Rooties recovery

Rootie started having trouble breathing 2 nights ago, he stopped finishing his bowls of food which is unusual for him, and then he became super tired and couldnt walk a few steps without running out of breath. the only relief he got was from sleeping on his side. we made an appointment with an amazing vet that took an ultrasound and found out that he has fluid in his lungs, we were then sent to tufts. at tufts they informed us that he is pale, unstable, and is a worry to the doctors. they have him on oxygen and he is in the ER. i got a call about an hour ago informing us that they had found a big blood clot in his heart, stopping the blood from flowing, which is why he is running out of breath. the doctor has him on anti coagulants for now to see if any progress is made but they will be running tests tonight to see what has caused it and if he is going to be able to be treated for it, if so..then the rest of his life looks like being a lazy dog who isnt able to be too active without straining himself. if not, then im not sure where we go from there. they have informed us that he is at risk of sudden death if the blood clot were to dislodge and he could go into cardiac arrest. he is currently 45 minutes away from home and to say i am worried sick is an understatement. i came home and immediately collapsed in his bed. i need him to pull through this because he is my everything. i literally call him my son, he is always there for me when i need him and i dont want to imagine a world where he isnt there. were already looking at upwards of $4,000 for the services he's recieving at the vet and i cant even think straight. please say a prayer for my baby boy.