Wiki CHF, acute on chronic

If diastolic/systolic is not documented I would ask the provider or go with 428.0. There's three choices for A on C CHF, so you'd have to know if it was diastolic, systolic or both.
I would query the physician. There is no combined unspecified code. According to what I have read and been told, the medications for each (sys and diast) are different.