High-Sensitivity Cardiac Troponin and the Risk Stratification of Patients With Renal Impairment Presenting With Suspected Acute Coronary Syndrome

Is the true clinical value of high-sensitivity troponins as a biomarker of risk? The concept that detection of high-sensitivity troponin 'never means nothing'

INTRODUCTION

High-sensitivity troponin (hs-cTn) assays are central to the diagnosis of myocardial infarction (MI). Their increased sensitivity has facilitated rapid pathways for the exclusion of MI. However, hs-cTn is now more readily detectable in patients without symptoms typical of MI, in whom a degree of myocardial injury is assumed. Recently, the practice of using the 99^th centile of hs-cTn as a working 'upper reference limit' has been challenged. There is increasing evidence that hs-cTn may provide useful prognostic information, regardless of any suspicion of MI, and as such these assays may have potential as a general biomarker for mortality. This raises the concept that detection of hs-cTn 'never means nothing.'

AREAS COVERED

In this review, we will evaluate the evidence for the use of hs-cTn assays outside their common clinical indication to rule out or diagnose acute MI.

EXPERT OPINION

The data presented suggest that hs-cTn testing may in the future have a generalized role as a biomarker of mortality risk and may be used less as a test for ruling in acute MI, but will remain a frontline test to exclude that diagnosis in ED. Further, the data suggest that the detection of hs-cTn 'never means nothing.'

Ideal high sensitivity troponin baseline cutoff for patients with renal dysfunction

OBJECTIVE

High-sensitivity cardiac troponin assays (hs-cTn) aid in diagnosis of myocardial infarction (MI). These assays have lower specificity for non-ST Elevation MI (NSTEMI) in patients with renal disease. Our objective was to determine an optimized cutoff for patients with renal disease.

METHODS

We conducted an a priori secondary analysis of a prospective FDA study in adults with suspected MI presenting to 29 academic urban EDs between 4/2015 and 4/2016. Blood was drawn 0, 1, 2-3, and 6-9 h after ED arrival. We recorded cTn and estimated glomerular filtrate rate (eGFR) by Chronic Kidney Disease Epidemiology Collaboration equation. The primary endpoint was NSTEMI (Third Universal Definition of MI), adjudicated by physicians blinded to hs-cTn results. We generated an adjusted hscTn rule-in cutoff to increase specificity.

RESULTS

2505 subjects were enrolled; 234 were excluded. Patients were mostly male (55.7%) and white (57.2%), median age was 56 years 472 patients [20.8%] had an eGFR <60 mL/min/1.73 m2. In patients with eGFR <15 mL/min/1.73 m2, a baseline rule-in cutoff of 120 ng/L led to a specificity of 85.0% and Positive Predictive Value (PPV) of 62.5% with 774 patients requiring further observation. Increasing the cutoff to 600 ng/L increased specificity and PPV overall and in every eGFR subgroup (specificity and PPV 93.3% and 78.9%, respectively for eGFR <15 mL/min/1.73m²), while increasing the number (79) of patients requiring observation.

CONCLUSIONS

An eGFR-adjusted baseline rule-in threshold for the Siemens Atellica hs-cTnI improves specificity with identical sensitivity. Further study in a prospective cohort with higher rates of renal disease is warranted.

Sex-Specific Thresholds of High-Sensitivity Troponin in Patients With Suspected Acute Coronary Syndrome

BACKGROUND

Major disparities between women and men in the diagnosis, management, and outcomes of acute coronary syndrome are well recognized.

OBJECTIVES

The aim of this study was to evaluate the impact of implementing a high-sensitivity cardiac troponin I assay with sex-specific diagnostic thresholds for myocardial infarction in women and men with suspected acute coronary syndrome.

METHODS

Consecutive patients with suspected acute coronary syndrome were enrolled in a stepped-wedge, cluster-randomized controlled trial across 10 hospitals. Myocardial injury was defined as high-sensitivity cardiac troponin I concentration >99th centile of 16 ng/l in women and 34 ng/l in men. The primary outcome was recurrent myocardial infarction or cardiovascular death at 1 year.

