Troponin as a risk factor for mortality in critically ill patients without acute coronary syndromes

Cardiorenal syndromes

Cardiorenal syndromes (CRS) have been subclassified as five defined entities which represent clinical circumstances in which both the heart and the kidney are involved in a bidirectional injury and dysfunction via a final common pathway of cell-to-cell death and accelerated apoptosis mediated by oxidative stress. Types 1 and 2 involve acute and chronic cardiovascular disease (CVD) scenarios leading to acute kidney injury or accelerated chronic kidney disease. Types 2 and 3 describe acute and chronic kidney disease leading primarily to heart failure, although it is possible that acute coronary syndromes, stroke, and arrhythmias could be CVD outcomes in these forms of CRS. Finally, CRS type 5 describes a simultaneous insult to both heart and kidneys, such as sepsis, where both organs are injured simultaneously. Both blood and urine biomarkers are reviewed in this paper and offer a considerable opportunity to enhance the understanding of the pathophysiology and known epidemiology of these recently defined syndromes.

Critical care "normality": individualized versus protocolized care

Patients with critical illness are heterogeneous, with differing physiologic requirements over time. Goal-directed therapy in the emergency room demonstrates that protocolized care could result in improved outcomes. Subsequent studies have confirmed benefit with such a "bundle-based approach" in the emergency room and in preoperative and postoperative scenarios. However, this cannot be necessarily extrapolated to the medium-term and long-term care pathway of the critically ill patient. It is likely that the development of mitochondrial dysfunction could result in goal-directed types of approaches being detrimental. Equally, arterial pressure aims are likely to be considerably different as the patient's physiology moves toward "hibernation." The agents we utilize as sedative and pressor agents have considerable effects on immune function and the inflammatory profile, and should be considered as part of the total clinical picture. The role of gut failure in driving inflammation is considerable, and the drive to feed enterally, regardless of aspirate volume, may be detrimental in those with degrees of ileus, which is often a difficult diagnosis in the critically ill. The pathogenesis of liver dysfunction may be, at least in part, related to venous engorgement that will contribute toward portal hypertension and gut edema. This, in association with loss of the hepatosplanchnic buffer response, it is likely to contribute to venous pooling in the abdominal cavity, impaired venous return, and decreased central blood volumes. Therapies such as those used in "small-for-size syndrome" may have a role in the chronic stages of septic vascular failure.

Circulating high sensitivity troponin T in severe sepsis and septic shock: distribution, associated factors, and relation to outcome

PURPOSE

To assess the clinical utility of a recently developed highly sensitive cardiac troponin T (hs-cTnT) assay for providing prognostic information on patients with sepsis.

METHODS

cTnT levels were measured by the novel hs-cTnT assay at two time points (inclusion and 72 h thereafter) in a subgroup of patients from the FINNSEPSIS study and associations with clinical outcomes were examined. Results for the hs-cTnT assay were compared to those of the established fourth-generation cTnT assay.

RESULTS

cTnT measured by the fourth-generation and hs-cTnT assay was detectable in 124 (60%) and 207 (100%) patients, respectively, on inclusion in this study. hs-cTnT levels on inclusion correlated with several indices of risk in sepsis, including the simplified acute physiology score (SAPS) II and sequential organ failure assessment (SOFA) scores. The level of hs-cTnT on inclusion was higher in hospital non-survivors (n = 47) than survivors (n = 160) (median 0.054 [Q1-3, 0.022-0.227] versus 0.035 [0.015-0.111] μg/L, P = 0.047), but hs-cTnT level was not an independent predictor of in-hospital mortality. hs-cTnT levels on inclusion were also higher in patients with septic shock during the hospitalization (0.044 [0.024-0.171] versus 0.033 [0.012-0.103] μg/L, P = 0.03), while this was not the case for the fourth-generation cTnT assay or NT-proBNP levels.

CONCLUSIONS

Circulating hs-cTnT is present in patients with severe sepsis and septic shock, associates with disease severity and survival, but does not add to SAPS II score for prediction of mortality. hs-cTnT measurement could still have a role in sepsis as an early marker of shock.

Electrocardiographic ST-segment elevation myocardial infarction in critically ill patients: an observational cohort analysis

OBJECTIVE

To investigate the specificity of the electrocardiographic diagnosis of ST-segment elevation myocardial infarction in the critical care unit setting.

DESIGN

Retrospective observational cohort analysis.

SETTING

An 880-bed tertiary care teaching hospital with 120 intensive care unit beds.

PATIENTS

The population included medical, surgical, trauma, and neurosurgical intensive care unit patients.

INTERVENTIONS

Electrocardiograms were systematically collected to include all consecutive recordings over a 15-month period in which the interpretation software indicated ***ACUTE MI***. Patient demographics, markers of intensive care unit complexity, and hospital mortality were ascertained. The electrocardiograms were then further evaluated by a blinded, board-certified cardiologist for agreement or disagreement with the interpretation software. Serum troponin measurements obtained within 96 hrs of electrocardiogram acquisition were used to determine the likelihood of myocardial infarction.

MEASUREMENTS AND MAIN RESULTS

Over the 15-month study period, the interpretation software diagnosed ST-segment elevation myocardial infarction in 67 of 2243 intensive care unit patients (2.99%) who had an electrocardiogram performed. In the final study population of 46 cases with electrocardiographic ST-segment elevation myocardial infarction, 85% had peak troponin elevation<5 ng/mL, a strong suggestion against clinical ST-segment elevation myocardial infarction. The cardiologist agreed with the computer interpretation in 39% (18 of 46) of cases, but of those 18 patients, only six showed a significant rise in the troponin level. The cardiologist disagreed with the computer interpretation in 60.9% (28 of 46) of cases and of those, one patient had a marked elevation of the cardiac troponin.

