Prospective validation of a 1-hour algorithm to rule-out and rule-in acute myocardial infarction using a high-sensitivity cardiac troponin T assay

Evaluating Rapid Rule-out of Acute Myocardial Infarction Using a High-Sensitivity Cardiac Troponin I Assay at Presentation

BACKGROUND

Low concentrations of cardiac troponin (cTn) have been recommended for rapid rule-out of acute myocardial infarction (AMI). We examined the Beckman Coulter Access high-sensitivity cardiac troponin I (hs-cTnI) assay to identify a single test threshold that can safely rule out AMI.

METHODS

This analysis used stored samples collected in 2 prospective observational studies. In all, 1871 patients presenting to a tertiary emergency department with symptoms of acute coronary syndrome had blood taken for measurement of cTnI on presentation. The endpoint was type 1 myocardial infarction (T1MI). Sensitivity and negative predictive value (NPV) were calculated for hs-cTnI values below the 99th percentile.

RESULTS

Ninety-eight patients had T1MI (5.2%), and 638 (34.1%) patients had an hs-cTnI <2 ng/L (limit of detection), with sensitivity of 99.0% (95% CI, 94.4%–100%) and NPV of 99.8% (95% CI, 99.1%–100%). No hs-cTnI value above a concentration of 2 ng/L achieved sensitivity of 99%. However, an NPV of 99.5% was achieved at values <6 ng/L. A cutoff <6 ng/L enabled 1475 (78.8%) patients to be ruled out on presentation with sensitivity of 93.9% (95% CI, 87.1%–97.7%).

CONCLUSIONS

A single baseline cTn <2 ng/L measured with the Access hs-cTnI assay performed well for rule-out of AMI. This cutoff concentration identified 99% of patients with AMI and could reduce the number of patients requiring lengthy assessment. A cutoff of <6 ng/L yielded a high NPV but missed more cases of AMI than would be acceptable to clinicians.

0/1-Hour Triage Algorithm for Myocardial Infarction in Patients With Renal Dysfunction

BACKGROUND

The European Society of Cardiology recommends a 0/1-hour algorithm for rapid rule-out and rule-in of non-ST-segment elevation myocardial infarction using high-sensitivity cardiac troponin (hs-cTn) concentrations irrespective of renal function. Because patients with renal dysfunction (RD) frequently present with increased hs-cTn concentrations even in the absence of non-ST-segment elevation myocardial infarction, concern has been raised regarding the performance of the 0/1-hour algorithm in RD.

METHODS

In a prospective multicenter diagnostic study enrolling unselected patients presenting with suspected non-ST-segment elevation myocardial infarction to the emergency department, we assessed the diagnostic performance of the European Society of Cardiology 0/1-hour algorithm using hs-cTnT and hs-cTnI in patients with RD, defined as an estimated glomerular filtration rate <60 mL/min/1.73 m2, and compared it to patients with normal renal function. The final diagnosis was centrally adjudicated by 2 independent cardiologists using all available information, including cardiac imaging. Safety was quantified as sensitivity in the rule-out zone, accuracy as the specificity in the rule-in zone, and efficacy as the proportion of the overall cohort assigned to either rule-out or rule-in based on the 0- and 1-hour sample.

RESULTS

Among 3254 patients, RD was present in 487 patients (15%). The prevalence of non-ST-segment elevation myocardial infarction was substantially higher in patients with RD compared with patients with normal renal function (31% versus 13%, P<0.001). Using hs-cTnT, patients with RD had comparable sensitivity of rule-out (100.0% [95% confidence interval {CI}, 97.6-100.0] versus 99.2% [95% CI, 97.6-99.8]; P=0.559), lower specificity of rule-in (88.7% [95% CI, 84.8-91.9] versus 96.5% [95% CI, 95.7-97.2]; P<0.001), and lower overall efficacy (51% versus 81%, P<0.001), mainly driven by a much lower percentage of patients eligible for rule-out (18% versus 68%, P<0.001) compared with patients with normal renal function. Using hs-cTnI, patients with RD had comparable sensitivity of rule-out (98.6% [95% CI, 95.0-99.8] versus 98.5% [95% CI, 96.5-99.5]; P=1.0), lower specificity of rule-in (84.4% [95% CI, 79.9-88.3] versus 91.7% [95% CI, 90.5-92.9]; P<0.001), and lower overall efficacy (54% versus 76%, P<0.001; proportion ruled out, 18% versus 58%, P<0.001) compared with patients with normal renal function.

CONCLUSIONS

In patients with RD, the safety of the European Society of Cardiology 0/1-hour algorithm is high, but specificity of rule-in and overall efficacy are decreased. Modifications of the rule-in and rule-out thresholds did not improve the safety or overall efficacy of the 0/1-hour algorithm.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00470587.

Cardiac troponins: 25 years on the stage and still improving their clinical value

Twenty-five years ago, non-isotopic immunoassays for measuring the cardiac specific isoforms of troponin I (cTnI) and T (cTnT) were developed. Both biomarkers radically changed the diagnosis, prognosis, and therapy indication of acute coronary syndromes (ACS) and, particularly, of myocardial infarction (MI). However, cardiac troponins (cTn) rapidly demonstrated their usefulness in other cardiac and non-cardiac conditions, a part of the ischemic coronary diseases. Consequently, the number of patients to be tested for cTn and the number of tests requested to clinical laboratories sharply increased. Though the manufacturers continuously improved the analytical characteristics of the first cTn assays and produced different cTn assay "generations", the universal definition of myocardial infarction required less-than-available analytical imprecision at the cTn concentration used to assess MI (i.e. the 99th reference percentile). To address the clinical requirements, manufacturers developed the high-sensitivity cTn (hs-cTn) assays that allow to measure the 99th reference percentile with adequate precision, to detect cTn in many healthy subjects and, hence, to calculate the hs-cTn biological variation and especially to observe in very short time intervals serial differences in hs-cTn attributable to cardiac ischemia. Since the number of patients attending the emergency departments (ED) for a suspected ACS or MI is increasing, the improved properties of hs-cTn assays, allowing faster and safer patient assessment, will help to alleviate the sometimes overcrowded EDs. However, there are many biological, analytical, and clinical factors that can influence the true hs-cTn values of a patient. Clinicians and laboratory professionals should know about them for the best interpretation of the otherwise largely useful hs-cTn measurements. In conclusion, 25 years after their introduction for clinical use, "cTn are still on the stage and improving their clinical value".

