Prayers for Chester, and hoping for a good report from the tests.........
Your Vet may put him on fruisamide (think that's how you spell it) or something similar which gets expells water building up in the lungs when the heart is tired and isn't functioning as well anymore. My old dog Rosie was on that for quite a number of years, but they do empty the bladder a lot more though so be prepared.
Keep us posted on progress