Left atrial (LA) systolic and diastolic function were analyzed in an animal model of acute left ventricular ischemia with LA ischemia by proximal left circumflex coronary artery occlusion or without LA ischemia by midleft anterior descending coronary artery occlusion (7 sheep in each group). LA pressures and LA volumes were simultaneously recorded using a catheter and real-time 3-dimensional echocardiography, respectively. LA stroke volume represented 63% of left ventricular stroke volume during left anterior descending coronary artery occlusion, but only 32% during left circumflex coronary artery occlusion. This animal study with 3-dimensional echocardiographic determination of absolute LA volumes demonstrated dramatic depression of LA function during proximal left circumflex coronary artery occlusion as compared with left anterior descending coronary artery occlusion.