On the Effect of Heterophilic Antibodies on Serum Levels of Cardiac Troponins: A Brief Descriptive Review

Serum levels of cardiac troponins can be increased both with myocardial damage and in the absence of myocardial damage. In the second case, this is due to the influence of false-positive factors, among which heterophilic antibodies play a significant role. Understanding the causes of the formation of heterophilic antibodies, the features and mechanisms of their effect on serum levels of cardiac troponins, is an important condition for interpreting a false-positive result due to the influence of heterophilic antibodies. This brief, descriptive review presents the causes of heterophilic-antibodies formation and discusses their effect on serum levels of cardiac troponins.

Clinical impact of using a more sensitive troponin assay in patients with acute chest pain

Background

More sensitive troponin assays have the potential to better evaluate patients with suspected acute coronary syndrome (ACS). Meanwhile, they may result in avoidable diagnostic testing.

Hypothesis

Our aim was to determine the clinical impact of implementing a more sensitive cardiac troponin I (cTnI) assay in patients with acute non‐traumatic chest pain presenting to the emergency department (ED).

Methods

This is a pre‐post cohort study. A total of 1201 consecutive patients with acute non‐traumatic chest pain or equivalent ischemic symptoms suggestive of ACS were allocated to two groups according to the cTnI assay used. The outcomes included the ED length of stay (LOS), hospital admission rate, the use of procedures and the incidence of major adverse cardiac events (MACE) at 30 days.

Results

The introduction of the more sensitive troponin assay shortened ED LOS (odds ratio [OR] 0.39, 95% confidence interval [CI] 0.28‐0.54) regarding patients discharged home directly, increased the hospital admission rate (OR 1.43, 95% CI 1.12‐1.84), the use of echocardiography (OR 1.58, 95% CI 1.22‐2.06), coronary computed tomography angiography (OR 1.78, 95% CI 1.04‐3.06), coronary angiography (OR 1.53, 95% CI 1.10‐2.12) and percutaneous coronary intervention (OR 2.42, 95% CI 1.58‐3.70) regarding patients discharged or admitted. The incidence of MACE did not decrease significantly (OR 0.61, 95% CI 0.27‐1.37).

Conclusions

The introduction of the more sensitive troponin assay appeared to result in less time spent in the ED regarding patients discharged home directly, but prompted more hospitalizations and procedures without impacting the incidence of MACE.

Analytical Concordance of Diverse Point-of-Care and Central Laboratory Troponin I Assays

BACKGROUND

Cardiac troponin I (cTnI) 99th percentile cutoffs, used in the diagnosis of acute myocardial infarction, are not standardized across cTnI assays. We compared 3 point-of-care (POC) and 1 central laboratory contemporary cTnI assays against the Abbott high-sensitivity (hs) cTnI to evaluate the analytical concordance and the feasibility of using a single cutoff value for all assays.

METHODS

Fresh blood samples collected from 102 inpatients in the coronary care unit were measured on central laboratory instruments (Beckman Coulter DxI AccuTnI+3 TnI, Abbott Architect hs-TnI) and cTnI POC analyzers (Alere Triage Troponin I, Radiometer AQT90, Abbott i-STAT). Agreement and correlation between the contemporary cTnI assays and hs-cTnI assay were assessed using regression analysis. Proportional bias was assessed using Bland-Altman plots. Concordance between the contemporary cTnI and hs-cTnI assays was determined by diagnostic contingency tables at specific cutoffs.

RESULTS

Most POC cTnI assays had excellent correlation with the Abbott hs-cTnI method (r ² = 0.955-0.970) except for Alere Triage (r ² = 0.617), while proportional bias is evident between all cTnI assays. Overall concordance between POC contemporary cTnI assays and hs-cTnI assay was 80% to 90% at their respective 99th percentile cutoffs. The concordance increased to 90% to 95% when a fixed cutoff of 0.03 to 0.05 ng/mL was used across the assays.

CONCLUSIONS

This study demonstrates poor analytical concordance between cTnI assays at the 99th percentile and supports the notion of a single clinical decision limit for cTnI and consequently standardization of diagnostic protocols despite the analytical differences among these assays.

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.

Two-hour diagnostic algorithms for early assessment of patients with acute chest pain--Implications of lowering the cardiac troponin I cut-off to the 97.5th percentile

AIMS

Assessment of patients with suspected non-ST elevation myocardial infarction (NSTEMI) is based on cardiac troponin (cTn) levels with the 99th percentile as cut-off. However, cardiovascular risk starts already at lower troponin concentrations. We therefore, aimed to investigate the utility of 2-hour algorithms using the high-sensitivity cardiac troponin I (hs-cTnI) 97.5th percentile as cut-off which corresponds to the standard URL for most biomarkers.

METHODS

Hs-cTnI was measured at presentation and 2h in 1624 chest pain patients. Diagnostic algorithms were developed applying hs-cTnI levels dichotomized at the 99th and 97.5th percentiles combined with hs-cTnI changes and/or ECG findings.

RESULTS

The prevalence of NSTEMI was 13.9%. The adjusted odds ratios for 1-year mortality were 2.7 (95% CI 1.4-5.1) for the 99th percentile and 3.1 (95% CI 1.6-5.9) for the 97.5th percentile. The best-performing 99th percentile-based algorithms provided a positive predictive value (PPV) of 86.3% and a negative predictive value (NPV) of 99.3%. Using 97.5th percentile-based algorithms to define NSTEMI resulted in few reclassifications and yielded similar diagnostic estimates (PPV 85.4%, NPV 99.4%).

