Clinical Utility and Prognostic Significance of Measuring Troponin I Levels in Patients Presenting to the Emergency Room With Atrial Fibrillation

Abstract

Background:The clinical significance of mildly elevated troponins in patients presenting to the emergency room (ER) with atrial fibrillation (AF) is not well understood. Hypothesis: We hypothesized that mildly elevated troponin in these patients is associated with adverse cardiovascular outcomes. Methods: In a multi-center, retrospective study, 662 patients with AF were divided into 3 groups based on troponin levels: group 1, mildly elevated; group 2, normal; and group 3, troponin not measured. Primary outcome was the combined endpoint of all-cause mortality and myocardial infarction (MI) at one year. Results: Levels of TnI were measured in 503 (76%) patients. They were elevated in 220 patients (33%, group 1; mean, 0.56 ng/mL), normal in 283 patients (43%, group 2), and not measured in 159 patients (24%, group 3). Significantly more cardiac testing was done at index hospitalization in group 1 (50%) compared with groups 2 and 3 (28% and 29%, P ≤ 0.001) and in the following year (29%, vs 20% and 17%, P = 0.02). Group 1 had more positive tests (62%) compared with groups 2 and 3 (25% and 43%, P ≤ 0.001). Group 1 had a significantly higher occurrence of the primary endpoint (22%, vs 10% and 15%, P = 0.002), driven primarily by a higher incidence of MI in group 1 (7%, vs 1% and 2%, P = 0.001). Conclusions: Troponin levels are routinely checked in a majority of patients presenting to the emergency department with AF. Even mildly elevated TnI is associated with a greater incidence of coronary artery disease on diagnostic testing and a higher 1-year incidence of MI.

Dynamic high-sensitivity troponin elevations in atrial fibrillation patients might not be associated with significant coronary artery disease

“…All of these studies used older non-sensitivity troponin I assays, resulting in a smaller proportion of patients with troponin values classified as elevated and consequently higher troponin values in the “elevated troponin group”. For example, in a study by Conti et al only 6% of the study population had elevated troponin I values (defined as >100 ng/L, 99th percentile) compared to 46% with hsTnT above the 99th percentile in our study and Gupta et al report a mean troponin I of 560 ng/L (>10 times higher than the 99th percentile) in patients with elevated troponin compared to a mean hsTnT of 54 ng/L (approximately 4 times higher than the 99th percentile) in our study [3, 26]. This could be the reason why our results differ, since the risk of adverse outcomes has been shown to increase proportionally to troponin levels [27, 28].…”

Predictors of Elevated Cardiac Enzyme Levels in Hospitalized Patients with Atrial Fibrillation and No Known Coronary Artery Disease

“…These results contradict those of a recent study by Gupta and colleagues 12 that showed an increased incidence of MI and CAD in patients with elevated cardiac enzyme concentrations who presented with AF. A possible reason for this conflict is that those investigators did not exclude patients who had existing CAD (prevalence, 36%-46% at baseline).…”

“…Investigators have suggested a link between myocardial ischemia and AF in patients with acute MI and in patients with CAD [7][8][9][10][11][12] who are at high risk of recurrent acute MI; however, no one apparently has studied the predictors and outcomes of patients with AF, elevated cardiac enzyme concentrations, and no known CAD. To our knowledge, ours is the first comprehensive study to evaluate patients without previous CAD who were hospitalized for AF at a tertiary care center.…”

“…A possible reason for this conflict is that those investigators did not exclude patients who had existing CAD (prevalence, 36%-46% at baseline). 12 Nevertheless, the long-term (>1-yr) risk of CAD might increase because of risk factors common to AF patients and CAD patients. 17 …”

A Review of the Relationship of Atrial Fibrillation and Acute Coronary Syndrome

“…And while an elevated troponin could be considered an NSTEMI, controlling a RVR can reveal the underlying disease and if the patient is on the ACS continuum. Gupta et al investigated the association of minor troponin levels of patients who were admitted from ED with a primary diagnosis of AF and their prognosis [33]. They excluded patients with primary diagnoses of STEMI, NSTEMI (troponin I > 5ng/ml), or patients treated as an NSTEMI, and stratified AF primary diagnoses groups based on troponin tested, troponin negative, and troponin not tested.…”