Abnormal cardiac atrium morphology Cor triatriatum 2010-04-29T10:07:24Z HP:0010774 UMLS:C4023708 Triatrial heart Fyler:3031 ICD-10:Q24.2 The presence of an additional membrane in the left or right cardiac atrium which results in the subdivision of the affected atrium (and thus in total three atria, whence the name).