CONCLUSION

The hs-cTnI 97.5th percentile integrated into 2-hour algorithms provided high diagnostic estimates and could, due to better prognostic properties serve as an alternative to the 99th percentile.

Cardiac troponin I for prediction of clinical outcomes and cardiac function through 3-month follow-up after primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

BACKGROUND

Circulating levels of cardiac troponin I (cTnI) after ST-segment elevation myocardial infarction (STEMI) are associated with infarct size and chronic left ventricular dysfunction, but the relation to clinical end points and biochemical measures of global cardiac function remains less well defined.

METHODS

One thousand sixty-six patients receiving primary percutaneous coronary intervention (PCI) in the PROTECTION AMI trial were studied in a post hoc analysis. Cardiac troponin I was measured at several time points during the index hospitalization, and patients were followed up for 3 months before reassessment including N-terminal pro-B-type natriuretic peptide (NT-proBNP) and left ventricular ejection fraction (LVEF) measurements.

RESULTS

The median (quartile 1-3) cTnI levels were 0.4 (0.1-0.4) μg/L at admission, 33.1 (12.8-72.1) μg/L after 16 to 24 hours, and 9.1 (3.9-17.5) μg/L after 70 to 80 hours. In adjusted models, all post-PCI single points, peak, and area under curve were found to be independently associated with clinical events, NT-proBNP >118 pmol/L, or LVEF <40% (P for all <.001). When cTnI was added to a baseline risk model for prediction of clinical events, the C statistic improved from 0.779 to 0.846 (16-24 hours) and 0.859 (70-80 hours). Quantified by integrated discrimination improvement, the addition of cTnI significantly augmented prediction ability (relative integrated discrimination improvement 44%-154%; P for all ≤.001). Consistent improvements in discrimination of NT-proBNP >118 pmol/L and LVEF <40% were observed.

CONCLUSIONS

Cardiac troponin I measured after primary PCI for STEMI is independently associated with clinical outcomes and cardiac function through 3-month follow-up. These results suggest that cTnI levels are a useful risk stratification tool in STEMI patients.

Predictive value for death and rehospitalization of 30-day postdischarge B-type natriuretic peptide (BNP) in elderly patients with heart failure. Sub-analysis of Italian RED Study

Our aim was to determine if, in elderly heart failure (eHF) patients, serial B-type natriuretic peptide (BNP) assessments obtained during follow-up after hospital discharge could have prognostic utility for death and rehospitalizations. In eHF patients, BNP assessment at hospital discharge has been demonstrated to have a high prognostic value; however, its predictive role for future cardiovascular events in eHF patients, when assessed in the period after discharge, both for the correct timing and cut-off levels, has not been completely elucidated.

This study is a monocentric subanalysis of the Italian RED (Rapid Emergency Department) study. We studied 180 consecutive patients admitted for acute HF through serial BNP assessments: at hospital arrival; at discharge; and at 30, 90, and 180 days follow-up outpatient visit.

Both a BNP >400 pg/mL at 30 days after discharge and the percentage variation of BNP from discharge to 30 days (Δ%BNP), compared with a BNP at discharge >400 pg/mL, showed a higher area under the curve (AUC) and odds ratio (OR) in predicting events [AUC=0.842, p<0.0001; OR 7.9 (3.3–19.0), p<0.001 for 30 days BNP and AUC=0.851, p<0.0001; OR 9.5 (4.065–22.572), p<0.0001 for Δ%BNP compared with AUC=0.638, p<0.002; OR 2.4 (1.1–5.3), p=0.032 for BNP at discharge].

In patients at a high risk for future events, BNP levels assessed 30 days after hospital discharge in the absence of signs and symptoms could be predictive of subsequent hospitalization and death. These patients should be considered for closer monitoring and treatment adjustment.

Kinetics of high-sensitivity cardiac troponin T or troponin I compared to creatine kinase in patients with revascularized acute myocardial infarction

Cardiac biomarkers are the cornerstone of the biological definition of acute myocardial infarction (AMI). The key role of troponins in diagnosis of AMI is well established. Moreover, kinetics of troponin I (cTnI) and creatine kinase (CK) after AMI are correlated to the prognosis. New technical assessment like high-sensitivity cardiac troponin T (hs-cTnT) raises concerns because of its unclear kinetic following the peak. This study aims to compare kinetics of cTnI and hs-cTnT to CK in patients with large AMI successfully treated by percutaneous coronary intervention (PCI).

We prospectively studied 62 patients with anterior AMI successfully reperfused with primary angioplasty. We evaluated two consecutive groups: the first one regularly assessed by both CK and cTnI methods and the second group by CK and hs-cTnT. Modeling of kinetics was realized using mixed effects with cubic splines.

Kinetics of markers showed a peak at 7.9 h for CK, at 10.9 h (6.9–12.75) for cTnI and at 12 h for hs-cTnT. This peak was followed by a nearly log linear decrease for cTnI and CK by contrast to hs-cTnT which appeared with a biphasic shape curve marked by a second peak at 82 h. There was no significant difference between the decrease of cTnI and CK (p=0.63). CK fell by 79.5% (76.1–99.9) vs. cTnI by 86.8% (76.6–92.7). In the hs-cTnT group there was a significant difference in the decrease by 26.5% (9–42.9) when compared with CK that fell by 79.5% (64.3–90.7).

