Left atrial function after myocardial infarction in swine

Background Atrial fibrillation is the most common arrhythmia in United States, and is associated with atrial fibrosis. Although the cause of atrial fibrosis development is not understood, its etiology is related to cardiac dysfunction, mitral regurgitation (MR), and coronary artery disease. This study focuses on determining the acute effects of myocardial infarction (MI) on left atrial (LA) function. Our hypothesis is that MI may result in changes in left ventricular relaxation, MR, and LA pressure and volume overload, leading to changes in LA geometry and mechanics, which will result in later atrial fibrosis. We studied the changes in LA size, ejection fraction, and the relative contributions of passive and active emptying, comparing controls with post-MI animals. Methods Eleven Yorkshire pigs (average weight 37 ± 7 kg) were studied, including 5 control animals, and 6 pigs imaged one to two weeks after a transmural MI. The MI was induced by percutaneous balloon occlusion of left coronary artery (90 min) followed by reperfusion. All animals were imaged on a 1.5T Siemens scanner (Siemens Healthcare, Erlangen, Germany). A stack of short-axis cine images covering the left atrium were obtained with balanced SSFP, with a 1.3 x 1.3 x 3 mm spatial resolution (no gaps), and 25 frames, breath-holding and retrospective ECG-gating. All image processing was performed in Matlab (v 2014). To measure LA volume through the cardiac cycle, the cine images were segmented using thresholding, and regions of