Left atrial (LA) maximal volume contains prognostic information in patients with heart failure and acute myocardial infarction. However, only few studies have investigated the detailed mechanical function of the LA in these patients. We assessed the feasibility of evaluating LA volume and mechanical function with Multi Slice Computed Tomography (MSCT) in patients with ischemic heart disease. Furthermore, the LA and left ventricular (LV) function was evaluated in relation to signs of clinical heart failure. Methods and results: MSCT was performed in 40 patients with sinus rhythm and ischemic heart disease. We enrolled 20 patients with reduced LV ejection fraction (LVEF ≤ 45%) and 20 with preserved LVEF (> 45%). LA volumes, reservoir, channel and pump function were measured. Interobserver variation for LA volume measures was 1.5% (SD: 6.6%). In patients with reduced LVEF, LA volumes were larger throughout the cardiac cycle (LA-max 66.8 ml/m2 vs 57.4 ml/m2 and LA-min: 45.8 ml/m2 vs 31.6 ml/m2, p < 0.05) and LA reservoir and pump function were all significantly impaired (Fractional change: 43% vs 31%, LAEF 31% vs 19%, p < 0.05). Patients with clinical signs of heart failure during hospitalisation had significantly lower LAEF than patients without (16(9)% vs. 30(17)% p < 0.05). In a multivariate linear regression analyses the presence of clinical signs of heart failure and reduced LVEF were independent determinants of impaired LA reservoir and pump function (p < 0.05). Conclusion: Reproducible assessment of LA size and mechanical function throughout the cardiac cycle using MSCT is feasible and potentially useful clinically.