Background: Cardiac troponin (cTn) T and cTnI are considered cardiac specific and equivalent in the diagnosis of acute myocardial infarction. Previous studies suggested rare skeletal myopathies as a noncardiac source of cTnT. We aimed to confirm the reliability/cardiac specificity of cTnT in patients with various skeletal muscle disorders (SMDs). Methods: We prospectively enrolled patients presenting with muscular complaints (≥2 weeks) for elective evaluation in 4 hospitals in 2 countries. After a cardiac workup, patients were adjudicated into 3 predefined cardiac disease categories. Concentrations of cTnT/I and resulting cTnT/I mismatches were assessed with high-sensitivity (hs-) cTnT (hs-cTnT–Elecsys) and 3 hs-cTnI assays (hs-cTnI–Architect, hs-cTnI–Access, hs-cTnI–Vista) and compared with those of control subjects without SMD presenting with adjudicated noncardiac chest pain to the emergency department (n=3508; mean age, 55 years; 37% female). In patients with available skeletal muscle biopsies, TNNT/I1-3 mRNA differential gene expression was compared with biopsies obtained in control subjects without SMD. Results: Among 211 patients (mean age, 57 years; 42% female), 108 (51%) were adjudicated to having no cardiac disease, 44 (21%) to having mild disease, and 59 (28%) to having severe cardiac disease. hs-cTnT/I concentrations significantly increased from patients with no to those with mild and severe cardiac disease for all assays (all P <0.001). hs-cTnT–Elecsys concentrations were significantly higher in patients with SMD versus control subjects (median, 16 ng/L [interquartile range (IQR), 7–32.5 ng/L] versus 5 ng/L [IQR, 3–9 ng/L]; P <0.001), whereas hs-cTnI concentrations were mostly similar (hs-cTnI–Architect, 2.5 ng/L [IQR, 1.2–6.2 ng/L] versus 2.9 ng/L [IQR, 1.8–5.0 ng/L]; hs-cTnI–Access, 3.3 ng/L [IQR, 2.4–6.1 ng/L] versus 2.7 ng/L [IQR, 1.6–5.0 ng/L]; and hs-cTnI–Vista, 7.4 ng/L [IQR, 5.2–13.4 ng/L] versus 7.5 ng/L [IQR, 6–10 ng/L]). hs-cTnT–Elecsys concentrations were above the upper limit of normal in 55% of patients with SMD versus 13% of control subjects ( P <0.01). mRNA analyses in skeletal muscle biopsies (n=33), mostly (n=24) from individuals with noninflammatory myopathy and myositis, showed 8-fold upregulation of TNNT2 , encoding cTnT (but none for TNNI3 , encoding cTnI) versus control subjects (n=16, P _Wald <0.001); the expression correlated with pathological disease activity ( R =0.59, P _t-statistic <0.001) and circulating hs-cTnT concentrations ( R =0.26, P _t-statistic =0.031). Conclusions: In patients with active chronic SMD, elevations in cTnT concentrations are common and not attributable to cardiac disease in the majority. This was not observed for cTnI and may be explained in part by re-expression of cTnT in skeletal muscle. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03660969.

Background: The early non-invasive discrimination of Type 2 versus Type 1 Myocardial Infarction (T2MI, T1MI) is a major unmet clinical need. We aimed to externally validate a recently derived clinical score (Neumann) combing female sex, no radiating chest pain, and high-sensitivity cardiac troponin I (hs-cTnI) concentration ≤40.8 ng/L. Methods: Patients presenting with acute chest discomfort to the emergency department were prospectively enrolled into an international multicenter diagnostic study. The final diagnoses of T2MI and T1MI were centrally adjudicated by two independent cardiologists using all information including cardiac imaging and serial measurements of hs-cTnT/I according to the fourth universal definition of MI. Model performance for T2MI diagnosis was assessed by formal tests and graphical means of discrimination and calibration. Results: Among 6684 enrolled patients, MI was the adjudicated final diagnosis in 1079 (19%) patients, of which 242 (22%) had T2MI. External validation of the Neumann Score showed a moderate discrimination (C-statistic 0.67 (95%CI 0.64–0.71)). Model calibration showed underestimation of the predicted probabilities of having T2MI for low point scores. Model extension by adding the binary variable heart rate >120/min significantly improved model performance (C-statistic 0.73 (95% CI 0.70–0.76, p < 0.001) and had good calibration. Patients with the highest score values of 3 (Neumann Score, 9.9%) and 5 (Extended Neumann Score, 3.3%) had a 53% and 91% predicted probability of T2MI, respectively. Conclusion: The Neumann Score provided moderate discrimination and suboptimal calibration. Extending the Neumann Score by adding heart rate >120/min improved the model’s performance.

Little is known about the epidemiology, clinical presentation, management, and outcome of acute pericarditis and myopericarditis. The final diagnoses of acute pericarditis, myopericarditis, and non-ST-segment elevation myocardial infarction (NSTEMI) of patients presenting to seven emergency departments in Switzerland with acute chest pain were centrally adjudicated by two independent cardiologists using all information including serial measurements of high-sensitivity cardiac troponin T. The overall incidence of pericarditis and myopericarditis was estimated relative to the established incidence of NSTEMI. Current management and long-term outcome of both conditions were also assessed. Among 2533 chest pain patients, the incidence of pericarditis, myopericarditis, and NSTEMI were 1.9% (n = 48), 1.1% (n = 29), and 21.6% (n = 548), respectively. Accordingly, the estimated incidence of pericarditis and myopericarditis in Switzerland was 10.1 [95% confidence interval (95% CI) 9.3–10.9] and 6.1 (95% CI 5.6–6.7) cases per 100 000 population per year, respectively, vs. 115.0 (95% CI 112.3–117.6) cases per 100 000 population per year for NSTEMI. Pericarditis (85% male, median age 46 years) and myopericarditis (62% male, median age 56 years) had male predominance, and commonly (50% and 97%, respectively) resulted in hospitalization. No patient with pericarditis or myopericarditis died or had life-threatening arrhythmias within 30 days [incidence 0% (95% CI 0.0–4.8%)]. Compared with NSTEMI, the 2-year all-cause mortality adjusted hazard ratio of pericarditis and myopericarditis was 0.40 (95% CI 0.05–2.96), being 0.59 (95% CI 0.40–0.88) for non-cardiac causes of chest pain. Pericarditis and myopericarditis are substantially less common than NSTEMI and have an excellent short- and long-term outcome. ClinicalTrial.gov, number NCT00470587, https://clinicaltrials.gov/ct2/show/NCT00470587.