Much depends on how this was diagnosed. Sounds like mine. If the cardo looked at section aVL of a 12-lead ECG, and saw a line that looks flatter than the section just above it, aVR, or looks like it is just sort of humming, there are some diseases you will come to know. There is not much treatment apart from large (80) Methotrexate injections each week, and very strict diet. You can look it up on the Mayo-MN site, or the University of Helsinki Hospital/school site. I am 80 years old now, and still moving around, and I have Finnish Amy. But it must be diagnosed by molecular studies now. And I have a list of over 200 signs and symptoms, many of which support the dX. Organomegaly of almost every internal organ, blood issues, Stiff Heart, various cancers, leukemias, skin eruptions, brittle teeth, facial anomalies, purpura, brittle nails. I have written my stuff up, and you or anyone else is welcome to it, electronically. https://bit.Ly/2jtypp9 But do get a top lab, like johns hopkins, or Boston to talk with you. It is very under-diagnosed everywhere.

@yac53 one other thing here is an article on Heart Failure which includes diastolic
https://www.mayoclinic.org/diseases-conditions/heart-failure/symptoms-causes/syc-20373142