I was just put on an ACE Inhibitor too. Although I have high BP, it was not the reason for my being put on it. It was explained that it helps the heart muscles out when it isn't beating sufficiently. I have mitral valve prolapse and enlarged left ventricle. My heart is having compensation problems I believe. Apparently there are a lot of causes for the valves and muscles to weaken. Hopefully they will be able to find the cause and repair/stop the damage. Like me, it is a concern but not an immediate one or they would have had you in surgery by now. I gather we just pay attention to any new symptoms or symptoms that worsen and call the doctor right away
so they can monitor it. I am frustrated too.
In your case, it sounds as if they did everything possible to research what is going on. I would be more comfortable with that. A heart cath. is the best it gets. They should be able to see everything in that. If there are no immediate/emergent problems or blockage then usually you will be okay for now. The ACE inhibitor should strengthen the muscle enough to get it working better. I never did like the wait and see approach. My foot or something okay, but I'm a little touchy when it comes to my vital organs. It takes forever to get into these specialists. Or at least it seems that way. I'm sure time is on our side though or we would be in the E.R.
Hope for the best for you - Kristin