Hi there and welcome to TrainerRoad! I have had exactly the same heart issue as you, except I had a totally blocked LAD artery which required drilling out before stenting. Background:
I have been cycling since 2006, and joined TrainerRoad in the winter of 2016, did a good winter’s training and bumped up my FTP by 20% (beginner’s gains). I had a good summer of 2017, doing lots of hard rides with some pretty fast groups, pushing myself harder and harder. I was on a pretty steady ride in Sept 2017 with 2 friends when I started to get chest pain. Thinking it was just heartburn I carried on and the pain came back a few more times till eventually I couldn’t turn the pedals. Still thinking nothing of it I called the broom wagon to pick me up, got home and as I climbed the stairs I had what turned out to be a pretty big heart attack. Still refusing to believe this was happening, I had a call with the NHS 111 helpline (I’m in the UK), played it down and told them I was ok now but a bit worried. They sent me for an appointment later that day at the local hospital. Basically the nurse mis-diagnosed me as my BP etc was fine, and advised me to get an ECG at my local doctor’s surgery. Did this 2 days’ later and it turned out I’d had a pretty bad heart attack and went straight into hospital. I spent 11 days waiting for my procedure as it was no longer an emergency (the downside to the NHS!) and was a specialist procedure to drill through the blocked artery.
A bit like yourself, the cardiologist told me that he thought my artery had been totally blocked for a long time, at least 3 months and maybe a year or 2! My heart had grown capilleries across from the right side to help take up the slack and was also backfilling from the rear artery - absolutely amazing! I had done a whole summer of really pushing my limits with a blocked LAD artery - I am lucky to still be here!
My advice - ever heart issue is different, so all advice needs to be taken and assessed against your own situation. I was very lucky in that I had zero dead heart tissue - I have a cycling acquaintance who had a slightly less severe heart attack but lost a few % of his heart muscle.
He did give me a lot of advice and I learnt from his mistakes - he pushed himself too hard too soon and had further issues, but he was and still is a very strong cyclist and doesn’t seem to be human!
What did I learn? Firstly, your heart won’t recover unless you use it! i started off my recovery with diagnosed heart failure, my ejection fraction was around 45% - it recovered to 55% within maybe 6 weeks though. I started off just walking - the first day I managed maybe 300 yards, had massive chest pains and had to stop. I then managed a mile, again had massive chest pain and ended up back in A&E - the chest pains turned out to be anxiety and I was having zero issues! A lot of your recovery is going to be mental - I would say it took at least 6 months for the chest pains to stop (like fake angina I guess).
I ended up having CBT because I was coping very badly with what had happened. I was 47 at the time, I’m now 51. this helped me massively, also my cardiologist gave me a treadmill ramp test which I passed with flying colours (it’s just brisk walking!) and helped me a lot.
i started back on the bike once I was walking 5 miles a day. I set up my FTP on TrainerRoad at a level I felt would keep my heart rate in the safe zone (I knocked my FTP back by 10%) and I started doing the Traditional Base workouts (60-70% FTP) ensuring that my heart rate matched my power zones. By then it was November so I also started riding outside doing Z2 stuff. I did join some friends for a group ride, they promised me they’d stick to Z2 but on the first hill my heart went into Z4, and I stopped, totally demoralised and considered going home - they convinced me to stay, I stuck out the ride and felt really wasted the rest of that day - big mistake!
What I did - 3 months of Z2, when that gave me no issues, I started venturing into Z3 (mostly!) for another 3 months. All on my own, at my own pace. After that went quite well I re-joined friends for group rides. The main thing I remember is feeling really tired after a ride! I would often get dropped, that was demoralising but I had zero need that year to push myself! I even had to walk my bike up a hill for the first time ever, but I preferred to do that than have my heart in Z4 for too long!
So 2018 was basically a year of slowly recovering physically, getting myself mentally recovered as well. I ended 2018 with my FTP roughly 10% down on 2017, and 5% up from where I started after the heart attack. I dived back into full training that winter, it was a bit up and down and I found it hard to push myself mentally, but I maybe improved by another few % power-wise, but my endurance improved massively. I then had a year of trying to enjoy my riding, backing off when I needed to, pushing it when I could.
i went into 2019 winter with an FTP as high as I was prior to my heart attack. I didn’t really improve much beyond that in 2020 due to Covid and having to shield etc. I had a crash at the end of summer 2020 and then took a month off, so lost fitness again and went back to 2018 numbers - I’m now just back to winter 2019 power numbers.
I would say - give yourself a year to recover and just enjoy your cycling. Your heart is a muscle and it’s been stunned and had a bad injury! Allow it to recover, allow yourself to mentally recover and slowly start to trust it again. I am now training to higher numbers than I was prior to my heart attack and can push myself on workouts without freaking out what my heart rate is doing - that wasn’t the case for a few years!
You can recover, you can still enjoy your cycling, and TrainerRoad workouts can help you but you may need to tailor your plans and take extra rest etc when you need it.
We’re both lucky to still be here, and cycling can only help to keep our hearts healthy!