CONCLUSIONS

ST-segment elevation myocardial infarction in the intensive care unit is a relatively common electrocardiographic reading both by standard interpretation software and by expert evaluation. In contrast to nonintensive care unit patients who present with chest pain, the electrocardiographic ST-segment elevation myocardial infarction diagnosis seems to be a nonspecific finding in the intensive care unit that is frequently the result of a variety of nonischemic processes. The vast majority of such patients do not have frank ST-segment elevation myocardial infarction.

Cardiorenal syndromes: pathophysiology to prevention

There is a strong association between both acute and chronic dysfunction of the heart and kidneys with respect to morbidity and mortality. The complex interrelationships of longitudinal changes in both organ systems have been difficult to describe and fully understand due to a lack of categorization of the common clinical scenarios where these phenomena are encountered. Thus, cardiorenal syndromes (CRSs) have been subdivided into five syndromes which represent clinical vignettes in which both the heart and the kidney are involved in bidirectional injury and dysfunction via a final common pathway of cell-to-cell death and accelerated apoptosis mediated by oxidative stress. Types 1 and 2 involve acute and chronic cardiovascular disease (CVD) scenarios leading to acute kidney injury (AKI) or accelerated chronic kidney disease (CKD). Types 3 and 4 describe AKI and CKD, respectively, leading primarily to heart failure, although it is possible that acute coronary syndromes, stroke, and arrhythmias could be CVD outcomes in these forms of CRS. Finally, CRSs type 5 describe a systemic insult to both heart and the kidneys, such as sepsis, where both organs are injured simultaneously in persons with previously normal heart and kidney function at baseline. Both blood and urine biomarkers, including the assessment of catalytic iron, a critical element to the generation of oxygen-free radicals and oxidative stress, are reviewed in this paper.

The clinical significance of cardiac troponins in medical practice

Troponins are regulatory proteins that form the cornerstone of muscle contraction. The amino acid sequences of cardiac troponins differentiate them from that of skeletal muscles, allowing for the development of monoclonal antibody-based assay of troponin I (TnI) and troponin T (TnT). Along with the patient history, physical examination and electrocardiography, the measurement of highly sensitive and specific cardiac troponin has supplanted the former gold standard biomarker (creatine kinase-MB) to detect myocardial damage and estimate the prognosis of patients with ischemic heart disease. The current guidelines for the diagnosis of non-ST segment elevation myocardial infarction are largely based on an elevated troponin level. The implementation of these new guidelines in clinical practice has led to a substantial increase in the frequency of myocardial infarction diagnosis. Automated assays using cardiac-specific monoclonal antibodies to cardiac TnI and TnT are commercially available. They play a major role in the evaluation of myocardial injury and prediction of cardiovascular outcome in cardiac and non-cardiac causes. In this review we discuss the clinical applications of cardiac troponins and the interpretation of elevated levels in the context of various clinical settings.

The utility of troponin measurement to detect myocardial infarction: review of the current findings

Myocardial infarction (MI) is defined by the presence of myocardial necrosis in combination with clinical evidence of myocardial ischemia. Cardiac troponins are regulatory proteins within the myocardium that are released into the circulation when damage to the myocyte has occurred. Therefore, serum troponin is an exquisitely sensitive marker of myocardial injury and is necessary for establishing the diagnosis of MI. High-sensitivity troponin assays are improving the diagnostic accuracy and rapid detection of myocardial infarction. The early identification of MI is vital for the institution of anti-thrombotic therapy to limit myocardial damage and preserve cardiac function. Troponin has both diagnostic and prognostic significance in the setting of acute coronary syndrome (ACS). Increased troponin levels in the absence of ACS should prompt an evaluation for an alternative, non-thrombotic mechanism of troponin elevation and direct management at the underlying cause. This review describes the role of troponin in the evaluation of patients with suspected myocardial infarction.

Clinical applications of highly sensitive troponin assays

Cardiac troponin is the biomarker of choice for the diagnosis of acute myocardial infarction. Recent consensus recommendations have adopted a concentration of troponin above the 99th percentile of a healthy population to diagnose myocardial infarction. Until recently, there was no assay capable of achieving recommended precision; however, with the development of "highly sensitive" troponin assays, it is now possible to accurately measure troponin concentrations at and below the current 99th percentile of a healthy population. These assays have enormous potential in not only identifying more patients with acute myocardial infarction, and providing superior risk prediction in those so afflicted, in addition highly sensitive troponins assays may be useful for long-term risk assessment of the patient with coronary disease. In this article, we will review the clinical applications, novel concepts, challenges, and limitations of using highly sensitive troponins assays.

Elevated cardiac troponin I in sepsis and septic shock: no evidence for thrombus associated myocardial necrosis

Background

Elevated cardiac troponin I (cTnI) is frequently observed in patients with severe sepsis and septic shock. However, the mechanisms underlying cTnI release in these patients are still unknown. To date no data regarding coagulation disturbances as a possible mechanism for cTnI release during sepsis are available.

Methodology/Principal Findings

Consecutive patients with systemic inflammatory response syndrome (SIRS), sepsis or septic shock without evidence of an acute coronary syndrome were analyzed. Coagulation parameters (clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), α-angle) were assessed in native whole blood samples, and using specific activators to evaluate the extrinsic and intrinsic as well as the fibrin component of the coagulation pathway with the use of rotational thrombelastometry (ROTEM).

Thirty-eight patients were included and 22 (58%) were cTnI-positive. Baseline characteristics between TnI-positive and -negative patients were similar. The CT, CFT, MCF and the α-angle were similar between the groups with trends towards shorter CT in the extrinsic and fibrin activation.

Conclusions/Significance

We found no differences in coagulation parameters analyzed with rotational thrombelastometry between cTnI-positive and -negative patients with SIRS, severe sepsis, and septic shock. These findings suggest that pathophysiological mechanisms other than thrombus-associated myocardial damage might play a major role, including reversible myocardial membrane leakage and/or cytokine mediated apoptosis in these patients.

