My understanding is that, stroke or HF, they are all statistical probabilities, not absolute end-states. That is to say, enough people do go on to get these if left uncontrolled that the literature warns of those consequences.
I understand that HF is likely for those who have intractable, difficult, or prolonged arrythmias of pretty much any/every kind. The heart is a composite of four chambers, but also four valves meant to greatly reduce backflow between them based on sequential contractions. Arrhythmias mess that process up, and it affects the substrate of the heart. We know of the problems with 'remodeling' that come from arrythmias, and that very lengthy article posted by sidabrowski yesterday described it all very comprehensively. The structural changes impose geometric and mass distributions not meant for a healthy heart. The myocytes begin to lose ground over pretty lengthy periods, bless their wee hearts, but those losses mean the heart begins to weaken. I know nothing about the treatment for HF, but I have read on other fora that many go on for many years in controlled HF.
And, bless you, Susan. If the world had just another ten people with your fortitude, it would be a vastly different place.