I have a 16 year old terrier mix and she started this last year. I took her to the vets and they did a thorough exam on her and said it wasn't her heart or lungs, but he said that sometimes when dogs are that old they develop a condition where the esophagus flattens and it causes them to hack, they gave her a pill for her cough, and also an antibiotic in case it was the start of bronchitis which small dogs are also prone to with old age. I gave her both and within 24 hours her cough improved. She started it again about 6 months later, I gave her the cough pill and no abx and the coughing stopped. The cough pill has a steroid in it also that is good for scratching also, since she has really dry skin and scratched alot. Hope this helps, good luck. Jen
Heart failure is certainly one possibility, but it may even be a virus or allergies. Since she's well into her senior years, it's time to have a vet check her out. Congestive heart failure can be treated with meds for some time, and like most illnesses, it's better to have it diagnosed and treated earlier rather than later.