Sepsis and the heart

Septic shock, the most severe complication of sepsis, accounts for approximately 10% of all admissions to intensive care. Our understanding of its complex pathophysiology remains incomplete but clearly involves stimulation of the immune system with subsequent inflammation and microvascular dysfunction. Cardiovascular dysfunction is pronounced and characterized by elements of hypovolaemic, cytotoxic, and distributive shock. In addition, significant myocardial depression is commonly observed. This septic cardiomyopathy is characterized by biventricular impairment of intrinsic myocardial contractility, with a subsequent reduction in left ventricular (LV) ejection fraction and LV stroke work index. This review details the myocardial dysfunction observed in adult septic shock, and discusses the underlying pathophysiology. The utility of using the regulatory protein troponin for the detection of myocardial dysfunction is also considered. Finally, options for the management of sepsis-induced LV hypokinesia are discussed, including the use of levosimendan.

Cardio-renal syndromes: report from the consensus conference of the acute dialysis quality initiative

A consensus conference on cardio-renal syndromes (CRS) was held in Venice Italy, in September 2008 under the auspices of the Acute Dialysis Quality Initiative (ADQI). The following topics were matter of discussion after a systematic literature review and the appraisal of the best available evidence: definition/classification system; epidemiology; diagnostic criteria and biomarkers; prevention/protection strategies; management and therapy. The umbrella term CRS was used to identify a disorder of the heart and kidneys whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction in the other organ. Different syndromes were identified and classified into five subtypes. Acute CRS (type 1): acute worsening of heart function (AHF–ACS) leading to kidney injury and/or dysfunction. Chronic cardio-renal syndrome (type 2): chronic abnormalities in heart function (CHF-CHD) leading to kidney injury and/or dysfunction. Acute reno-cardiac syndrome (type 3): acute worsening of kidney function (AKI) leading to heart injury and/or dysfunction. Chronic reno-cardiac syndrome (type 4): chronic kidney disease leading to heart injury, disease, and/or dysfunction. Secondary CRS (type 5): systemic conditions leading to simultaneous injury and/or dysfunction of heart and kidney. Consensus statements concerning epidemiology, diagnosis, prevention, and management strategies are discussed in the paper for each of the syndromes.

Cardiovascular biomarkers in the ICU

PURPOSE OF REVIEW

Natriuretic peptides are markers of heart failure and/or cardiac dysfunction that provide useful diagnostic and prognostic information in patients with dyspnea and/or respiratory failure in the emergency department. Cardiac troponins (cTn) have markedly simplified the diagnosis of myocardial infarction. In critically ill patients, conditions like coexisting organ dysfunction multiorgan involvement or altered synthesis/clearance may confound interpretation of designated biomarkers, including natriuretic peptides and cTn. This review focuses on recently published articles relating to the use of natriuretic peptides and cTn in critically ill patients.

RECENT FINDINGS

One new study addresses diagnostic utility of B-type natriuretic peptide to distinguish low-pressure pulmonary edema (acute lung injury/acute respiratory distress syndrome) from high-pressure (cardiogenic) pulmonary edema. Other studies highlight the prognostic value of natriuretic peptides either in unselected and general noncardiac ICU patients and reveal an important reason for elevated B-type natriuretic peptide levels in septic shock.Interesting data focusing on diagnostic and prognostic ability of systematic cTn screening measurements in ICU patients became available.

SUMMARY

Recent studies confirm the excellent prognostic value of natriuretic peptide measurements in ICU patients. Diagnostic properties of natriuretic peptide in ICU patients still remain ambiguous and require further evaluation. Systematic screening with cTn reveals more myocardial infarctions and provides important prognostic information.

Tenecteplase for ST-elevation myocardial infarction in a patient treated with drotrecogin alfa (activated) for severe sepsis: a case report

INTRODUCTION

Drotrecogin alfa (activated) (DrotAA), an activated protein C, promotes fibrinolysis in patients with severe sepsis. There are no reported cases or studies that address the diagnosis and treatment of myocardial infarction in septic patients treated with DrotAA.

CASE PRESENTATION

A 59-year-old Caucasian man with septic shock secondary to community-acquired pneumonia treated with DrotAA, subsequently developed an ST-elevation myocardial infarction 12 hours after starting DrotAA. DrotAA was stopped and the patient was given tenecteplase thrombolysis resulting in complete resolution of ST-elevation and no adverse bleeding events. DrotAA was restarted to complete the 96-hour course. The sepsis resolved and the patient was discharged from hospital.

CONCLUSION

In patients with severe sepsis or septic shock complicated by myocardial infarction, it is difficult to determine if the myocardial infarction is an isolated event or caused by the sepsis process. The efficacy and safety of tenecteplase thrombolysis in septic patients treated with DrotAA need further study.

Pseudo myocardial infarction - a condition in need to be redefined?

Since the introduction of cardiac plasma troponin measurements, a significant number of patients were seen with chest pain, elevated troponin levels but no significant coronary artery disease. Pulmonary embolism, aortic valve disease, myocarditis, sepsis, trauma, arrythmias, stress cardiomyopathy and dilated cardiomyopathy stand among possible causes for this syndrome. In some cases, myocardial strain could be the mechanism underlying this phenomenon, since it is known that the stimulation of stretch-responsive integrins may lead to the release of cardiac troponin I. In the present text, a case is made in favour of classifying this syndrome, of chest pain with increased values for plasma cardiac troponin, with or without ECG changes, in the absence of definite myocardial infarction or coronary artery disease, as pseudo myocardial infarction (PMI). This constitutes a new definition for a concept with decades, formerly centered on clinical and electrocardiographic changes mimicking infarct. The case is based on the search of scientific truth, on avoidance of unnecessary cardiac examinations, on avoidance of unnecessary drug therapy and on avoidance of unnecessary legal liability. PMI should be seen as a working diagnosis, since a more definitive diagnosis can be reached at all time. It should also be seen as a heterogeneous group of patients - several different diseases and conditions can lead to this phenomenon. But it must certainly not be seen as a benign condition, since published studies point in a totally different direction.

