Risk factors and outcomes associated with acute kidney injury following ruptured abdominal aortic aneurysm

Background

Current data describing the epidemiology of acute kidney injury (AKI) following repair of ruptured abdominal aortic aneurysm (rAAA) are limited and long-term outcomes are largely unknown. Our objectives were to describe the incidence rate, risk factors, clinical course and long-term outcomes of AKI following rAAA repair.

Methods

Retrospective population-based cohort study of all referrals undergoing emergency repair of rAAA in Northern Alberta from January 1, 2002 to December 31 2009. Demographic, clinical, physiologic and laboratory data were extracted. AKI was defined and classified according to the AKIN criteria.

Results

In total, 140 patients survived to receive emergent rAAA repair. Post-operative AKI occurred in 75.7% of patients (n = 106), 78.3% (n = 83) of which occurred during the initial 24 hours of ICU admission. AKIN stage 1, 2, and 3 occurred in 47 (33.6%), 36 (25.7%) and 23 (16.4%), respectively, with 19 patients receiving renal replacement therapy (RRT). Several clinical and biochemical patient factors were associated with incident AKI, including baseline estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m² (odds ratio [OR] 2.94; 95% CI, 1.15-7.51, p = 0.03), need for mechanical ventilation (OR 22.7; 95% CI, 7.0-72.1, p < 0.0001) and vasoactive therapy (OR 9.9; 95% CI, 3.0-32.2, p < 0.0001) and higher mean APACHE II scores (25.7 [8.2] vs. 16.3 [4.9], p < 0.0001). AKI was associated with a higher ICU (28.3% vs. 0%; p = 0.0008) and in-hospital case-fatality rate (35.9% vs. 0%, p = 0.0001). Of 102 survivors to discharge, 65.7% (n = 67) recovered to baseline kidney function. In multivariable analysis, greater severity of AKI (OR 5.01; 95% CI, 2.34-10.7, p < 0.001) and lower baseline eGFR (OR 0.96; 95% CI, 0.93-0.99, p = 0.03) were associated with non-recovery. AKI remained independently associated with 1-year mortality after adjusting for age, sex, comorbidity, and illness severity (OR 5.21; 95% CI, 1.04-26.2, p = 0.045; AUC 0.83; H-L GoF, p = 0.26). Among survivors at 1-year, only 63.4% (n = 55) had complete kidney recovery.

Conclusions

Following rAAA repair, AKI is a common complication independently associated with long-term post-operative mortality. A significant proportion of AKI sufferers in this setting fail to recover to baseline kidney function.

Different roles for contracture and calpain in calcium paradox-induced heart injury

The Ca(2+) paradox represents a good model to study Ca(2+) overload injury in ischemic heart diseases. We and others have demonstrated that contracture and calpain are involved in the Ca(2+) paradox-induced injury. This study aimed to elucidate their roles in this model. The Ca(2+) paradox was elicited by perfusing isolated rat hearts with Ca(2+)-free KH media for 3 min or 5 min followed by 30 min of Ca(2+) repletion. The LVDP was measured to reflect contractile function, and the LVEDP was measured to indicate contracture. TTC staining and the quantification of LDH release were used to define cell death. Calpain activity and troponin I release were measured after Ca(2+) repletion. Ca(2+) repletion of the once 3-min Ca(2+) depleted hearts resulted in almost no viable tissues and the disappearance of contractile function. Compared to the effects of the calpain inhibitor MDL28170, KB-R7943, an inhibitor of the Na(+)/Ca(2+) exchanger, reduced the LVEDP level to a greater extent, which was well correlated with improved contractile function recovery and tissue survival. The depletion of Ca(2+) for 5 min had the same effects on injury as the 3-min Ca(2+) depletion, except that the LVEDP in the 5-min Ca(2+) depletion group was lower than the level in the 3-min Ca(2+) depletion group. KB-R7943 failed to reduce the level of LVEDP, with no improvement in the LVDP recovery in the hearts subjected to the 5-min Ca(2+) depletion treatment; however, KB-R7943 preserved its protective effects in surviving tissue. Both KB-R7943 and MDL28170 attenuated the Ca(2+) repletion-induced increase in calpain activity in 3 min or 5 min Ca(2+) depleted hearts. However, only KB-R7943 reduced the release of troponin I from the Ca(2+) paradoxic heart. These results provide evidence suggesting that contracture is the main cause for contractile dysfunction, while activation of calpain mediates cell death in the Ca(2+) paradox.

A comprehensive review of upper reference limits reported for (high-)sensitivity cardiac troponin assays: the challenges that lie ahead

Cardiac troponins (cTn) are the preferred markers for the diagnosis of acute myocardial infarction (AMI). The guidelines recommend the use of the 99th percentile upper reference concentration of a healthy population as the diagnostic cut-off for AMI. However, a broad range of upper reference limits is still employed, complicating the diagnosis of AMI. This overview is meant to assist laboratory specialists to define an appropriate cut-off value for the diagnosis of AMI. Therefore, we provide an overview of the analytical performance and upper reference limits of seven (high-)sensitivity cTn assays: Roche high-sensitivity cTnT and ADVIA Centaur, Stratus CS, Dimension Vista, Vitros ECi, Access and Architect cTnI assays. It is shown that none of the reference populations completely met the guidelines, including those in package inserts. Forty percent of the studies collected less than the advised minimum of 300 subjects. Many studies (50%) did not report their inclusion criteria, while lower 99th percentile limits were observed when more stringent selection criteria were applied. Higher troponin cut-offs were found in men and elderly subjects, suggesting sex- and age-specific cut-offs would be considered. Therefore, there is still need for a large, rigorously screened reference population to more accurately establish cTn upper reference limits.