RESULTS

A total of 48,282 patients (47% women) were included. Use of the high-sensitivity cardiac troponin I assay with sex-specific thresholds increased myocardial injury in women by 42% and in men by 6%. Following implementation, women with myocardial injury remained less likely than men to undergo coronary revascularization (15% vs. 34%) and to receive dual antiplatelet (26% vs. 43%), statin (16% vs. 26%), or other preventive therapies (p < 0.001 for all). The primary outcome occurred in 18% (369 of 2,072) and 17% (488 of 2,919) of women with myocardial injury before and after implementation, respectively (adjusted hazard ratio: 1.11; 95% confidence interval: 0.92 to 1.33), compared with 18% (370 of 2,044) and 15% (513 of 3,325) of men (adjusted hazard ratio: 0.85; 95% confidence interval: 0.71 to 1.01).

CONCLUSIONS

Use of sex-specific thresholds identified 5 times more additional women than men with myocardial injury. Despite this increase, women received approximately one-half the number of treatments for coronary artery disease as men, and outcomes were not improved. (High-Sensitivity Troponin in the Evaluation of Patients With Acute Coronary Syndrome [High-STEACS]; NCT01852123).

Implications of the complex biology and micro-environment of cardiac sarcomeres in the use of high affinity troponin antibodies as serum biomarkers for cardiac disorders

Cardiac troponin I (cTnI), the inhibitory-unit, and cardiac troponin T (cTnT), the tropomyosin-binding unit together with the Ca-binding unit (cTnC) of the hetero-trimeric troponin complex signal activation of the sarcomeres of the adult cardiac myocyte. The unique structure and heart myocyte restricted expression of cTnI and cTnT led to their worldwide use as biomarkers for acute myocardial infarction (AMI) beginning more than 30 years ago. Over these years, high sensitivity antibodies (hs-cTnI and hs-cTnT) have been developed. Together with careful determination of history, physical examination, and EKG, determination of serum levels using hs-cTnI and hs-cTnT permits risk stratification of patients presenting in the Emergency Department (ED) with chest pain. With the ability to determine serum levels of these troponins with high sensitivity came the question of whether such measurements may be of diagnostic and prognostic value in conditions beyond AMI. Moreover, the finding of elevated serum troponins in physiological states such as exercise and pathological states where cardiac myocytes may be affected requires understanding of how troponins may be released into the blood and whether such release may be benign. We consider these questions by relating membrane stability to the complex biology of troponin with emphasis on its sensitivity to the chemo-mechanical and micro-environment of the cardiac myocyte. We also consider the role determinations of serum troponins play in the precise phenotyping in personalized and precision medicine approaches to promote cardiac health.

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Serum levels of cardiac TnI and cardiac TnT permit stratification of patients with chest pain.

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Release of troponins into blood involves not only frank necrosis but also programmed necroptosis.

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Genome wide analysis of serum troponin levels in the general population may be prognostic about cardiovascular health.

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Significant levels of serum troponins with exhaustive exercise may not be benign.

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Troponin in serum can lead to important data related to personalized and precision medicine.

The Liver and Kidneys mediate clearance of cardiac troponin in the rat

Cardiac-specific troponins (cTn), troponin T (cTnT) and troponin I (cTnI) are diagnostic biomarkers when myocardial infarction is suspected. Despite its clinical importance it is still not known how cTn is cleared once it is released from damaged cardiac cells. The aim of this study was to examine the clearance of cTn in the rat. A cTn preparation from pig heart was labeled with fluorescent dye or fluorine 18 (¹⁸ F). The accumulation of the fluorescence signal using organ extracts, or the 18 F signal using positron emission tomography (PET) was examined after a tail vein injection. The endocytosis of fluorescently labeled cTn was studied using a mouse hepatoma cell line. Close to 99% of the cTnT and cTnI measured with clinical immunoassays were cleared from the circulation two hours after a tail vein injection. The fluorescence signal from the fluorescently labeled cTn preparation and the radioactivity from the 18F-labeled cTn preparation mainly accumulated in the liver and kidneys. The fluorescently labeled cTn preparation was efficiently endocytosed by mouse hepatoma cells. In conclusion, we find that the liver and the kidneys are responsible for the clearance of cTn from plasma in the rat.

Performance of Novel High-Sensitivity Cardiac Troponin I Assays for 0/1-Hour and 0/2- to 3-Hour Evaluations for Acute Myocardial Infarction: Results From the HIGH-US Study

STUDY OBJECTIVE

We determine the accuracy of high-sensitivity cardiac troponin I (hs-cTnI), European-derived, rapid, acute myocardial infarction, rule-out/rule-in algorithms applied to a US emergency department (ED) population.

