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

High sensitivity troponin measurement in critical care: Flattering to deceive or 'never means nothing'?

INTRODUCTION

Troponin elevation is central to the diagnosis of acute type 1 myocardial infarction. It is, however, elevated in a range of other conditions, including type 2 myocardial infarction, and this setting is increasingly associated with adverse clinical outcomes. Patients within intensive care frequently have at least one organ failure together with a range of co-morbidities. Interpretation of troponin assay results in this population is challenging. This clinical uncertainty is compounded by the introduction of ever more sensitive troponin assays.

AREAS COVERED

The aims of this review are to (a) describe the currently available literature about the use of troponin assays in intensive care, (b) analyse the challenges presented by the introduction of increasingly sensitive troponin assays and (c) assess whether the role of troponin assays in intensive care may change in the future, dependent upon recent and ongoing research suggesting that they are predictive of outcome regardless of the underlying cause: the 'never means nothing' hypothesis.

[Diagnosis of myocardial infarction in critically ill, ventilated patients]

Elevated cardiac troponin values are frequently observed in critically ill patients. These are often not due to myocardial infarction (MI) but caused by various other etiologies of myocardial injury. Understanding the etiology of any troponin elevation is of enormous importance for management and therapy. According to the fourth version of the Universal Definition of MI, myocardial injury is present if at least one troponin value is above the 99th percentile upper reference limit and considered acute, when a rise and/or fall occurs. Patients with acute MI are a subgroup of patients with acute myocardial injury, who present in an ischemic clinical context. Variables defining the clinical criteria of MI include symptoms of ischemia, presumably new electrocardiographic (ECG) changes or imaging evidence of new loss of viable myocardium or regional wall motion abnormalities, or detection of an intracoronary thrombus. In critically ill or mechanically ventilated patients, the diagnosis of MI is challenging due to limitations in history taking, co-existence of comorbidities, overlapping symptoms and equivocal or unspecific ECG changes. This article presents the diagnostic criteria of the Universal MI definition, discusses subtypes of MI and focuses on various differential diagnoses. Furthermore, implications of diagnosis of MI in critically ill patients, especially regarding the use of ECG and troponin assays, are discussed.

Cardiac troponin T is associated with mortality in patients admitted to critical care in a UK major trauma centre: a retrospective database analysis

Background

Elevated levels of cardiac troponin T are associated with poor outcome in critically ill patients and have been proposed as a prognostic marker in major trauma. This study investigated the relationship between cardiac troponin T levels on admission to intensive care unit (ICU) and all-cause mortality in major trauma patients.

Methods

A retrospective database analysis of cardiac troponin T levels on admission to the ICU in major trauma patients between 1 August 2015 and 31 December 2016 at a UK Major Trauma Centre was performed.

Results

Of the 243 patients, 69 (28.4%) died. Cardiac troponin T levels were significantly higher in patients who died compared to survivors: 42 vs. 13 ng/L, respectively (p < 0.0001); the odds of all-cause mortality increased significantly as troponin increased, independent of age or Acute Physiology and Chronic Health Evaluation score.

Discussion

This confirms cardiac troponin T at ICU admission as a marker of mortality in major trauma. Elevated cardiac troponin T may be seen in patients without evidence of direct cardiac trauma.

Stress cardiomyopathy of the critically ill: Spectrum of secondary, global, probable and subclinical forms

Stress cardiomyopathy (SC) typically presents as potential acute coronary syndrome (ACS) in previously healthy people. While there may be physical or mental stressors, the initial symptom is usually chest pain. This form conforms to the published Mayo diagnostic criteria, is well reported and as the presentation is initially cardiac, is considered primary SC. Increasingly we see SC develop several days into the hospitalization secondary to medical or surgical critical illness. This condition is more complex, presents atypically, is not easy to recognize and carries a much worse prognosis. Label of Secondary SC is appropriate as it manifests in sicker hospitalized patients with numerous comorbidities. We review the limited but provocative literature pertinent to SC in the critically ill and describe important clues to identify global, subclinical and probable forms of SC. We illustrate the several unique clinical features, demographic differences and propose a diagnostic algorithm to optimize cardiac care in the critically ill.

