The MVP should't be the source of your symptoms. When MVP becomes serious (moderate to severe) there almost always is shortness of breath and possibly chest pains, etc. Very oftened MVP is not serious and the leakage is mild, trivial, etc. and never progresses nor cause problems.
Ischemia can cause the symptoms you are having. Ischemia diagnoses indicates there may not be could blood circulation due to vessel constriction and/or occlusions. An abnormal constriction of vessels can be due to abnormal central nervous system reaction to stimuli or lack thereof. There can be blood clots, calification or plaque that reduces the blood flow.
Rather than a reduction of blood flow the quantity of oxygen in the circulating blood can be the problem, and that can be caused by blood disorders such as anemia, asthma, etc. and some respiratory disorders.
There are non-evasive tests that can help make a diagnosis. Hope this helps and if you have any further questions or comments you are welcome to respond. Take care and thanks for sharing.