A single centre prospective cohort study addressing the effect of a rule-in/rule-out troponin algorithm on routine clinical practice

AIMS

In 2015, the European Society of Cardiology introduced new guidelines for the diagnosis of acute coronary syndromes in patients presenting without persistent ST-segment elevation. These guidelines included the use of high-sensitivity troponin assays for 'rule-in' and 'rule-out' of acute myocardial injury at presentation (using a '0 hour' blood test). Whilst these algorithms have been extensively validated in prospective diagnostic studies, the outcome of their implementation in routine clinical practice has not been described. The present study describes the change in the patient journey resulting from implementation of such an algorithm in a busy innercity Emergency Department.

METHODS AND RESULTS

Data were prospectively collected from electronic records at a large Central London hospital over seven months spanning the periods before, during and after the introduction of a new high-sensitivity troponin rapid diagnostic algorithm modelled on the European Society of Cardiology guideline. Over 213 days, 4644 patients had high-sensitivity troponin T measured in the Emergency Department. Of these patients, 40.4% could be 'ruled-out' based on the high-sensitivity troponin T concentration at presentation, whilst 7.6% could be 'ruled-in'. Adoption of the algorithm into clinical practice was associated with a 37.5% increase of repeat high-sensitivity troponin T measurements within 1.5 h for those patients classified as 'intermediate risk' on presentation.

CONCLUSIONS

Introduction of a 0 hour 'rule-in' and 'rule-out' algorithm in routine clinical practice enables rapid triage of 48% of patients, and is associated with more rapid repeat testing in intermediate risk patients.

Contemporary Emergency Department Management of Patients with Chest Pain: A Concise Review and Guide for the High-Sensitivity Troponin Era

This article synthesizes current best evidence for the evaluation of patients with suspected acute coronary syndrome (ACS) using high-sensitivity troponin assays, enabling physicians to effectively incorporate them into practice. Unlike conventional assays, high-sensitivity assays can precisely measure blood cardiac troponin concentrations in the vast majority of healthy individuals, facilitating the creation of rapid diagnostic algorithms. Very low troponin concentrations on presentation accurately rule out acute myocardial infarction (AMI) and enable the discharge of approximately 20% of patients after a single test, whereas an additional 30%-40% of patients can be safely discharged after short-interval serial sampling in as little as 1 or 2 hours. In contrast, highly abnormal troponin concentrations on presentation (more than 5 times the upper reference limit) or rapidly rising levels on serial testing can rapidly rule in AMI with high specificity. However, approximately one-third of patients remain in a biomarker-indeterminate "observation zone" even after serial sampling. These patients pose a disposition challenge to clinicians because although the differential diagnosis of elevated troponin concentrations is broad, these patients have an increased risk for short-term major adverse cardiac events. Use of repeated serial troponin sampling and structured clinical prediction tools may assist disposition for these patients, because no validated pathways currently exist to guide clinicians. Ongoing research to tailor diagnostic thresholds to individual patient characteristics may enable improved diagnostic accuracy and usher in a new era of personalized medicine in the evaluation of suspected ACS.

Using High-Sensitivity Cardiac Troponin T for Acute Cardiac Care

The recent approval of the fifth-generation cardiac troponin T assay, which has characteristics clinically of a high-sensitivity assay, has led to concern that the problems of increased sensitivity will be greater than the benefits. This will not be the case if cardiology, emergency medicine, and laboratory medicine combine to develop procedures for use of the assay. We advocate sex-specific 99th percentile upper reference limit values of 15 ng/L for men and 10 ng/L for women. We suggest a 2-hour rule-out strategy, including a value less than the 99th percentile upper reference limit and the lack of a change in values of <4 ng/L. Those with values >100 ng/L and or a changing pattern of values ≥10 ng/L are a population much more likely to have acute myocardial infarction. Most of the increment in elevated values will occur not in those with acute coronary problems but in those with primary cardiac disease like heart failure and those with primary noncardiac problems. The former belong on a cardiac service because they are at high risk. The latter should have therapy on the service most apt to provide optimal care for their primary diagnosis, with cardiac consultation as needed.

Safety of a 1-hour Rule-out High-sensitive Troponin T Protocol in Patients With Chest Pain at the Emergency Department

BACKGROUND

The 1-hour rule-out high-sensitive cardiac troponin T protocol (hs-cTnT), in which a serial troponin measurement is performed 1 hour after the first to assess the possibility of acute coronary syndrome (ACS), has been implemented in the European guidelines in 2015. Our aim was to assess the safety of this protocol in low-risk patients in the Emergency Department (ED) when implemented in daily practice.

METHODS

Patients with acute chest pain presenting to the ED of our hospital and younger than 75 years were included (May 2013 to October 2014, The Netherlands). Hs-cTnT was measured at presentation (T0) and 1-1.5 hours after T0 (T1). Patients with a first troponin (T0) ≥ 0.012 ug/l were excluded. Primary endpoint was the 6-week occurrence of major adverse cardiac events (MACEs), defined as unstable angina, acute myocardial infarction (AMI), percutaneous coronary intervention, significant stenosis managed conservatively, coronary artery bypass grafting, and death.

RESULTS

Of the 374 analyzed patients, 16 patients (4.3%) developed 35 MACE. Of these 16 patients with endpoints, 3 were primarily discharged with noncardiac chest pain but returned within 6 weeks with unstable angina. Importantly, no patients experienced an AMI or died during follow-up.

CONCLUSION

No AMIs or deaths occurred after introducing the 1-hour hs-cTnT protocol to rule-out ACS in chest pain patients, but other MACE such as unstable angina occurred. Our results suggest the protocol is safe to implement in the ED in The Netherlands.

