Objectives: Elevations of cardiac troponin T (cTnT) levels are common after strenuous exercise. We assessed whether the composition of cTnT release after marathon race differs from that of acute myocardial infarction (MI). Methods: Troponin composition was analysed in plasma samples taken from 45 runners after marathon race and from 84 patients with type 1 MI. The concentration of long cTnT (intact and mildly fragmented cTnT) was measured with a novel upconversion luminescence immunoassay, total cTnT with a commercial high-sensitivity cTnT assay, and the ratio of long to total cTnT (troponin ratio) was determined as a measure of troponin fragmentation. Results: Total cTnT exceeded the upper reference limit (>14 ng/L) in 37 (82%) runners. Troponin ratio was lower in runners ((IQR) 0.17 (0.11–0.24) vs 0.62 (0.29–0.96), p<0.001). With increasing troponin release the troponin ratio decreased (r=−0.497, p<0.001) in marathon runners and the concentration of long cTnT remained in all runners below 8.4 ng/L. In contrast to marathon runners, troponin ratio increased (r=0.565, p<0.001) with the increase of cTnT release in patients with MI. The median total and long cTnT concentrations were lower in marathon runners than in patients with MI (25 ng/L vs 835 ng/L and 4.1 vs 385 ng/L, p<0.001 for both). Conclusion: In contrast to type 1 MI, only a small fraction of circulating cTnT exists as intact cTnT or long molecular forms after strenuous exercise and the difference in troponin composition is more pronounced in runners with higher troponin release. Trial registration number: NCT06000930.

Aims: Cardiac troponin levels are elevated in Takotsubo syndrome (TTS) with significant overlap to acute myocardial infarction (MI). Long and intact cardiac troponin T (cTnT) forms are typical for MI. This study sought to assess whether the fragmentation composition of cTnT release in TTS differs from MI. Methods and results: The concentration of long molecular forms of cTnT (long cTnT) was measured with a novel upconversion luminescence immunoassay and total cTnT with a commercial high-sensitivity cTnT assay in 24 TTS patients and in 84 Type 1 MI patients. The ratio of long to total cTnT (troponin ratio) was determined as a measure of cTnT fragmentation. Troponin ratio was lower in TTS patients [0.13 (0.10–0.20) vs. 0.62 (0.29–0.96), P < 0.001]. In the receiver operating characteristic curve analyses, troponin ratio showed a better predictive power than total cTnT in discriminating TTS and MI patients {area under the curve [AUC] 0.869 [95% confidence interval (CI) 0.789–0.948] vs. 0.766 [95% CI 0.677–0.855], P = 0.047}. When restricting the analysis to patients with total cTnT below 1200 ng/L (maximal value in TTS patients), the respective AUC values for total cTnT and troponin ratio were 0.599 (95% CI 0.465–0.732) and 0.816 (95% CI 0.712–0.921) (P = 0.003). At a cut-off point of 0.12, troponin ratio correctly identified 95% of MI patients and 50% of TTS patients. Conclusion: In contrast to Type 1 MI, only a small fraction of circulating cTnT in TTS exists in intact or long molecular forms. This clear difference in troponin composition could be of diagnostic value when evaluating patients with cTnT elevations and suspicion of TTS. Clinical trial registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04465591

Background and Aims: Elevated cardiac troponin levels are a frequent finding in emergency department patients, often without a clear cause. Current high-sensitivity cardiac troponin T (cTnT) assays measure intact and fragmented cardiac troponin T (total cTnT) molecules, without distinguishing between them. This study investigated whether measuring only intact and minimally fragmented cTnT (long cTnT) provides additional value for myocardial infarction (MI) identification. Methods: Consecutive emergency department patients with standard high-sensitivity cTnT levels (Roche Diagnostics) above the upper reference limit (≥14 ng/L) were recruited. Long cTnT levels were measured using a novel immunoassay. The additional diagnostic value of long cTnT in identifying patients with type 1 MI or any MI was assessed. Results: A total of 1811 patients participated in the study, 1145 (63.2%) presenting with chest pain or dyspnoea. Overall, 205 (11.3%) had MI, including 148 classified as type 1 MI. Only .7% of patients in the lowest long cTnT tertile (<3.7 ng/L) had type 1 MI. The discriminative ability of long cTnT was superior to total cTnT in identifying patients with MI (area under curve [95% confidence intervals]) for any MI: .833 (.804–.863) vs .782 (.744–.819), and for type 1 MI: .839 (.807–.872) vs .777 (.735–.819), both (P < .001). Integrating the predictive data from long cTnT with total cTnT provided additional value in both reclassification and decision curve analyses, compared to total cTnT data alone. Conclusions: The long cTnT assay demonstrated good diagnostic performance in identifying MI in patients with elevated total cTnT levels, with the potential to improve the accuracy of MI diagnosis.

Patients with atrial fibrillation (AF) presenting to the emergency department (ED) often have elevated cardiac troponin T (TnT) levels without evidence of type 1 myocardial infarction. We sought to explore the causes and significance of minor TnT elevations in patients with AF at the ED. All patients with AF admitted to the ED of Turku University Hospital between 1 March, 2013 and 11 April, 2016, and at least two TnT measurements, were screened. Overall, 2911 patients with a maximum TnT of 100 ng/L during hospitalization were analyzed. TnT was between 15 and 100 ng/L in 2116 patients. The most common primary discharge diagnoses in this group were AF (18.1%), infection (18.3%), ischemic stroke/transient ischemic attack (10.7%), and heart failure (5.0%). Acute coronary syndrome (ACS) was equally uncommon both in patients with normal TnT and elevated TnT (4.4% vs. 4.5%). Age ≥75 years, low estimated glomerular filtration rate (eGFR), high C-reactive protein (CRP), and hemoglobin 93%) finding in elderly (≥75 years) AF patients with either low eGFR or high CRP. In conclusion, minor TnT elevations carry limited diagnostic value in elderly AF patients with comorbidities.

The CHA₂DS₂-VASc score is a reliable tool used to estimate the risk of ischemic stroke (IS) in patients with atrial fibrillation (AF). Few tools exist for the prediction of new-onset AF (NOAF) after myocardial infarction (MI) and its relation to IS. We studied the usefulness of CHA₂DS₂-VASc in predicting NOAF and IS in a long-term follow-up after MI. Consecutive MI patients without baseline AF (n = 70,922; mean age: 68.2 years), discharged from 20 hospitals in Finland during 2005–2018, were retrospectively studied using national registries. The outcomes of interest after discharge were NOAF- and IS-assessed with competing risk analyses at one and ten years. The median follow-up was 4.2 years. The median baseline CHA₂DS₂-VASc score was 3 (IQR 2–5). The likelihood of both NOAF and NOAF-related IS increased stepwise with this score at one and ten years (all p < 0.0001). The one-year-adjusted subdistribution hazard ratio (sHR) was 4.03 (CI 3.68–4.42) for NOAF in patients with CHA₂DS₂-VASc scores ≥6 points. The cumulative incidence of IS was 15.2% in patients with NOAF vs. 6.2% in patients without AF at 10 years after MI (adj. sHR 2.12; CI 1.98–2.28; p < 0.0001). Coronary artery bypass surgery was associated with a higher NOAF incidence compared to percutaneous coronary intervention (adj. sHR 1.87; CI 1.65–2.13; p < 0.0001 one year after MI). The CHA₂DS₂-VASc score is a simple tool used to estimate the long-term risk of NOAF and IS after MI in patients without baseline AF. Coronary bypass surgery is associated with an increased NOAF incidence after MI.