The Deferred Consent Model in a Prospective Observational Study Evaluating Myocardial Injury in the Intensive Care Unit

BACKGROUND

Informed consent is a hallmark of ethical clinical research. An inherent challenge in critical care research is obtaining consent when patients lack decision-making capacity. One solution is deferred consent, which is often used for studies that are low risk or involve emergency interventions. Our objective was to describe a deferred consent model in a low-risk critical care study.

METHODS

Prognostic Value of Elevated Troponins in Critical Illness Study was a prospective, pilot observational study of critically ill patients in 3 intensive care units, involving serial electrocardiograms and cardiac biomarkers. Newly admitted patients were enrolled over 1 month. When possible, informed consent was obtained a priori from the patient or substitute decision maker (SDM); otherwise, consent was deferred until the patient regained consent capacity or until their SDM was available. Logistic regression analysis was used to determine the association between patient's sex, Acute Physiology and Chronic Health Evaluation II score, study center, person providing consent (patient vs SDM), method of consent (telephone vs in person), and the provision or not of informed consent.

RESULTS

The overall consent rate was 80.1% (213 of 266 persons approached). Of the 53 persons declining consent, 37 (69.8%) agreed to the use of data collected up until that point. Over half of all consent encounters were with patients rather than SDMs. Median interval delay between enrollment and the consent encounter was 1 day. On multivariate analysis, the only variable associated with consent was male sex of the patient (odds ratio for males 2.59, confidence interval: 1.19-5.63).

CONCLUSION

Deferred consent facilitates implementation of time-sensitive research protocols until a consent encounter is possible. As a feasible alternative to exclusive a priori consent, the deferred consent model can be useful in low-risk studies in critically ill patients.

Prognostic value of initial elevation in cardiac troponin I level in critically ill patients without acute coronary syndrome

BACKGROUND

Cardiac troponin I levels are often obtained to help rule out acute coronary syndrome.

OBJECTIVE

To determine if elevation of troponin level within 24 hours for patients without acute coronary syndrome admitted to the intensive care unit provides important prognostic information.

METHODS

Patients without acute coronary syndrome admitted to the intensive care unit were prospectively divided into 2 groups according to highest serum level of cardiac troponin I within 24 hours of admission (elevated > 0.049 ng/mL; control ≤ 0.049 ng/mL). Hospital mortality, incidence of intubation, and other parameters were compared between the 2 groups.

RESULTS

Patients with elevated troponin level (n = 40) had higher mortality than did control patients (n = 50) (35% vs 12%; P= .01). Compared with control patients, patients with elevated levels were more likely to be intubated (41% vs 17%; P= .02).

CONCLUSION

Critically ill patients without acute coronary syndrome with elevated levels of cardiac troponin I at admission had higher mortality and more intubations than did control patients.

Myocardial infarction in intensive care units: A systematic review of diagnosis and treatment

INTRODUCTION

Patients in the intensive care unit are vulnerable to myocardial injury from a variety of causes, both ischaemic and non-ischaemic. It is challenging for ICU clinicians to apply the conventional guidance concerning diagnosis and treatment. We conducted this review to examine the evidence concerning diagnosis and treatment of myocardial infarction in the ICU.

METHODS

A systematic review was performed to identify relevant studies.

RESULTS

19 studies concerning use of ECG, cardiac enzymes, echocardiography and angiography were identified. 4 studies considered treatment of myocardial infarction.

CONCLUSIONS

Regular 12 lead ECG or 12 lead ECG monitoring is more sensitive than 2 lead monitoring, regular measurement of cardiac enzymes is more sensitive than when provoked by symptoms. Coronary angiography rarely identifies treatable lesions, without regional wall motion abnormality on echocardiography. Evidence relating to treatment was limited. A potential strategy to diagnose myocardial infarctions in the ICU is proposed.