[Management of acute coronary syndrome without ST-segment elevation]

Acute coronary syndrome without persistent ST-segment elevation (non-ST segment elevation myocardial infarction and instable angina pectoris NSTEMI-ACS) is common and is associated with a high mortality. In addition to 12-channel echocardiograph (ECG) assessment, measurement of cardiac troponins I and T are important for risk stratification and diagnosis. The introduction of high-sensitivity cardiac troponin assays and their implementation into clinical practice has influenced risk stratification and treatment of these patients. Additional diagnostic validation must supplement routine clinical chemistry testing following the initial measurement to distinguish between different possible causes of troponin elevation above the 99th percentile. The time point for the additional troponin measurement depends on the different protocols and troponin assays and is stipulated in the current guidelines. The use of both 1‑hour and 3‑hour protocols together with the clinical presentation and work-up of possible differential diagnoses provide optimal care of patients. Patients who test positive for troponin dynamics should undergo invasive diagnostics and treatment within 24 h of presentation and within 2 h is recommended for unstable patients. Clopidogrel is indicated only in patients requiring oral anticoagulation.

Early diagnosis of acute coronary syndrome

The diagnostic evaluation of acute chest pain has been augmented in recent years by advances in the sensitivity and precision of cardiac troponin assays, new biomarkers, improvements in imaging modalities, and release of new clinical decision algorithms. This progress has enabled physicians to diagnose or rule-out acute myocardial infarction earlier after the initial patient presentation, usually in emergency department settings, which may facilitate prompt initiation of evidence-based treatments, investigation of alternative diagnoses for chest pain, or discharge, and permit better utilization of healthcare resources. A non-trivial proportion of patients fall in an indeterminate category according to rule-out algorithms, and minimal evidence-based guidance exists for the optimal evaluation, monitoring, and treatment of these patients. The Cardiovascular Round Table of the ESC proposes approaches for the optimal application of early strategies in clinical practice to improve patient care following the review of recent advances in the early diagnosis of acute coronary syndrome. The following specific 'indeterminate' patient categories were considered: (i) patients with symptoms and high-sensitivity cardiac troponin <99th percentile; (ii) patients with symptoms and high-sensitivity troponin <99th percentile but above the limit of detection; (iii) patients with symptoms and high-sensitivity troponin >99th percentile but without dynamic change; and (iv) patients with symptoms and high-sensitivity troponin >99th percentile and dynamic change but without coronary plaque rupture/erosion/dissection. Definitive evidence is currently lacking to manage these patients whose early diagnosis is 'indeterminate' and these areas of uncertainty should be assigned a high priority for research.

High-Sensitivity Cardiac Troponin T Improves the Diagnosis of Perioperative MI

BACKGROUND

The diagnosis of myocardial infarction (MI) after noncardiac surgery has traditionally relied on using relatively insensitive contemporary cardiac troponin (cTn) assays. We hypothesized that using a recently introduced novel high-sensitivity cTnT (hscTnT) assay would increase the detection rate of perioperative MI.

METHODS

In this ancillary study of the Vitamins in Nitrous Oxide trial, readjudicated incidence rates of myocardial injury (new isolated cTn elevation) and MI were compared when diagnosed by contemporary cTnI versus hscTnT. We probed various relative (eg, >50%) or absolute (eg, +5 ng/L) hscTnT change metrics. Inclusion criteria for this ancillary study were the presence of a baseline and at least 1 postoperative hscTnT value.

RESULTS

Among 605 patients, 70 patients (12%) had electrocardiogram changes consistent with myocardial ischemia; 82 patients (14%) had myocardial injury diagnosed by contemporary cTnI, 31 (5.1%) of which had an adjudicated MI. After readjudication, 67 patients (11%) were diagnosed with MI when using hscTnT, a 2-fold increase. Incidence rates of postoperative myocardial injury ranged from 12% (n = 73) to 65% (n = 393) depending on the hscTnT metric used. Incidence rates of MI using various hscTnT change metrics and the presence of ischemic electrocardiogram changes, but without event adjudication, ranged from 3.6% (n = 22) to 12% (n = 74), a >3-fold difference. New postoperative hscTnT elevation, either by absolute or relative hscTnT change metric, was associated with an up to 5-fold increase in 6-month mortality.

CONCLUSIONS

The use of hscTnT compared to contemporary cTnI increases the detection rate of perioperative MI by a factor of 2. Using different absolute or relative hscTnT change metrics may lead to under- or overdiagnosis of perioperative MI.

A 0-Hour/1-Hour Protocol for Safe, Early Discharge of Chest Pain Patients

OBJECTIVES

Guidelines recommend a 0-hour/1-hour high-sensitivity cardiac troponin T (hs-cTnT) diagnostic strategy in acute chest pain patients. There are, however, little data on the performance of this strategy when combined with clinical risk stratification. We aimed to evaluate the diagnostic accuracy of an accelerated diagnostic protocol (ADP) using the 0-hour/1-hour hs-cTnT strategy together with an adapted Thrombolysis In Myocardial Infarction (TIMI) score and electrocardiogram (ECG) for ruling out major adverse cardiac events (MACE) within 30 days.

METHODS

This prospective observational study enrolled consecutive emergency department (ED) chest pain patients. TIMI score variables, ED physicians' assessments of the ECG, and 0- and 1-hour hs-cTnT were collected. Thirty-day MACE was defined as acute myocardial infarction (AMI), unstable angina (UA), cardiogenic shock, ventricular arrhythmia, atrioventricular block, cardiac arrest, or death of cardiac or unknown cause.

RESULTS

A total of 1,020 patients were included in the final analysis. The combination of an adapted TIMI score ≤1, a nonischemic ECG, and either a 0-hour hs-cTnT < 5 ng/L or a 0-hour hs-cTnT < 12 ng/L combined with a 1-hour increase < 3 ng/L identified 432 (42.4%) patients as very low risk with a negative predictive value of 99.5% (95% confidence interval [CI] = 98.3%-99.9%) and a negative likelihood ratio of 0.04 (95% CI = 0.01-0.14) for 30-day MACE. The ADP missed only two patients with UA and no patients with AMI or other forms of MACE.

CONCLUSION

An ADP using the guideline recommended 0-hour/1-hour hs-cTnT strategy rapidly identified patients with a very low risk of 30-day MACE including UA where no further cardiac testing would be needed. This could potentially allow safe early discharge of about 40% of ED chest pain patients.

Novel Risk Stratification Assays for Acute Coronary Syndrome

PURPOSE OF REVIEW

Since identification of aspartate aminotransferase as the first cardiac biomarker in the 1950s, there have been a number of new markers used for myocardial damage detection over the decades. There have also been several generations of troponin assays, each with progressively increasing sensitivity for troponin detection. Accordingly, the "standard of care" for myocardial damage detection continues to change. The purpose of this paper is to review the clinical utility, biological mechanisms, and predictive value of these various biomarkers in contemporary clinical studies.