Determinants of cardiac troponin T elevation in COPD exacerbation - a cross-sectional study

Background

Cardiac Troponin T (cTnT) elevation during exacerbations of chronic obstructive pulmonary disease (COPD) is associated with increased mortality the first year after hospital discharge. The factors associated with cTnT elevation in COPD are not known.

Methods

From our hospital's database, all patients admitted with COPD exacerbation in 2000–03 were identified. 441 had measurement of cTnT performed. Levels of cTnT ≥ 0.04 μg/l were considered elevated. Clinical and historical data were retrieved from patient records, hospital and laboratory databases. Odds ratios for cTnT elevation were calculated using logistic regression.

Results

120 patients (27%) had elevated cTnT levels. The covariates independently associated with elevated cTnT were increasing neutrophil count, creatinine concentration, heart rate and Cardiac Infarction Injury Score (CIIS), and decreasing hemoglobin concentration. The adjusted odds ratios (95% confidence intervals in parentheses) for cTnT elevation were 1.52 (1.20–1.94) for a 5 × 10⁶/ml increase in neutrophils, 1.21 (1.12–1.32) for a 10 μmol/l increase in creatinine, 0.80 (0.69–0.92) for a 1 mg/dl increase in hemoglobin, 1.24 (1.09–1.42) for a 10 beats/minute increase in heart rate and 1.44 (1.15–1.82) for a 10 point increase in CIIS.

Conclusion

Multiple factors are associated with cTnT elevation, probably reflecting the wide panorama of comorbid conditions typically seen in COPD. The positive association between neutrophils and cTnT elevation is compatible with the concept that an exaggerated inflammatory response in COPD exacerbation may predispose for myocardial injury.

Frequency of elevated troponin I and diagnosis of acute myocardial infarction

This study evaluated the incidence and type of acute myocardial infarction (AMI) in a consecutive population with increased troponin I (TnI). AMI has recently been redefined and subclassified. Incidence, demographic data, angiographic findings, and hospital mortality of patients with various AMI subtypes or an increased TnI in the absence of AMI have not been previously reported in a prospective study. Over a 3-month period, all patients admitted from an emergency room or from in-patient services with >1 TnI level >0.04 ng/ml were evaluated and subclassified in AMI subgroups. In-hospital or recent coronary angiograms were reviewed. In-hospital mortality was noted. Of 2,944 patients with serial TnI measurements, 728 had an increased TnI and 701 (23.8%) were evaluated. Two hundred sixteen (30.8% with increased TnI and 42.7% with "rule-out MI" on admission) met criteria for AMI. One hundred forty-three (20.4%) had type 1, 64 (9.1%) had type 2, whereas 461 (65.8%) did not meet criteria for AMI. On multivariate analysis, use of angiography, peak TnI level, hyperlipidemia, and illicit drug use were independently associated with the diagnosis of AMI. TnI of 0.28 ng/ml had a 70% sensitivity and specificity for AMI diagnosis. In conclusion, a minority admitted with increased TnI have AMI by the universal definition. Type 1 is the most common AMI and is associated with higher TnI values and these patients are more likely to undergo angiography. Type 2 AMI is often associated with illicit drug use.

Initial troponin level as a predictor of prognosis in patients with intracerebral hemorrhage

OBJECTIVE

It has been suggested that elevated cardiac troponin T (cTnT) level is a marker of increased risk of mortality in acute ischemic stroke and subarachnoid hemorrhage (SAH). However, the association of serum cTnT level and prognosis of intracerebral hemorrhage (ICH) has been sparsely investigated. The aim of this study was to identify the relationship between cTnT level and the outcome in patients with spontaneous ICH.

METHODS

We retrospectively investigated 253 patients identified by a database search from records of patients admitted in our department for ICH between January 1, 2003 and December 31, 2007. The patients were divided into 2 groups; the patients in group 1 (n=225) with serum cTnT values of 0.01 ng/mL or less, and those in group 2 (n=28) with serum cTnT values greater than 0.01 ng/mL.

RESULTS

The serum cTnT level was elevated in 28 patients. There were significant differences in sex, hypertension, creatine kinase-myocardial band, midline shift, side of hematoma, and presence of intraventricular hemorrhage between the 2 groups. Logistic regression analysis identified the level of consciousness on admission, cTnT and midline shift as independent predictors of hospital mortality.

CONCLUSION

Theses results suggest that increased serum cTnT level at admission is associated with in-hospital mortality and the addition of a serum cTnT assay to routine admission testing should be considered in patients with ICH.

[Perioperative myocardial damage in non-cardiac surgery patients]

Perioperative myocardial damage occurs with a high incidence depending on the operative procedure and the patients examined and is considered to be among the most relevant risk factors for increased perioperative morbidity and mortality in patients undergoing non-cardiac surgery. The pathophysiology of myocardial damage in the perioperative period is still not well understood. Both ischemia with and without acute coronary occlusion and non-ischemic stimuli can put a substantial strain on the heart in the perioperative period. However, in many cases the clinical presentation does not allow a clear differentiation between ischemic and non-ischemic myocardial damage. In the majority of cases perioperative myocardial infarctions occur with only mild or even without any clinical symptoms. This is probably due to a considerable difference in phenotype and pathophysiology between perioperative and non-perioperative myocardial infarctions. As a result of this unexplained etiology of perioperative myocardial infarction it remains an open question whether the contemporary diagnostic and therapeutic recommendations for the acute coronary syndrome can be extrapolated to the perioperative situation. The present review reflects the current state of knowledge and presents an optional approach to the diagnosis and therapy of perioperative myocardial injury.