Detection of myocardial injury in patients with unstable angina using a novel nanoparticle cardiac troponin I assay: observations from the PROTECT-TIMI 30 Trial

BACKGROUND

At least 30% of patients with non-ST-elevation acute coronary syndrome present without evidence of myonecrosis using current generation troponin assays. A new generation of research assays for troponin that offer a >10-fold increase in analytical sensitivity has emerged.

METHODS

To perform a pilot study to evaluate the clinical sensitivity of a new ultra-sensitive nanoparticle assay for cardiac troponin I (nano-cTnI), we identified 50 patients with unstable angina (serial negative cTnI) and 50 patients with non-ST-elevation myocardial infarction with an initially negative current generation cTnI result. We measured cTnI using an assay (Nanosphere, Northbrook, IL) that can detect pg/mL concentrations of cTnI (detection-limit 0.0002 microg/L).

RESULTS

Measured at 0, 2, and 8 hours with the nano-cTnI assay 44%, 62%, and 82% of patients with unstable angina defined by the current-generation assay had an elevated nano-cTnI result (> or =0.003 microg/L, 99 th percentile decision-limit, coefficient of variation <10%). In patients with definite myocardial injury (current-generation cTnI > or =0.1 microg/L) but an initially negative cTnI, 72% and 98% had a nano-cTnI > or =0.003 microg/L at 0 and 2 hours. No patient had a positive current-generation cTnI without an elevated nano-cTnI level.

CONCLUSIONS

In this pilot study using a nanoparticle assay for cTnI, myocardial injury was detectable in a substantial proportion of patients presently classified as having unstable angina, suggesting that ischemia with rest pain without injury is rare. The emergence of a new generation of troponin assays has the potential to lead to new clinical applications based on enhanced analytical performance at very low concentrations of troponin.

Precision performance at low levels and 99th percentile concentration of the Access AccuTnl assay on two different platforms

BACKGROUND

Cardiac troponins currently represent the preferred biomarkers for the detection of myocardial necrosis. The objective of the present study was to compare the performance of the Access AccuTnl assay (Beckman Coulter) measured on two different platforms, the UniCel Dxl 800 and the Access 2 (Beckman Coulter). In particular, the serum cardiac troponin I (cTnl) concentration corresponding to 10% coefficient of variation (CV), the cTnl assay minimum detectable concentration (MDC), and the serum cTnl 99th percentile in healthy subjects were calculated.

METHODS

The Access AccuTnl is a paramagnetic particle chemiluminescent immunoassay. Imprecision profiles were determined according to the Clinical and Laboratory Standards Institute EP5-A protocol using serum pools. The MDC was calculated as mean +3 SD of 20 determinations of the zero calibrator during one run. The 99th percentile was determined analyzing serum samples from 679 healthy blood donors (523 males, 156 females; 18-71 years old).

RESULTS

cTnl concentrations are given in microg/L. 10% CV values (95% confidence interval, CI) were 0.0577 (0.0467-0.0750) (UniCel Dxl 800) and 0.0486 (0.0255-0.0596) (Access 2). MDC values were 0.011 (UniCel Dxl 800) and 0.012 (Access 2). The 99th percentile (95% CI) value was 0.0340 (0.0298-0.0410).

CONCLUSIONS

Our data confirm the reliability of the evaluated cTnl assay and demonstrate the comparability of the cTnl values between the platforms studied.

Short- and long-term risk stratification using a next-generation, high-sensitivity research cardiac troponin I (hs-cTnI) assay in an emergency department chest pain population

BACKGROUND

The next-generation, high-sensitivity cardiac troponin assays can measure quantifiable concentrations of cTn in a majority of individuals, but there are few studies assessing these assays for risk stratification. The present study was undertaken to determine if a research hs-cTnI assay can be useful for predicting death/myocardial infarction (MI), both short- and long-term, in an emergency department acute coronary syndrome (ACS) population.

METHODS

In a cohort of 383 subjects, originally recruited in 1996, presenting to the emergency department with symptoms suggestive of ACS, the heparin plasma obtained at initial presentation was thawed and measured in 2007 with a research hs-cTnI assay. AccuTnI (Beckman Coulter) measurements were made on these same samples in 2003. The population was divided into 4 groups by hs-cTnI: <5.00, 5.00-9.99, 10.00-40.00, and >40.00 ng/L. Kaplan-Meier, Cox proportional hazards, ROC curves, and logistic regression analyses were used to identify which hs-cTnI concentrations were predictive of death/MI within 10 years after presentation.

RESULTS

There were significant differences between the hs-cTnI groups for the probability of death/MI up to 10 years after presentation (P < 0.05). At 6 months, patients with hs-cTnI > or =10.00 ng/L were at higher risk for death/MI (hazard ratio >3.7; P < 0.05) compared with those having hs-cTnI <5.00 ng/L. ROC curve analysis for death/MI at 30 days with the hs-cTnI assay had an area under the curve of 0.74 (95% CI 0.65-0.82), with logistic models yielding an optimal assay threshold of 12.68 ng/L.