Obstructive coronary artery disease in patients hospitalized for severe sepsis or septic shock with concomitant acute myocardial infarction

PURPOSE

It is difficult to differentiate type 1 acute myocardial infarction (AMI) with obstructive coronary artery disease (OCAD) from type 2 AMI in patients admitted for severe sepsis. The aims of this study were to assess the risk factors and prognosis of OCAD in patients admitted to the intensive care unit for severe sepsis with concomitant AMI.

MATERIALS AND METHODS

This is a single-center retrospective cohort study including all consecutive patients who were hospitalized for severe sepsis or septic shock between March 2006 and September 2014 and who underwent coronary angiography in the intensive care unit to identify AMI.

RESULTS

Overall, 78 (5.5%) of 1418 patients hospitalized for severe sepsis underwent coronary angiography to identify concomitant AMI. Thirty-two patients (41%) had OCAD. Following multivariate analysis, the risk factors of OCAD were peripheral vascular disease (odds ratio [OR] =5.7; 95% confidence interval [CI], 1.1-30.4; P = .042) and at least 2 cardiovascular risk factors (OR = 6.7; 95% CI, 1.9-23.8; P = .003). Obstructive coronary artery disease was associated with a significant mortality increase at 60 days (OR = 8.1; 95% CI, 1.9-30.2; P = .004).

CONCLUSIONS

Obstructive coronary artery disease is a poor prognosis factor in patients hospitalized for severe sepsis with concomitant AMI. In this setting, medical treatment should be considered for patients with peripheral vascular disease or with at least 2 cardiovascular risk factors; the need to perform coronary angiography should be considered carefully.

Earliest Bedside Assessment of Hemodynamic Parameters and Cardiac Biomarkers: Their Role as Predictors of Adverse Outcome in Patients with Septic Shock

BACKGROUND

Early assessment and aggressive hemodynamic treatment have been shown to increase the survival of patients in septic shock. Current and past sepsis guidelines recommend a resuscitation protocol including central venous pressure (CVP), mean arterial blood pressure (MAP), urine output and central venous oxygen saturation (ScvO2) for resuscitation within the first six hours. Currently, the established severity score systems like APACHE II score, SOFA score or SAPS II score predict the outcome of critically ill patients on the bases of variables obtained only after the first 24 hours. The present study aims to evaluate the risk of short-term mortality for patients with septic shock by the earliest possible assessment of hemodynamic parameters and cardiac biomarkers as well as their role for the prediction of the adverse outcome.

METHODS

52 consecutive patients treated for septic shock in the intensive care unit of one centre (Marien Hospital Herne, Ruhr University Bochum, Germany) were prospectively enrolled in this study. Hemodynamic parameters (MAP, CVP, ScvO2, left ventricular ejection fraction, Hematocrit) and cardiac biomarkers (Troponin I) at the ICU admission were evaluated in regard to their influence on mortality. The primary endpoint was all-cause mortality within 28 days after the admission.

RESULTS

A total of 52 patients (31 male, 21 female) with a mean age of 71.4±8.5 years and a mean APACHE II score of 37.0±7.6 were enrolled in the study. 28 patients reached the primary endpoint (mortality 54%). Patients presenting with hypotension (MAP <65 mmHg) at ICU admission had significantly higher rates of 28-day mortality as compared with the group of patients without hypotension (28-day mortality rate 74 % vs. 32 %, p<0.01). Furthermore, the patients in the hypotension present group had significantly higher lactate concentration (p=0.002), higher serum creatinin (p=0.04), higher NTproBNP (p=0.03) and after the first 24 hours higher APACHE II scores (p=0.04). A MAP <65 mmHg was the only hemodynamic parameter significantly predicting the primary endpoint (OR: 4.1, CI: 1.1 - 14.8, p=0.008), whereas the remaining hemodynamic variables CVP, ScvO2, Hematocrit, Troponin I and left ventricular ejection fraction (LVEF) seemed to have no influence on survival. Besides, non-survivors had a significantly higher age (74.1±9.0 vs. 68.4±6.9, p=0.01). If hypotension coincided with an age ≥72 years, the 28-day mortality rate escalated to 88%.