Kinetic of hs-cTnT and not cTnI differs from CK. The role of hs-cTnT in prognosis has to be investigated.

The global need to define normality: the 99th percentile value of cardiac troponin

BACKGROUND

How to select a presumably normal population for the establishment of 99th percentile cutoffs for cardiac troponin assays has not been adequately addressed. Lack of attention to this question can result in misleading medical decision cutoffs.

CONTENT

From our review of the peer-reviewed literature, including international recommendations, no uniform procedure is followed and no uniform guideline has been published by experts or regulatory agencies to guide researchers or manufacturers of cardiac troponin assays in their quest to define the health or "normality" of a reference population that is used to establish an accurate 99th percentile value. As we progress globally into the era of high-sensitivity cardiac troponin assays, we propose several suggested approaches to define presumably normal individuals by use of clinical and biomarker surrogates.

SUMMARY

Our uniform approach to defining who is normal and who may not be normal will help to define diagnostic and risk outcomes assessments in the management of patients with suspected myocardial injury, both for use in current clinical practice and clinical research, as well as for the potential future use of cardiac troponin in primary prevention.

Interference from heterophilic antibodies in troponin testing. Case report and systematic review of the literature

Heterophilic antibodies, comprising both "true" heterophilic antibodies and human anti-mouse antibodies (HAMA), represent an important source of interference in laboratory medicine, thus including cardiospecific troponin(s) testing. We describe the case of a 76-years-old woman with implausible and persistent elevation of cardiospecific troponin I, which was finally attributed to interference from heterophilic antibodies. According to literature data, the frequency of this interference ranges between 0.1 and 3.1%, is almost unpredictable and unsuspected, may involve both cardiospecific troponins I and T, and may virtually affect any type of immunoassay, either one- or two-step. The presence of interfering antibodies should always be suspected when test results do not go hand in hand with the clinics, or with the results of additional radiological and laboratory investigations. Once other causes of interference have been ruled out, test repetition with an alternative assay and removal of interfering antibodies with heterophilic antibodies blocking reagent, normal mouse serum, immobilized protein A column or polyethylene glycol may be advisable. As a simple alternative, measurement of serial dilutions of suspected samples usually shows nonlinearity of test results in the presence of heterophilic antibodies.

Acceptable cardiac safety profile of neoadjuvant 5-fluorouracil, epirubicin, cyclophosphamide and celecoxib (FEC-C) for breast cancer: a subanalysis of biomarkers for cardiac injury

PURPOSES

This substudy aimed to examine the changes in biomarkers for cardiac injury in patients who received neoadjuvant 5-fluorouracil, epirubicin, cyclophosphamide with concurrent celecoxib (FEC-C).

METHODS

Thirty-four female patients with histologically confirmed locally advanced breast cancer preoperatively received 3 cycles of FEC-C (500 mg/m², 75 mg/m², 500 mg/m²) with concurrent celecoxib (400 mg bid). Blood samples were drawn from patients on day (D) 0, D3, D21, D42, and D63 (end of therapy), and the serum levels of lactate dehydrogenase (LDH) and plasma levels of cardiac troponin I (cTnI) and N-terminal prohormone brain-type natriuretic peptide (NT-proBNP) were measured with commercially available test kits.

RESULTS

All patients tolerated this regimen well. Neither life-threatening toxicity nor clinical symptoms of cardiac damage were observed. Serum LDH increased significantly from baseline after 3 cycles of FEC-C (p<0.0001), but the change was possibly brought about by chemotherapy-induced liver derangement. However, NT-proBNP decreased significantly (p=0.009), while cTnI increased nonsignificantly (p=0.078) after 3 cycles of FEC-C compared to baseline, although this increase was still regarded as normal.

CONCLUSIONS

Short-term use of the FEC-C regimen has proven to be effective in locally advanced breast cancer, with an acceptable cardiac safety profile.

Troponin-Specific Autoantibody Interference in Different Cardiac Troponin I Assay Configurations

BACKGROUND

Autoantibodies to cardiac troponins (cTnAAb) can interfere with the measurement of cardiac troponin I (cTnI) by immunoassays. The aim of this study was to explore the degree of cTnAAb interference in different cTnI assay configurations.

METHODS

Ternary troponin complex was added into samples (serum or plasma, n = 132, 68% cTnAAb positive) from individuals without known cardiac conditions. The recovery of cTnI was then measured with 6 investigational cTnI assays (2, 3, or 4 antibodies per assay). Three of these assays were then selected for further comparison by use of samples (plasma, n = 210, 33% cTnAAb positive) from non–ST-elevation acute coronary syndrome patients in the FRISC-II (FRagmin/Fast Revascularisation during InStability in Coronary artery disease) cohort. Finally, these results were compared to those obtained with 3 commercial cTnI assays.

RESULTS

Analytical recoveries varied widely among the 6 investigational assays. Notably the low recoveries (median 9%) of the midfragment-targeting reference assay were normalized (median 103%) with the use of the 4-antibody assay construct (3 capture, 1 tracer antibody) with only 1 antibody against a midfragment epitope. Reduced analytical recoveries correlated closely with measured autoantibody amounts. cTnI concentrations from cTnAAb-positive patient samples determined with 3 investigational assays confirmed the reduced concentrations expected from the low analytical recoveries. The results from the commercial cTnI assays with antibody selections representative for contemporary assay constructs revealed a similar underestimation (up to 20-fold) of cTnI in cTnAAb-positive samples.