CONCLUSIONS

This research hs-cTnI assay appears useful for risk stratification for death/MI in an ACS population.

Biochemical diagnosis of myocardial infarction evolves towards ESC/ACC consensus: Experiences from the Nordic countries

OBJECTIVES

To investigate the diagnostic approach in Nordic hospitals receiving patients suspected of acute myocardial infarction (MI), especially focusing on implementation of the recently proposed criteria by the European Society of Cardiology (ESC) and the American College of Cardiology (ACC) for the definition of MI.

DESIGN

A survey with questionnaires of the diagnostic approach was conducted among all relevant departments (220) in the Nordic countries.

RESULTS

Seventy-six percent (167) of hospitals responded. Troponins I and T (TnI and TnT) and creatinine kinase monobasic fraction (mass concentration) (CKMB(mass)) covered 93 and 65% of hospitals, respectively. Of troponin users, 34% indicated use of TnI vs 66% using TnT. Sporadic use of AST, CK, LD and myoglobin was reported. There was a tendency to lower cut-off levels in Sweden and Finland. Among troponin assays, there was considerable heterogeneity regarding cut-off levels.

CONCLUSIONS

The Nordic countries are approaching ESC/ACC consensus on cardiac markers. Compared with previous national surveys (1995-1999), there is a shift towards the use of troponins. However, differences in cut-off levels of troponin emphasize the need for harmonization of assays.

Clinical Performance of Two Highly Sensitive Cardiac Troponin I Assays

Background: The aim of this study was to compare the clinical performance of 2 sensitive cTnI assays with 10% CV imprecision below the 99th percentile upper reference limit.

Methods: We measured cardiac troponin and N-terminal pro-brain natriuretic peptide (NT-proBNP) concentrations in a random sample of the Global Use of Strategies To Open Occluded Coronary Arteries (GUSTO) IV cohort (n = 1251). Outcome data of 1-year mortality and the composite endpoint DMI [death and/or myocardial infarction (MI) within 30 days] were available in all patients. The 99th percentile of a healthy population was estimated from the Sweden Women and Men and Ischemic Heart Disease (SWISCH) cohort (n = 442). We measured cardiac troponin I (cTnI) using the Access AccuTnI (Beckman Coulter) and Centaur TnI Ultra (Siemens Healthcare Diagnostics) and NT-proBNP using the Elecsys 2010 (Roche Diagnostics).

Results: Applying the 10% CV cutoff, the sensitivity of the Access AccuTnI assay in identifying DMI and death was higher than that of the Centaur TnI Ultra (P = 0.02 and P &lt; 0.001), and the AccuTnI assay also identified more patients at risk (P &lt; 0.001) and with poor outcome. Applying the 99th percentile cutoffs, AccuTnI identified more patients at risk than the Centaur TnI (P &lt; 0.001) and with significant differences in outcome. Significantly more patients with cardiac troponins below the cutoffs as measured by Centaur TnI had increased NT-proBNP concentrations (P &lt; 0.001) compared with AccuTnI.

Conclusions: The AccuTnI assay identified more patients at risk than the Centaur cTnI Ultra assay. Our results demonstrate the clinical potential of high-sensitivity cardiac troponin assays for the identification of patients at risk of dying from cardiovascular disease.

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.

"Upstream markers" provide for early identification of patients at high risk for myocardial necrosis and adverse outcomes

BACKGROUND

For patients presenting with acute coronary syndrome (ACS) to the emergency department, early identification of those that are at high risk for subsequent myocardial necrosis or adverse outcomes would allow earlier or more aggressive treatment. We determined if a panel of biomarkers can be used to identify high risk patients.

METHODS

A cohort (84 females/132 males) from our 1996 ACS study population that had EDTA specimens stored (-70 degrees C) was selected and the earliest available specimen was analyzed for 11 biomarkers (IL-6, IL-8, MCP-1, VEGF, L-selectin, P-selectin, E-selectin, ICAM-1, VCAM-1, NT-proBNP, cTnT). These data were linked to the existing cTnI and health outcome databases for this population. ROC curve analysis for myocardial necrosis (i.e., peak cTnI >0.04 microg/l) identified 3 candidate biomarkers. These 3 biomarkers were applied together to generate a panel test (2 of the 3 biomarkers increased for a positive result) and assessed for its ability to identify patients at risk for myocardial necrosis and the combined endpoint of death, myocardial infarction (MI) and heart failure (HF).

RESULTS

The panel test (IL-6, NT-proBNP, E-selectin) alone detected 60% (95% CI: 49-69; false positive rate: 26%) of subjects that would be classified with myocardial necrosis. Kaplan-Meier and Cox proportional analyses indicated that patients positive by the biomarker panel (including those with cTnI < or =0.04 microg/l) had significantly worse outcomes (death/MI/HF) as compared to those negative by both cTnI and the panel test.

CONCLUSION

A biomarker panel analyzed early after pain onset can identify individuals at risk for both myocardial necrosis and the combined endpoint of death/MI/HF. Additional prospective studies are required to assess this panel for both early MI detection and to further refine which health outcomes (death, MI, HF) are associated with positive panel results.

