Temporal Trends, Patient Characteristics, and Outcomes of Type 2 Versus Type 1 Myocardial Infarction Among Medicare Beneficiaries

BACKGROUND: Type 2 myocardial infarction (MI) is common among older adults and is associated with adverse outcomes in single-center studies. We aimed to examine temporal trends and compare outcomes between type 1 and type 2 MI in Medicare beneficiaries. METHODS: Medicare beneficiaries with type 1 or type 2 MI were identified using International Classification of Diseases, Tenth Revision codes from Medicare Provider Analysis and Review 100% inpatient files. Temporal trends were assessed from 2018 to 2021. Patients with type 2 MI were matched 1:1 to type 1 MI by age, sex, race, and year. Outcomes included all-cause mortality, recurrent MI, heart failure hospitalization (HFH), and stroke. Time-to-event analyses used Cox models for mortality and Fine-Gray models for hospitalization outcomes, with short-term (≤30 days) and long-term (>30 days) outcomes assessed using landmark analysis. RESULTS: Among 1 816 926 Medicare beneficiaries, the proportion of type 2 MI increased from 19.4% in 2018 to 26.8% in 2021 ( P trend <0.001). In propensity-matched analyses of 94 132 patients (mean age 77.3±11 years, 53.3% male), patients with type 2 (versus type 1) MI had lower short-term all-cause mortality (hazard ratio, 0.61 [95% CI, 0.59–0.63]), recurrent MI (subdistribution hazard ratio [sHR], 0.56 [95% CI, 0.54–0.59]), HFH (sHR, 0.56 [95% CI, 0.47–0.67]), and similar risk of stroke (sHR, 1.04 [95% CI, 0.90–1.21]). In long-term, patients with type 2 (versus type 1) MI had higher risk of all-cause mortality (hazard ratio, 1.23 [95% CI, 1.20–1.26]) and stroke (sHR, 1.20 [95% CI, 1.10–1.31]). The risk of recurrent MI and HFH associated with type 2 (versus type 1) MI in long-term follow-up was lower but considerably attenuated in magnitude compared with short-term risk (recurrent MI: sHR, 0.89 [95% CI, 0.86–0.94]; HFH; sHR, 0.73 [95% CI, 0.66–0.81]). CONCLUSIONS: Type 2 MI now accounts for over one-quarter of all MIs and is increasingly diagnosed. While patients with type 1 MI had higher short-term all-cause mortality risk, those with type 2 MI demonstrated higher long-term all-cause mortality and stroke risk, with lower risk of recurrent MI and HFH. These results highlight an urgent need for evidence-based strategies in this high-risk population.