Normally you can catch it in broilers before it happens. Signs are labored breathing, panting hard, and lazyness. It's typically found in overfed broilers and broilers that have lived past their expiration date.
When you see this you need to restrict the feed and turn the lights out. Let them rest and clean their system out. A full crop and intestines just strains the heart that much more.
But once they get the fluid going in their lungs there isn't much to stop it. They get a dark purplish head too. By this time it's too late.