Where are the left atrium and left ventricle found on PA and lateral CXR?

The left atrium (LA) is the most posterior and superior chamber. It is nearly midline. The only border seen on a PA view is that of the left atrial appendage at the top of the left cardiac silhouette. The left ventricle (LV) forms all of the left heart border below the left atrial appendage on the PA view. On the lateral view, it forms the lower posterior border of the heart.