Troponin incidence, prevalence and prognosis among critically ill patients

Background

The diagnosis of acute myocardial infarction (AMI) in critically ill patients is usually dependent on the presence of ischemic changes on an electrocardiogram (ECG) and measurement of biochemical markers such as troponin. Among patients in the ICU, there is uncertainty surrounding the significance of elevated troponin values, their relation to coronary ischemia and infarction, and the prognostic and therapeutic implications.

Objective

To document the prevalence and incidence of elevated troponin levels in critically ill patients correlated with ECG findings (presence of ischemic changes [AMI], non-ischemic ECG changes, and normal ECG), and to evaluate the morbidity and mortality outcomes of each of these categories compared with patients with normal troponin values.

Methods

We conducted a retrospective chart review of 198 patients from 261 critically ill patients admitted to a university-affiliated, general medical–surgical ICU who were enrolled in a prospective cohort study evaluating the prevalence and incidence of deep vein thrombosis.

Data extraction

We reviewed daily medical records during the patient's ICU admission for signs and symptoms of AMI, laboratory and radiologic investigations, and collected morbidity and mortality outcomes.

Results

The prevalence of all elevated troponin levels was 36.4%; 19.2% had AMI (elevated troponin with ischemic ECG changes), 14.7% had elevated troponin without typical ischemic ECG changes, and 1.5% had elevated troponin and a normal ECG. The incidence of AMI over the ICU stay was 6.2%, of which 42% were diagnosed with AMI on admission (i.e. they had recurrent AMI). Morbidity (length of stay [LOS]) and mortality outcomes in patients with elevated troponin and associated ECG findings compared with patients with normal troponin are presented in Table 1.

Table 1

Conclusions

Elevated troponin levels are common in the critically ill, yet it is unclear under what circumstances they represent an adverse prognostic marker for ICU and hospital mortality. Additional studies are needed to determine the significance of elevated troponin values in the presence and absence of ECG changes, evaluating long-term outcomes and the efficacy of anti-ischemic treatments in critically ill patients.