CONCLUSIONS

A novel cTnI assay deviating from the conventional IFCC-recommended midfragment approach substantially improves cTnI detection in samples containing cTnAAbs.

A pilot randomized study of ranolazine for reduction of myocardial damage during elective percutaneous coronary intervention

BACKGROUND

Ranolazine is a new antianginal drug that reduces intracellular sodium and calcium accumulation during ischemia, thus potentially limiting myocardial ischemia. It remains unknown, however, if the drug can play a role in the pathophysiology of periprocedural myocardial infarction. The aim of this study was to verify in a randomized study if pretreatment with ranolazine before percutaneous coronary intervention (PCI) has any protective effect on periprocedural myocardial damage.

METHODS

Seventy patients with stable angina (age 62 ± 18 years, 42 men) scheduled for elective coronary intervention entered a randomized, double-blind, placebo-controlled pilot trial. For 7 days before the procedure, 35 patients were assigned to receive ranolazine (1,000 mg twice daily) and 35 patients had placebo. Creatine kinase-MB and troponin I levels were measured at baseline and at 8 and 24 hours postprocedure.

RESULTS

Comparison between the 2 groups did not show any difference in clinical features, extent of coronary artery disease, and technical aspects of PCI. Periprocedural myocardial infarction (ie, postprocedural increase of creatine kinase-MB ≥ 3 times above the upper limit of normal) was less commonly seen after PCI in the ranolazine than in the placebo group (6% vs 22%, P = .041). Detection of markers of myocardial injury above the upper limit of normal was less common [corrected] in the ranolazine vs placebo group: 23% vs 40% for creatine kinase-MB (P = .010) and 31% vs 48% for troponin I (P = .011). [corrected] Postprocedural peak markers levels were also significantly lower in the ranolazine vs placebo group (creatine kinase-MB: 3.1 ± 15.0 and 7.7 ± 19.1 ng/mL, P < .05; troponin I: 0.15 ± 0.35 and 0.47 ± 0.49 ng/mL, P < .05). No significant adverse effect was reported by the 2 groups of patients.

CONCLUSIONS

Pretreatment with ranolazine 1,000 mg twice daily for 7 days significantly reduced procedural myocardial injury in elective PCI.

Cardiac biomarkers are associated with an increased risk of stroke and death in patients with atrial fibrillation: a Randomized Evaluation of Long-term Anticoagulation Therapy (RE-LY) substudy

BACKGROUND

Cardiac biomarkers are strong predictors of adverse outcomes in several patient populations. We evaluated the prevalence of elevated troponin I and N-terminal pro-B-type natriuretic peptide (NT-proBNP) and their association to cardiovascular events in atrial fibrillation (AF) patients in the Randomized Evaluation of Long-Term Anticoagulation Therapy (RE-LY) trial.

METHODS AND RESULTS

Biomarkers at randomization were analyzed in 6189 patients. Outcomes were evaluated by Cox proportional hazards models adjusting for established cardiovascular risk factors and the CHADS(2) and CHA(2)DS(2)-VASc risk scores. Patients were stratified based on troponin I concentrations: <0.010 μg/L, n=2663; 0.010 to 0.019 μg/L, n=2006; 0.020 to 0.039 μg/L, n=1023; ≥0.040 μg/L, n=497; and on NT-proBNP concentration quartiles: <387; 387 to 800; 801 to 1402; >1402 ng/L. Rates of stroke were independently related to levels of troponin I with 2.09%/year in the highest and 0.84%/year in the lowest troponin I group (hazard ratio [HR], 1.99 [95% CI, 1.17-3.39]; P=0.0040), and to NT-proBNP with 2.30%/year versus 0.92% in the highest versus lowest NT-proBNP quartile groups, (HR, 2.40 [95% CI, 1.41-4.07]; P=0.0014). Vascular mortality was also independently related to biomarker levels with 6.56%/year in the highest and 1.04%/year the lowest troponin I group (HR, 4.38 [95% CI, 3.05-6.29]; P<0.0001), and 5.00%/year in the highest and 0.61%/year in the lowest NT-proBNP quartile groups (HR, 6.73 [3.95-11.49]; P<0.0001). Biomarkers increased the C-statistic from 0.68 to 0.72, P<0.0001, for a composite of thromboembolic events.

CONCLUSIONS

Elevations of troponin I and NT-proBNP are common in patients with AF and independently related to increased risks of stroke and mortality. Cardiac biomarkers seem useful for improving risk prediction in AF beyond currently used clinical variables.

Multiple immunoassay systems are negatively interfered by circulating cardiac troponin I autoantibodies

Circulating cardiac troponin I (cTnI) autoantibodies have recently been detected in more and more patients with myocardial injury. In the present study, a total of 121 patients with acute myocardial infarction (AMI) were screened for cTnI autoantibodies using an indirect ELISA. Positive results were further confirmed by Western blot analysis. As a result, 13 autoantibody-positive sera were identified, in which cTnI values detected by different immunoassay systems are very different. Further evaluation revealed low recovery in one of the 13 samples with the Access 2 system (Beckman Coulter, 2^ generation), one low and one moderate recovery sample with Architect i2000 (Abbott), one low and two moderate with AxSYM (Abbott), two low and three moderate with Dimension Xpand (Dade Behring, 2^ generation), and four low and one moderate with Vidas (bioMérieux). Our work demonstrates that circulating cTnI autoantibodies occur in part of patients with AMI and, for the first time to our knowledge, shows that these autoantibodies can result in considerable negative interference in all the five commonly used cTnI immunoassay systems, which may lead to incorrect diagnoses and following treatments. The indirect ELISA established in our laboratory is suitable for a rapid preliminary screening for cTnI autoantibody in clinical work.

