 MI codes on October 1, 2017.
Results: There were 2,680,323 hospitalizations for ICD-10 codes now attributed to type 1 MI; after adjustment for seasonality, there was a 13.7% decline in hospitalizations after the introduction of the new subtype codes. Patients with ICD-10 codes now attributed to type 1 MI after the coding change were less likely to be female, had lower prevalence of several cardiovascular and noncardiovascular comorbidities, and had higher rates of coronary angiography and revascularization. After introduction of the new codes, there was a positive deflection in the slope of risk-adjusted in-hospital mortality (0.007%; P <0.001) and a negative deflection in risk-adjusted 30-day readmission (-0.002%; P = 0.05) for patients with ICD-10 codes now attributed to type 1 MI.
Conclusions: The introduction of ICD-10 codes for type 2 and types 3-5 MI was associated with a decrease in hospitalizations for ICD-10 codes now attributed to type 1 MI and changes in the observed characteristics and treatment patterns of these patients.
Competing Interests: Funding Support and Author Disclosures Dr Wasfy has received a grant from the American Heart Association (18 CDA 34110215). Dr Januzzi is supported in part by the Hutter Family Professorship. Dr Vaduganathan serves on advisory boards and/or has received research grant support from American Regent, Amgen, AstraZeneca, Baxter Healthcare, Bayer AG, Boehringer Ingelheim, Cytokinetics, Lexicon Pharmaceuticals, and Relypsa; and participates on clinical endpoint committees for studies sponsored by Galmed and Novartis. Dr Januzzi is a Trustee of the American College of Cardiology; has received grant support from Novartis Pharmaceuticals, Innolife, Applied Therapeutics, and Abbott Diagnostics; has received consulting income from Abbott, Janssen, Novartis, Pfizer, Merck, and Roche Diagnostics; and participates in clinical endpoint committees/data safety monitoring boards for Abbott, AbbVie, Amgen, Bayer, CVRx, and Takeda. Dr Wasfy has received consulting fees from Pfizer, Biotronik, and the Institute for Clinical and Economic Review; serves as chair of New England CEPAC; and has received reimbursements for travel from non-profit professional and academic organizations. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
(Copyright © 2021 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)