I was recently asked how to code "diastolic dysfunction" in ICD-9. The inquirer asked if it should be coded as "heart failure, NOS based on something she had read.
In 2009, Q1, Coding Clinic noted that you could not assume heart failure in a patient with diastolic dysfunction, and that it should be coded as 429.9, heart disease, unspecified.
The term dysfunction is very non-specific, and runs the gamut from very mild, to extremely severe. There may be minimal dysfunction present, or life threatening dysfunction. As with a lot of documentation, there's simply not enough information there to select a specific diagnosis code. Therefore, the best you can do is choose a non-specific code, that is not more severe than the documentation.
In ICD-10, "heart dysfunction" is indexed to I51.89--Other ill-defined heart diseases. This seems like it follows similar logic, and it makes sense--ill defined documentation corresponding to an ill defined heart disease.