My Grandson Recently Had An Ultrasound Of His Heart. He

My grandson recently had an ultrasound of his heart. He is 22 with DMD. His lvef is 5. I know critically low. He has no need for 02 and no problem with swelling. He is well taken care of medically at Cleveland clinic. My question is I did not think someone could go that low and live. His rvef is 35. He has cardiopathy and is on cardiac meds. The ef has me surprised though.