Effects of contemporary troponin assay sensitivity on the utility of the early markers myoglobin and CKMB isoforms in evaluating patients with possible acute myocardial infarction

BACKGROUND

The 2003 American Heart Association (AHA) definition for myocardial infarction (MI) requires an "adequate set" (i.e. at least 6 h between measurements) of biomarkers and specifically troponin for the diagnosis of MI. The aim of the present study was to assess the performance of myoglobin, the CKMB isoforms, and cardiac troponin I (cTnI) in specimens earlier than the requisite 6 h after presentation, in a population originally characterized using World Health Organization (WHO) criteria.

METHODS

In 1996, 228 acute coronary syndrome patients with an "adequate sample set" had their specimens assayed for CKMB isoforms and myoglobin. In 2003, the same specimens were analyzed with the AccuTnI troponin I assay and myoglobin (Beckman Coulter Access immunoassay).

RESULTS

The clinical sensitivities for both myoglobin and the CKMB isoforms were >90% when the population was classified by WHO criteria. However the sensitivities were <70% when the ESC/ACC MI definition was used. Analyzing cTnI at earlier time points as long as there was at least 3 h between specimens or at least 1 specimen 6 h from pain onset did not misclassify subjects based on adverse outcomes in the year following their presentation.

CONCLUSION

Contemporary assays for cTnI with increased analytical sensitivity reduce the utility of myoglobin and CKMB isoforms to rule-out an AMI.

Elevated C-reactive protein in acute coronary syndrome presentation is an independent predictor of long-term mortality and heart failure

OBJECTIVES

To assess the ability of C-reactive protein (CRP) to predict long-term outcomes in a chest pain population.

DESIGN AND METHODS

CRP was measured at presentation in 446 emergency department patients with acute coronary syndromes. All-cause mortality and hospital discharges for acute myocardial infarction (AMI) and congestive heart failure (CHF) were obtained for up to 8 years following the event.

RESULTS

Kaplan-Meier analyses indicated that patients with CRP concentrations above the American Heart Association scientific statement cut-off had a higher rate for death and CHF admissions. After adjusting for troponin concentrations, in a Cox proportional hazard model, only CRP concentrations indicative of an acute phase response (i.e., >7.44 mg/L) were associated with a significant risk for death after 5 years and CHF readmission after 2 years.

CONCLUSIONS

Patients presenting early with chest pain with elevated CRP concentrations have a greater long-term risk for death and heart failure.

Detection of Coronary Microembolization by Doppler Ultrasound in Patients With Stable Angina Pectoris Undergoing Elective Percutaneous Coronary Interventions

Background— Intracoronary Doppler guidewires can be used for real-time detection and quantification of microembolism during percutaneous coronary interventions (PCIs). We investigated whether the frequency of Doppler-detected microembolism is related to the incidence of myonecrosis during elective PCI.

Methods and Results— The study population included 52 consecutive patients (aged 64±10 years; 36 men, 16 women) with coronary artery disease who underwent elective PCI of a single-vessel stenosis. Using intracoronary Doppler ultrasound, we compared the frequency of microembolism during PCI in 22 patients with periprocedural non–ST-segment elevation myocardial infarctions (pNSTEMI) and 30 patients without pNSTEMI. The 2 groups were comparable with regard to their clinical and procedural characteristics. In the group with pNSTEMI, the total number of coronary microemboli after PCI (27±10 versus 16±8, P <0.001) was higher than in the group without pNSTEMI. Although high-sensitivity C-reactive protein plasma levels were similar before PCI (2.9±2.2 versus 3.4±1.7 mg/L, P =NS), they were higher in the group with pNSTEMI after PCI (12.6±10.4 versus 6.1±5.1 mg/L, P <0.05). Microembolic count independently correlated to postprocedural cardiac troponin I elevation ( r =0.565, P <0.001), coronary flow velocity reserve ( r =−0.506, P <0.001), and baseline average peak velocity ( r =0.499, P <0.001).

Conclusions— Patients with pNSTEMI had a significantly higher frequency of coronary microembolization during PCI, and their systemic inflammatory response and microvascular impairment after PCI were more pronounced. Intracoronary Doppler ultrasound provides evidence that pNSTEMI in patients undergoing elective PCI is caused by microembolization during the procedure.

Long-Term Health Outcomes Associated with Detectable Troponin I Concentrations

Background: Recent data suggest that older men with detectable cardiac troponin I (cTnI) concentrations that remain below the 99th percentile concentration cutoff are at increased risk for subsequent cardiovascular events. We designed this study to extend this observation by examining risk prediction in both men and women presenting to an emergency department with chest discomfort.

Methods: We obtained data for all-cause mortality and hospital discharges associated with either acute myocardial infarction (AMI) or congestive heart failure (CHF) for up to 8 years after the initial presentation in 448 patients who originally presented in 1996 with acute coronary syndrome (ACS). We performed retrospective analysis for cTnI (AccuTnI™; Beckman Coulter) in frozen plasma samples based on the patients’ reported time from onset of symptoms. Peak cTnI concentration was used for risk assessment.