Prognostic value of elevated cardiac troponin I in ESRD patients with sepsis

BACKGROUND

Elevated cardiac troponin (cTn) levels have been reported to predict adverse cardiovascular outcomes in asymptomatic ESRD patients. However, the prognostic value of elevated cTn levels associated with sepsis in ESRD patients is unknown. Therefore, this study aimed to elucidate the clinical implications of elevated cTnI levels in ESRD patients with sepsis.

METHODS

Of the 305 ESRD patients in whom cTnI was measured between January 2003 and December 2005, sepsis developed in 121 patients during follow-up. Based on cTnI levels at the onset of sepsis, patients were classified as elevated cTnI group (ET, n = 50, >0.2 ng/ml) and lower cTnI group (LT, n = 71, < or =0.2 ng/ml). Study endpoints were short- and long-term mortality. Short-term mortality was defined as death occurring within 90 days after sepsis, and patients who survived during this period were followed till death after 90 days.

RESULTS

Before sepsis, the median concentration of cTnI was 0.05 (0.01-3.59) ng/ml and it was significantly increased to 0.11 (0.01-22.0) ng/ml when sepsis supervened (P < 0.01). Compared to the LT group, the short-term mortality rate was significantly higher in the ET group (P < 0.05). After adjustment for age, diabetes, serum albumin and CRP levels, presence of shock and previous cardiovascular disease history, the ET group had a greater odds ratio of short-term mortality (OR 5.13, P < 0.01). In addition, the Kaplan-Meier plot for long-term survival revealed a significantly higher mortality rate in the ET group. In a multivariate Cox regression analysis, the elevation of cTnI levels was an independent determinant for long-term mortality (HR 5.90, P < 0.01).

CONCLUSION

This study showed that elevated cTnI levels were significantly associated with short- and long-term mortality in ESRD patients with sepsis. Therefore, elevated cTnI levels in these patients should not be overlooked and be followed for adverse outcomes.

Elevated serum cardiac troponin in non-acute coronary syndrome

Cardiac troponins (CTn) are the most sensitive and specific biochemical markers of myocardial injury and risk stratification. The assay for troponin T (cTnI) is standardized, and results obtained from different institutions are comparable. This is not the case with troponin I (cTnT), and clinicians should be aware that each institution must analyze and standardize its own results. Elevated cTn levels indicate cardiac injury, but do not define the mechanical injury. The differentiation of cTn elevation caused by coronary events from those not related to an acute coronary syndrome (ACS) is tiresome, at times vexing, and often costly. Elevation of cTn in non-ACS is a marker of increased cardiac and all-cause morbidity and mortality. The cause of these elevations may involve serious medical conditions that require meticulous diagnostic evaluation and aggressive therapy. At present, there are no guidelines to treat patients with elevated troponin levels and no coronary disease. The current strategy of treatment of patients with elevated troponin and non-ACS involves treating the underlying causes.

Considerations in caring for the critically ill older patient

People over age 65 are the fastest growing segment of the population and account for 42% to 52% of the intensive care unit admissions in the United States. There are many physiologic changes that occur with aging which can impact on both the presentation and management of older patients with critical illness. Older patients have an increased risk for the development of sepsis, and age itself impacts on outcomes related to sepsis. Delirium is also very prevalent among older intensive care unit patients and is associated with adverse outcomes. While outcome studies suggest that chronologic age itself is not a risk factor for poor outcomes after adjusting for severity of illness, older patients clearly have physiologic changes which need to be considered when providing critical care. This article will review important physiologic changes of aging, as well as sepsis and delirium and outcomes of older ICU patients.

The impact of the 2007 ESC-ACC-AHA-WHF Universal definition on the incidence and classification of acute myocardial infarction: a retrospective cohort study

OBJECTIVE

To investigate the impact on the apparent incidence and classification of acute myocardial infarction (AMI) after employing the ESC-ACC-AHA-WHF 2007 Universal definition of myocardial infarction (the 2007 definition).

SETTING

Retrospective cohort study in a single hospital serving a geographically well-defined population.

METHODS AND RESULTS

Retrospectively, the medical records for all patients hospitalized with suspected AMI during 2004 were reviewed (915 with AMI discharge diagnosis, 1037 with elevated troponin T>0.03 µg/L without AMI diagnosis, 948 undergoing revascularisation and 34 with sudden death possible due to AMI). After correcting for misclassification (49 overdiagnosed and 236 underdiagnosed AMI) the number of AMI according to the 2000 definition was 1102 (20.5% overall underdiagnosed). After reclassification to the 2007 definition the total number of AMI cases decreased with 9 patients mainly due to increase of the troponin decision limit for PCI related AMI (reducing the number of PCI related AMI from 111 to 69). The percentages of patients of each type according to the 2007 subclassification were spontaneous AMI (type 1) 88.5%; AMI due to myocardial oxygen deficit (type 2) 1.6%; sudden death without troponin elevation (type 3) 2.6%; PCI related AMI (type 4) 6.8%; and AMI after coronary artery bypass (type 5) 0.5%.

CONCLUSIONS

Employing the 2007 revision of the Universal definition of AMI did not substantially alter the apparent incidence of acute AMI substantially in our population. The level of misclassification of acute coronary syndromes after introduction of the 2007 definition may depend on the clinical acceptance of AMI subgrouping.

Present and Future Biochemical Markers for Detection of Acute Coronary Syndrome

The use of biochemical markers in the diagnosis and management of patients with acute coronary syndrome has increased continually in recent decades. The development of highly sensitive and cardiac-specific troponin assays has changed the view on diagnosis of myocardial infarction and also extended the role of biochemical markers of necrosis into risk stratification and guidance for treatment. The consensus definition of myocardial infarction places increased emphasis on cardiac marker testing, with cardiac troponin replacing creatine kinase MB as the "gold standard" for diagnosis of myocardial infarction. Along with advances in the use of more cardiac-specific markers of myocardial necrosis, biochemical markers that are involved in the progression of atherosclerotic plaques to the vulnerable state or that signal the presence of vulnerable plaques have recently been identified. These markers have variable abilities to predict the risk of an individual for acute coronary syndrome. The aim of this review is to provide an overview of the well-established markers of myocardial necrosis, with a special focus on cardiac troponin I, together with a summary of some of the potential future markers of inflammation, plaque instability, and ischemia.