CONCLUSIONS

In our study, we identified a risk group with an exceedingly high mortality rate: the patients with an age ≥72 years and presenting with hypotension (MAP <65 mmHg). These data can be easily obtained at the time of the very first patient contact. As a result, an aggressive and a more effective treatment can be initiated within the first minutes of the primary care, possibly reducing organ failure and short-term mortality in this risk group.

The diagnostic challenge of myocardial infarction in critically ill patients: do high-sensitivity troponin measurements add more clarity or more confusion?

In ICU settings, the diagnosis and treatment of acute myocardial infarction (AMI) are challenging, partly because cardiac troponin increase occurs frequently. In the previous issue of Critical Care, Ostermann and colleagues reported that myocardial infarction (MI), screened by plasma troponin and electrocardiography changes, is common and often clinically unrecognized in the ICU. Although the clinical significance of underdiagnosed MIs remains unclear, this approach may help to target and further investigate the at-risk population for appropriate therapy.

A prospective study of the impact of serial troponin measurements on the diagnosis of myocardial infarction and hospital and six-month mortality in patients admitted to ICU with non-cardiac diagnoses

INTRODUCTION

Troponin T (cTnT) elevation is common in patients in the Intensive Care Unit (ICU) and associated with morbidity and mortality. Our aim was to determine the epidemiology of raised cTnT levels and contemporaneous electrocardiogram (ECG) changes suggesting myocardial infarction (MI) in ICU patients admitted for non-cardiac reasons.

METHODS

cTnT and ECGs were recorded daily during week 1 and on alternate days during week 2 until discharge from ICU or death. ECGs were interpreted independently for the presence of ischaemic changes. Patients were classified into four groups: (i) definite MI (cTnT ≥15 ng/L and contemporaneous changes of MI on ECG), (ii) possible MI (cTnT ≥15 ng/L and contemporaneous ischaemic changes on ECG), (iii) troponin rise alone (cTnT ≥15 ng/L), or (iv) normal. Medical notes were screened independently by two ICU clinicians for evidence that the clinical teams had considered a cardiac event.

RESULTS

Data from 144 patients were analysed (42% female; mean age 61.9 (SD 16.9)). A total of 121 patients (84%) had at least one cTnT level ≥15 ng/L. A total of 20 patients (14%) had a definite MI, 27% had a possible MI, 43% had a cTNT rise without contemporaneous ECG changes, and 16% had no cTNT rise. ICU, hospital and 180-day mortality was significantly higher in patients with a definite or possible MI.

CONCLUSIONS

The majority of critically ill patients (84%) had a cTnT rise and 41% met criteria for a possible or definite MI of whom only 20% were recognised clinically. Mortality up to 180 days was higher in patients with a cTnT rise.

Cardiac ischemia in patients with septic shock randomized to vasopressin or norepinephrine

Introduction

Cardiac troponins are sensitive and specific biomarkers of myocardial necrosis. We evaluated troponin, CK, and ECG abnormalities in patients with septic shock and compared the effect of vasopressin (VP) versus norepinephrine (NE) on troponin, CK, and ECGs.

Methods

This was a prospective substudy of a randomized trial. Adults with septic shock randomly received, blinded, a low-dose infusion of VP (0.01 to 0.03 U/min) or NE (5 to 15 μg/min) in addition to open-label vasopressors, titrated to maintain a mean blood pressure of 65 to 75 mm Hg. Troponin I/T, CK, and CK-MB were measured, and 12-lead ECGs were recorded before study drug, and 6 hours, 2 days, and 4 days after study-drug initiation. Two physician readers, blinded to patient data and drug, independently interpreted ECGs.

Results

We enrolled 121 patients (median age, 63.9 years (interquartile range (IQR), 51.1 to 75.3), mean APACHE II 28.6 (SD 7.7)): 65 in the VP group and 56 in the NE group. At the four time points, 26%, 36%, 32%, and 21% of patients had troponin elevations, respectively. Baseline characteristics and outcomes were similar between patients with positive versus negative troponin levels. Troponin and CK levels and rates of ischemic ECG changes were similar in the VP and the NE groups. In multivariable analysis, only APACHE II was associated with 28-day mortality (OR, 1.07; 95% CI, 1.01 to 1.14; P = 0.033).