Results: Patients with cTnI concentrations ≥0.02 μg/L (i.e., limit of detection), including those whose peak values remained below the 99th percentile (0.04 μg/L), were at greater risk for death and AMI/CHF readmissions at 2, 5, and 8 years of follow-up compared with those with peak cTnI &lt;0.02 μg/L. All results were statistically significant (P &lt;0.05) except for death within 2 years among patients with normal but detectable cTnI (0.02 to 0.03 μg/L), relative to the group with values &lt;0.02 μg/L. Kaplan–Meier analyses indicated that both men and women with cTnI ≥0.02 μg/L had worse outcomes (P &lt;0.001).

Conclusion: Both men and women who present with possible ACS with detectable cTnI concentrations that remain below the 99th percentile are at a greater risk for future adverse events.

Health Outcomes Categorized by Current and Previous Definitions of Acute Myocardial Infarction in an Unselected Cohort of Troponin-Naïve Emergency Department Patients

Background: In a population originally classified for acute myocardial infarction (AMI) by the World Health Organization (WHO) definition, we compared the health outcomes after retrospectively reclassifying with the European Society of Cardiology and the American College of Cardiology (ESC/ACC) AMI definition, using the peak cardiac troponin I (cTnI) concentrations. The health outcomes were based on the WHO definition and occurred in an era that preceded the use of cardiac troponin biomarkers.

Methods: For 448 patients who presented to the emergency department with symptoms suggestive of cardiac ischemia in 1996, we obtained data for all-cause mortality and recurrent AMI for up to 1 year after the initial presentation. We performed retrospective analysis of the patients’ frozen plasma samples to measure cTnI (AccuTnI®, Beckman Coulter).

Results: At 30, 120, and 360 days, the risk for AMI/death in patients positive for AMI by only the ESC/ACC criteria was significantly lower than the risk in patients positive by both ESC/ACC and WHO criteria, and significantly higher than in patients negative according to both criteria. In a separate analysis, patients with a peak cTnI &gt;0.10 μg/L were at greater risk for AMI/death than patients with cTnI concentrations of 0.04–0.10 μg/L. Patients negative by both definitions or with peak cTnI concentrations &lt;0.04 μg/L had the highest event-free survival rates (92% and 94%, respectively) at 1 year.

Conclusion: In a troponin-naïve population, patients classified as positive for AMI by only the ESC/ACC criteria have a prognosis that appears to be intermediate between those classified positive by both the WHO and ESC/ACC definitions and those who meet neither criteria.

Usefulness of clinical evaluation, troponins, and C-reactive protein in predicting mortality among stable hemodialysis patients

This study prospectively examined the hypothesis that dividing stable dialysis patients into different clinical subsets by presence or absence of coronary disease equivalent will lead to clearer risk stratification by abnormal troponins and highly sensitive C-reactive protein (hs-CRP). Patients with end-stage renal disease have an annual mortality of 18%. Previous studies have shown that elevated cardiac troponins T and I and hs-CRP predict increased mortality, although these studies have not taken clinical parameters into account. Stable patients with end-stage renal disease (n = 173) were divided into 2 groups: 115 patients with coronary disease equivalent (known coronary or peripheral vascular disease or diabetes mellitus) and 58 patients without it. The 2 groups were then stratified by biomarkers (cardiac troponins T and I and hs-CRP) and followed for 27 months. The primary outcome was all-cause mortality. Patients with coronary disease equivalent had twofold greater annual mortality than those without (20.4% vs 9.8%, p = 0.003). Among patients with coronary disease equivalent, those with elevated troponins had a further increase in the risk for death relative to patients with normal troponins (25% vs 9% with cardiac troponin I elevation, p <0.001; 24% vs 12% with cardiac troponin T elevation, p = 0.04). hs-CRP did not add to the risk stratification of patients with coronary disease equivalent. Conversely, in patients without coronary disease equivalent, neither troponin further predicted the risk for death. In the small subset of patients without coronary disease equivalent who had hs-CRP >or=3 mg/L, mortality was significantly increased (p = 0.01). In conclusion, initial clinical assessment, followed by the addition of biomarkers, can be used to risk-stratify stable patients with end-stage renal disease.

Dosage des isoformes cardiaques des troponines T ou I : intérêt en cardiologie et en anesthésie–réanimation

Measurement of cardiac troponin I or T in serum (highly specific for the myocardium) have replaced classical markers, such as creatine kinase MB. Cardiac troponins are preferred markers because of their high specificity and sensitivity. This had led to modifications of the original World Health Organization criteria for acute myocardial infarction. Furthermore, the place of the troponins as superior markers of subsequent cardiac risk in acute coronary syndrome has now become firmly established, for both diagnostic and risk stratification purposes. The use of C-reactive protein and/or other inflammatory biomarkers may add independent information in this context. After non cardiac surgery, the total cardiospecificity of cardiac troponins explains why other biomarkers of necrosis should no longer be used. Recent studies suggest that any elevation of troponin in the postoperative period is indicative of increased risk of long-term cardiac complications. This prognostic value has been previously demonstrated in other clinical settings such as invasive coronary intervention (surgical myocardial revascularization and percutaneous coronary intervention) and after heart valve surgery. Increases of troponin indicate cardiac damage, whatever the mechanism (ischemic or not). Other causes of cardiac injury include: pulmonary embolism, myocarditis, pericarditis, congestive heart failure, septic shock, myocardial contusion. In most cases, elevation of troponins has been shown to be associated with a bad outcome.