METHODS

Adults presenting to the ED with suspected acute myocardial infarction were included. Plasma samples collected at baseline and between 40 and 90 minutes and 2 and 3 hours later were analyzed in core laboratories using the Siemens Healthineers hs-cTnI assays. Acute myocardial infarction diagnosis was independently adjudicated. The sensitivity, specificity, and negative and positive predictive values for rapid acute myocardial infarction rule-out/rule-in using European algorithms and 30-day outcomes are reported.

RESULTS

From 29 US medical centers, 2,113 subjects had complete data for the 0/1-hour algorithm analyses. With the Siemens Atellica Immunoassay hs-cTnI values, 1,065 patients (50.4%) were ruled out, with a negative predictive value of 99.7% and sensitivity of 98.7% (95% confidence interval 99.2% to 99.9% and 96.3% to 99.6%, respectively), whereas 265 patients (12.6%) were ruled in, having a positive predictive value of 69.4% and specificity of 95.7% (95% confidence interval 63.6% to 74.7% and 94.7% to 96.5%, respectively). The remaining 783 patients (37.1%) were classified as having continued evaluations, with an acute myocardial infarction incidence of 5.6% (95% confidence interval 4.2% to 7.5%). The overall 30-day risk of death or postdischarge acute myocardial infarction was very low in the ruled-out patients but was incrementally increased in the other groups (rule-out 0.2%; continued evaluations 2.1%; rule-in 4.8%). Equivalent results were observed in the 0/2- to 3-hour analyses and when both algorithms were applied to the hs-cTnI ADVIA Centaur measurements.

CONCLUSION

The European rapid rule-out/rule-in acute myocardial infarction algorithm hs-cTnI cut points can be harmonized with a demographically and risk-factor diverse US ED population.

Performance of the ESC 0/1-h and 0/3-h Algorithm for the Rapid Identification of Myocardial Infarction Without ST-Elevation in Patients With Diabetes

OBJECTIVE

Patients with diabetes mellitus (DM) have elevated levels of high-sensitivity cardiac troponin (hs-cTn). We investigated the diagnostic performance of the European Society of Cardiology (ESC) algorithms to rule out or rule in acute myocardial infarction (AMI) without ST-elevation in patients with DM.

RESEARCH DESIGN AND METHODS

We prospectively enrolled 3,681 patients with suspected AMI and stratified those by the presence of DM. The ESC 0/1-h and 0/3-h algorithms were used to calculate negative and positive predictive values (NPV, PPV). In addition, alternative cutoffs were calculated and externally validated in 2,895 patients.

RESULTS

In total, 563 patients (15.3%) had DM, and 137 (24.3%) of these had AMI. When the ESC 0/1-h algorithm was used, the NPV was comparable in patients with and without DM (absolute difference [AD] -1.50 [95% CI -5.95, 2.96]). In contrast, the ESC 0/3-h algorithm resulted in a significantly lower NPV in patients with DM (AD -2.27 [95% CI -4.47, -0.07]). The diagnostic performance for rule-in of AMI (PPV) was comparable in both groups: 0/1-h (AD 6.59 [95% CI -19.53, 6.35]) and 0/3-h (AD 1.03 [95% CI -7.63, 9.7]). Alternative cutoffs increased the PPV in both algorithms significantly, while improvements in NPV were only subtle.

CONCLUSIONS

Application of the ESC 0/1-h algorithm revealed comparable safety to rule out AMI comparing patients with and without DM, while this was not observed with the ESC 0/3-h algorithm. Although alternative cutoffs might be helpful, patients with DM remain a high-risk population in whom identification of AMI is challenging and who require careful clinical evaluation.

Optimal cut-off value of high-sensitivity troponin I in diagnosing myocardial infarction in patients with end-stage renal disease

End-stage renal disease (ESRD) is a major risk factor for cardiovascular disease and the prognosis after myocardial infarction (MI) is dismal. Although cardiac troponin is a key diagnostic test, troponin levels are often elevated in ESRD patients without evidence of MI. Thus, this study attempted to determine the optimal diagnostic value of high-sensitivity troponin I (hsTnI) by dialysis modality in ESRD patients.Medical records of adult dialysis patients who visited tertiary emergency department (ED) were collected retrospectively. Diagnosis of MI was made according to the fourth universal definition of MI. The cut-off values were calculated using a receiver operating characteristic (ROC) curve.Medical records of 1144 patients were analyzed and MI was diagnosed in 82 patients (75 on hemodialysis and 7 on peritoneal dialysis). The optimal cut-off value of hsTnI in hemodialysis patients was 75 ng/L, with 93.33% sensitivity and 60.76% specificity. Area under the curve (AUC) was .870 (95% confidence interval (CI) .833-.906). The optimal cut-off value of hsTnI in peritoneal dialysis patients was 144 ng/L, with 100.00% sensitivity and 83.10% specificity. AUC was .943 (95% CI .893-.992).The dialysis modality should also be considered when diagnosing MI using hsTnI in ESRD patients.