Conclusions

Troponin elevation is common in adults with septic shock. We observed no significant differences in troponin, CK, and ECGs in patients treated with vasopressin and norepinephrine. Troponin elevation was not an independent predictor of mortality.

Trial registration

Controlled-trials.com ISRCTN94845869

Coronary artery disease in patients clinically diagnosed with myocardial infarction in the medical intensive care unit

PURPOSE

The purpose of this study is to compare the clinical characteristics and outcomes of patients with and without coronary artery disease (CAD) confirmed by coronary angiography in critically ill patients clinically diagnosed with myocardial infarction.

MATERIALS AND METHODS

This retrospective observational study involved 56 patients who were clinically diagnosed with myocardial infarction and subsequently underwent coronary angiography during their intensive care unit stay.

RESULTS

Only 18 patients (32%) were finally confirmed to have CAD by coronary angiography. There were no significant differences in laboratory findings and clinical outcomes between patients with and without CAD. However, patients who developed shock (P = .009) and needed vasopressor support (P = .021) were less likely to be diagnosed with CAD. In addition, regional wall motion abnormality on echocardiography was more frequently observed in patients with CAD (P = .072). In a multiple logistic regression analysis, male sex (adjusted odds ratio [OR], 5.093; 95% confidence interval [CI], 1.177-22.037) and focal hypokinesia on echocardiography (adjusted OR, 5.134; 95% CI, 1.071-24.614) were independently associated with CAD. However, development of shock was inversely associated with CAD (adjusted OR, 0.107; 95% CI, 0.019-0.606).

CONCLUSION

Coronary angiography in critically ill patients should only be performed in highly selected patients with predicting factors for CAD.

Treatment of acute coronary syndrome: part 2: ST-segment elevation myocardial infarction

OBJECTIVE

Familiarize clinicians with recent information regarding the diagnosis and treatment of ST-segment elevation myocardial infarction.

DATA SOURCES

PubMed search and review of relevant medical literature.

SUMMARY

Definition, pathophysiology, clinical presentation, diagnosis, and treatment of ST-segment elevation myocardial infarction are reviewed.

CONCLUSIONS

Patients with ST-segment elevation myocardial infarction benefit from prompt reperfusion therapy. Adjunctive antianginal, antiplatelet, antithrombotic, beta blocker, angiotensin-converting enzyme inhibitor, and statin agents minimize ongoing cardiac ischemia, prevent thrombus propagation, and reduce the risk of recurrent cardiovascular events.

Raised serum cardiac troponin I concentrations predict hospital mortality in intensive care unit patients

BACKGROUND

Recent work suggests that increased plasma concentrations of cardiac troponin I (cTnI) are common in critically ill patients and are associated with poor outcome. We measured the frequency of increased plasma cTnI concentrations during patients' stay in a mixed medical/surgical intensive care unit (ICU) and compared our findings with hospital mortality.

METHODS

Basic details, organ support, and hospital mortality were recorded for all patients treated in ICU during a 6 month period. cTnI concentrations were sampled daily for all patients, using 0.04 µg litre(-1) as the upper limit of normal, and 0.12 µg litre(-1) as an additional stratification point.

RESULTS

Of 663 patients, 54% were male, with a mean (sd) age of 60 (18) yr, 65% were surgical patients, and the median Acute Physiology and Chronic Ill Health II (APACHE II) score was 15 (inter-quartile range 12-20). Increased cTnI concentrations were found in 345 patients (52%) while in ICU. One hundred and twenty patients (18%) died in hospital. cTnI concentration >0.04 µg litre(-1) was associated with reduced odds of hospital survival, independent of age, medical admission, unplanned admission, APACHE II score, mechanical ventilation, and haemofiltration (adjusted odds ratio 0.25, 95% confidence interval 0.08-0.75, P=0.014). Stratification by the degree of cTnI increase revealed an incremental trend towards a lower odds of hospital survival, including for patients with 'minor' elevations of cTnI (0.05-0.12 µg litre(-1)).

