Personally, I have no experience of heart failure but, after having read a lot about it in the posts of other people, here is what it looks like from the technical standpoint.
If BP starts being very high and there is no reaction to different tested medications, it is not rare case that people get the diagnoses of HF, with the ejection fraction being very low (the lowest data I can remember is 15%, not meaning that it can't be still lower).
In several posts, there was said that, after some time, ejection fraction has improved from itself, reaching say 40%. It has often been explained as the consequence of having used some medications, but the truth may be quite different.
In the attempt to control the BP, which is critically high, "the pump" is at first regulated via BPM, which is lowered, lowering that way the blood output flowrate, and lowering the BP at the same time. It is known that people with extremely high BP often get bradycardic, with the HR in the low 40-ties. If such one regulation gives no result and the BP remains still very high, the control system of the heart has no other option, but to switch from RPM regulation to additional volume regulation. It means, the heart does not squize fully in each cycle, but uses only (adjustable) part of its disposable ventricle volumes, reducing this way output flowrate further, and this way reducing the BP further. When the cause of the increased BP goes away, the control system will increase ejection fraction from itself.
The idea is that, despite "heart failure" sounds very odd and could be understood as the irreversible process of deteriorating heart condition, it may be just temporary reduction for the needs of heart output flowrate regulation, with good chances to revert to the old normal value. Just as an idea...
AF and heart failiure
Heart failure 
Heart Failure 
Heart failure?
