The Use of Very Low Concentrations of High-sensitivity Troponin T to Rule Out Acute Myocardial Infarction Using a Single Blood Test

Age-sex distribution of patients with high-sensitivity troponin T levels below the 99th percentile

Background

Recently, very low concentrations of high-sensitivity cardiac troponin T (hs-cTnT), below the 99th percentile, have been used to immediately exclude acute myocardial infarction in certain patients without taking their age and sex into consideration.

Results

The hs-cTnT values below the 99th percentile (≤ 14 ng/L) were higher in men (p = 0.000) and significantly increased with age (p = 0.000) among both men and women. In addition, hs-cTnT was positively associated with age (r = 0.459, p = 0.000), myoglobin (r = 0.392, p = 0.000), and creatine kinase-MB (r = 0.133, p = 0.000). Moreover, males were younger (p = 0.001) and had higher myoglobin (p = 0.000) and creatine kinase-MB (p = 0.000) concentrations than females.

Materials and Methods

A total of 5585 consecutive subjects who presented with non-traumatic chest pain/discomfort to the inpatient, outpatient, or emergency department and who underwent high-sensitivity troponin T, myoglobin and creatine kinase-MB testing at presentation, with hs-cTnT below the 99thpercentile (≤ 14 ng/L), were eligible for enrollment.

Conclusions

We suggest that patients’ age, sex and levels of myocardial injury biomarkers should be taken into consideration when ruling out acute myocardial infarction and/or adverse prognostic implications in patients who have very low hs-cTnT concentrations.

Outcomes in Patients With Chest Pain Discharged After Evaluation Using a High-Sensitivity Troponin T Assay

BACKGROUND

Most patients with chest pain are discharged from the emergency department (ED) with the diagnosis "unspecified chest pain." It is unknown if evaluation with a high-sensitivity troponin T (hsTnT) assay affects prognosis in this large population.

OBJECTIVES

The aim was to investigate whether the introduction of an hsTnT assay is associated with reduced incidence of major adverse cardiac events (MACEs) and cardiovascular (CV) risk profile in patients with chest pain discharged from the ED.

METHODS

The study included 65,696 patients with "unspecified chest pain" discharged from 16 Swedish hospital EDs between 2006 and 2013 in which an hsTnT assay was introduced as the clinical routine. Patients evaluated with a conventional and an hsTnT assay were compared regarding the occurrence of 30-day MACE and CV risk profile based on information from national registries. Patients directly discharged and those discharged after an initial admission were analyzed separately.

RESULTS

Fewer directly discharged patients experienced a MACE when evaluated with an hsTnT compared with a conventional assay (0.6% vs. 0.9%; odds ratio [OR]: 0.7; 95% confidence interval [CI]: 0.57 to 0.83). In contrast, more patients discharged after an initial admission experienced a MACE when evaluated with an hsTnT (7.2% vs. 3.4%; OR: 2.18; 95% CI: 1.76 to 2.72). Admitted patients had a higher general CV risk profile when evaluated with hsTnT, whereas directly discharged patients had a lower general CV risk profile with the same test.

CONCLUSIONS

Patients directly discharged from the ED with unspecified chest pain experienced fewer MACEs and had a better risk profile when evaluated with hsTnT. Our findings suggest that more true at-risk patients were identified and admitted. The implementation of hsTnT assays in Swedish hospitals has improved evaluations in the ED.

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.

High sensitivity cardiac troponin T in patients not having an acute coronary syndrome: results from the TRAPID-AMI study

PURPOSE

To describe the baseline, 1 hr and delta high sensitivity cardiac troponin (hs-cTnT) values in patients with suspected acute myocardial infarction (AMI) but without a final acute coronary syndrome (ACS) diagnosis.

MATERIALS AND METHODS

hs-cTnT assay for RAPID rule out of acute myocardial infarction (TRAPID-AMI) was a prospective diagnostic trial that enrolled emergency department (ED) patients with suspected AMI. Final patient diagnoses were adjudicated by a clinical events committee and subjects placed in different clinical groups: AMI, unstable angina, non-ACS cardiac, non-cardiac and unknown origin. The baseline, 1 hr and delta hs-cTnT values were analysed in the 902 non-ACS patients.

RESULTS

Amongst the 1282 studied the patient groups were 213 (17%) AMI, 167 (13%) unstable angina, 113 (9%) non-ACS cardiac, 288 (22%) non-cardiac and 501 (39%) unknown origin. The hs-cTnT values in the non-cardiac and unknown origin groups were combined. The median hs-cTnT values (ng/L) were higher (p < 0.001) in the non-ACS cardiac compared to the non-cardiac/unknown origin group at baseline (11.8, <5) and 1 hr (12.3, <5). Their negative predictive values were 0.955 (baseline) and 0.954 (1 hr) for predicting non-ACS cardiac versus non-cardiac/unknown origin diagnoses.

CONCLUSIONS

Hs-cTnT may help predict whether non-ACS ED patients have a final non-ACS cardiac or non-cardiac/unknown origin diagnoses.