CONCLUSIONS

Increased serum cTnI concentrations during ICU stay independently predicts hospital mortality, even when the threshold is low. We found a trend towards an association between 'minor' elevations in cTnI and higher in-hospital mortality.

Panoramic ECG display versus conventional ECG: ischaemia detection by critical care nurses

AIM

To compare accuracy and certainty of diagnosis of cardiac ischaemia using the Panoramic ECG display tool plus conventional 12-lead electrocardiogram (ECG) versus 12-lead ECG alone by UK critical care nurses who were members of the British Association of Critical Care Nurses (BACCN).

BACKGROUND

Critically ill patients are prone to myocardial ischaemia. Symptoms may be masked by sedation or analgesia, and ECG changes may be the only sign. Critical care nurses have an essential role in detecting ECG changes promptly. Despite this, critical care nurses may lack expertise in interpreting ECGs and myocardial ischaemia often goes undetected by critical care staff.

METHOD

British Association of Critical Care Nurses (BACCN) members were invited to complete an online survey to evaluate the analysis of two sets of eight ECGs displayed alone and with the new display device.

RESULTS

Data from 82 participants showed diagnostic accuracy improved from 67·1% reading ECG traces alone, to 96·0% reading ECG plus Panoramic ECG display tool (P < 0·01, significance level α = 0·05). Participants' diagnostic certainty score rose from 41·7% reading ECG alone to 66·8% reading ECG plus Panoramic ECG display tool (P < 0·01, α = 0·05).

CONCLUSION

The Panoramic ECG display tool improves both accuracy and certainty of detecting ST segment changes among critical care nurses, when compared to conventional 12-lead ECG alone. This benefit was greatest with early ischaemic changes. Critical care nurses who are least confident in reading conventional ECGs benefit the most from the new display.

RELEVANCE TO CLINICAL PRACTICE

Critical care nurses have an essential role in the monitoring of critically ill patients. However, nurses do not always have the expertise to detect subtle ischaemic ECG changes promptly. Introduction of the Panoramic ECG display tool into clinical practice could lead to patients receiving treatment for myocardial ischaemia sooner with the potential for reduction in morbidity and mortality.

Increased blood troponin levels in ICU patients

PURPOSE OF REVIEW

Cardiac troponins in serum have become the biomarkers of choice for the diagnosis of myocardial infarction. Yet, troponin can also be elevated by a multitude of causes in the absence of overt myocardial ischemia. Such nonspecific elevations are particularly common in the critically ill. This article aims to provide information on the significance of troponin elevations in unselected critically ill patients and in patients with sepsis or septic shock.

RECENT FINDINGS

Recent studies reconsider the possible association of troponin elevations with myocardial infarction in unselected critically ill patients. There are also more data on the prognostic significance of troponin in this population. In patients with sepsis, recent studies suggest that troponin may be a reliable index of sepsis-induced myocardial dysfunction, although the implications of this finding in the management of sepsis remain unclear for the time being. Troponin also appears to be a predictor of short and possibly also long-term outcome in septic patients. The advent of newer assays with even higher sensitivity, may lead to further redefinition of the role of troponin in the ICU.

SUMMARY

Troponin is frequently elevated in critically ill patients. More research is needed on the diagnostic and prognostic significance and possible clinical applications of troponin measurements in patients with sepsis and critical illness.

Agreement in electrocardiogram interpretation in patients with septic shock

OBJECTIVE

The reliability of electrocardiogram interpretation to diagnose myocardial ischemia in critically ill patients is unclear. In adults with septic shock, we assessed intra- and inter-rater agreement of electrocardiogram interpretation, and the effect of knowledge of troponin values on these interpretations.

DESIGN

Prospective substudy of a randomized trial of vasopressin vs. norepinephrine in septic shock.

SETTING

Nine Canadian intensive care units.

PATIENTS

Adults with septic shock requiring at least 5 μg/min of norepinephrine for 6 hrs.

INTERVENTIONS

Twelve-lead electrocardiograms were recorded before study drug, and 6 hrs, 2 days, and 4 days after study drug initiation.

