Myocardial dysfunction in sepsis: injury or depression?

Association between troponin T and ICU mortality, a changing trend

Background

Initially elevated levels of troponin predict adverse outcomes in patients admitted to the intensive care unit (ICU). No research team has investigated the changes in concentration of cardiac troponin T (cTnT) during ICU stay and their association with patient outcome.

Objective

We investigated whether the change in cTnT levels during ICU stay could predict outcomes (death or survival).

Methods

In this cohort study, all patients admitted to the medical ICU (10 beds) from January to July 2008 were enrolled. Troponin levels were evaluated within the first 24 hours of ICU admission and on the fourth, seventh and 10th days after admission.

Results

The study population (135 patients) had a mean age of 60.9 ± 21.5 years. The outcome was significantly different with regard to normal or elevated cTnT concentrations on the first and seventh days of follow up (p = 0.03 and 0.023, respectively). This difference was non-significant for cTnT levels on the fourth and 10th days after admission (p = 0.69 and 0.78, respectively). The change in cTnT levels was not significantly different between the deceased and discharged patients (p = 0.4).

Conclusion

Changes in cTnT levels during ICU stay did not show a significant trend (power: 0.26). Patients whose cTnT levels were increased on the first and seventh days of ICU stay had a worse survival, which could be associated with cardiac events on admission or at specific times during the stay in ICU.

The role of cardiac troponin I as a prognosticator in critically ill medical patients: a prospective observational cohort study

Introduction

Myocardial injury is frequently unrecognized in intensive care unit (ICU) patients. Cardiac troponin I (cTnI), a surrogate of myocardial injury, has been shown to correlate with outcome in selected groups of patients. We wanted to determine if cTnI level measured upon admission is an independent predictor of mortality in a heterogeneous group of critically ill medical patients.

Methods

We conducted a prospective observational cohort study; 128 consecutive patients admitted to a medical ICU at a tertiary university hospital were enrolled. cTnI levels were measured within 6 h of admission and were considered positive (>0.7 ng/ml) or negative. A variety of clinical and laboratory variables were recorded.

Results

Both cTnI positive and negative groups were similar in terms of age, sex and pre-admission co-morbidity. In a univariate analysis, positive cTnI was associated with increased mortality (OR 7.0, 95% CI 2.44–20.5, p < 0.001), higher Acute Physiology and Chronic Health Evaluation (APACHE) II scores and a higher rate of multi-organ failure and sepsis. This association between cTnI and mortality was more pronounced among elderly patients (>65 years of age). Multivariate analysis controlling for APACHE II score revealed that elevated cTnI levels are not independently associated with 28-day mortality.

Conclusion

In critically ill medical patients, elevated cTnI level measured upon admission is associated with increased mortality rate. cTnI does not independently contribute to the prediction of 28-day mortality beyond that provided by APACHE II.

Effect of Isoproterenol on the Cardiac Troponin I Degradation and Release during Early TNFα-Induced Ventricular Dysfunction in Isolated Rabbit Heart

We studied the consequences of an early phase of TNFalpha-induced LV dysfunction and of its treatment by isoproterenol on an isolated rabbit heart preparation. Two dosages of TNFalpha (2 and 4 microg) were infused, followed by isoproterenol (ISO), infused by increasing concentrations from 10 to 10 M. Left ventricular developed pressure (DP) was recorded. Creatine kinase (CKtot) and cardiac Troponin I (cTnI) were measured in the effluent perfusate. An anatomic score was calculated by histologic examination of the hearts while a structural analysis of cTnI was done. TNFalpha induced a dose-dependent decrease in DP (-43 +/- 18% for 4 microg) without change in coronary vascular resistances, which was not followed by biochemical or structural abnormalities. TNFalpha reduced the maximum effect (Emax) of ISO on DP (mean DeltaDPmaxISO = -40% for 4 microg) without change in the concentration leading to half Emax (ED50ISO). ISO treatment of TNFalpha (4 microg)-induced LV dysfunction resulted in a selective release of cTnI, myocardial tissue contraction bands, and a significant proteolysis of cTnI. Within the limits of the model, the myocardial injury reported during severe sepsis would not be related to an early cytotoxic effect of TNFalpha but could be attributed to an enhancement of the effects of isoproterenol by TNFalpha.

