Predicting new onset atrial fibrillation post acute myocardial infarction: Echocardiographic assessment of left atrial size.

BACKGROUND: Atrial fibrillation (AF) commonly occurs following acute myocardial infarction (AMI). Left atrial (LA) size has been reported to predict new onset AF in this cohort, however, the optimal metric of left atrial size for risk stratification following AMI is unknown. METHODS: Patients presenting to a tertiary hospital with incident AMI (NSTEMI or STEMI) and no history of AF were recruited. All patients underwent guideline-based workup and management for AMI, including transthoracic echocardiographic assessment. Three alternative metrics of left atrial size were determined: LA area, maximal and minimal LA volume indexed to body surface area (LAVImax and LAVImin). The primary endpoint was new onset AF diagnoses. RESULTS: Four hundred thirty three patients were included in the analysis, of which 7.1% had a new diagnosis of AF within a median follow-up of 3.8 years. Univariate predictors of incident AF included age, hypertension, revascularization with CABG, NSTEMI presentation, right atrial area, and all three metrics of LA size. Among three multivariable models created for the prediction of new onset AF utilizing alternate metrics of LA size, LAVImin was the only LA size metric found to be an independent predictor. CONCLUSIONS: LAVImin is an independent predictor of new onset AF post AMI. LAVImin outperforms echocardiographic assessment of diastolic dysfunction and alternative metrics of LA size (including LA area and LAVImax) for risk stratification. Further studies are needed to validate our findings in post AMI patients, and evaluate whether LAVImin holds similar advantages over LAVImax in other cohorts.