Elevated Cardiac Troponin Levels as a Predictor of Increased Mortality Risk in Non-Cardiac Critically Ill Patients Admitted to a Medical Intensive Care Unit

Abstract

Background: Cardiac troponin I (TnI) is a specific marker of myocardial damage used in the diagnosis of acute coronary syndrome (ACS). TnI levels can also be elevated in patients without ACS, which is linked to a worse prognosis and mortality. We evaluated the clinical implications and prognostic significance of serum TnI levels in critically ill non-cardiac patients admitted to the intensive care unit (ICU) at a tertiary-level hospital. Materials and Methods: A three-year retrospective study including the years 2017-2020 was conducted to evaluate in-hospital mortality during ICU stay and mortality rates at 28 and 90 days, as well as one and two years after admission, in 557 patients admitted to the medical ICU for non-cardiac causes. Results: TnI levels were elevated in 206 (36.9%) patients. Patients with elevated TnI levels were significantly older and had higher rates of comorbidities, including chronic heart failure, coronary heart disease, and chronic kidney disease (p < 0.05 for all). Patients with elevated TnI levels required more invasive mechanical ventilation, vasopressor infusion, and dialysis in the ICU and experienced more shock within the first 72 h (p = 0.001 for all). High TnI levels were associated with higher Acute Physiological and Chronic Health Evaluation (APACHE) II (27.6 vs. 20.3, p = 0.001) and Sequential Organ Failure assessment (8.8 vs. 5.26, p = 0.001) scores. Elevated TnI levels were associated with higher mortality rates at 28 days (58.3% vs. 19.4%), 90 days (69.9% vs. 35.0%), one year (78.6% vs. 46.2%), and two years (82.5% vs. 55.6%) (p < 0.001 for all). Univariate logistic regression analysis revealed that high TnI levels were a strong independent predictor of mortality at all time points: 28 days (OR = 1.2, 95% CI: 1.108-1.3, p < 0.001), 90 days (OR = 1.207, 95% CI: 1.095-1.33, p = 0.001), one year (OR = 1.164, 95% CI: 1.059-1.28, p = 0.002), and two year (OR = 1.119, 95% CI: 1.026-1.22, p = 0.011). Multivariate analysis revealed that age, albumin level, APACHE II score, and requirements for dialysis and vasopressor use in the ICU were important predictors of mortality across all timeframes, but elevated TnI levels were not. Conclusions: Elevated TnI levels in critically ill non-cardiac patients are markers of disease severity. While elevated TnI levels were significant predictors of mortality in the univariate analysis, they lost significance in the multivariate model when adjusted for other factors. Patients with elevated TnI levels had higher mortality rates across all timeframes, from 28 days to two years.

Keywords: APACHE II scores; SOFA scores; Troponin I (TnI); long-term mortality; medical intensive care unit (MICU); short-term mortality.

Figure 1

Patients’ exclusion flowchart.

Figure 2

(A) ROC curves for the 28 motality; (B) ROC curves for the 90 days mortality; (C) ROC curves for the 1-year motality; (D) ROC curves for the 2-years motality.

Figure 2

(A) ROC curves for the 28 motality; (B) ROC curves for the 90 days mortality; (C) ROC curves for the 1-year motality; (D) ROC curves for the 2-years motality.