Hi James,
Sorry to hear about your mothers recent health problems. This doesn't sound like a typical case of heart failure. We can generalize heart failure in two categories:
systolicBlood pressure
Mitral valve prolapse and
diastolicBlood pressure. Systolic heart failure is the one that is usually talked about. Patients usually have a lower ejection fraction and the traditional symptoms of heart failure like swelling in the legs, trouble breathing when lying flat, shortness of breath with exertion. Diastolic heart failure occurs with both normal and abnormal ejection fractions. It sounds like they are diagnosing her with diastolic heart failure.
Short of having a stroke or having a prolong period without enough oxygen, I haven't seen any cases of heart failure that cause normal function and then profound abnormal function without some sort of dramatic change like a recent heart attack, stroke, renal failure, etc. Did she have an elevated carbon monoxide level?
I will admit, the story doesn't make complete sense to me, but it may be pretty complicated. She may just have significant diastolic dysfunction with only subtle symptoms of heart failure prior to this episode. If you are concerned, a second opinion can sometimes help.
I wish you and your family the best and hope this helps.
I hope this helps
www.newheartandbody.com good luck.