Hello and welcome to the forum. This is the type of question best answered by the physicians that he has seen. They've examined him and will be able to best guide you for what is the best course of treatment.
To go over what you are talking about though, here is information on Mitral Valve Regurgitation https://www.mayoclinic.org/diseases-conditions/mitral-valve-regurgitation/symptoms-causes/syc-20350178 which basically means the mitral valve doesn't close tightly. This causes your blood to not be able to move easily which in turn would make someone easily tired and out of breath. Some people with mild regurgitation don't require treatment and doctors will take wait and see approach. Others begin medication and some cases require surgery. Surgical options for repair and replacement when the valve can't be repaired have come a long way. The miralclip is used in patients who have severe regurgitation and aren't candidates for surgery or if it is the treatment chosen as best by their doctor. Could this be the case for your son? Possibly. Speak to his doctor.
The ejection fraction of the left ventricle is fairly low. Normal is between 50 to 70 percent. Under 40 percent is considered very low. https://www.heart.org/en/health-topics/heart-failure/diagnosing-heart-failure/ejection-fraction-heart-failure-measurement What is the doctor recommending for this?
How old is your son? Are they saying he is has heart failure?
Your question is a good one but only able to be answered by the doctors treating your son. Please follow up with us and let us know more details and when he next visits his doctor. We wish you and your son the best of luck.