Echo was born with a broken heart

Echo was a rescue kitten that my husband and I adopted from the local shelter July 2020. We fell in love with him right away. He was the funniest little kitty that would snuggle up with us to sleep and follow us around the house just like a 2 year old. He was suck a healthy little ball of furry energy until the end of Febuary 2021. That is when he started making what we thought was the hiccups. We went to serveral vets and they did tests on Echo, including an x-ray, blood work and an echogram. When the tests came back we were told that

Echo was born with a rare heart defect. The defect has caused a shelf in his heart and it prevents the blood from flowing properly.. It also causes the blood to be pushed back into his lungs. The diagnosis we were given was : Supravalvular mitral stenosis leading to pulmony hypertention, sever heart enloagement and congestive heart failure. We were devasted as Echo is not even one year old yet. This condition requires a hybrid heart surgery by a cardio vet specialist. They quoted us $6,000 for the precedure. They told us that without the procedure Echo probably has less than 6 months to live. Echo is currently on 4 differnt medications and they are helping to stablize him for now. The video shows the difficulty Echo has breathing. We have to try and keep him as calm as possible due to the vet saying that his heart could just stop if it is over worked. We desperately want to save him.

Any help with Echo's heart surgery would be deeply apprecitate.