RECENT FINDINGS

As of this writing, a fifth "next" generation troponin assay has now been cleared by the US Food and Drug Administration for clinical use in the USA for subjects presenting with suspected acute coronary syndromes. Use of these high-sensitivity assays has allowed for earlier detection of myocardial damage as well as greater negative predictive value for infarction after only one or two serial measurements. Recent algorithms utilizing these assays have allowed for more rapid rule-out of myocardial infarction in emergency department settings. In this review, we discuss novel assays available for the risk assessment of subjects presenting with chest pain, including both the "next generation" cardiac troponin assays as well as other novel biomarkers. We review the biological mechanisms for these markers, and explore the positive and negative predictive value of the assays in clinical studies, where reported. We also discuss the potential use of these new markers within the context of future clinical care in the modern era of higher sensitivity troponin testing. Finally, we discuss advances in new platforms (e.g., mass spectrometry) that historically have not been considered for rapid in vitro diagnostic capabilities, but that are taking a larger role in clinical diagnostics, and whose prognostic value and power promise to usher in new markers with potential for future clinical utility in acute coronary syndrome.

National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand: Australian clinical guidelines for the management of acute coronary syndromes 2016

INTRODUCTION

The modern care of suspected and confirmed acute coronary syndrome (ACS) is informed by an extensive and evolving evidence base. This clinical practice guideline focuses on key components of management associated with improved clinical outcomes for patients with chest pain or ACS. These are presented as recommendations that have been graded on both the strength of evidence and the likely absolute benefit versus harm. Additional considerations influencing the delivery of specific therapies and management strategies are presented as practice points.

MAIN RECOMMENDATIONS

This guideline provides advice on the standardised assessment and management of patients with suspected ACS, including the implementation of clinical assessment pathways and subsequent functional and anatomical testing. It provides guidance on the: diagnosis and risk stratification of ACS; provision of acute reperfusion therapy and immediate post-fibrinolysis care for patients with ST segment elevation myocardial infarction; risk stratification informing the use of routine versus selective invasive management for patients with non-ST segment elevation ACS; administration of antithrombotic therapies in the acute setting and considerations affecting their long term use; and implementation of an individualised secondary prevention plan that includes both pharmacotherapies and cardiac rehabilitation. Changes in management as a result of the guideline: This guideline has been designed to facilitate the systematic integration of the recommendations into a standardised approach to ACS care, while also allowing for contextual adaptation of the recommendations in response to the individual's needs and preferences. The provision of ACS care should be subject to continuous monitoring, feedback and improvement of quality and patient outcomes.

National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand: Australian clinical guidelines for the management of acute coronary syndromes 2016

INTRODUCTION

The modern care of suspected and confirmed acute coronary syndrome (ACS) is informed by an extensive and evolving evidence base. This clinical practice guideline focuses on key components of management associated with improved clinical outcomes for patients with chest pain or ACS. These are presented as recommendations that have been graded on both the strength of evidence and the likely absolute benefit versus harm. Additional considerations influencing the delivery of specific therapies and management strategies are presented as practice points.

MAIN RECOMMENDATIONS

This guideline provides advice on the standardised assessment and management of patients with suspected ACS, including the implementation of clinical assessment pathways and subsequent functional and anatomical testing. It provides guidance on the: diagnosis and risk stratification of ACS; provision of acute reperfusion therapy and immediate post-fibrinolysis care for patients with ST segment elevation myocardial infarction; risk stratification informing the use of routine versus selective invasive management for patients with non-ST segment elevation ACS; administration of antithrombotic therapies in the acute setting and considerations affecting their long term use; and implementation of an individualised secondary prevention plan that includes both pharmacotherapies and cardiac rehabilitation. Changes in management as a result of the guideline: This guideline has been designed to facilitate the systematic integration of the recommendations into a standardised approach to ACS care, while also allowing for contextual adaptation of the recommendations in response to the individual's needs and preferences. The provision of ACS care should be subject to continuous monitoring, feedback and improvement of quality and patient outcomes.

Troponin Testing for Clinicians

The analytical performance of troponin assays has improved markedly in the last 2 decades. The variety of assays, their evolution over time, and their critical importance in influencing care, mandates the need for skills in their use. There are 3 critical elements necessary for optimal use of troponin testing in clinical care, as follows: 1) the analytical performance of the assay; 2) the clinical sensitivity and specificity of the test result; and 3) the clinical reasoning for ordering and the proper clinical context for interpreting the test result. This paper provides further explanation that will assist clinicians in their clinical decision making and interpretation of troponin test results. Schematic visual explanations are provided to help clinicians develop a more intuitive understanding of troponin testing.

The organisational value of diagnostic strategies using high-sensitivity troponin for patients with possible acute coronary syndromes: a trial-based cost-effectiveness analysis

OBJECTIVES

To evaluate hospital-specific health economic implications of different protocols using high-sensitivity troponin I for the assessment of patients with chest pain.

DESIGN

A cost prediction model and an economic microsimulation were developed using a cohort from a single centre recruited as part of the (ADAPT) trial, a prospective observational trial conducted from 2008 to 2011. The model was populated with 40 000 bootstrapped samples in five high-sensitivity troponin I-enabled algorithms versus standard care.

SETTING

Adult emergency department (ED) of a tertiary referral hospital.

PARTICIPANTS

Data were available for 938 patients who presented to the ED with at least 5 min of symptoms suggestive of acute coronary syndrome. The analyses included 719 patients with complete data.

MAIN OUTCOMES/MEASURES

This study examined direct hospital costs, number of false-negative and false-positive cases in the assessment of acute coronary syndrome.

RESULTS

High-sensitivity troponin I-supported algorithms increased diagnostic accuracy from 90.0% to 94.0% with an average cost reduction per patient compared with standard care of $490. The inclusion of additional criteria for accelerated rule-out (limit of detection and the modified 2-hour ADAPT trial rules) avoided 7.5% of short-stay unit admissions or 25% of admissions to a cardiac ward. Protocols using high-sensitivity troponin I alone or high-sensitivity troponin I within accelerated diagnostic algorithms reduced length of stay by 6.2 and 13.6 hours, respectively. Overnight stays decreased up to 43%. Results were seen for patients with non-acute coronary syndrome; no difference was found for patients with acute coronary syndrome.

