Question: I’m looking through my cardiologist’s medical documentation, and she included a primary diagnosis of “dilation of the left atrium.” Should I report this as I77.819? Maryland Subscriber Answer: No. You should not report I77.819 (Aortic ectasia, unspecified site) because the atrium and the aorta are distinct components of the heart. Referencing the ICD-10-CM alphabetic index, Dilation -> cardiac gives you expanded options to choose between subterms “congenital” or “valve.” If the documentation supports a congenital pathology, then continue down that route. You should note that subterm “valve” is not an option since the atrium is a chamber of the heart, not a heart valve. If there’s no documentation that the condition is congenital, refer to Dilation ? cardiac ? see also Hypertrophy, cardiac. There, you’ve got more subterm options to consider including “fatty” and “hypertensive.” If those don’t match, go with the default code I51.7 (Cardiomegaly).