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I would actually have your dog on a combination of Lasix, Enalapril and Vetmedin. This is my typical approach for congestive heart failure dogs. The three meds work synergistic with each other to give the best chance of getting the condition controlled and giving a good long term survival.
If the coughing is part due to some tracheal collapse, then a cough suppressant may help. If it's heart related, then we prefer to use more Lasix to control the cough. I would try giving an extra dose of Lasix first and see if that helps. If it's not helping, then you could try an over the counter cough suppressant. Robitussin DM is safe to use in dogs. You could give 1/4 teaspoon every 8-12 hours, as needed.
If still no help, then I would get to an ER vet and shoot some x-rays to see what's going on in there.
I hope this helps, let me know if you have any other questions.