Background: The interpretation of elevated troponin levels in the context of Non-ST-Elevation Myocardial Infarction (NSTEMI) diagnosis in patients with atrial fibrillation (AF) is challenging.
Methods: We retrospectively analyzed a cohort of 1614 consecutive patients who presented with NSTEMI and underwent coronary angiography. Patients were divided according to the presence or absence of AF on admission ECG, irrespective of a prior history of AF. Patients with and without AF were compared regarding clinical presentation, the presence of a culprit lesion and troponin on admission as well as maximum troponin angiographic findings. A multivariate logistic regression model was used to identify independent predictors for the absence of a culprit lesion. As different troponin assays were used during the study period, absolute troponin values could not be directly compared. Therefore, all analyses of troponin elevation were based on fold increase relative to the assay-specific upper limit of normal (ULN).
Results: At admission, AF was present in 117 patients (7.2 %). Compared to patients without AF, those with AF were significantly older (78.2 ± 9.4 vs. 67.8 ± 11.5 years, p < 0.001) and had a lower LVEF at admission (41 ± 13.3 % vs. 45 ± 12.7 %, p = 0.003). There was no difference in gender distribution or BMI (p > 0.05). AF patients presented more often with atypical or vegetative symptoms such as palpitations or dizziness (68.0 % vs. 45.1 %, p = 0.051) and less often with typical chest pain (62.5 % vs. 75.0 %, p = 0.006). Among patients with AF, 74.4 % had an identifiable culprit lesion on angiography, compared to 82.1 % in those without AF (p = 0.002). In multivariate logistic regression, AF was an independent predictor of the absence of a culprit lesion (OR 0.583, 95 % CI 0.358–0.950, p = 0.030). At admission, troponin elevation was more frequent in patients with AF compared to those without AF (88.9 % vs. 62.7 %, p <0.001). When stratified by the presence of a culprit lesion, the frequency of elevated troponin at admission was highest in patients with AF and a culprit lesion, followed by patients with AF without a culprit lesion, patients without AF without a culprit lesion, and finally patients without AF and with a culprit lesion (89.7 %, 86.7 %, 82.2 %,59.5 % respectively; p <0.001; Figure 1).
Conclusion: AF was present in approximately 7 % of patients admitted with NSTEMI. While AF was identified as an independent predictor for the absence of a culprit lesion, the overwhelming majority of patients with AF and troponin elevation had an identifiable culprit lesion and the extent of troponin elevation on admission did not differ between AF patients with and without culprit lesion. Consequently, interpretation of troponin levels in AF requires caution, and the presence of AF should not preclude invasive workup.
