While left ventricular (LV) remodeling lead to heart failure and mortality after a myocardial infarction (MI), left atrial dilatation remain poorly described. We sought to evaluate left atrial ejection fraction (LAEF) after MI and its impact on prognosis.

Out of 477 patients presenting a first ST-segment elevation MI with successful revascularization, LAEF was measurable in 374 patients who constituted the population study. Cardiac magnetic resonance imaging (CMR) was performed at baseline and after a 3-month follow-up.

A reduced LAEF represented its lower quartile (LAEF<27.5±6.5%) and was used for analysis (redLAEF group). redLAEF patients were older with more hypertension, presented higher rate of anterior infarction [74.7% vs 52.1% P<0.05], lower LVEF [41.2% vs 48.3%, P<0.05], and greater infarct size [25.7%LV vs 17.6%LV, P<0.05]. After multivariate analysis and adjustment on age, arterial hypertension, LVEF, smocking status, infarct size, gender, renal function, and anterior infarction, redLAEF was related to 1-year cardiovascular outcome combining death and heart failure (OR: 0.47 [IQR 0.25;0.91], p=0.025) (see Fig. 1). More, we found an interaction between redLAEF and age on its effect on heart failure during follow-up (OR=0.47, P=0.022), with the effect of redLAEF being more prominent amongst >65 years old patients. Overall, LAEF improved from 40.9±10.3% to 42±11.2% (P=0.038) but did not differ amongst non-redLAEF patients (P=0.77). LAEF improved over time in redLAEF patients (n=75) who did not suffer from cardiovascular outcomes (from 27.7±6.5% to 34.2±13.3, P<0.001), while remaining low amongst redLAEF patients who presented a cardiovascular outcomes (n=17).

LAEF was a good predictor of cardiovascular outcomes in patients after an myocardial infarction, independently of LVEF and infarct size, and more specifically amongst >65 years old patient.