Hi Mary Ann,
I found several websites with good info re: heart murmurs:
Since Rocky's murmur is congenital, but because he's approaching feline 'senior' status (cats are considered seniors at age 7), I would consider allowing the vet to at least do a CBC blood test to check for any abnormalities.
The above site was a link at this site (below), which has more info and links re: heart murmurs, other heart conditions, chronic renal failure and hyperthyroidism, which can all be interconnected:
I like these sites; they explain things in a very easy to understand way.
Did the vet give any alternative possibilities for the current coughing/gagging? Was his mouth/throat examined?
My daughter's cat was diagnosed with cardiomyopathy when he was only 1½. It was also a congenital condition which had laid dormant for all that time. His first symptom was coughing, but it was much more frequent and also accompanied by labored breathing. I'm not trying to scare you, just relating this info.
In my opinion, because he's older now, you're aware of the heart murmur, and he's developed this daily coughing, I think it bears further investigation. At first, I don't think you need to do $600 worth of tests...do one test at a time to find if there are any 'markers' or indications of a more serious, underlying cardiac (or other) condition, then take it from there. An x-ray to see if there have been any changes in the shape or size of his heart, might be a good idea, too.
Cats are masters at hiding illness/pain, so sometimes, if there's something wrong, you'll only become aware of it when a symptom becomes obvious,
like the coughing, now.
You can also shop around other local vets (who have good reputations, of course) and ask how much it would be for the tests that are needed.
Well, I hope Rocky and his sister are just fine and this is a passing thing. Please keep me posted on them and you can PM (private message) me anytime!
Cher : )