Study design and population

Hospitalizations for AMI were identified using the National Inpatient Sample (NIS). The NIS is part of the Healthcare Cost and Utilization Project and is the largest inpatient database in the United States, capturing approximately 20% of hospitalizations nationwide. Data in the NIS are derived from billing data submitted by hospitals to statewide data organizations and contain demographic and clinical characteristics. The NIS reports data using the International Classifications of Diseases-9th Revision (ICD-9) until September 2015 and International Classification of Diseases-10th Revision (ICD-10) afterward. This study was deemed exempt by the New York University Grossman School of Medicine Institutional Review Board given that the data are publicly available and deidentified.

All hospitalizations with a primary diagnosis of AMI between January 1, 2006, and December 31, 2018, were included. Patients with ET (ICD-9 238.71, ICD-10 D47.3), PV (ICD-9 238.4 and 207.10-12, ICD-10 D45), and PMF (ICD-9 238.76 and 289.83, ICD-10 D47.1, D75.81, and D47.4) were identified using ICD-9 and ICD-10 codes.^13,14 Procedures, including left heart catheterization, PCI, mechanical circulatory support (MCS), and coronary artery bypass grafting (CABG), were captured using ICD-9 and ICD-10 procedure codes. Comorbidities were captured via ICD-9 and ICD-10 codes and Elixhauser comorbidities.¹⁵ The ICD-9 and ICD-10 codes used for this study are listed in Supplemental Table 1.