In a nutshell:
If the furosemide is helping and Hobkin gets worse without it, it means fluid is accumulating in his lungs again, which is bad, because that means his cardiomyopathy is getting worse. Prognosis worrisome.
If the furosemide is not helping, chances are it's an infection, probably a reprise of the one he had before which the amoxycillin didn't completely wipe out—which isn't a big deal as they've already cultured it and know what it is, and it's of a variety that's generally pretty responsive to antibiotic therapy. It might actually clear up by itself, and if not, treatment either with another course of (a different) antibiotic or an antibiotic injection should take care of it. Prognosis good.
Feels weird to hope that Hobkin has an infection, but there you go.