The impact of the ESC/ACC redefinition of myocardial infarction and new sensitive troponin assays on the frequency of acute myocardial infarction

BACKGROUND

The prevalence of acute myocardial infarction (AMI) has increased due to the recent definitions, but the magnitude of this effect using contemporary highly sensitive troponin assays is unclear. The objective of this study is to compare the diagnosis of AMI using a contemporary troponin I (cTnI) biomarker and the 2003 American Heart Association (AHA) case definition with diagnoses made using the 1994 World Health Organization MONICA definition.

METHODS

Contemporary troponin I measurements were performed with the Beckman Coulter AccuTnI assay (Chaska, MN) on plasma specimens originally assayed in 1996 for creatine kinase (CK)-MB mass from 486 emergency department patients presenting within 24 hours of onset of symptoms suggestive of cardiac ischemia.

RESULTS

In a subgroup of 258 patients with 2 specimens drawn at least 6 hours apart (the AHA "adequate set of biomarkers"), AMI prevalence using CK-MB was 19.4% (95% CI 15.0-24.7) based on MONICA and 19.8% (15.4-25.1) based on the AHA case definition using the criterion for change of > or = 20% between specimens. Using cTnI as the biomarker of choice, under the AHA definition, the prevalence increased to as high as 35.7% (30.1-41.7, a relative increase of 84%, P < .001) using the 99th percentile cutoff. In 121 patients with a lower index of suspicion and without the requisite 6-hour interval between measurements, positivity increased from 5% with CK-MB by MONICA up to 12% to 16% with cTnI by AHA.

CONCLUSIONS

A highly sensitive contemporary cTnI assay used with the AHA case definition results in a 62% to 84% increase in the frequency of AMI diagnosis compared with MONICA criteria.

The Antibody Configurations of Cardiac Troponin I Assays May Determine Their Clinical Performance

Background: Previous studies have shown superior clinical performance of the cardiac troponin I (cTnI) assay from Beckman-Coulter Diagnostics. This assay had a unique combination of monoclonal antibodies with 2 monoclonal antibodies directed against epitopes near the NH2 terminus of the heart-specific region of troponin I. The approach has been adopted by the new cTnI assay from Abbott Diagnostics. The aim of our study was to investigate whether this approach affects the clinical performance of cTnI assays.

Methods: Cardiac troponin concentrations were measured in a random sample of patients with unstable coronary artery disease included in the GUSTO IV trial (n = 696) by the AccuTnI (Beckman-Coulter Diagnostics), Architect cTnI (Abbott Diagnostics), Immulite 2500 cTnI (Diagnostics Products Corporation), and Elecsys 2010 cTnT (Roche Diagnostics) assays and related to the 1-year mortality. The primary cutoff concentrations were based on the 99th percentile upper reference limits and an imprecision (CV) ≤10%.

Results: The sensitivities of the AccuTnI and Architect cTnI assays in identifying patients who died within 1 year were equal and were significantly higher (P &lt;0.05) than those of the Immulite 2500 cTnI and the Elecsys cTnT assays. The concordance between the AccuTnI and Architect cTnI assays was 97%, but concordances between the Architect cTnI and the Elecsys cTnT assays were 89%–92% with more at-risk patients (P &lt;0.01 to P &lt;0.001) identified by the Architect cTnI assay.

Conclusions: The Architect cTnI assay has clinical performance similar to that of the AccuTnI, probably as a result of the inclusion of a monoclonal antibody against troponin I epitope 41–49 in the assay.

Assessing the Requirement for the 6-Hour Interval between Specimens in the American Heart Association Classification of Myocardial Infarction in Epidemiology and Clinical Research Studies

Background: The American Heart Association (AHA) case definition for acute myocardial infarction (AMI) requires an “adequate set” of biomarkers: 2 measurements of the same marker at least 6 h apart. A sensitive troponin assay might detect significant changes in concentration earlier. We determined AMI prevalence, using protocols with shorter intervals between measurements, with and without incorporating the time from onset of symptoms.

Methods: The AHA case definition was used to retrospectively assign a diagnosis in 258 patients presenting to the emergency department with symptoms of cardiac ischemia. AMI was diagnosed if either specimen in an adequate set had a cardiac troponin I (cTnI) above the 99th percentile (AccuTnI® &gt;0.04 μg/L; Beckman Coulter) with a ≥20% change in concentration between specimens. We assessed positivity for AMI after progressively decreasing the time interval between specimens in specimen sets. In addition, for each patient, 2 additional specimen pairs were selected: pairs collected at least 1 h apart with 1 specimen being either ≥3 h after onset or ≥6 h after onset.

Results: When we used the AHA definition, the AMI prevalence was 35.7%. Prevalence was not significantly diminished when the interval between specimens was ≥5, ≥4, or ≥3 h (36.4%, 34.5%, and 33.7%, respectively) compared with the AHA ≥6 h interval. When the time from onset of symptoms was included in the specimen selection algorithm, a 1-h interval was sufficient provided that at least one specimen was collected ≥6 h after onset (prevalence, 34.1%; P = 0.48 vs AHA definition).

