I didn’t say that they didnt know what it was but that they were investigating it. They have two possibilities one of which is what you describe and the cause of that is unclear though it may be due to the scarring on the heart from my first MI. The second is a small blocked artery (left circumflex) which is too small to get a stent in. It shouldn’t cause a problem but if it does it would mean open heart surgery to correct. However, good as the internet is, I wouldn’t expect any Consultant to be able to wave a magic wand and give a reason for the problem until they have checked out everything. Incidentally they could never give a reason for my first MI twenty years ago and similarly since then I have had regular cardiac checkups and blood tests with no problems yet still ended up with three blocked arteries.