Incidence and significance of a positive troponin test in bacteremic patients without acute coronary syndrome

BACKGROUND

Since the introduction of troponin for the diagnosis of myocardial infarction, several studies have shown additional conditions in which troponin is elevated, including sepsis. The objective of this study was to determine the incidence of an elevated troponin in patients with bacteremia and its significance.

METHODS

This was a prospective, noninterventional study. Patients with a positive blood culture were included. Cardiac troponin I (cTnI) was determined within 4 days of blood culture. A repeat electrocardiogram was obtained in a sample of patients with elevated cTnI and in patients with a negative troponin test. Demographic, clinical, and microbiological data were obtained for all patients.

RESULTS

A total of 159 bacteremic patients were included. Positive cTnI was detected in 69 patients (43%). Elevated cTnI was associated with a number of underlying diseases, hospitalization ward, severity of the systemic inflammatory condition, and kidney function (P<.05-.001). A repeat electrocardiogram was performed in 39 patients with a positive cTnI and in 28 patients with a negative cTnI. Two of 39 patients (5%) in the positive cTnI group had ischemic changes and 2 patients (5%) had nonspecific changes, whereas only 1 patient (4%) with a negative cTnI had nonspecific changes. Bivariate analysis revealed a statistically significant association for positive cTnI and mortality; however, on multivariate analysis this was no longer significant.

CONCLUSION

Forty-three percent of bacteremic patients had an elevated cTnI. Risk factors for elevated cTnI were severity of the underlying infection, renal function, and underlying cardiac disease. Increased cTnI was found to be a dependent risk factor and a surrogate marker for death.

Elevated serum cardiac troponin I in older patients with hip fracture: incidence and prognostic significance

INTRODUCTION

Cardiovascular complications are the main causes of morbidity and mortality in patients with osteoporotic hip fracture (HF). The aim of this prospective study was to evaluate the incidence and prognostic significance of elevated cardiac troponin I (cTnI) in the early peri-operative period in older patients with HF.

MATERIALS AND METHODS

A blind evaluation of myocardial injury as detected by cTnI elevation in 238 consecutive older patients with low-trauma HF (mean age 81.9 +/- 7.8 (SD) years; 72% females). Data on demographic and clinical characteristics, in-hospital mortality, hospital length of stay and discharge destination were collected prospectively. Serum cTnI level was analysed from blood collected routinely in the first 72 h of hospital admission.

RESULTS

Sixty-nine (29%) patients had elevated cTnI (>0.06 microg/l) but myocardial injury was clinically recognised in only 23 (33%) and only 24 (34.8%) had a history of coronary artery disease (CAD). Patients with elevated cTnI were significantly older, more often had American Society of Anaesthesiologist status score >or=3, a history of CAD or stroke and more often were current smokers than the patients without cTnI elevation. In multivariate regression analysis only age was an independent predictor of cTnI elevation. Patients with cTnI release were twice as likely to have a length of stay >or=20 days (P = 0.047) and 2.7 times more likely to be discharged to a long-term residential care facility (RCF) (P = 0.013). cTnI level >or=1 microg/l was a strong independent predictor of all-cause mortality with 98.3% specificity and 89.1% negative predictive value.

CONCLUSION

Peri-operative myocardial injury is common in older HF patients but is frequently unrecognised clinically. Elevated blood cTnI level is an independent predictor of prolonged length of hospital stay (>or=20 days), need for long-term RCF and mortality (if cTnI >or=1 microg/l).

Prognostic implications of normal (<0.10 ng/ml) and borderline (0.10 to 1.49 ng/ml) troponin elevation levels in critically ill patients without acute coronary syndrome

Borderline increase of troponin I (cTnI) is associated with higher rates of cardiovascular events compared with normal levels in the setting of acute coronary syndrome (ACS), but the significance of borderline cTnI levels in patients without chest pain may differ. The aim of this study was to determine the prognostic implications of intermediate serum cTnI levels in patients without ACS in the intensive care unit (ICU). This was a 12-month retrospective study of 240 patients without ACS in the ICU with normal (<0.1 ng/ml) or intermediate (0.1 to 1.49 ng/ml) cTnI levels. End points included in-hospital mortality, lengths of ICU and hospital stays, and rates of postdischarge readmission and mortality. Overall in-hospital mortality was 13%, with 5% in the normal cTnI group and 28% in the intermediate cTnI group. By multivariate analysis, intermediate cTnI was independently associated with in-hospital mortality (p = 0.004) and length of ICU stay (p = 0.028). The only other independent risk factor for inpatient mortality was a standardized ICU prognostic measurement (Simplified Acute Physiology Score II score). Intermediate cTnI had no prognostic implications regarding length of hospital stay, readmission rate, or postdischarge mortality at 6 months. In conclusion, an intermediate level of cTnI in patients without ACS in the ICU is an independent prognostic marker predicting in-hospital mortality and length of ICU stay. Patients with intermediate cTnI levels who survive to discharge have equivalent out-of-hospital courses for up to 6 months compared with patients with normal cTnI levels.

Bench-to-bedside review: the value of cardiac biomarkers in the intensive care patient

The use of cardiac biomarkers in the intensive care setting is gaining increasing popularity. There are several reasons for this increase: there is now the facility for point-of-care biomarker measurement providing a rapid diagnosis; biomarkers can be used as prognostic tools; biomarkers can be used to guide therapy; and, compared with other methods such as echocardiography, the assays are easier and much more affordable. Two important characteristics of the ideal biomarker are disease specificity and a linear relationship between the serum concentration and disease severity. These characteristics are not present, however, in the majority of biomarkers for cardiac dysfunction currently available. Those clinically useful cardiac biomarkers, which naturally received the most attention, such as troponins and B-type natriuretic peptide, are not as specific as was originally thought. In the intensive care setting, it is important for the user to understand the degree of specificity of these biomarkers and that the interpretation of the results should always be guided by other clinical information. The present review summarizes the available biomarkers for different cardiac conditions. Potential biomarkers under evaluation are also briefly discussed.