MEASUREMENTS

Two physician readers, blinded to patient data and group, independently interpreted electrocardiograms on three occasions (first two readings were blinded to patient data; third reading was unblinded to troponin). To calibrate and refine definitions, both readers initially reviewed 25 trial electrocardiograms representing normal to abnormal. Cohen's Kappa and the φ statistic were used to analyze intra- and inter-rater agreement.

RESULTS

One hundred twenty-one patients (62.2 ± 16.5 yrs, Acute Physiology and Chronic Health Evaluation II 28.6 ± 7.7) had 373 electrocardiograms. Blinded to troponin, readers 1 and 2 interpreted 46.4% and 30.0% of electrocardiograms as normal, and 15.3% and 12.3% as ischemic, respectively. Intrarater agreement was moderate for overall ischemia (κ 0.54 and 0.58), moderate/good for "normal" (κ 0.69 and 0.55), fair to good for specific signs of ischemia (ST elevation, T inversion, and Q waves, reader 1 κ 0.40 to 0.69; reader 2 κ 0.56 to 0.70); and good/very good for atrial arrhythmias (κ 0.84 and 0.79) and bundle branch block (κ 0.88 and 0.79). Inter-rater agreement was fair for ischemia (κ 0.29), moderate for ST elevation (κ 0.48), T inversion (κ 0.52), and Q waves (κ 0.44), good for bundle branch block (κ 0.78), and very good for atrial arrhythmias (κ 0.83). Inter-rater agreement for ischemia improved from fair to moderate (κ 0.52, p = .028) when unblinded to troponin.

CONCLUSIONS

In patients with septic shock, inter-rater agreement of electrocardiogram interpretation for myocardial ischemia was fair, and improved with troponin knowledge.

Outcomes of hospitalized patients with non-acute coronary syndrome and elevated cardiac troponin level

OBJECTIVE

Cardiac troponin levels help risk-stratify patients presenting with an acute coronary syndrome. Although cardiac troponin levels may be elevated in patients presenting with non-acute coronary syndrome conditions, specific diagnoses and long-term outcomes within that cohort are unclear.

METHODS

By using the Veterans Affairs centralized databases, we identified all hospitalized patients in 2006 who had a troponin assay obtained during their initial reference hospitalization. On the basis of the diagnostic codes of the International Classification of Diseases, 9th Revision, primary diagnoses were categorized as acute coronary syndrome or non-acute coronary syndrome conditions.

RESULTS

Of a total of 21,668 patients with an elevated troponin level who were discharged from the hospital, 12,400 (57.2%) had a non-acute coronary syndrome condition. Among that cohort, the most common diagnostic category involved the cardiovascular system, and congestive heart failure (N=1661) and chronic coronary artery disease (N=1648) accounted for the major classifications. At 1 year after hospital discharge, mortality in patients with a non-acute coronary syndrome condition was 22.8% and was higher than in the acute coronary syndrome cohort (odds ratio 1.39; 95% confidence interval, 1.30-1.49). Despite the high prevalence of cardiovascular diseases in patients with a non-acute coronary syndrome diagnosis, use of cardiac imaging within 90 days of hospitalization was low compared with that in patients with acute coronary syndrome (odds ratio 0.25; 95% confidence interval, 0.23-0.27).

CONCLUSIONS

Hospitalized patients with an elevated troponin level more often have a primary diagnosis that is not an acute coronary syndrome. Their long-term survival is poor and justifies novel diagnostic or therapeutic strategy-based studies to target the highest risk subsets before hospital discharge.

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.

Year in review 2008: Critical Care--cardiology

We review key research papers in cardiology and intensive care published during 2008 in Critical Care. We quote studies on the same subject published in other journals if appropriate. Papers have been grouped into three categories: (a) cardiovascular biomarkers in critical illness, (b) haemodynamic management of septic shock, and (c) haemodynamic monitoring.

