I don't know how much of this you know already, but here's my understanding of processes. They don't usually give you ablation as a standard treatment for Atrial Fibrillation (afib). First, they give you a collection of different drugs for afib and, if the rhythm doesn't correct itself, then the docs do cardioversion, an electric shock reset of the heart rhythm. Ablation is usually done to correct blockages, they effectively burn out the blockage with a hot/cold wire. Sometimes a clot causes abnormal rhythms, but if that was the case, the patient usually has a heart attack and the ablation is done in hospital pretty quickly, before they're discharged.
As far as I know, there is no real treatment for heart failure, they just usually give you more drugs, such as beta blockers, to lower the heart rate and take some of the strain off the heart. The only treatment for heart failure is a transplant, but that's not usually an option for most people.
Yes, heart failure sounds terrifying, and fatal, but there are plenty of people living with a 'heart failure' diagnosis. Think of it more as 'heart struggling', as opposed to 'heart ending'. Valve replacement is a pretty safe procedure- they do hundreds of these operations every year. valves get floppy, bow, or don't close properly because of structural issues with the heart or connective tissue and if the valve doesn't close properly it can cause regurgitation and sometimes cause heart attack.
When a pacemaker is fitted to fix afib, they usually do an ablation first. In this instance ablation is not a clot buster, but a way to 'knock out' the hearts computer, and then fitting the pacemaker is like installing a new data chip. The pacemaker doesn't stop the afib, the heart still beats irregularly, but the heart's 'computer' section gets its readings from the pacemaker box instead of the natural computer, which the ablation overrides (hope that makes sense).
if the pacemaker is fitted to control bradycardia, a slow heartbeat, then it doesn't touch the afib, unless its a specific 'mode-switching' dynamic pacemaker. With these, if the heart beats too slow, you get a buzz, too fast, you get a buzz. You still have the slow and fast abnormal rhythms, and you can feel fluttering and such, but the machine does it job and stops problems occurring.
About 51% of patients recover in 3 months from ablation/pacemaker install for afib, so that suggests 49% of people don't recover within three months. The people who don't recover within that 'gold standard' 3 months are people who have other heart issues, and it sounds like with the heart failure, valve issues, and such, your man has a complicated issue and therefore probably a more complicated recovery.
Cardioversion can be done with a pacemaker, to try to fix the afib, but it makes it all much more complicated than just a quick wham with the paddles. Same too, with another ablation for afib with a pacemaker. It can occasionally cause the pacemaker to malfunction, which means more operations and procedures, more recovery, more risks, etc. Sometimes infection causes afib, sometimes a struggling heart just goes a bit haywire and then fixes itself. Sometimes going in and fixing things causes more issues.
When you're sitting there hearing about heart operations, failures, afib at 350 bpm, etc, it's all bloody scary and sounds massively serious, which it is, but the cardiac teams in the NHS are actually quite good.
Like heart failure, people live with afib, too. If it's been beating crazily for longer than a few weeks, it's treated, mainly because of the elevated stroke risk. Presumably your man is on blood thinners, that lessens the risk massively. If there are no other 'danger symptoms', with the afib, such as serious breathlessness, severe chest pains, dizziness, fainting, etc, they tend to treat things 'conservatively'. And that sometimes feels like they're not doing anything, and the places your mind goes are horrible places to visit.
My husband has Marfan's syndrome. His heart is wrecked. The rest of him, on paper, seems pretty buggered too. But, he's out at work every day, he's had all kinds of scary heart issues and procedures and he's still here. He received all his care in Liverpool heart and chest hospital: they are brilliant. The best in the country, apparently.
If your man is having any scary symptoms, severe chest pains, serious breathlessness, fainting, dizziness, then take him to A and E. They'll run tests, maybe bump him up the list if that's needed. But it might just be he needs to wait. I hope some of this helps a little.