Influence of hemolysis on troponin testing: studies on Beckman Coulter UniCel Dxl 800 Accu-TnI and overview of the literature

Hemolyzed specimens are the leading pre-analytical problem in the laboratory practice, and exert a negative impact on test results. We assessed the reliability of Beckman Coulter UniCel Dxl 800 Accu-TnI testing on hemolyzed specimens.

Twelve non-hemolyzed K

As compared with aliquot #A (HI: 0), a progressive increase of hemolysis occurred in aliquots #B (HI: 25) and #C (HI: 45). The concentration of Accu-TnI gradually decreased from aliquots #A (0.89 μg/L, 0.20–20.16 μg/L), to aliquots #B (0.81 μg/L, 95% CI 0.17–18.37 μg/L; p=0.041) and #C (0.78 μg/L, 95% CI 0.15–17.48 μg/L; p=0.026). In 0/12 (aliquots #B) and 3/12 cases (aliquots #C) the percent decrease exceeded 20% variation. The values remained unchanged in nine samples with Accu-TnI <0.04 μg/L.

Accu-TnI values decrease in hemolyzed samples, but the bias might not be clinically significant in samples with hemoglobin <14.5 g/L.

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.

Effectiveness of in-laboratory high-dose clopidogrel loading versus routine pre-load in patients undergoing percutaneous coronary intervention: results of the ARMYDA-5 PRELOAD (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty) randomized trial

OBJECTIVES

This study sought to evaluate safety and effectiveness of in-laboratory (in-lab) 600-mg clopidogrel loading pre-percutaneous coronary intervention (PCI) versus routine 6-h pre-load.

BACKGROUND

Clopidogrel pre-treatment significantly improves outcome in patients undergoing PCI; however, efficacy of an in-lab loading strategy before PCI after coronary angiography versus routine pre-load has not been fully characterized.

METHODS

A total of 409 patients (39% with acute coronary syndrome) were randomized to receive a 600-mg clopidogrel loading dose 4 to 8 h before PCI (pre-load group, n = 204) or a 600-mg loading dose given in the catheterization lab after coronary angiography, but prior to PCI (in-lab group, n = 205). Primary end point was 30-day incidence of major adverse cardiac events: cardiac death, myocardial infarction (MI), or unplanned target vessel revascularization.

RESULTS

There was no significant difference in primary end point between the 2 randomization arms (8.8% in-lab vs. 10.3% pre-load; p = 0.72); this was mainly driven by periprocedural MI (8.8% vs. 9.3%, p = 0.99). No increased risk of bleeding or vascular complications was observed in the pre-load arm (5.4% vs. 7.8%; p = 0.42). As determined by the VerifyNow assay (Accumetrics, San Diego, California), patients in the in-lab group showed higher platelet reactivity during PCI and 2 h after intervention versus those in the pre-load arm (p < or = 0.043).

CONCLUSIONS

ARMYDA-5 PRELOAD (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty) trial indicates that a strategy of 600-mg in-lab clopidogrel load pre-PCI may have similar clinical outcomes as routine 4- to 8-h pre-load. Thus, when indicated, in-lab clopidogrel administration can be a safe alternative to routine pre-treatment given before knowing patients' coronary anatomy.

Recommendations for the use of cardiac troponin measurement in acute cardiac care

The release of cardiomyocyte components, i.e. biomarkers, into the bloodstream in higher than usual quantities indicates an ongoing pathological process. Thus, detection of elevated concentrations of cardiac biomarkers in blood is a sign of cardiac injury which could be due to supply-demand imbalance, toxic effects, or haemodynamic stress. It is up to the clinician to determine the most probable aetiology, the proper therapeutic measures, and the subsequent risk implied by the process. For this reason, the measurement of biomarkers always must be applied in relation to the clinical context and never in isolation. There are a large number of cardiac biomarkers, but they can be subdivided into four broad categories, those related to necrosis, inflammation, haemodynamic stress, and/or thrombosis. Their usefulness is dependent on the accuracy and reproducibility of the measurements, the discriminatory limits separating pathology from physiology, and their sensitivity and specificity for specific organ damage and/or disease processes. In recent years, cardiac biomarkers have become important adjuncts to the delivery of acute cardiac care. Therefore, the Working Group on Acute Cardiac Care of the European Society of Cardiology established a committee to deal with ongoing and newly developing issues related to cardiac biomarkers. The intention of the group is to outline the principles for the application of various biomarkers by clinicians in the setting of acute cardiac care in a series of expert consensus documents. The first of these will focus on cardiac troponin, a pivotal marker of cardiac injury/necrosis.

