Analysis of Predictors of Myocardial Infarction in Trauma With Development of a Trauma Cardiac Risk Index

Study objective: Trauma has historically been considered a disorder of the young and healthy, with a low risk of cardiac ischemia; hence most research on myocardial infarction in trauma has focused on direct cardiac damage from blunt chest trauma. However, the age and comorbidity of trauma patients are increasing, making the trauma population more vulnerable to myocardial infarction (MI). Cardiac risk assessment has emphasized morbidity and mortality in an elective surgical setting, but it is also important in acute trauma. Our study analyzes the risk factors for MI in a trauma population to create a scoring system to predict the risk of MI. Design: Retrospective cohort analysis of a national trauma registry over a five-year period. Potential predictors of MI in trauma patients were identified and tested with univariate and multivariate statistics. A numerical score was created to predict the risk of MI based on these criteria. Setting: The National Trauma Data Bank (NTDB) is a large registry of selected trauma centers in the United States. Data include demographic, injury, treatment, and outcome variables pertaining to the index admission of each patient. The institutions range from community hospitals through level 1 trauma centers. The time period is the entire inpatient hospital admission from arrival from the field, through the emergency department, ICU, and floor up to discharge. Patients: 3,437,959 trauma patients aged 18 years and older from various US trauma centers. 62.8% were male. The median age is 50 years with a standard deviation of 21.25. The median Injury Severity Score is 9 with a standard deviation of 9.04. Measurements: Demographic, traumatic, and comorbidity variables were collected from the NTDB. The primary outcome was MI during the initial trauma admission. Multivariate analysis was performed with logistic regression. Main results: Over 8010 (0.23%) suffered an MI. The strongest risk factors for MI were a history of MI with an adjusted odds ratio (OR) of 7.0, and angina with an OR of 3.4. A procedure under general anesthesia (GA) conferred an OR of 2.3. Minor risk factors included torso injury and 10-year age interval over 50, both with an OR of 1.7, a 20-point interval of the Injury Severity Score (ISS) with OR 1.6, male gender with OR of 1.5, and various chronic disease comorbidities with OR ranging from 1.4 to 1.9. A Trauma Cardiac Risk Index (TCRI) was derived from these risk factors. The model showed good discrimination with a C statistic of 0.85. Conclusions: Overall the trauma population has a low risk of MI. However, the risk is much higher for older patients with chronic comorbidity. The TCRI can be used to assess cardiac risk in trauma patients to help direct monitoring, testing, and risk reduction measures to those at the highest risk.