Background: The most recent myocardial infarction definition has classified type 2 myocardial infarction (T2MI) as a different entity from myocardial injury and other myocardial infarction subtypes. Despite the high burden of patients with T2MI, current guidelines lack specific diagnostic and therapeutic recommendations. Additionally, distinguishing T2MI from myocardial injury remains important to establish a consistent clinical management. In this study, we demonstrate the prevalence of T2MI misclassification, and the heterogeneity of its presentation, diagnosis and management.
METHODS AND RESULTS: We conducted a retrospective cohort study at a tertiary Canadian high-volume center, including all adult patients admitted with a diagnosis of non-ST elevation myocardial infarction (NSTEMI). Demographic data, clinical characteristics, laboratory and imaging results, medical management, and discharge plan were extracted. Patients were classified as having T1MI, T2MI, or myocardial injury based on adjudicated clinical criteria. Data were presented as number (percent) for categorical variables. P-values were calculated using Chi-squared test, with p-value < 0.05 for statistical significance. Between January 2020 and October 2023, a total of 233 patients were included, with 59(25.3%) classified as T1MI and 174(74.7%) as T2MI. More than one third (n=73, 31.3%) of T2MI patients should have received the diagnosis of myocardial injury. Patients with myocardial injury had lower prevalence of known coronary artery disease (CAD) (34.2% vs. 52.5% vs. 54.2%; p=0.027) and congestive heart failure (15.0% vs. 47.5% vs. 32.0%; p< 0.01) compared to T2MI and T1MI, respectively. The most common ischemic precipitating factor, in T2MI, was acute infection (47.5%), followed by acute anemia (35.6%), arrhythmia (29.7%), hypotension (27.7%), and surgery (25.7%). T2MI patients were less likely to undergo coronary angiography (22.8%) compared to T1MI patients (62.7%; p< 0.01). Among T2MI patients undergoing angiography, 82.6% had significant CAD. T2MI patients received less intensive antithrombotic therapy: aspirin (64.4% vs. 81.4%; p=0.036), P2Y12 inhibitor (32.7% vs 67.8%; p< 0.01), and dual antiplatelet therapy (25.7% vs. 57.6%, p< 0.01) as compared to T1MI patients, respectively. Median hospitalization duration was longer in T2MI patients, 12 vs. 6 days as compared to T1MI. Only 45.5% of T2MI patients had documented cardiology follow-up post-discharge, as compared to 66.1% of T1MI patients (p=0.019).
Conclusion: T2MI patients had a significant cardiovascular risk burden and received less aggressive diagnostic and therapeutic interventions compared to T1MI patients. Despite current myocardial infarction definition, misclassification with myocardial injury remains common. These findings highlight the need for improved diagnostic tools and the development of tailored management pathways to optimize patient’s care in this heterogenous population.
