I am struggling with losing my cat to heart failure when it was not brought up in her past appointments

I just lost my sweet 14 year old kitty Sunday night when all of a sudden the day prior, she showed signs of respiratory distress. This came out of nowhere. She spent the night in the ER after she had a chest tap and given oxygen. There was a good amount of fluid in her chest cavity.

Brought her home the following day and only within hours she was showing even more severe signs of respiratory distress, heavier panting with her tongue out. I rushed her back and already there was more fluid built up. They suggested euthanasia because it came back so quickly and she would likely have passed away later that night if I brought her home. I had to let her go and I am so guilty that I didn’t do something sooner that could have prevented this. Could I have?

She was being treated for CKD, in stage 3 but it was being managed well. She had been in stage 3 for about a year with no crashes. So that was the concern and what her vet had been treating her for. He mentioned in her last appointment about 6 months ago she had a mild heart murmur but he wasn’t too concerned about it but more concerned about treating her CKD. He also mentioned he saw cysts in her liver but again, but again was more concerned about the CKD. Offered in addition to her regular kidney panel that if I wanted to do a lot more testing like echocardiogram that I could. Since he mentioned he didn’t think it was the big issue at that point, I opted not to.

Fast forward to last weekend when my baby was in the ER, they said she was in heart failure and they detected a mass in her stomach through x-ray. Her regular vet didn’t feel a mass. When she initially got send home after the procedure, they sent me home with Lasix but warned me that it would worsened her CKD.

Here is where I am struggling so please, anyone with insight please help me. If I had not waited 5-6 months to get her checked with her regular vet, could he have seen these changes early enough to have saved her? Like he could’ve detected more changes with her heart and I could’ve put her on meds then to have prevented this occurrence? I am feeling a tremendous amount of pain and guilt over this.