Increases of cardiac troponin in conditions other than acute coronary syndrome and heart failure

BACKGROUND

Although cardiac troponin (cTn) is a cornerstone marker in the assessment and management of patients with acute coronary syndrome (ACS) and heart failure (HF), cTn is not diagnostically specific for any single myocardial disease process. This narrative review discusses increases in cTn that result from acute and chronic diseases, iatrogenic causes, and myocardial injury other than ACS and HF.

CONTENT

Increased cTn concentrations have been reported in cardiac, vascular, and respiratory disease and in association with infectious processes. In cases involving acute aortic dissection, cerebrovascular accident, treatment in an intensive care unit, and upper gastrointestinal bleeding, increased cTn predicts a longer time to diagnosis and treatment, increased length of hospital stay, and increased mortality. cTn increases are diagnostically and prognostically useful in patients with cardiac inflammatory diseases and in patients with respiratory disease; in respiratory disease cTn can help identify patients who would benefit from aggressive management. In chronic renal failure patients the diagnostic sensitivity of cTn for ACS is decreased, but cTn is prognostic for the development of cardiovascular disease. cTn also provides useful information when increases are attributable to various iatrogenic causes and blunt chest trauma.

SUMMARY

Information on the diagnostic and prognostic uses of cTn in conditions other than ACS and heart failure is accumulating. Although increased cTn in settings other than ACS or heart failure is frequently considered a clinical confounder, the astute physician must be able to interpret cTn as a dynamic marker of myocardial damage, using clinical acumen to determine the source and significance of any reported cTn increase.

Acute bacterial pneumonia is associated with the occurrence of acute coronary syndromes

A link between acute infections and the development of acute coronary syndromes (ACS) has been proposed. We used retrospective cohort and self-controlled case series analyses to define the closeness of the association between acute bacterial pneumonia due to Streptococcus pneumoniae or Haemophilus influenzae and ACS. For the retrospective cohort analysis we included a control group of patients with admission diagnoses other than pneumonia or ACS. For the self-controlled case series analysis, we made within-person comparisons of the risk for ACS during the 15 days after admission for pneumonia with that of 365 days before and after that event. In 206 pneumonia patients (144 S. pneumoniae, 62 H. influenzae) we identified 22 (10.7%) cases of ACS, which compared to 6 (1.5%) among 395 controls resulted in an odds ratio (OR) of 7.8 (95% confidence interval [CI], 3.1-19.4). With multivariate logistic regression analysis, the OR for ACS in the pneumonia group remained elevated (OR, 8.5; 95% CI, 3.4-22.2). By the self-controlled case series method, the risk of ACS remarkably increased during the first 15 days after the diagnosis of pneumonia (incidence rate ratio, 47.6; 95% CI, 24.5-92.5). The characteristics and strength of these associations suggest a causal role for the acute infection in this relationship.

Troponin I rise after pacemaker implantation at the time of "universal definition of myocardial infarction"

We assessed incidence, magnitude, and time course of cardiac troponin I (cTnI) increase after pacemaker implantation in patients without acute coronary syndromes (ACSs). Seventy patients (mean age 71 years, interquartile range 44 to 92, 38 men) undergoing elective implantation of a single-/dual-chamber pacemaker with active/passive fixation leads were enrolled, excluding subjects with clinical suspicion of ACS, abnormal basal cTnI level, or presenting conditions predisposing to abnormal cTnI. Cardiac TnI concentrations were determined in basal conditions, at the end of the procedure, and after 8, 12, and 24 hours. Single-/dual-chamber devices were implanted in 31 of 39 patients. Cardiac TnI peak concentration occurred within the 12-hour assay in 69 of 70 patients; 26 of 70 had a cTnI above the normal cut-off range. All patients presented normal cTnI at 24-hour assay. In conclusion, pacemaker implantation is associated with increases of cTnI levels in up to 37% of patients. This can affect the specificity of cTnI assessment for ruling out ACS, especially within 12 hours after the procedure. These data deserve consideration in a contemporary setting, in which troponin has gathered a pivotal role in the diagnosis and therapy of ACS, and in particular clinical presentations in which electrocardiogram loses its diagnostic capabilities (due to paced rhythms) and symptoms may be lacking or confusing.

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.