Abstract Body (Do not enter title and authors here): Background: Myocardial infarction (MI) is a leading cause of mortality worldwide, and adverse outcomes among hospitalized patients are notable, particularly among older patients who experience frailty. Frailty is characterized by poor physiologic reserve and often results in poor response to medical insults. This study aims to assess the utility of a health record-based Electronic Frailty Index (eFI) in predicting clinical outcomes among these patients.

Methods: This study is a single-center, retrospective cohort study of 390 patients aged 65 and older admitted with MI from October 2017 to January 2021. Data was collected using the ACC Chest Pain-MI registry and the electronic health record. Patients were divided into two cohorts: Fit (eFI <0.1) and Not Fit (eFI ≥0.1). Data was analyzed using descriptive statistics and multivariate nominal logistic regression. The primary outcome was in-hospital mortality. Secondary outcomes included revascularization strategy, Major Adverse Cardiac Events (MACE), adverse bleeding, development of cardiogenic shock, need for mechanical circulatory support, hospital length of stay, and discharge destination.

Results: The mean age and standard deviation (SD) of the study cohort was 75 ± 6.97 years, with 130 (33%) females, 334 (86%) Caucasians, and 292 (75%) designated as Not Fit. Not Fit patients had a higher frequency of comorbid disease than Fit patients (Table 1). In-hospital mortality was significantly greater among Not Fit patients (8 vs. 2%, p = 0.03). Not-fit patients were more likely to be discharged to a hospice facility (6 vs. 1%, p = 0.05). Fit patients were more likely to undergo surgical revascularization (28 vs. 17%, p = 0.02). Additional secondary outcomes did not differ significantly between groups. A multivariate nominal logistic regression found that the patient’s Fit status (p = 0.03) and age (p = 0.05) were significant drivers of in-hospital mortality.

Conclusion: Among patients admitted with MI, Not Fit patients had a greater likelihood of in-hospital mortality. Age and Fit status drove this association significantly, suggesting that lower physiologic reserve may lead to poorer clinical outcomes. Further study is needed to better characterize eFI as a risk-stratification tool for older patients with MI.