Background Dilatation of left atrium (LA) reflects chronic LA pressure or volume overload that possesses considerable prognostic information. Little is known regarding the interaction between LA remodeling after acute myocardial infarction (MI) and left atrial pressure at rest and during exercise. The objective was to assess changes in LA volume early after MI in patients with diastolic dysfunction and the relation to invasive hemodynamics and natriuretic peptides. Methods 62 patients with left ventricle ejection fraction (LVEF) ≥ 45%, diastolic E/e' > 8 and LA volume index > 34 ml/m 2 within 48 h of MI were enrolled. After 1 and 4 months blood sampling, echocardiography and right heart catheterization were performed during exercise test. Results LA remodeling was considered in patients with a change from mild (35–41 ml/m 2), to severe (> 48 ml/m 2) dilatation after 4 months (Found in 22 patients (35%)). Patients with LA remodeling were characterized by lower a’ (1 month 8.9 ± 2.0 vs. 10.4 ± 2.5 cm/s, p = 0.002; 4 month 8.8 ± 2.0 vs. 10.4 ± 2.4 cm/s, p = 0.007) and higher MR-proANP (1 month 162 ± 64 vs. 120 ± 44 pg/l, p = 0.005; 4 months 175 ± 48 vs. 129 ± 56 pg/l, p = 0.002). With exercise, pulmonary artery pressure, right atrial pressure and pulmonary capillary wedge pressure increased markedly in all patients. There were however, no significant differences in filling pressure at rest or during exercise irrespective of whether LA remodeling occurred. Conclusion Contrary to our hypothesis early LA dilatation after MI was weakly associated with resting and exercise induced changes in LA pressure overload. The dilatation was however associated with lower e’ and higher MR-proANP.