Conclusion: A sensitive cTnI assay in specimen sets with time intervals ≥3 h, or having one specimen ≥6 h after onset, gave an AMI prevalence equivalent to the AHA definition.

Positive Interference from Contrast Media in Cardiac Troponin I Immunoassays

Cardiac troponin I (cTnI) has been found to be a sensitive and reliable marker of myocardial damage, and elevated levels of cTnI can indicate high risk for acute coronary syndrome. To determine how to intervene in possible cases of acute coronary syndrome, cTnI levels must be measured by immunoassay. However, cTnI immunoassay results are prone to interference from many substances such as heparin and common drugs. The contrast media used in the coronary angiography might also interfere with results. To explore this possibility, we performed two in vivo and two in vitro studies. In the first in vivo study, we evaluated the effects of contrast media on cTnI immunoassays by collecting blood samples from 45 patients undergoing coronary angiography before and after the procedure. We used the Opus Magnum immunoassay system to measure cTnI levels. In the second in vivo study, we collected 25 blood samples from another group of patients also undergoing angiography at various times before and after the procedure to determine cTnI values by both the Opus Magnum and ACCESS systems. In the first in vitro study, 12 different contrast media were treated as samples to disclose the potential interference of measurement in the two assay systems. In the second in vitro study, we made sequential dilutions of iopromide (Ultravist; Schering) with serum to explore their potential for interfering with the detection of cTnI by the Opus Magnum and ACCESS assays. In the first in vivo study using the Opus Magnum assay, cTnI concentrations in samples taken after angiography were significantly higher at 5 minutes than at 30 minutes, and, at 60 minutes, all cTnI concentrations had dropped below the cutoff point. In the second in vivo study, we found a substantial difference in detection of cTnI by the Opus Magnum and ACCESS assays. All cTnI concentrations checked by ACCESS assay were below the cutoff value. In our first in vitro study, the Opus Magnum assay gave false positive results for all 12 contrast media; the ACCESS assay gave a positive result for only one contrast medium, poppy-seed oil (Lipiodol; Guebert). In our second in vitro study, we found that, in the Opus Magnum assay, the more concentrated the contrast medium, the higher the cTnI value, but not in the ACCESS assay. We conclude that contrast media may cause false-positive results in cTnI assays and that, when contrast media are being used for angiography, cTnI results, especially those based on samples taken within the first hour of the procedure, should be interpreted carefully.

Troponin I as a predictor of coronary heart disease and mortality in 70-year-old men: a community-based cohort study

BACKGROUND

Cardiac troponin I (cTnI), a standard for detection of myocardial damage, has recently been reported to predict acute myocardial infarction or death in patients with unstable coronary heart disease (CHD). Cardiac TnI concentrations increase with age in subjects free from clinical signs of CHD, suggesting silent myocardial damage. We investigated the association between cTnI and future CHD and mortality in a community-based cohort of men.

METHODS AND RESULTS

A community-based study was conducted from August 1991 to May 1995 among 1203 men in Uppsala, Sweden, aged 70 years at baseline with a follow-up of up to 10.4 years with the use of registry data (National Board of Health and Welfare, Sweden). CHD was defined with the use of data taken from the Cause of Death Registry or from first-time hospitalization for CHD as recorded in the Hospital Discharge Registry. Cardiac TnI concentrations were measured blinded for outcome, in frozen baseline plasma samples, with the use of the AccuTnI from Beckman Coulter, Inc. Hazard ratios (HRs) from Cox proportional hazards are presented with 95% confidence intervals (CIs) for a 1-SD increase. In men free from cardiovascular disease (CVD), cTnI predicted death (HR, 1.26; 95% CI, 1.08 to 1.46; P=0.003) or first CHD event (HR, 1.31; 95% CI, 1.11 to 1.54; P=0.001) after adjustment for conventional risk factors: total and HDL cholesterol, plasma glucose, body mass index, smoking, and systolic blood pressure.

CONCLUSIONS

In this first longitudinal report, cTnI was shown to predict death and first CHD event in men free from CVD at baseline, indicating the importance of silent cardiac damage in the development of CHD and mortality.

Troponins in acute coronary syndromes

Cardiac troponins have replaced creatine kinase-MB as the preferred biomarker for establishing the diagnosis of myocardial infarction (MI). Expert recommendations set the diagnostic decision-limit for each assay at the 99th percentile of troponin levels in an apparently healthy reference population, which due to a lack of standardization, will vary depending upon the manufacturer. Among patients presenting with an acute coronary syndrome (ACS), even low-level elevations of cardiac troponin T or I correlate with higher risk of death and recurrent ischemic events compared to patients with levels of troponin below the decision limit. Renal failure does not appear to diminish the prognostic value of troponins among patients with a high clinical probability of ACS. Moreover, patients with elevated levels of troponin derive the most benefit from more intense medical therapy with antithrombin and antiplatelet medications, as well as an early invasive management strategy. Whereas cardiac troponins are extremely specific for myocardial necrosis, they do not discriminate between ischemic and non-ischemic etiologies of myocardial injury. Clinicians must, therefore, determine whether a patient's presenting symptoms are consistent with ACS. Combining troponin with other cardiac biomarkers may offer complimentary information on the underlying pathobiology and prognosis in an individual patient. Future generations of troponin assays may detect specific posttranslational modifications of troponins that may increase the analytic sensitivity for myocardial damage and offer insight into the timing and mechanism of myocardial injury.