CONCLUSIONS

High-sensitivity troponin I algorithms are likely to be cost-effective on a hospital level compared with sensitive troponin protocols. The positive effect is conferred by patients not diagnosed with acute coronary syndrome. Implementation could improve referral accuracy or facilitate safe discharge. It would decrease costs and provide significant hospital benefits.

TRIAL REGISTRATION

The original ADAPT trial was registered with the Australia-New Zealand Clinical trials Registry, ACTRN12611001069943.

A 1-h Combination Algorithm Allows Fast Rule-Out and Rule-In of Major Adverse Cardiac Events

BACKGROUND

A 1-h algorithm based on high-sensitivity cardiac troponin T (hs-cTnT) testing at presentation and again 1 h thereafter has been shown to accurately rule out acute myocardial infarction.

OBJECTIVES

The goal of the study was to evaluate the diagnostic accuracy of the 1-h algorithm when supplemented with patient history and an electrocardiogram (ECG) (the extended algorithm) for predicting 30-day major adverse cardiac events (MACE) and to compare it with the algorithm using hs-cTnT alone (the troponin algorithm).

METHODS

This prospective observational study enrolled consecutive patients presenting to the emergency department (ED) with chest pain, for whom hs-cTnT testing was ordered at presentation. Hs-cTnT results at 1 h and the ED physician's assessments of patient history and ECG were collected. The primary outcome was an adjudicated diagnosis of 30-day MACE defined as acute myocardial infarction, unstable angina, cardiogenic shock, ventricular arrhythmia, atrioventricular block, cardiac arrest, or death of a cardiac or unknown cause.

RESULTS

In the final analysis, 1,038 patients were included. The extended algorithm identified 60% of all patients for rule-out and had a higher sensitivity than the troponin algorithm (97.5% vs. 87.6%; p < 0.001). The negative predictive value was 99.5% and the likelihood ratio was 0.04 with the extended algorithm versus 97.8% and 0.17, respectively, with the troponin algorithm. The extended algorithm ruled-in 14% of patients with a higher sensitivity (75.2% vs. 56.2%; p < 0.001) but a slightly lower specificity (94.0% vs. 96.4%; p < 0.001) than the troponin algorithm. The rule-in arms of both algorithms had a likelihood ratio >10.

CONCLUSIONS

A 1-h combination algorithm allowed fast rule-out and rule-in of 30-day MACE in a majority of ED patients with chest pain and performed better than the troponin-alone algorithm.

Comparison of the Efficacy and Safety of Early Rule-Out Pathways for Acute Myocardial Infarction

BACKGROUND

High-sensitivity cardiac troponin assays enable myocardial infarction to be ruled out earlier, but the optimal approach is uncertain. We compared the European Society of Cardiology rule-out pathway with a pathway that incorporates lower cardiac troponin concentrations to risk stratify patients.

METHODS

Patients with suspected acute coronary syndrome (n=1218) underwent high-sensitivity cardiac troponin I measurement at presentation and 3 and 6 or 12 hours. We compared the European Society of Cardiology pathway (<99th centile at presentation or at 3 hours if symptoms <6 hours) with a pathway developed in the High-STEACS study (High-Sensitivity Troponin in the Evaluation of Patients With Acute Coronary Syndrome) population (<5 ng/L at presentation or change <3 ng/L and <99th centile at 3 hours). The primary outcome was a comparison of the negative predictive value of both pathways for index type 1 myocardial infarction or type 1 myocardial infarction or cardiac death at 30 days. We evaluated the primary outcome in prespecified subgroups stratified by age, sex, time of symptom onset, and known ischemic heart disease.

RESULTS

The primary outcome occurred in 15.7% (191 of 1218) patients. In those less than the 99th centile at presentation, the European Society of Cardiology pathway ruled out myocardial infarction in 28.1% (342 of 1218) and 78.9% (961 of 1218) at presentation and 3 hours, respectively, missing 18 index and two 30-day events (negative predictive value, 97.9%; 95% confidence interval, 96.9-98.7). The High-STEACS pathway ruled out 40.7% (496 of 1218) and 74.2% (904 of 1218) at presentation and 3 hours, missing 2 index and two 30-day events (negative predictive value, 99.5%; 95% confidence interval, 99.0-99.9; P<0.001 for comparison). The negative predictive value of the High-STEACS pathway was greater than the European Society of Cardiology pathway overall (P<0.001) and in all subgroups, including those presenting early or known to have ischemic heart disease.

CONCLUSIONS

Use of the High-STEACS pathway incorporating low high-sensitivity cardiac troponin concentrations rules out myocardial infarction in more patients at presentation and misses 5-fold fewer index myocardial infarctions than guideline-approved pathways based exclusively on the 99th centile.

CLINICAL TRIAL REGISTRATION

URL: http://clinicaltrials.gov. Unique identifier: NCT01852123.

Direct Comparison of 4 Very Early Rule-Out Strategies for Acute Myocardial Infarction Using High-Sensitivity Cardiac Troponin I

Background:

Four strategies for very early rule-out of acute myocardial infarction using high-sensitivity cardiac troponin I (hs-cTnI) have been identified. It remains unclear which strategy is most attractive for clinical application.

Methods:

We prospectively enrolled unselected patients presenting to the emergency department with symptoms suggestive of acute myocardial infarction. The final diagnosis was adjudicated by 2 independent cardiologists. Hs-cTnI levels were measured at presentation and after 1 hour in a blinded fashion. We directly compared all 4 hs-cTnI–based rule-out strategies: limit of detection (LOD, hs-cTnI<2 ng/L), single cutoff (hs-cTnI<5 ng/L), 1-hour algorithm (hs-cTnI<5 ng/L and 1-hour change<2 ng/L), and the 0/1-hour algorithm recommended in the European Society of Cardiology guideline combining LOD and 1-hour algorithm.

