Incidence and prognostic significance of silent atrial fibrillation in acute myocardial infarction

- Silent atrial fibrillation (AF) is more frequent than symptomatic AF after MI.
- Left atrial area enlargement is associated with an increased risk of silent AF.
- In-hospital heart failure rate is higher in silent AF group than in no-AF patients.
- Death rate is higher in silent AF group than in no-AF patients.

BackgroundSilent atrial fibrillation (AF) has been suggested to be frequent after acute myocardial infarction (MI). Continuous ECG monitoring (CEM) has been shown to improve AF screening in patients at risk of stroke.ObjectivesWe aimed to assess the incidence and prognosis of silent AF in patients with acute MI.MethodsAll the consecutive patients with acute MI were prospectively analyzed by CEM ≥ 48 h after admission. Silent AF was defined as asymptomatic episodes lasting at least 30 s. The population was divided into three groups: no-AF, silent AF and symptomatic AF.ResultsAmong the 849 patients, 135 (16%) developed silent AF and 45 (5%) symptomatic AF. Compared with the no-AF group, patients with silent AF were markedly older (80 vs. 62 y, p < 0.001), more frequently women (43% vs. 30%, p = 0.006) and less likely to be smokers (20% vs. 36%, p < 0.001). They had impaired left ventricular ejection fraction (LVEF) and left atrial (LA) enlargement. By multivariate analysis, age, history of AF, indexed LA area and LVEF were identified as independent predictors of silent AF. In-hospital heart failure and death rates were markedly higher in silent AF group when compared with no-AF patients (41.8% vs 21.0% and 10.4% vs. 1.3%, respectively).ConclusionOur large prospective study showed for the first time that silent AF is more frequent than symptomatic AF after MI. Our work suggests that indexed LA area could help to predict the risk of developing silent AF. Moreover, the onset of silent AF is associated with worse hospital prognosis.