Isolated and reversible impairment of ventricular relaxation in patients with septic shock

OBJECTIVE

Many patients with septic shock and increased cardiac troponin I (cTnI) do not exhibit significant left ventricular systolic dysfunction. We hypothesized that an isolated and reversible impairment of ventricular relaxation may be associated with the increase in cTnI.

DESIGN

Prospective, observational study.

SETTING

Surgical intensive care unit in a university hospital.

PATIENTS

Total of 54 patients with septic shock.

INTERVENTIONS

Fractional area change, early diastolic velocity of mitral annulus, flow propagation velocity of early diastolic mitral inflow, cTnI, tumor necrosis factor-alpha, interleukin (IL)-6, -1beta, -8, and -10 were measured at days 1, 2, 3, 4, 7, and 10 after onset of septic shock. Patients were classified into three groups: normal cTnI (group 1), increased cTnI and fractional area change <50% (group 2), and increased cTnI and fractional area change >50% (group 3).

MEASUREMENTS AND MAIN RESULTS

A total of 22 patients had an increase in cTnI, 11 with both systolic and diastolic dysfunctions and 11 with isolated impairment of left ventricular relaxation. At day 1, early diastolic velocity of mitral annulus and flow propagation velocity of early diastolic mitral inflow were significantly lower and tumor necrosis factor-alpha, IL-8, and IL-10 significantly higher in groups 2 and 3 compared with group 1. With resolution of septic shock, early diastolic velocity of mitral annulus and flow propagation velocity of early diastolic mitral inflow measured in patients of groups 2 and 3 returned progressively to values observed in group 1, with a parallel normalization of tumor necrosis factor-alpha, IL-8, and IL-10.

CONCLUSIONS

Isolated and reversible impairment of left ventricular relaxation, associated with transient increases in cTnI, tumor necrosis factor-alpha, IL-8, and IL-10, was observed in 20% of patients with septic shock.

Biomarkers and Bioassays for Cardiovascular Diseases: Present and Future

Stratification of cardiac patients arriving at the emergency department is now being made according to the levels of acute cardiac biomarkers (i.e. cardiac troponin (cTn) or creatine kinase myocardial band (CK-MB)). Ongoing efforts are undertaken in an attempt to identify and validate additional cardiac biomarkers, for example, interleukin-6, soluble CD40L, and C-reactive protein, in order to further risk stratify patients with acute coronary syndrome. Several studies have also now shown an association of platelet transcriptome and genomic single nucleotide polymorphisms with myocardial infarction by using advanced genomic tools. A number of markers, such as myeloid-related protein 14 (MRP-14), cyclooxygenase-1 (COX-1), 5-lipoxygenase activating protein (FLAP), leukotriene A4 hydrolase (LTA4H) and myocyte enhancing factor 2A (MEF2A), have been linked to acute coronary syndromes, including myocardial infarction. In the future, these novel markers may pave the way toward personalized disease-prevention programs based on a person's genomic, thrombotic and cardiovascular profiles. Current and future biomarkers and bioassays for identifying at-risk patients will be discussed in this review.

Cardiac troponin I elevation in hospitalized patients without acute coronary syndromes

Increase of cardiac troponins occurs in a variety of clinical situations in the absence of an acute coronary syndrome (ACS). Few data exist regarding the incidence, clinical characteristics, and predictive value of various cardiac diagnostic tests and outcome of patients with a non-ACS-related troponin increase. We studied 883 consecutive hospitalized patients with increased cardiac troponin I levels. The discharge diagnosis was reclassified and troponin increase attributed to ACS or another process. Clinical data and results of cardiac diagnostic tests were collected. Patients were followed for a median of 30 months. Three hundred eleven patients were classified as having a non-ACS-related troponin increase (35.2%). An alternative explanation for troponin increase was found in 99% of these patients. Troponin level had poor accuracy in discriminating patients with and without ACS (area under the receiver operating characteristics curve 0.63). Coronary angiography was frequently unhelpful in excluding a non-ACS-related troponin increase because 77% of patients in the non-ACS group had significant flow-limiting coronary artery disease. Patients with non-ACS-related troponin increase had significantly higher in-hospital (hazard ratio 2.8, 95% confidence interval 2.0 to 3.8) and long-term (hazard ratio 2.0, 95% confidence interval 1.6 to 2.5) mortalities compared with patients with ACS. In conclusion, cardiac troponin level is frequently increased in hospitalized patients in the absence of an ACS and portends poor short- and long-term outcomes. Most of these patients have an alternative explanation for cardiac troponin increase. Cardiac diagnostic procedures are frequently unhelpful in excluding a non-ACS-related troponin increase.

Relation of troponin elevation to outcome in patients with infective endocarditis

Elevated troponin is increasingly recognized as a marker of cardiac injury and poor outcomes in diverse disease states. It was hypothesized that patients with infective endocarditis (IE) and elevated cardiac troponin would have more extensive IE and worse clinical outcomes. Patients were enrolled as part of the International Collaboration on Endocarditis (ICE) prospective cohort study; analysis of these patients was done retrospectively. Data from 83 consecutively enrolled patients from a single center were evaluated. Cardiac troponin I (cTnI) was drawn for clinical indications and before any cardiac surgery in 51 of the 83 patients. Outcomes evaluated were hospital mortality, annular or myocardial abscess on the basis of echocardiography or surgery, and central nervous system events. Of 51 patients with cTnI drawn, 33 (65%) had elevated cTnI > or =0.1 mg/dl. There were no differences in age, gender, prosthetic valve IE, Staphylococcus aureus IE, or history of coronary artery disease, congestive heart failure, or diabetes mellitus between patients with and without cTnI elevations. Patients with elevated cTnI were less likely to have isolated right-sided IE and more likely to have left ventricular systolic dysfunction or renal dysfunction (p <0.05 for each). In conclusion, elevated cTnI was associated with the composite of death, abscess, and central nervous system events (p <0.001).

