The Respiratory Rate, Age, and Mean Arterial Pressure (RAM) Index: A Novel Prognostic Tool to Predict Mortality among Adult Patients with Acute Heart Failure in the Emergency Department.

Abstract

Background and Objectives: Acute heart failure (AHF) is a life-threatening condition frequently encountered in the emergency department (ED). Identifying reliable prognostic indicators for in-hospital mortality is crucial for risk stratification and the appropriate management of AHF patients. This study aimed to assess the most effective method for predicting in-hospital mortality among various physiological parameters in patients with AHF presenting to the ED. Additionally, the study evaluated the effectiveness of the RAM index-respiratory rate (RR), age, and mean arterial pressure (MAP)-derived from the shock index (SI) by replacing heart rate with RR, as a novel prognostic tool. This was compared with the SI and its other derivatives to predict in-hospital mortality in adult patients with AHF presenting to the ED. Materials and Methods: This is a retrospective study conducted in the ED of an urban medical center, enrolling adult patients with signs and symptoms of AHF, who met the epidemiological diagnosis criteria, between January 2017 and December 2021. Baseline physiological parameters, including the RR, heart rate, systolic blood pressure, and diastolic blood pressure, were recorded upon ED admission. The RAM index was calculated as the RR multiplied by the age divided by the MAP. Statistical analysis was performed, including univariate analysis, logistic regression, and receiver operating characteristic (ROC) curve analysis. Results: A total of 2333 patients were included in the study. A RAM index > 18.6 (area under ROC curve (AUROC): 0.81; 95% confidence interval (CI): 0.79-0.83) had a superior mortality discrimination ability compared to an SI > 0.77 (AUROC: 0.75; 95% CI: 0.72-0.77), modified shock index > 1.11 (AUROC: 0.75; 95% CI: 0.73-0.77), age shock index > 62.7 (AUROC: 0.74; 95% CI: 0.72-0.76), and age-modified shock index > 79.9 (AUROC: 0.75; 95% CI: 0.73-0.77). A RAM index > 18.6 demonstrated a 7.36-fold higher risk of in-hospital mortality with a sensitivity of 0.80, specificity of 0.68, and negative predictive value of 0.97. Conclusions: The RAM index is an effective tool to predict mortality in AHF patients presenting to the ED. Its superior performance compared to traditional SI-based parameters suggests that the RAM index can aid in risk stratification and the early identification of high-risk patients, facilitating timely and aggressive treatment strategies.