Troponins, Acute Coronary Syndrome and Renal Disease: From Acute Kidney Injury Through End-stage Kidney Disease

The diagnosis of acute coronary syndromes (ACS) is heavily dependent on cardiac biomarker assays, particularly cardiac troponins. ACS, particularly non-ST segment elevation MI, are more common in patients with acute kidney injury, chronic kidney disease (CKD) and end-stage kidney disease (ESKD), are associated with worse outcomes than in patients without kidney disease and are often difficult to diagnose and treat. Hence, early accurate diagnosis of ACS in kidney disease patients is important using easily available tools, such as cardiac troponins. However, the diagnostic reliability of cardiac troponins has been suboptimal in patients with kidney disease due to possible decreased clearance of troponin with acute and chronic kidney impairment and low levels of troponin secretion due to concomitant cardiac muscle injury related to left ventricular hypertrophy, inflammation and fibrosis. This article reviews the metabolism and utility of cardiac biomarkers in patients with acute and chronic kidney diseases. Cardiac troponins are small peptides that accumulate in both acute and chronic kidney diseases due to impaired excretion. Hence, troponin concentrations rise and fall with acute kidney injury and its recovery, limiting their use in the diagnosis of ACS. Troponin concentrations are chronically elevated in CKD and ESKD, are associated with poor prognosis and decrease the sensitivity and specificity for diagnosis of ACS. Yet, the evidence indicates that the use of high-sensitivity troponins can confirm or exclude a diagnosis of ACS in the emergency room in a significant proportion of kidney disease patients; those patients in whom the results are equivocal may need longer in-hospital assessment.

The assessment of coronary artery disease in patients with end-stage renal disease

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality among patients with end-stage renal disease (ESRD). Clustering of traditional atherosclerotic and non-traditional risk factors drive the excess rates of coronary and non-coronary CVD in patients with ESRD. Coronary artery disease (CAD) is a key disease process, present in ∼50% of the haemodialysis population ≥65 years of age. Patients with ESRD are more likely to be asymptomatic, posing a challenge to the correct identification of CAD, which is essential for appropriate risk stratification and management. Given the lack of randomized clinical trial evidence in this population, current practice is informed by observational data with a significant potential for bias. For this reason, the most appropriate approach to the investigation of CAD is the subject of considerable discussion, with practice patterns largely varying between different centres. Traditional imaging modalities are limited in their diagnostic accuracy and prognostic value for cardiac events and survival in patients with ESRD, demonstrated by the large number of adverse cardiac outcomes among patients with negative test results. This review focuses on the current understanding of CAD screening in the ESRD population, discussing the available evidence for the use of various imaging techniques to refine risk prediction, with an emphasis on their strengths and limitations.

Glomerular Filtration Rate-Specific Cutoffs Can Refine the Prognostic Value of Circulating Cardiac Biomarkers in Advanced Chronic Kidney Disease

BACKGROUND

Using standard cutoffs derived from healthy adults, high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) are frequently elevated in patients with reduced glomerular filtration rate (GFR), with unclear implications. We sought to compare GFR-specific cutoffs of each biomarker with standard cutoffs for discrimination of cardiovascular risk in asymptomatic patients with chronic kidney disease.

METHODS

We investigated a prospective cohort of 1956 participants with median GFR of 27 mL/min/1.73 m². Cox proportional hazards models were used to examine the association between each biomarker and first adjudicated cardiovascular event (unstable angina, myocardial infarction, heart failure, stroke, cardiovascular death). We used an outcome-based approach to identify optimal risk-based cutoffs for each biomarker within GFR strata (< 20, 20-29, 30-44 mL/min/1.73 m²). We evaluated the added prognostic value of each biomarker to a multivariable base model, comparing GFR-specific with standard cutoffs.

