
I had a golden retriever diagnosed with an enlarged heart (DCM) at about 11/12 years. She was coughing sometimes and had a sort of feinting episode. The vet thought laryngeal paralysis and took her in to test, but it wasn’t that. He took an X-ray to check her lungs and that was when he saw the enlarged heart. She was prescribed a water pill and a heart pill (can’t recall the names offhand) and she did amazingly well. The vet said to let her do what she wants rather then restricting her and there were several times my heart was in my mouth when she took off after a rabbit, but she seemed to know how to self regulate herself. She lived until she was 14.5 years.
Of course it may not be DCM so try not to worry until she is diagnosed. It’s not an immediate death sentence and the right drugs can help enormously although it can’t be cured