Results:

Among 2828 enrolled patients, acute myocardial infarction was the final diagnosis in 451 (16%) patients. The LOD approach ruled out 453 patients (16%) with a sensitivity of 100% (95% confidence interval [CI], 99.2%–100%), the single cutoff 1516 patients (54%) with a sensitivity of 97.1% (95% CI, 95.1%–98.3%), the 1-hour algorithm 1459 patients (52%) with a sensitivity of 98.4% (95% CI, 96.8%–99.2%), and the 0/1-hour algorithm 1463 patients (52%) with a sensitivity of 98.4% (95% CI, 96.8%–99.2%). Predefined subgroup analysis in early presenters (≤2 hours) revealed significantly lower sensitivity (94.2%, interaction P =0.03) of the single cutoff, but not the other strategies. Two-year survival was 100% with LOD and 98.1% with the other strategies ( P <0.01 for LOD versus each of the other strategies).

Conclusions:

All 4 rule-out strategies balance effectiveness and safety equally well. The single cutoff should not be applied in early presenters, whereas the 3 other strategies seem to perform well in this challenging subgroup.

Clinical Trial Registration:

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00470587.

Association Between High-Sensitivity Cardiac Troponin Levels and Myocardial Ischemia During Mental Stress and Conventional Stress

OBJECTIVES

This study sought to investigate whether patients with mental stress-induced myocardial ischemia will have high resting and post-mental stress high-sensitivity cardiac troponin I (hs-cTnI).

BACKGROUND

Hs-cTnI is a marker of myocardial necrosis, and its elevated levels are associated with adverse outcomes. Hs-cTnI levels may increase with exercise in patients with coronary artery disease. Mental stress-induced myocardial ischemia is also linked to adverse outcomes.

METHODS

In this study, 587 patients with stable coronary artery disease underwent technetium Tc 99m sestamibi-single-photon emission tomography myocardial perfusion imaging during mental stress testing using a public speaking task and during conventional (pharmacological/exercise) stress testing as a control condition. Ischemia was defined as new/worsening impairment in myocardial perfusion using a 17-segment model.

RESULTS

The median hs-cTnI resting level was 4.3 (interquartile range [IQR]: 2.9 to 7.3) pg/ml. Overall, 16% and 34.8% of patients developed myocardial ischemia during mental and conventional stress, respectively. Compared with those without ischemia, median resting hs-cTnI levels were higher in patients who developed ischemia either during mental stress (5.9 [IQR: 3.9 to 8.3] pg/ml vs. 4.1 [IQR: 2.7 to 7.0] pg/ml; p < 0.001) or during conventional stress (5.4 [IQR: 3.9 to 9.3] pg/ml vs. 3.9 [IQR: 2.5 to 6.5] pg/ml; p < 0.001). Patients with high hs-cTnI (cutoff of 4.6 pg/ml for men and 3.9 pg/ml for women) had greater odds of developing mental (odds ratio [OR]: 2.4; 95% confidence interval [CI]: 1.5 to 3.9; p < 0.001) and conventional (OR: 2.4; 95% CI: 1.7 to 3.4; p < 0.001) stress-induced ischemia. Although there was a significant increase in 45-min post-treadmill exercise hs-cTnI levels in those who developed ischemia, there was no significant increase after mental or pharmacological stress test.

CONCLUSIONS

In patients with coronary artery disease, myocardial ischemia during either mental stress or conventional stress is associated with higher resting levels of hs-cTnI. This suggests that hs-cTnI elevation is an indicator of chronic ischemic burden experienced during everyday life. Whether elevated hs-cTnI levels are an indicator of adverse prognosis beyond inducible ischemia or whether it is amenable to intervention requires further investigation.

Myocardial Ischemia on Exercise Stress Echocardiography Testing Is Not Associated with Changes in Troponin T Concentrations

BACKGROUND

Some posit that any amount of myocardial ischemia can be detected by high-sensitivity cardiac troponin assays. We hypothesized that patients with myocardial ischemia induced by exercise stress would have significantly higher increases in high-sensitivity cardiac troponin T (hs-cTnT) concentrations than patients without ischemia.

METHODS

We prospectively recruited for a biorepository 317 adult patients who presented to an academic hospital emergency department for evaluation possible ischemic symptoms and who were scheduled for exercise echocardiography. Blood samples were obtained before stress testing and 2-h post-testing. For this study, plasma hs-cTnT (Roche Diagnostics) concentrations were determined in a core laboratory blinded to clinical status. Absolute and relative changes between baseline and 2-h post-stress measurements were compared between patients with and without ischemia induced by stress testing.

RESULTS

The median age was 51 (44.0, 60.0) years, 45.9% were male, and 37.8% were African American. In total, 26 patients (8.1%) had myocardial ischemia induced by exercise. Median baseline, 2-h post-stress, and absolute δ concentrations were, respectively, 6.0, 8.0, and 0.2 ng/L for patients with evidence of ischemia; 3.8, 4.6, and 0.0 ng/L for those without; and 3.9, 4.9, and 0.0 ng/L overall. Baseline and 2-h hs-cTnT concentrations were higher among patients with abnormal stress tests (all P ≤0.05), but absolute and relative changes in hs-cTnT concentrations were not significantly different between individuals with ischemia and individuals without.

CONCLUSIONS

There was no evidence of change in hs-cTnT values in response to exercise stress testing, regardless of the presence of myocardial ischemia.

State-of-the-Art Evaluation of Emergency Department Patients Presenting With Potential Acute Coronary Syndromes

It is well established that clinicians cannot use clinical judgment alone to determine whether an individual patient who presents to the emergency department has an acute coronary syndrome. The history and physical examination do not distinguish sufficiently between the many conditions that can cause acute chest pain syndromes. Cardiac risk factors do not have sufficient discriminatory ability in symptomatic patients presenting to the emergency department. Most patients with non-ST-segment-elevation myocardial infarction do not present with electrocardiographic evidence of active ischemia. The improvement in cardiac troponin assays, especially in conjunction with well-validated clinical decision algorithms, now enables the clinician to rapidly exclude myocardial infarction. In patients in whom unstable angina remains a concern or there is a desire to evaluate for underlying coronary artery disease, coronary computed tomography angiography can be used in the emergency department. Once a process that took ≥24 hours, computed tomography angiography now can rapidly exclude myocardial infarction and coronary artery disease in patients in the emergency department.

