NPPB and congestive heart failure: Figure 2B displays the correlation between EI and other CHF indicators, such as cardiac troponin I, left ventricular ejection fraction (LVEF), NT-proBNP, and creatinine. It revealed that EI had no significant correlation with LVEF (p = 0.754) but was negatively correlated with cardiac troponin (R2 = 0.014, p = 0.044). Moreover, EI was positively correlated with creatinine (R2 = 0.014, p = 0.018) and NT-proBNP (R2 = 0.015, p = 0.014).