Positive troponin in diabetic ketoacidosis without evident acute coronary syndrome predicts adverse cardiac events

BACKGROUND

Elevated troponin I has been associated with increased mortality in critically ill patients without acute coronary syndrome (ACS). However, the prognostic significance of troponin elevation in patients with diabetic ketoacidosis (DKA) without evident ACS has not been studied.

METHODS

Retrospective study of all patients admitted to a U.S. tertiary center between 01/98 and 12/00 with DKA and had troponin I level measured. Patients with evidence of ACS or who met the American College of Cardiology/European Society of Cardiology (ACC/ESC) definition for myocardial infarction were excluded. Baseline characteristics, cardiac evaluation and 2 year major adverse coronary event (MACE) rate were compared between patients with positive and negative troponin.

RESULTS

Ninety-six patients fulfilled the inclusion criteria of this study, 26 had positive troponin. There were no differences in baseline characteristics between the two groups. After a 2 year follow-up, there was significantly increased mortality in patients with elevated troponin (50.0% versus 27.1%, hazard-ratio (HR) 2.3, 95% confidence interval (CI) 1.2-4.8, p = 0.02). Patients with elevated troponin also had significantly increased MACE rate at 2 years (50.0% versus 28.6%, HR 2.6, 95% CI 1.3-5.3, p = 0.007) driven primarily by mortality. Using Cox Proportional Hazard Analysis, elevated troponin was a predictor of increased MACE after adjusting for confounding variables. (Adjusted HR 2.3, 95% CI 1.1-4.6, p = 0.02)

CONCLUSIONS

Elevated troponin I in diabetic patients admitted with DKA identifies a group at very high risk for future cardiac events and mortality. Whether cardiac risk stratification of these patients will improve long term outcome remains to be studied.

Myocardial infarction on the ICU: can we do better?

Myocardial infarction remains a major cause of death despite contemporary therapeutic strategies. Diagnosis in the intensive care unit is challenging, but is essential to target therapy accurately. In this issue of Critical Care Lim and colleagues present the results of a prospective non-interventional screening study for acute myocardial infarction in patients admitted to the intensive care unit. Myocardial infarction is observed to occur frequently, often without being clinically apparent, with a high associated mortality. Such approaches may facilitate accurate diagnosis of myocardial infarction in this setting, hence opening the way to improved therapy.

Detecting myocardial infarction in critical illness using screening troponin measurements and ECG recordings

INTRODUCTION

To use screening cardiac troponin (cTn) measurements and electrocardiograms (ECGs) to determine the incidence of elevated cTn and of myocardial infarction (MI) in patients admitted to the intensive care unit (ICU), and to assess whether these findings influence prognosis. This is a prospective screening study.

MATERIALS AND METHODS

We enrolled consecutive patients admitted to a general medical-surgical ICU over two months. All patients underwent systematic screening with cTn measurements and ECGs on ICU admission, then daily for the first week in ICU, alternate days for up to one month and weekly thereafter until ICU death or discharge, for a maximum of two months. Patients without these investigations ordered during routine clinical care underwent screening for study purposes but these results were unavailable to the ICU team. After the study, all ECGs were interpreted independently in duplicate for ischaemic changes meeting ESC/ACC criteria supporting a diagnosis of MI. Patients were classified as having MI (elevated cTn and ECG evidence supporting diagnosis of MI), elevated cTn only (no ECG evidence supporting diagnosis of MI), or no cTn elevation.

RESULTS

One hundred and three patients were admitted to the ICU on 112 occasions. Overall, 37 patients (35.9 per cent) had an MI, 15 patients (14.6 per cent) had an elevated cTn only and 51 patients (49.5 per cent) had no cTn elevation. Patients with MI had longer duration of mechanical ventilation (p < 0.0001), longer ICU stay (p = 0.001), higher ICU mortality (p < 0.0001) and higher hospital mortality (p < 0.0001) compared with those with no cTn elevation. Patients with elevated cTn had higher hospital mortality (p = 0.001) than patients without cTn elevation. Elevated cTn was associated with increased hospital mortality (odds ratio 27.3, 95 per cent CI 1.7 - 449.4), after adjusting for APACHE II score, MI and advanced life support. The ICU team diagnosed 18 patients (17.5 per cent) as having MI on clinical grounds; four of these patients did not have MI by adjudication. Thus, screening detected an additional 23 MIs not diagnosed in practice, reflecting 62.2 per cent of MIs ultimately diagnosed. Patients with MI diagnosed by the ICU team had similar outcomes to patients with MI detected by screening alone.

CONCLUSION

Systematic screening detected elevated cTn measurements and MI in more patients than were found in routine practice. Elevated cTn was an independent predictor of hospital mortality. Further research is needed to evaluate whether screening and subsequent treatment of these patients reduces mortality.

Troponin I in the intensive care unit setting: from the heart to the heart

When measured in the plasma, cardiac troponins T (cTnT) and I (cTnI) are considered to be highly specific markers of myocardial cell damage; however, research has demonstrated that troponin elevation may associated with causes other than coronary artery disease. In the intensive care unit (ICU) setting, increased cTnI levels are quite common findings and when documented, even on admission, intensivists should bear in mind that this laboratory finding holds a prognostic role independent of the reason for ICU admission. The mechanism(s) (such as demand ischemia, myocardial strain, etc.) and not simply the cause (i.e., renal failure) of the increment in serum cTnI should be investigated to better tailor the therapeutical regimen in the single patient. In this review, we therefore consider the nonthrombotic causes of troponin elevation in the critical setting.