1. A method of segmenting a left atrium (LA) in a 3D volume comprising: segmenting an LA chamber body mesh, an appendage mesh, and a plurality of pulmonary vein (PV) meshes in the 3D volume; generating a volume mask from the LA chamber mesh, the appendage mesh, and the plurality of PV meshes; refining each of a plurality of ostia regions in the volume mask using region growing, wherein the plurality of ostia regions includes an appendage ostia region and a plurality of PV ostia regions; fitting a smooth mesh to each of the plurality of ostia regions; and generating a consolidated LA mesh from the volume mask including the smooth mesh fit to each of the plurality of ostia regions.