Use of the HEART Pathway with high sensitivity cardiac troponins: A secondary analysis

OBJECTIVES

The HEART Pathway combines a decision aid and serial contemporary cardiac troponin I (cTnI) measures to achieve >99% sensitivity for major adverse cardiac events (MACE) at 30days and early discharge rates >20%. However, the impact of integrating high-sensitivity troponin (hs-cTn) measures into the HEART Pathway has yet to be determined. In this analysis we compare test characteristics of the HEART Pathway using hs-cTnI, hs-cTnT, or cTnI.

DESIGN & METHODS

A secondary analysis of participants enrolled in the HEART Pathway RCT was conducted. Each patient was risk stratified by the cTn-HEART Pathway (Siemens TnI-Ultra at 0- and 3-h) and a hs-cTn-HEART Pathway using hs-cTnI (Abbott) or hs-cTnT (Roche) at 3-h. The early discharge rate, sensitivity, specificity, and negative predictive value (NPV) for MACE (death, myocardial infarction, or coronary revascularization) at 30days were calculated.

RESULTS

hs-cTnI measures were available on 133 patients. MACE occurred in 11/133 (8%) of these patients. Test characteristics for the HEART Pathway using serial cTnI vs 3hour hs-cTnI were the same: sensitivity (100%, 95%CI: 72-100%), specificity (49%, 95%CI: 40-58%), NPV (100%, 95%CI: 94-100%), and early discharge rate (45%, 95%CI: 37-54%). The HEART Pathway using hs-cTnT missed one MACE event (myocardial infarction): sensitivity (91%, 95%CI: 59-100%), specificity (48%, 95%CI: 39-57%), NPV (98%, 95%CI: 91-100%), and early discharge rate (45%, 95%CI: 37-54%).

CONCLUSIONS

There was no difference in the test characteristics of the HEART Pathway whether using cTnI or hs-cTnI, with both achieving 100% sensitivity and NPV. Use of hs-cTnT with the HEART Pathway was associated with one missed MACE.

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.

Fast track protocols using highly sensitive troponin assays for ruling out and ruling in non-ST elevation acute coronary syndrome

The introduction of “highly sensitive” cardiac troponin assays (hsTn) has reinforced the evidence that only serial testing incorporated in running algorithms allows a more accurate diagnosis of acute myocardial infarction. In this report, we consider the available evidence supporting the use of fast track protocols for ruling out and ruling in non-ST elevation myocardial infarction (NSTEMI) and compare it with the content of recently released guideline by the European Society of Cardiology, noting some uncomfortable aspects that need urgent clarification and/or revision. Firstly, the guideline drafters have to reconsider the available evidence that does not permit to assign the same class and level of evidence to the very well-validated 0–3 h algorithm and to the 0–1 h algorithm. In agreement with the validity of available data, the limitations of fast track protocols, in particular of the 0–1 h algorithm for NSTEMI rule-in, calls for caution. Secondly, as the current diagnostics guidance by the UK National Institute for Health and Care Excellence recommends, rapid diagnostic protocols should be performed only using well-validated hsTn; recommending the use of an assay before being commercially available is not fair and scientifically sound.

Early Rule-Out and Rule-In Strategies for Myocardial Infarction

BACKGROUND

Patients with chest pain comprise a large proportion of emergency presentations and place a major burden on healthcare resources. Therefore, efforts to safely and rapidly identify those with and without acute myocardial infarction (AMI) are needed. The challenge for clinicians is to accurately identify patients with acute coronary syndromes, while balancing the need to safely and rapidly reassure and discharge those without serious conditions.

CONTENT

This review summarizes the evidence to date on optimum accelerated strategies for the rule-in and rule-out of AMI, using strategies focused on optimum use of troponin results. Evidence based on both sensitive and highly sensitive troponin assay results is presented. The use of novel biomarkers is also addressed and the combination of biomarkers with other clinical information in accelerated diagnostic strategies is discussed.

SUMMARY

The majority of patients, who are not at risk of myocardial infarction or other serious harm, may be suitable for discharge directly from the emergency setting using approaches focused on troponin algorithms and accelerated diagnostic protocols. Evidence about the clinical and health economic impact of use of such strategies is needed, as they may have major benefits for both patients and healthcare providers.

Strategies to overcome misdiagnosis of type 1 myocardial infarction using high sensitive cardiac troponin assays

High sensitive cardiac troponin assays have become the gold standard in the diagnosis of an acute type 1 myocardial infarction (MI) in the absence of ST-segment elevation. Several acute or chronic conditions that impact cardiac troponin levels in the absence of a MI might lead to a misdiagnosis of MI. For example, patients with impaired renal function as well as elderly patients often present with chronically increased cardiac troponin levels. Therefore, the diagnosis of MI type 1 based on the 99th percentile upper limit of normal threshold is more difficult in these patients. Different diagnostic approaches might help to overcome this limitation of reduced MI specificity of sensitive troponin assays. First, serial troponin measurement helps to differentiate chronic from acute troponin elevations. Second, specific diagnostic cut-offs, optimized for a particular patient group, like elderly patients, are able to regain specificity. Such an individualized use and interpretation of sensitive cardiac troponin measurements improves diagnostic accuracy and reduces the amount of misdiagnosed MI type 1.