Prognostic significance of cardiac troponin I levels in hospitalized patients presenting with supraventricular tachycardia

Although cardiac troponin I (cTnI) elevation in patients presenting to the hospital with supraventricular tachycardia (SVT) is well recognized, the prevalence, predictors, and prognostic significance of cTnI elevation associated with SVT presentation are not known. We screened records of all patients presenting to 2 hospitals over a 4-year period with the diagnosis of SVT confirmed by 12-lead electrocardiogram, and who had at least 1 measured cTnI level and at least 1 year of follow-up after discharge. The primary endpoint was the occurrence of 1 of the following outcomes: death, myocardial infarction, or cardiovascular rehospitalization. Seventy-eight patients met the study criteria (54% female; mean age, 62.2 +/- 15.8 yr), and 29 patients (37.2%) had an elevated cTnI level of > or =0.06 ng/mL (range, 0.06-7.78 ng/mL). Univariate predictors of elevated cTnI included left ventricular ejection fraction (LVEF) <50%, renal dysfunction, ST-segment depression or left bundle branch block on the electrocardiogram, and moderate or severe regurgitation of any cardiac valve. Predictors of elevated cTnI after multivariate analysis included peak heart rate during SVT (per 15 bpm) (odds ratio [OR], 1.58; 95% confidence interval [CI], 1.01-2.46; p = 0.04) and LVEF <50% (OR, 6.12; 95% CI, 1.40-26.7; p = 0.02). After multivariable adjustment, the presence of elevated cTnI with SVT was associated with increased risk of the primary endpoint of death, myocardial infarction, or cardiovascular rehospitalization (hazard ratio [HR], 3.67; 95% CI, 1.22-11.1; p = 0.02). Mild elevation of cTnI is common in patients presenting to the hospital with SVT, and is associated with increased risk of future cardiovascular events. Further study is needed to determine the mechanisms of SVT-related cTnI elevation and its association with elevated cardiovascular risk.

Efficacy of atorvastatin reload in patients on chronic statin therapy undergoing percutaneous coronary intervention: results of the ARMYDA-RECAPTURE (Atorvastatin for Reduction of Myocardial Damage During Angioplasty) Randomized Trial

OBJECTIVES

This study was designed to investigate whether an acute atorvastatin reload before percutaneous coronary intervention (PCI) protects patients receiving chronic statin therapy from periprocedural myocardial damage.

BACKGROUND

Previous ARMYDA (Atorvastatin for Reduction of Myocardial Damage During Angioplasty) studies demonstrated that short-term pre-treatment with atorvastatin reduces myocardial infarction during PCI in statin-naïve patients with both stable angina and acute coronary syndromes.

METHODS

A total of 383 patients (age 66 +/- 10 years, 305 men) with stable angina (53%) or non-ST-segment elevation acute coronary syndromes (47%) and chronic statin therapy (55% atorvastatin) undergoing PCI were randomized to atorvastatin reload (80 mg 12 h before intervention, with a further 40-mg pre-procedural dose [n = 192]) or placebo (n = 191). All patients received long-term atorvastatin treatment thereafter (40 mg/day). The primary end point was 30-day incidence of major adverse cardiac events (cardiac death, myocardial infarction, or unplanned revascularization).

RESULTS

The primary end point occurred in 3.7% of patients treated with atorvastatin reload and in 9.4% in the placebo arm (p = 0.037); this difference was mostly driven by reduction in periprocedural myocardial infarction. There was lower incidence of post-procedural creatine kinase-myocardial band and troponin-I elevation greater than the upper limit of normal in the atorvastatin arm (13% vs. 24%, p = 0.017, and 37% vs. 49%, p = 0.021, respectively). Multivariable analysis identified atorvastatin reload as a predictor of decreased risk of 30-day incidence of major adverse cardiac events (odds ratio: 0.50, 95% confidence interval: 0.20 to 0.80; p = 0.039), mainly in patients with acute coronary syndromes (82% relative risk reduction; p = 0.027).

CONCLUSIONS

The ARMYDA-RECAPTURE trial suggests that reloading with high-dose atorvastatin improves the clinical outcome of patients on chronic statin therapy undergoing PCI. These findings may support a strategy of routine reload with high-dose atorvastatin early before intervention even in the background of chronic therapy.

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.

Pathophysiologic mechanisms of persistent cardiac troponin I elevation in stabilized patients after an episode of acute coronary syndrome

BACKGROUND

Recently, a high prevalence of small persistent cardiac troponin I (cTnI) elevations has been reported in patients who had been stabilized after a recent episode of acute coronary syndrome (ACS). We now have studied the associations of persistently elevated cTnI levels to cardiac performance, inflammation, coagulation, coronary status, and treatment strategy in these patients.

METHODS AND RESULTS

Cardiac troponin I was determined at 6 weeks, 3 months, and 6 months after randomization in 898 stabilized ACS patients from the FRagmin and Fast Revascularization during InStability in Coronary artery disease (FRISC) II trial and using the high-sensitive Access AccuTnI assay (Beckman Coulter, Fullerton, CA). All patients were followed up for at least 5 years. Persistent cTnI elevation >0.01 microg/L at the 3 measurement instances was detected in 233 patients (26%). N-terminal pro-brain natriuretic peptide (NT-proBNP) at 6 months (OR 2.5, 95% CI 2.0-3.1), male sex (OR 2.2, 95% CI 1.4-3.7), and randomization to an early invasive strategy (OR 1.8, 95% CI 1.2-2.7) independently predicted persistently elevated cTnI levels. Persistently cTnI-positive patients in the invasive cohort had significantly lower NT-proBNP levels compared to noninvasively treated patients, indicating that the mechanisms causing cTnI elevation in this group may be prognostically less harmful. No independent associations were found for markers of inflammation or coagulation.