Serial Sampling of High-Sensitivity Cardiac Troponin T May Not Be Required for Prediction of Acute Myocardial Infarction Diagnosis in Chest Pain Patients with Highly Abnormal Concentrations at Presentation

BACKGROUND

Guidelines for diagnosing acute myocardial infarction (AMI) recommend adding kinetic changes to the initial cardiac troponin (cTn) blood concentration to improve AMI diagnosis. We hypothesized that kinetic changes may not be required in patients presenting with highly abnormal cTn.

METHODS

Patients presenting with suspected AMI to the emergency department were enrolled in a prospective diagnostic study. We assessed the positive predictive value (PPV) of initial high-sensitivity cardiac troponin T (hs-cTnT) blood concentrations alone and in combination with kinetic changes for AMI. Predefined relative changes (δ change of ≥20%) and absolute changes (Δ change ≥9.2 ng/L) within different time intervals (1 h, 2 h, and 4-14 h after presentation) were assessed. The final diagnosis was adjudicated by 2 independent cardiologists.

RESULTS

Among 1282 patients, 213 (16.6%) patients had a final diagnosis of AMI. For AMI prediction, PPVs increased from 48.8% for an initial hs-cTnT >14 ng/L to 87.2% for >60 ng/L, whereas PPVs remained unchanged for higher hs-cTnT concentrations at baseline (87.1% for both >80 ng/L and >100 ng/L). With addition of 20% relative Δ change, PPVs were not further improved in patients with baseline hs-cTnT >80 ng/L using the 1-h (84.0%) and 2-h (88.9%) intervals, and only minimally when extending the interval to 4-14 h (91.2% for >80 ng/L and 90.4% for >100 ng/L, respectively). Similar findings were observed when applying absolute changes.

CONCLUSIONS

In chest pain patients with highly abnormal hs-cTnT concentrations at presentation, subsequent blood draws may not be required, as they do not provide incremental diagnostic value for prediction of AMI diagnosis.

Immediate Rule-Out of Acute Myocardial Infarction Using Electrocardiogram and Baseline High-Sensitivity Troponin I

AIMS

Serial measurements of high-sensitivity troponin are used to rule out acute myocardial infarction (AMI) with an assay specific cutoff at the 99th percentile. Here, we evaluated the performance of a single admission troponin with a lower cutoff combined with a low risk electrocardiogram (ECG) to rule out AMI.

METHODS

Troponin I measured with a high-sensitivity assay (hs-TnI) was determined at admission in 1040 patients presenting with suspected AMI (BACC study). To rule out AMI we calculated the negative predictive value (NPV) utilizing the optimal hs-TnI cutoff combined with a low risk ECG. The results were validated in 3566 patients with suspected AMI [2-h Accelerated Diagnostic Protocol to Assess Patients With Chest Pain Symptoms Using Contemporary Troponins as the Only Biomarker (ADAPT) studies]. Patients were followed for 6 or 12 months.

RESULTS

184 of all patients were diagnosed with AMI. An hs-TnI cutoff of 3 ng/L resulted in a NPV of 99.3% (CI 97.3-100.0), ruling out 35% of all non-AMI patients. Adding the information of a low risk ECG resulted in a 100% (CI 97.5-100.0) NPV (28% ruled out). The 2 validation cohorts replicated the high NPV of this approach. The follow-up mortality in the ruled out population was low (0 deaths in BACC and Stenocardia, 1 death in ADAPT).

CONCLUSIONS

A single hs-TnI measurement on admission combined with a low risk ECG appears to rule out AMI safely without need for serial troponin testing.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT02355457).

Safety and efficacy of the 0 h/3 h protocol for rapid rule out of myocardial infarction

BACKGROUND

The early and accurate diagnosis of acute myocardial infarction (AMI) is an important medical and economic challenge. We aimed to prospectively evaluate the performance of the new European Society of Cardiology rapid 0-hour/3-hour (0 h/3 h) rule out protocol for AMI.

METHODS

We enrolled 2,727 consecutive patients presenting with suspected AMI without persistent ST-segment elevation to the emergency department in a prospective international multicenter study. The final diagnosis was adjudicated by 2 independent cardiologists. The performance of the 0 h/3 h rule out protocol was evaluated using 4 high-sensitivity (primary analysis) and 3 sensitive cardiac troponin (cTn) assays.

RESULTS

Acute myocardial infarction was the final diagnosis in 473 patients (17.3%). Using the 4 high-sensitivity cTn assays, the 0-hour rule out protocol correctly ruled out 99.8% (95% [confidence interval] CI, 98.7%-100%), 99.6% (95% CI, 98.5%-99.9%), 100% (95% CI, 97.9%-100%), and 100% (95% CI, 98.0%-100%) of late presenters (>6 h from chest pain onset). The 3-hour rule out protocol correctly ruled out 99.9% (95% CI, 99.1%-100%), 99.5% (95% CI, 98.3%-99.9%), 100% (95% CI, 98.1%-100%), and 100% (95% CI, 98.2%-100%) of early presenters (<6 h from chest pain onset). Using the 3 sensitive cTn assays, the 0-hour rule out protocol correctly ruled out 99.6% (95% CI, 98.6%-99.9%), 99.0% (95% CI, 96.9%-99.7%), and 99.1% (95% CI, 97.2%-99.8%) of late presenters; and the 3-hour rule out protocol correctly ruled out 99.4% (95% CI, 98.3%-99.8%), 99.2% (95% CI, 97.3%-99.8%), and 99.0% (95% CI, 97.2%-99.7%) of early presenters. Overall, the 0 h/3 h rule out protocol assigned 40% to 60% of patients to rule out. None of the patients assigned rule out died during 3-months follow-up.

CONCLUSIONS

The 0 h/3 h rule out protocol seems to allow the accurate rule out of AMI using both high-sensitivity and sensitive cTn measurements in conjunction with clinical assessment. Additional studies are warranted for external validation.

Assessment of the European Society of Cardiology 0-Hour/1-Hour Algorithm to Rule-Out and Rule-In Acute Myocardial Infarction

BACKGROUND

The new European Society of Cardiology guidelines to rule-in and rule-out acute myocardial infarction (AMI) in the emergency department include a rapid assessment algorithm based on high-sensitivity cardiac troponin and sampling at 0 and 1 hour. Emergency department physicians require high sensitivity to confidently rule-out AMI, whereas cardiologists aim to minimize false-positive results.