RESULTS

Hs-cTnT and NT-proBNP were elevated in 76% and 82% of participants, respectively. A total of 401 events were recorded during 6772 person-years at risk. Both biomarkers were independent predictors of cardiovascular events. Optimal cutoffs for each biomarker were higher than standard thresholds, being highest at GFR values < 20 mL/min/1.73 m². Addition of hs-cTnT to the base model using GFR-specific cutoffs significantly improved reclassification for events (52%) and nonevents (21%). Similar findings were observed for NT-proBNP. In contrast, use of standard cutoffs failed to reclassify patients who had no event as lower risk.

CONCLUSIONS

Among asymptomatic patients with advanced chronic kidney disease, optimal cutoffs for hs-cTnT and NT-proBNP differed according to GFR level and outperformed standard cutoffs for discrimination of cardiovascular risk.

Initial Concentrations of miR-1 MicroRNA Precursor and High-Sensitivity Troponin in the Diagnosis of Non-ST Myocardial Infarction among Patients with and Those without Chronic Kidney Disease

Background: The early diagnosis of non-ST-segment elevation myocardial infarction (NSTEMI) in patients with chronic kidney disease (CKD) remains a challenge. Methods: The study consecutively enrolled patients who had suffered from chest pain within 3 h whose electrocardiogram had no elevation in the ST segment. CKD was defined as an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2, and the diagnostic criteria for NSTEMI were defined according to the recommended guideline. Circulating microRNA-1 was collected and determined by quantitative real-time reverse transcription polymerase chain reaction. Results: A total of 456 patients with suspected NSTEMI were included. There were 115 patients in the CKD group, including 67 with NSTEMI, 20 with stable angina, 7 with unstable angina, 18 with heart failure, and 3 with other disorders. Compared with the NSTEMI group, the non-NSTEMI group just had significant differences in microRNA-1 and high-sensitivity cardiac troponin I (hs-cTnI) (both p < 0.05). The relative expression of microRNA-1 was significantly increased in the NSTEMI group as compared with that in the other disease groups (all p < 0.05). A receiver operating characteristic (ROC) curve analysis suggested that microRNA-1 and hs-cTnI had advantages in the early diagnosis of NSTEMI with CKD (AUC [area under the ROC curve] 0.879 and 0.812, respectively, both p < 0.05). Compared with that in the non-CKD group, the accuracy of microRNA-1 was almost as good in the CKD group (84.3 vs. 89.4%, p > 0.05). However, the diagnostic accuracy of hs-cTnI was significantly decreased (79.1 vs. 91.5%, p < 0.05), as was its specificity (75.0 vs. 95.5%, p < 0.05). There was no significant difference in the correlation between microRNA-1 and eGFR (p > 0.05), but a statistically significantly negative correlation between hs-cTnI and eGFR (p < 0.05). Conclusion: Circulating microRNA-1 is capable of early diagnosis of NSTEMI in patients with CKD suffering from chest pain.

Diagnosis and treatment of myocardial infarction in patient with end - stage renal disease on chronic hemodialysis

This review represents different aspects of myocardial infarction in patient with end - stage renal disease on chronic hemodialysis. We discuss difficulties in diagnosis, optimal method of coronary revascularization, timing of hemodialysis session, medical therapy, as well as epidemiology and prognosis. There are no unambiguous answers to these problems because patients with end - stage renal disease were excluded from most of the studies.

The impact of coronary angiography on renal transplant function

INTRODUCTION

There may be reluctance to perform coronary angiography in kidney transplant patients due to perceived risk of iodinated contrast, despite an increased risk of cardiovascular disease compared with the general population.

AIM

We sought to determine if renal transplant function was adversely affected within 7, 30 and 180 days of coronary angiography.

DESIGN AND METHODS

Renal transplant recipients undergoing coronary angiography in a single centre (01/2006-02/2018) were identified retrospectively. Baseline and highest SCr within 7, 30 and 180 days of coronary angiography were extracted from the electronic patient record. Rise in creatinine >26 micromol/l was considered significant [equivalent to Acute Kidney Injury (AKI) Network criteria stage 1 AKI] and case note review performed to determine circumstance of renal decline.

RESULTS

There were 127 coronary angiographies conducted in 90 patients: 67.7% were male and mean age was 58.0 (±10.1) years. There was AKI within 7 days in 18.9% cases, but SCr returned to baseline within 7 days or there was an alternative explanation for AKI in 83.3% of these. In the remaining four cases, there was progressive decline in renal transplant function. In the absence of critical illness, no patient required dialysis or extended hospital stay for contrast-associated AKI.

