Cardiovascular Magnetic Resonance is increasingly used to differentiate the aetiology of cardiomyopathies. Late Gadolinium Enhancement (LGE) is the reference standard for non-invasive imaging of myocardial scar and focal fibrosis and is valuable in the differential diagnosis of ischaemic versus non-ischaemic cardiomyopathy. Diffuse fibrosis may go undetected on LGE imaging. Tissue characterisation with parametric mapping methods has the potential to detect and quantify both focal and diffuse alterations in myocardial structure not assessable by LGE. Native and post-contrast T1 mapping in particular has shown promise as a novel biomarker to support diagnostic, therapeutic and prognostic decision making in ischaemic and non-ischaemic cardiomyopathies as well as in patients with acute chest pain syndromes. Furthermore, changes in the myocardium over time may be assessed longitudinally with this non-invasive tissue characterisation method.

Using a simple algorithm incorporating hs-cTnT baseline values and absolute changes within the first hour allowed a safe rule-out as well as an accurate rule-in of AMI within 1 hour in 77% of unselected patients with acute chest pain. This novel strategy may obviate the need for prolonged monitoring and serial blood sampling in 3 of 4 patients.

Abstract

Background-Current guidelines for the diagnosis of acute myocardial infarction (AMI), among other criteria, also require a rise and/or fall in cardiac troponin (cTn) levels. It is unknown whether absolute or relative changes in cTn have higher diagnostic accuracy and should therefore be preferred. Methods and Results-In a prospective, observational, multicenter study, we analyzed the diagnostic accuracy of absolute (⌬) and relative (⌬%) changes in cTn in 836 patients presenting to the emergency department with symptoms suggestive of AMI. Blood samples for the determination of high-sensitive cTn T and cTn I ultra were collected at presentation and after 1 and 2 hours in a blinded fashion. The final diagnosis was adjudicated by 2 independent cardiologists. The area under the receiver operating characteristic curve for diagnosing AMI was significantly higher for 2-hour absolute 001).The receiver operating characteristic curve-derived cutoff value for 2-hour absolute (⌬) change was 0.007 g/L for high-sensitivity cTn T and 0.020 g/L for cTn I ultra (both cutoff levels are half of the 99th percentile of the respective cTn assay). Absolute changes were superior to relative changes in patients with both low and elevated baseline cTn levels. Conclusions-Absolute changes of cTn levels have a significantly higher diagnostic accuracy for AMI than relative changes, and seem therefore to be the preferred criteria to distinguish AMI from other causes of cTn elevations. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT00470587.

An early-discharge strategy using an hs-TnI assay and TIMI score ≤ 1 had similar safety as previously reported, with the potential to decrease the observation periods and admissions for approximately 40% of patients with suspected ACS. (Advantageous Predictors of Acute Coronary Syndromes Evaluation [APACE] Study, NCT00470587; A 2 hr Accelerated Diagnostic Protocol to Assess patients with chest Pain symptoms using contemporary Troponins as the only biomarker [ADAPT]: a prospective observational validation study, ACTRN12611001069943).

Sensitive cTn assays have high diagnostic accuracy also in the elderly. Mild elevations are common in elderly non-AMI patients, therefore the optimal cut-off levels are substantially higher in elderly as compared with younger patients. Furthermore, sensitive cTn assays yielded different prognostic value.

Interpretation: This rapid strategy incorporat ing highsensitivity cardiac troponin T baseline values and absolute changes within the first hour substantially accelerated the manage ment of suspected acute MI by allowing safe ruleout as well as accurate rulein of acute MI in 3 out of 4 patients. Trial registration: Clinical Trials.gov, NCT00470587 AbstractResearch

Objectives. To address the diagnostic value of circulating microRNAs (miRNAs) in patients presenting with acute chest pain.Design. In a prospective, international, multicentre study, six miRNAs (miR-133a, miR-208b, miR-223, miR-320a, miR-451 and miR-499) were simultaneously measured in a blinded fashion in 1155 unselected patients presenting with acute chest pain to the emergency department. The final diagnosis was adjudicated by two independent cardiologists. The clinical follow-up period was 2 years.Results. Acute myocardial infarction (AMI) was the adjudicated final diagnosis in 224 patients (19%). Levels of miR-208b, miR-499 and miR-320a were significantly higher in patients with AMI compared to those with other final diagnoses. MiR-208b provided the highest diagnostic accuracy for AMI (area under the receiver operating characteristic curve 0.76, 95% confidence interval 0.72-0.80). This diagnostic value was lower than that of the fourth-generation cardiac troponin T (cTnT; 0.84) or the high-sensitivity cTnT (hs-cTnT; 0.94; both P < 0.001 for comparison). None of the six miRNAs provided added diagnostic value when combined with cTnT or hs-cTnT (ns for the comparison of combinations vs. cTnT or hs-cTnT alone). During follow-up, 102 (9%) patients died. Levels of MiR208b were higher in patients who died within 30 days, but the prognostic accuracy was low to moderate. None of the miRNAs predicted long-term mortality.Conclusion. The miRNAs investigated in this study do not seem to provide incremental diagnostic or prognostic value in patients presenting with suspected AMI.