High-sensitivity troponin T as a rule-out marker for myocardial inflammation detectable by CMR imaging.

Background: Acute myocarditis is a potentially life-threatening cardiac condition and immediate assessment of this disease is imminent. While laboratory tests, electrocardiography or transthoracic echocardiography can provide indirect signs for the presence of acute myocarditis, cardiac magnetic resonance (CMR) imaging enables direct visualisation of myocardial inflammation and confirms the diagnosis.Since there is limited accessibility to CMR, the goal of this study was to evaluate the sensitivity and specificity of an elevation of established biomarkers for the diagnosis of myocarditis and to define a specific rule-out threshold for deferring CMR.

Methods: 244 consecutive patients with clinical suspicion of acute myocarditis underwent comprehensive CMR imaging. CMR data and laboratory parameters were retrospectively analysed.

Results: Based on the CMR results, the diagnosis of acute myocarditis was confirmed in 72 individuals. Significant differences regarding age, cardiac function and biomarker levels were present between these groups. Receiver operating characteristics analysis revealed high-sensitivity troponin T (hsTNT) with high sensitivity and specificity for the result of the CMR examination. With a negative predictive value of 0.96 and a sensitivity of 0.92, a hsTNT cut-off of 18 pg/mL was defined as a safe rule-out value for suspected myocarditis.

Conclusions: CMR imaging is the gold standard for the non-invasive confirmation of acute myocarditis. However, in this cohort, patients with a hsTNT level of ≤18 pg/mL have a very low likelihood of acute myocarditis, suggesting that CMR may not be necessary to exclude the diagnosis.