CONCLUSIONS

In this cohort of renal transplant recipients undergoing coronary angiography, AKI occurred in a minority of cases, and in more than 95% of such cases this effect was transient, with progressive renal decline a rare and predictable event. Renal transplant should not be regarded as a contraindication to coronary angiography.

Troponin I at admission in the intensive care unit predicts the need of dialysis in septic patients

Background

In a previous study we showed that troponin I (TnI) > 0.42 ng/mL predicted the need of dialysis in a group of 29 septic patients admitted to the intensive care unit (ICU). We aimed to confirm such finding in a larger independent sample.

Methods

All septic patients admitted to an ICU from March 2016 to February 2017 were included if age between 18 and 90 years, onset of sepsis < 24 h, normal left ventricular ejection fraction, and no previous coronary or kidney diseases. TnI was measured on day 1. Patients were followed by 30 days or until death.

Results

A total of 120 patients were included (51% male, 74 ± 13 years old). At ICU admission, 70 patients had TnI > 0.42 ng/mL. These patients had serum creatinine slightly higher (1.66 ± 0.34 vs. 1.32 ± 0.39 mg/dL; P <  0.0001) than those with lower TnI and similar urine output (1490 ± 682 vs. 1406 ± 631 mL; P = 0.44). At the end of the follow-up period, 70.0% of the patients with lower TnI were alive in comparison with 38.6% of those with higher TnI (p = 0.0014). After 30 days, 69.3 and 2.9% of the patients with lower and higher TnI levels remained free of dialysis, respectively (p <  0.0001). In a Cox regression model, after adjustment for gender, age, Charlson comorbidity index, serum creatinine, potassium, pH, brain natriuretic peptide and urine output, TnI > 0.42 ng/mL persisted as a strong predictor of dialysis need (hazard ratio 3.48 [95%CI 1.69–7.18]).

Conclusions

TnI levels at ICU admission are a strong independent predictor of dialysis need in sepsis.

Cardiac Troponin - diagnostic problems and impact on cardiovascular disease

The definition of a high-sensitivity cardiac Troponin (cTn) assay describes the ability to quantify a cardiac biomarker level in at least 50% of healthy individuals. This advance in analytic sensitivity has come with a perceived loss of specificity in the most classic application - chest pain triage and the diagnosis of acute myocardial infarction (AMI). As cardiac Troponin can no longer be used as a dichotomous test, the medical field is increasingly moving towards a more granular interpretation. However, rapid rule-out/rule-in algorithms for AMI still rely on concrete thresholds for efficient triage, irrespective of the patient's comorbidities. Owing to a slightly elevated cTn value, evermore patients appear to fall into an indeterminate risk zone of diagnostic uncertainty. The reasons are manifold, spanning biological variation, analytical issues, increased plasma membrane permeability and the potential cytosolic release of cTn. This review provides a contemporary overview of the literature concerning the use of cardiac Troponin in chronic and acute cardiovascular care. Key messages High-sensitivity cardiac Troponin assays have transformed the assessment of cardiovascular disease. Rapid rule-out algorithms for chest pain triage have become increasingly complicated, but enable safe rule-out. Cardiac Troponin tracks mid- to long-term risk in patients with hyperlipidaemia, heart failure and renal dysfunction.

High-Sensitivity Cardiac Troponin I and Clinical Risk Scores in Patients With Suspected Acute Coronary Syndrome

BACKGROUND

High-sensitivity cardiac troponin assays can help to identify patients who are at low risk of myocardial infarction in the emergency department. We aimed to determine whether the addition of clinical risk scores would improve the safety of early rule-out pathways for myocardial infarction.

METHODS

In 1935 patients with suspected acute coronary syndrome, we evaluated the safety and efficacy of 2 rule-out pathways alone or in conjunction with low-risk TIMI (Thrombolysis In Myocardial Infarction) (0 or 1), GRACE (Global Registry of Acute Coronary Events) (≤108), EDACS (Emergency Department Assessment of Chest Pain Score) (<16), or HEART (History, ECG, Age, Risk factors, Troponin) (≤3) scores. The European Society of Cardiology 3-hour pathway uses a single diagnostic threshold (99th percentile), whereas the High-STEACS (High-Sensitivity Troponin in the Evaluation of Patients With Acute Coronary Syndrome) pathway applies different thresholds to rule out (<5 ng/L) and rule in (>99th percentile) myocardial infarction.