METHODS

High-sensitivity troponin I and T assays were used to measure troponin concentrations in patients presenting with chest-pain symptoms and being investigated for possible acute coronary syndrome at hospitals in New Zealand, Australia, and Canada. AMI outcomes were independently adjudicated by at least 2 physicians. The European Society of Cardiology algorithm performance with each assay was assessed by the sensitivity and proportion with AMI ruled out and the positive predictive value and proportion ruled-in.

RESULTS

There were 2222 patients with serial high-sensitivity troponin T and high-sensitivity troponin I measurements. The high-sensitivity troponin T algorithm ruled out 1425 (64.1%) with a sensitivity of 97.1% (95% confidence interval [CI], 94.0%-98.8%) and ruled-in 292 (13.1%) with a positive predictive value of 63.4% (95% CI, 57.5%-68.9%).The high-sensitivity troponin I algorithm ruled out 1205 (54.2%) with a sensitivity of 98.8% (95% CI, 96.4%-99.7%)) and ruled-in 310 (14.0%) with a positive predictive value of 68.1% (95% CI, 62.6%-73.2%).

CONCLUSIONS

The sensitivity of the European Society of Cardiology rapid assessment 0-/1-hour algorithm to rule-out AMI with high-sensitivity troponin may be insufficient for some emergency department physicians to confidently send patients home. These algorithms may prove useful to identify patients requiring expedited management. However, the positive predictive value was modest for both algorithms.

A Plaque Disruption Index Identifies Patients with Non-STE-Type 1 Myocardial Infarction within 24 Hours of Troponin Positivity

Background

Markers of plaque destabilization and disruption may have a role in identifying non-STE- type 1 Myocardial Infarction in patients presenting with troponin elevation. We hypothesized that a plaque disruption index (PDI) derived from multiple biomarkers and measured within 24 hours from the first detectable troponin in patients with acute non-STE- type 1 MI (NSTEMI-A) will confirm the diagnosis and identify these patients with higher specificity when compared to individual markers and coronary angiography.

Methods

We examined 4 biomarkers of plaque destabilization and disruption: myeloperoxidase (MPO), high-sensitivity interleukin-6, myeloid-related protein 8/14 (MRP8/14) and pregnancy-associated plasma protein-A (PAPP-A) in 83 consecutive patients in 4 groups: stable non-obstructive coronary artery disease (CAD), stable obstructive CAD, NSTEMI-A (enrolled within 24 hours of troponin positivity), and NSTEMI-L (Late presentation NSTEMI, enrolled beyond the 24 hour limit). The PDI was calculated and the patients’ coronary angiograms were reviewed for evidence of plaque disruption. The diagnostic performance of the PDI and angiography were compared.

Results

Compared to other biomarkers, MPO had the highest specificity (83%) for NSTEMI-A diagnosis (P<0.05). The PDI computed from PAPP-A, MRP8/14 and MPO was higher in NSTEMI-A patients compared to the other three groups (p<0.001) and had the highest diagnostic specificity (87%) with 79% sensitivity and 86% accuracy, which were higher compared to those obtained with MPO, but did not reach statistical significance (P>0.05 for all comparisons). The PDI had higher specificity and accuracy for NSTEMI-A diagnosis compared to coronary angiography (P<0.05).

Conclusions

A PDI measured within 24 hour of troponin positivity has potential to identify subjects with acute Non-ST-elevation type 1 MI. Additional evidence using other marker combinations and investigation in a sufficiently large non-selected cohort is warranted to establish the diagnostic accuracy of the PDI and its potential role in differentiating type 1 and type 2 MI in patients presenting with troponin elevation of uncertain etiology.

Acute chest pain in the high-sensitivity cardiac troponin era: A changing role for noninvasive imaging?

Management of patients with acute chest pain remains challenging. Cardiac biomarker testing reduces the likelihood of erroneously discharging patients with acute myocardial infarction (AMI). Despite normal contemporary troponins, physicians have still been reluctant to discharge patients without additional testing. Nowadays, the extremely high negative predictive value of current high-sensitivity cardiac troponin (hs-cTn) assays challenges this need. However, the decreased specificity of hs-cTn assays to diagnose AMI poses a new problem as noncoronary diseases (eg, pulmonary embolism, myocarditis, cardiomyopathies, hypertension, renal failure, etc) may also cause elevated hs-cTn levels. Subjecting patients with noncoronary diseases to unnecessary pharmacological therapy or invasive procedures must be prevented. Attempts to improve the positive predictive value to diagnose AMI by defining higher initial cutoff values or dynamic changes over time inherently lower the sensitivity of troponin assays. In this review, we anticipate a potential changing role of noninvasive imaging from ruling out myocardial disease when troponin values are normal toward characterizing myocardial disease when hs-cTn values are (mildly) abnormal.

High Sensitivity Cardiac Troponin Assays - How to Implement them Successfully

High sensitivity troponin (hsTn) assays provide an unprecedented opportunity to improve the detection and treatment of cardiac injury from coronary and non-coronary causes. They may also play a role in guiding the primary and secondary prevention of cardiovascular disease. However, to derive maximal benefit from their use, careful planning for the implementation of these new assays is required. In this manuscript, we will discuss actions that can be taken during hsTn pre-implementation, implementation and post-implementation phases. Key concepts for consideration in the pre-implementation phase include: the establishment of a multi-disciplinary implementation team; development of quality control procedures; education of clinical staff; modification of existing clinical workflow and provision of computerized decision support. Strategies for ensuring successful implementation and post-implementation phases will also be discussed.

Diagnostic algorithms for acute coronary syndrome-is one better than another?

The rather short history of diagnostic algorithms for investigating patients with a suspected acute coronary syndrome (ACS) has led to a constantly evolving and unquestionably chaotic scenario. Although the recent development and introduction of high-sensitivity immunoassays for the measurement of cardiac troponins has represented a paradigm shift for dispersing part of the overwhelming fog, many uncertainties remain, especially concerning the appropriate timing for serial testing and the interpretation of cardiac troponin variations over time. Therefore, the aim of this article is to review the available evidence about diagnostic algorithms for ACS which incorporate the measurement of cardiac troponins, and generate a final algorithm attempting to integrate and harmonize the many clinical and laboratory findings emerged from the recent scientific literature.