CONCLUSION

Persistent cTnI elevation occurs frequently late after an ACS. The NT-proBNP level at 6 months was the strongest predictor for elevated cTnI levels that thus appear to be predominantly related to impaired left ventricular function.

Heart-type fatty acid-binding protein predicts long-term mortality after acute coronary syndrome and identifies high-risk patients across the range of troponin values

OBJECTIVES

Our aim was to determine if a high-performance assay for heart-type fatty acid-binding protein (H-FABP) has a role in predicting all-cause mortality after acute coronary syndrome (ACS).

BACKGROUND

Heart-type fatty acid-binding protein is released into the circulation following myocardial ischemia and necrosis and therefore may be of value to physicians when caring for patients admitted to hospital with a clinical diagnosis of ACS.

METHODS

This was a prospective observational study with a follow-up of 12 months. The H-FABP was measured 12 to 24 h after onset of symptoms in 1,448 patients admitted to hospital with ACS. The main outcome measure was all-cause mortality 1 year after index hospital admission. Multivariable analyses were conducted using the well validated GRACE (Global Registry of Acute Coronary Events) variables together with troponin I and highly sensitive C-reactive protein (hs-CRP).

RESULTS

After 12 months of follow-up, 296 patients had died. Multivariable analysis demonstrated that H-FABP quartiles were strongly predictive of outcome: Q1 hazard ratio (HR) 1.0; Q2 HR 2.32 (95% confidence interval [CI] 1.25 to 4.30; p = 0.007); Q3 HR 3.17 (95% CI 1.73 to 5.82; p < 0.001); Q4 HR 4.88 (95% CI 2.67 to 8.93; p < 0.001). The crude all-cause 1-year mortality for unstable angina patients with H-FABP <5.8 microg/l was 2.1% compared with 22.9% for patients above this cutoff. The adjusted all-cause mortality HR in this group was 11.35 (95% CI 2.00 to 64.34; p = 0.006).

CONCLUSIONS

Heart-type fatty acid-binding protein predicts long-term mortality after ACS and identifies high-risk patients in a manner that is additive to the GRACE clinical risk factors, troponin, and hs-CRP, possibly as a result of identifying the occurrence of myocardial ischemia with or without necrosis.

Persistent cardiac troponin I elevation in stabilized patients after an episode of acute coronary syndrome predicts long-term mortality

BACKGROUND

In patients with non-ST-elevation acute coronary syndrome, any troponin elevation is associated with an increased risk for cardiovascular events. However, the prevalence and prognostic importance of persistent troponin elevation in stabilized patients after an episode of non-ST-elevation acute coronary syndrome are unknown and were therefore assessed in this study.

METHODS AND RESULTS

Cardiac troponin I (cTnI) was measured in 1092 stabilized patients at 6 weeks and 3 and 6 months after enrollment in the FRagmin and Fast Revascularization during InStability in Coronary artery disease (FRISC-II) trial. cTnI was analyzed with the Access AccuTnI assay with the application of different prognostic cutoffs. Outcomes were assessed through 5 years. Elevated cTnI levels >0.01 microg/L were found in 48% of the study patients at 6 weeks, in 36% at 6 months, and in 26% at all 3 measurements. cTnI elevation was associated with increased age and other cardiovascular high-risk features. The lowest tested cTnI cutoff (0.01 microg/L) was prognostically most useful and was independently predictive of mortality (hazard ratio, 2.1 [95% confidence interval, 1.3 to 3.3]; P=0.001) on multivariable analysis adjusted for cardiovascular risk factors and randomization to an invasive versus noninvasive treatment strategy, whereas it was related to myocardial infarction only on univariate analysis.

CONCLUSIONS

Persistent minor cTnI elevation can be detected frequently in patients stabilized after an episode of non-ST-elevation acute coronary syndrome with the use of a sensitive assay. Elevated cTnI levels >0.01 microg/L predict mortality during long-term follow-up. Our results emphasize the importance of further troponin testing in non-ST-elevation acute coronary syndrome patients after hospital discharge.

Early prediction of anthracycline induced cardiotoxicity

AIM

The purpose of this study is to evaluate echocardiographically determined cardiac functions with serum levels of brain natriuretic peptide (BNP), cardiac troponin I (cTnI) and total antioxidant status (TAOS) in childhood leukemia treated with chemotherapeutics containing anthracyclines.

METHODS

A study group of 29 patients who have been followed for acute lymphoblastic leukemia (ALL) and administered a treatment protocol containing chemotherapy of anthracyclines were included in the analysis. Levels of BNP, cTnI and TAOS were studied in serum samples of the patients.

RESULTS

We demonstrated that as the drug dosage increased, systolic ejection fraction (EF) and shortening fraction (FS) values decreased (EF r2=0.2327, FS r2=0.251). On the other hand, increased dosage of anthracycline therapy was associated with significant raise in plasma BNP levels (r2=0.246) and significant decrease in serum TAOS levels (r2=0.317) without any change in serum cTnI levels.

CONCLUSION

Our study suggest that serum TAOS and BNP levels may be useful as an early and sensitive indicator of anthracycline induced cardiotoxicity.