RESULTS

Myocardial infarction or cardiac death during the index presentation or at 30 days occurred in 14.3% of patients (276/1935). The European Society of Cardiology pathway ruled out 70%, with 27 missed events giving a negative predictive value of 97.9% (95% CI, 97.1-98.6). The addition of a HEART score ≤3 reduced the proportion ruled out by the European Society of Cardiology pathway to 25% but improved the negative predictive value to 99.7% (95% CI, 99.0-100; P<0.001). The High-STEACS pathway ruled out 65%, with 3 missed events for a negative predictive value of 99.7% (95% CI, 99.4-99.9). No risk score improved the negative predictive value of the High-STEACS pathways, but all reduced the proportion ruled out (24% to 47%; P<0.001 for all).

CONCLUSIONS

Clinical risk scores significantly improved the safety of the European Society of Cardiology 3-hour pathway, which relies on a single cardiac troponin threshold at the 99th percentile to rule in and rule out myocardial infarction. Where lower thresholds are used to rule out myocardial infarction, as applied in the High-STEACS pathway, risk scores halve the proportion of patients ruled out without improving safety.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01852123.

High-sensitivity troponin in the evaluation of patients with suspected acute coronary syndrome: a stepped-wedge, cluster-randomised controlled trial

BACKGROUND

High-sensitivity cardiac troponin assays permit use of lower thresholds for the diagnosis of myocardial infarction, but whether this improves clinical outcomes is unknown. We aimed to determine whether the introduction of a high-sensitivity cardiac troponin I (hs-cTnI) assay with a sex-specific 99th centile diagnostic threshold would reduce subsequent myocardial infarction or cardiovascular death in patients with suspected acute coronary syndrome.

METHODS

In this stepped-wedge, cluster-randomised controlled trial across ten secondary or tertiary care hospitals in Scotland, we evaluated the implementation of an hs-cTnI assay in consecutive patients who had been admitted to the hospitals' emergency departments with suspected acute coronary syndrome. Patients were eligible for inclusion if they presented with suspected acute coronary syndrome and had paired cardiac troponin measurements from the standard care and trial assays. During a validation phase of 6-12 months, results from the hs-cTnI assay were concealed from the attending clinician, and a contemporary cardiac troponin I (cTnI) assay was used to guide care. Hospitals were randomly allocated to early (n=5 hospitals) or late (n=5 hospitals) implementation, in which the high-sensitivity assay and sex-specific 99th centile diagnostic threshold was introduced immediately after the 6-month validation phase or was deferred for a further 6 months. Patients reclassified by the high-sensitivity assay were defined as those with an increased hs-cTnI concentration in whom cTnI concentrations were below the diagnostic threshold on the contemporary assay. The primary outcome was subsequent myocardial infarction or death from cardiovascular causes at 1 year after initial presentation. Outcomes were compared in patients reclassified by the high-sensitivity assay before and after its implementation by use of an adjusted generalised linear mixed model. This trial is registered with ClinicalTrials.gov, number NCT01852123.

FINDINGS

Between June 10, 2013, and March 3, 2016, we enrolled 48 282 consecutive patients (61 [SD 17] years, 47% women) of whom 10 360 (21%) patients had cTnI concentrations greater than those of the 99th centile of the normal range of values, who were identified by the contemporary assay or the high-sensitivity assay. The high-sensitivity assay reclassified 1771 (17%) of 10 360 patients with myocardial injury or infarction who were not identified by the contemporary assay. In those reclassified, subsequent myocardial infarction or cardiovascular death within 1 year occurred in 105 (15%) of 720 patients in the validation phase and 131 (12%) of 1051 patients in the implementation phase (adjusted odds ratio for implementation vs validation phase 1·10, 95% CI 0·75 to 1·61; p=0·620).

INTERPRETATION

Use of a high-sensitivity assay prompted reclassification of 1771 (17%) of 10 360 patients with myocardial injury or infarction, but was not associated with a lower subsequent incidence of myocardial infarction or cardiovascular death at 1 year. Our findings question whether the diagnostic threshold for myocardial infarction should be based on the 99th centile derived from a normal reference population.

FUNDING

The British Heart Foundation.