Clinical and analytical performance of the liaison cardiac troponin I assay in unstable coronary artery disease, and the impact of age on the definition of reference limits. A FRISC-II substudy

BACKGROUND

Measurements of cardiac troponins are currently used as the standard for the detection of myocardial injury. None of the current assays complies with the new requirements on assay imprecision as proposed by the European Society of Cardiology/American College of Cardiology. Our aim was to evaluate the clinical and analytical performance of the Liaison cardiac troponin I (cTnI) assay.

METHODS

EDTA-plasma was used, and cardiac troponins were assayed with the first-generation AxSYM assay, the second-generation AccuTnI assay, the third-generation Elecsys assay, and the first-generation Liaison assay.

RESULTS

In a 6-day imprecision study, the Liaison cTnI assay had mean CV < or =10% at 0.027 microg/L and < or =20% at 0.015 microg/L. The 99th percentile of the upper reference limit (URL) of a reference population was 0.041 microg/L (age range, 41-76 years). Individuals <60 years had a significantly (P = 0.001) lower 99th percentile, 0.022 microg/L. The FRISC-II study participants with cTnI > or =0.041 microg/L had a poorer outcome relating to death/acute myocardial infarction than those with cTnI <0.041 microg/L (P <0.001). Treatment with low-molecular-weight heparin (dalteparin) or an invasive strategy reduced cardiac events only in patients with concentrations >0.041 microg/L (P = 0.002 and 0.02, respectively). Comparison with the AccuTnI assay showed that a large cohort of the patients with poor prognosis was identified by the AccuTnI assay but not by the Liaison cTnI assay.

CONCLUSION

The Liaison cTnI assay is a sensitive assay with a CV < or =10% at the 99th percentile URL. The ability to detect age-related differences among apparently healthy individuals is unique among today's commercial assays. The results indicate that different assays seem to identify different patient cohorts for cardiac risk in the lower range of cTnI concentrations.

Multicenter Evaluation of an Automated Assay for Troponin I

Background: Cardiac troponin I (cTnI) is a powerful tool to aid in the diagnosis of myocardial infarction and cardiac muscle damage. We describe an assay that overcomes problems of early assays that were often affected by cTnI degradation, assay interference, poor sensitivity, and imprecision.

Methods: The analytical performance of the Access® AccuTnITM assay (Beckman Coulter) was evaluated at five institutions. Controls, zero calibrator, and diluted patient samples were used to determine precision, detection limit, functional sensitivity, and linearity. The 97.5 and 99 percentiles of a reference population were determined. Common interferents and heterophilic patient samples were tested. Equimolarity was determined by assaying samples with various ratios of free and complexed cTnI. Matched samples drawn into serum, EDTA, lithium heparin, and sodium heparin sample tubes were compared.

Results: Total imprecision (CVs) was 4.0–8.8% between 0.40 and 31 μg/L cTnI. The detection limit was &lt;0.01 μg/L. The 97.5 percentile upper reference limit (URL) was 0.03 μg/L (CV = 20%), and the 99 percentile URL was 0.04 μg/L (CV = 14%). Total CVs of 10% and 20% were seen at and above 0.06 and 0.03 μg/L, respectively. The assay was linear to &gt;60 μg/L and not affected by common assay interferents. An equimolar response was observed with free, complexed, phosphorylated, and dephosphorylated forms of cTnI. Results were 4% lower in serum and 14% lower in EDTA plasma than in lithium heparin plasma (P &lt;0.01), independent of cTnI concentration.

Conclusion: AccuTnI is a sensitive and precise assay for the measurement of cTnI.

Clinical performance of three cardiac troponin assays in patients with unstable coronary artery disease (a FRISC II substudy)

The assay of cardiac-specific troponins (cTroponins) is a sensitive and specific means to diagnose myocardial injury. Several assays for the measurement of cardiac-specific troponin I (cTnI), but only 1 for the assay of cardiac specific troponin T (cTnT), are commercially available. The aim of this study was to compare 3 of these assays (i.e., Access AccuTnI [cTnI], AxSym [cTnI], and Elecsys 3(rd) generation [cTnI]) and their clinical performances in a group of patients (n = 1,763) with unstable coronary artery disease (Fragmin and fast Revascularisation during InStability in Coronary artery disease [FRISC II] trial). Clinical events after 1-year follow-up, such as death and death and/or acute myocardial infarction, were recorded and the effects of invasive or noninvasive treatment evaluated in relation to cTroponin levels. Overall the 2 cTnI methods showed good correlation (r(s) = 0.96), whereas correlations to the cTnT assay were somewhat lower (r(s) = 0.93). Patients with nonelevated levels, as measured with any of the 3 biomarkers, had a significantly better prognosis than patients with elevated levels (p <0.001). A cohort of 10% to 12.4% of patients with a poor prognosis was identified only by the Access AccuTnI assay. Invasive treatment reduced clinical events only in the group of patients with elevated cTroponin levels. We conclude that stratification of patients with unstable coronary artery disease by means of cTroponin measurements is important in clinical management. It is also apparent that assays with superior sensitivity, such as the Access AccuTnI, identify more patients with poor prognosis who are candidates for early invasive procedures.