I51.8Other ill-defined heart diseases

I51.8 is the ICD-10-CM diagnosis code for other ill-defined heart diseases. It belongs to category I51 (complications and ill-defined descriptions of heart disease), block I30-I5A (other forms of heart disease) and chapter 9 (diseases of the circulatory system). It is a header code, so it can't be reported by itself; one of its 2 subcodes must be used instead.

Within I51, choose I51.8 (Other ill-defined heart diseases) only when documentation doesn't support a more specific option: cardiac septal defect, acquired (I51.0), rupture of chordae tendineae, not elsewhere classified (I51.1), rupture of papillary muscle, not elsewhere classified (I51.2), intracardiac thrombosis, not elsewhere classified (I51.3), myocarditis, unspecified (I51.4), myocardial degeneration (I51.5), Cardiomegaly (I51.7) and heart disease, unspecified (I51.9).

To report this condition, pick the subcode that matches the documentation: I51.81 (syndrome) and I51.89 (diseases).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.