[Circulating troponin I assay: uses and misuses in medical practice]

Cardiac troponin I (cTnI) contributes to the modulation of the myocardial contractile function in the troponins complex. The assay of circulating cTnI is highly specific of the cardiac isoform and allows a quantification of the myocardial injury provided that both free and combined cTnI were recognized by the antibodies. The assay is a major contribution to the diagnosis of postoperative cardiac complications through its specificity because peripheral muscle trauma is a confounding factor during this period. Circulating cTnI mirrors the magnitude of an acute circulatory failure whatever the origin (cardiac, hemorrhagic or septic). A positive cTnI assay in an "asymptomatic" patient has to be confirmed and needs some investigations to discard an occult cardiac disease; cTnI has a limited role by itself in predicting mortality and hospital admissions. Circulating cTnI confirms the severity of an acute coronary syndrome and has a level-dependent prognostic value.

Clinical significance of elevated troponin I levels in patients with nontraumatic subarachnoid hemorrhage

OBJECT

Aneurysmal subarachnoid hemorrhage (SAH) is associated with electrocardiographic abnormalities, regional or focal wall-motion abnormalities on echocardiograms, and/or increased creatine kinase MB isoenzyme (CK-MB) or cardiac troponin I (cTnI). The goal of this prospective study was to compare the sensitivity and specificity of cTnI with those of CK-MB in the prediction of left ventricular dysfunction on echocardiograms in patients with nontraumatic SAH. In addition, those patients with abnormal findings on their echocardiograms and elevated cTnI levels were further evaluated for the presence of coronary artery disease (CAD) by a cardiologist and to determine whether any left ventricular dysfunction that had been detected was reversible.

METHODS

The authors obtained electrocardiograms and echocardiograms, and measured serial levels of cardiac enzymes (CK-MB and cTnI) in 43 patients with nontraumatic SAH. Patients with known CAD were excluded. Those patients found to have elevated enzyme levels and abnormal findings on their echocardiograms underwent additional evaluation for CAD. The sensitivity and specificity of both cTnI and CK-MB for detecting left ventricular function were determined. Twenty-eight percent of patients with SAH in the study had elevated cTnI levels within the first 24 hours after hemorrhage. Seven of the 12 patients had evidence of left ventricular dysfunction on echocardiograms. In all these patients a return to baseline function was found during follow-up examinations. The authors found that cTnI is much more sensitive than CK-MB (100% compared with 29%) in the detection of left ventricular dysfunction in patients with SAH.

CONCLUSIONS

An elevated level of cTnI is a good indicator of left ventricular dysfunction in patients with SAH. In this study cardiac dysfunction was reversible and should not necessarily preclude these patients from undergoing operative interventions or becoming heart donors. Clinical management may require more aggressive hemodynamic monitoring until cardiac function returns to normal.

Reversible myocardial dysfunction in critically ill, noncardiac patients: a review

OBJECTIVE

To review reversible myocardial dysfunction affecting critically ill patients without cardiac pathology.

DATA SOURCES

The bibliography for the study was compiled through a search of different databases for the period 1966-2001. References cited in the selected articles also were reviewed.

STUDY SELECTION

The selection criteria included all articles published on reversible myocardial dysfunction in critically ill patients.

CONCLUSIONS

Reversible myocardial dysfunction may develop in a situation of critical pathology, but the etiology of reversible myocardial dysfunction is not fully understood. This dysfunction may be accompanied by increases in enzyme concentrations and electrocardiographic changes. Reversible myocardial dysfunction probably is underdiagnosed, although its presence is associated with a worsening of the prognosis and with more specific therapeutic options. Further studies are necessary to define its true incidence and clinical implications.