Atorvastatin Pretreatment Improves Outcomes in Patients With Acute Coronary Syndromes Undergoing Early Percutaneous Coronary Intervention

OBJECTIVES

This study sought to investigate potential protective effects of atorvastatin in patients with acute coronary syndromes (ACS) undergoing percutaneous coronary intervention (PCI).

BACKGROUND

Randomized studies have shown that pretreatment with atorvastatin may reduce periprocedural myocardial infarction in patients with stable angina during elective PCI; however, this therapy has not been tested in patients with ACS.

METHODS

A total of 171 patients with non-ST-segment elevation ACS were randomized to pretreatment with atorvastatin (80 mg 12 h before PCI, with a further 40-mg preprocedure dose [n = 86]) or placebo (n = 85). All patients were given a clopidogrel 600-mg loading dose. All patients received long-term atorvastatin treatment thereafter (40 mg/day). The main end point of the trial was a 30-day incidence of major adverse cardiac events (death, myocardial infarction, or unplanned revascularization).

RESULTS

The primary end point occurred in 5% of patients in the atorvastatin arm and in 17% of those in the placebo arm (p = 0.01); this difference was mostly driven by reduction of myocardial infarction incidence (5% vs. 15%; p = 0.04). Postprocedural elevation of creatine kinase-MB and troponin-I was also significantly lower in the atorvastatin group (7% vs. 27%, p = 0.001 and 41% vs. 58%, p = 0.039, respectively). At multivariable analysis, pretreatment with atorvastatin conferred an 88% risk reduction of 30-day major adverse cardiac events (odds ratio 0.12, 95% confidence interval 0.05 to 0.50; p = 0.004).

CONCLUSIONS

The ARMYDA-ACS trial indicates that even short-term pretreatment with atorvastatin may improve outcomes in patients with ACS undergoing early invasive strategy. These findings may support routine use of high-dose statins before intervention in patients with ACS.

Safety and efficacy of short-term celecoxib before elective percutaneous coronary intervention for stable angina pectoris

Fifty patients with stable angina pectoris entered a randomized, double-blind study and were assigned to receive celecoxib (200 mg 2 times daily) or placebo 7 days before percutaneous coronary intervention (PCI). Results showed that detection of markers of myocardial injury above the upper normal limit was significantly lower in the celecoxib than in the placebo group: 12% versus 35% for creatine kinase-MB (CK-MB; p = 0.001), 20% versus 48% for troponin I (p = 0.0004), and 22% versus 51% for myoglobin (p = 0.0005). Myocardial infarction by CK-MB determination was less commonly seen after PCI in the celecoxib than in the placebo group (5% vs 18%, p = 0.025). Postprocedural peak levels of CK-MB (2.9 +/- 18 vs 7.5 +/- 18 ng/ml, p = 0.0002) were also significantly lower in the celecoxib than in the placebo group. No significant side effect was reported by the 2 groups of patients. In conclusion, pretreatment with celecoxib 200 mg 2 times daily for 7 days significantly decreased procedural myocardial injury in elective PCI. These findings indicate that the antiphlogistic action of cyclo-oxygenase-2 inhibition may provide a friendly protection to ischemic cardiomyocytes.

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.

Protection From Procedural Myocardial Injury by Atorvastatin Is Associated With Lower Levels of Adhesion Molecules After Percutaneous Coronary Intervention

OBJECTIVES

The goal of this work was to investigate whether protection from myocardial injury during percutaneous coronary intervention (PCI) by atorvastatin is related to reduction of endothelial inflammatory response.

BACKGROUND

In the randomized ARMYDA (Atorvastatin for Reduction of MYocardial Damage during Angioplasty) trial, 7-day pre-treatment with atorvastatin before PCI significantly reduced procedural myocardial injury; mechanisms underlying this effect are not characterized.

METHODS

In a planned subanalysis of the ARMYDA trial, a subgroup of 76 patients was blind-tested for measurement of plasma levels of vascular cell adhesion molecule-1 (VCAM-1), intercellular cell adhesion molecule-1 (ICAM-1), and E-selectin: 38 patients belonged to atorvastatin (40 mg/day) and 38 to the placebo arm. Adhesion molecules were evaluated 7 days before intervention, immediately before PCI, and after 8 and 24 h.

RESULTS

Reduction of procedural myocardial injury after statin pre-treatment was also confirmed in this subgroup. Intercellular cell adhesion molecule-1, E-selectin, and VCAM-1 levels were not different at randomization and before intervention in either arm. At 8 h, increase of ICAM-1 levels was similar in the 2 arms, whereas 24-h levels were significantly lower in the atorvastatin versus placebo group (282 +/- 56 vs. 325 +/- 70 ng/ml; p = 0.007). Attenuation of E-selectin elevation occurred at 8 h in the atorvastatin group (50 +/- 8 vs. 59 +/- 13 ng/ml; p = 0.002) and became even more significant at 24 h (57 +/- 9 vs. 73 +/- 18 ng/ml; p = 0.0008). Vascular cell adhesion molecule-1 levels were not different at any time point in the 2 arms.

CONCLUSIONS

In patients undergoing PCI, reduction of procedural myocardial injury after 7-day pre-treatment with atorvastatin is paralleled by concomitant attenuation of post-procedural increase of ICAM-1 and E-selectin levels; thus, reduction of endothelial inflammatory response may explain this protective effect of statins.

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.

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.