MVD: Mitral Valve Disease
The ideal situation is to be monitoring a Cavalier for murmurs and heart disease BEFORE he starts to cough or show other signs of congestive heart failure. The course of the disease is better if you can prevent a crisis and stay ahead of the symptoms.
Some background - mitral valve disease is the most common heart disease in small breed dogs, but in Cavaliers it is unique in that they develop the disease at a much younger age, the disease progresses much faster, and it can cause death as young as 7 to 9. Probably 60% of Cavaliers at age 6 have a heart murmur of some degree. Near 100% have a murmur at age 10. Murmurs are graded from I to VI - VI being the loudest. Coughing indicates that a dog is already in congestive heart failure. Congestive heart failure -- CHF -- is when the heart can no longer work efficiently and pump blood through the body because of the volume of the regurgitation (backflow) of blood from the atrium back into the lungs. The heart is already enlarged and working poorly when CHF begins, after years of compensating for the valve disease. As fluid gathers in the lungs, the dog starts to cough. He can also show difficulty breathing, especially when lying down. He will cough during exertion. The fluid can also gather in the abdomen (this is called ascites). Another symptom is fainting (called syncope). You will often hear the cough more in the early morning after he has been lying down all night. Start a log and write down all his symptoms, time of day, duration, etc.
There is great variability in the course of the disease in Cavaliers - some can start symptoms which will continuously and quickly worsen, leading to death within a year. MOST Cavaliers can have years of alleviation of symptoms with the proper use of medications. I'd say the average Cavalier lives to be 9 to 11, but many do live into their teens. One thing you can do once a dog is diagnosed is closely monitor the disease to get an idea of the rate of progression. After six months to a year, you will have a much better idea of a dog's prognosis.
Have a talk with your vet to find out how much he/she knows about Cavaliers and mitral valve disease. There are many web sites (breed clubs, etc.) that have lots of info. You can print out info to discuss with your vet. Also, be aware that some vets aren't very good at grading murmurs. Most of us use a board certified cardiologist, an expert. I've had one for 12 years, and he has made a world of difference in the lives of my Cavaliers. (I have two 15 year old Cavaliers - one is in end stage heart failure and on five meds which keep him symptom free at the moment. His litter sister is in mid stage but with no symptoms and on no meds because she has kidney disease. I also have two 12 year old Cavaliers, one with mild heart disease and the other with fairly advanced disease. Both of the 12 year olds are on heart meds. Lastly, I have a 14 year old shih tzu with moderate MVD, no symptoms - no meds as she has only one kidney and had a liver shunt at birth.)
If a dog is coughing, the vet should want to do a chest x-ray immediately. This will tell you whether or not the heart is already enlarged, and if so, how much. It will also show any fluid in the lungs. (you can read about the different heart tests later in this MVD thread) Your vet should also run a superchem/CBC (bloodwork). If your vet is not familiar with Cavalier heart profiles, he/she may think there is enlargement. A cardiologist or internist can look at the x-rays if there is a question about heart size. With these tests, you'll have baseline information. It is important to know before starting heart meds whether or not there are existing kidney, liver problems, etc. After heart meds are started, another superchem is run 7-10 days later because some of the meds can cause kidney failure (luckily, this is rare) so you want to make sure the meds aren't hurting. Then you run another one in 30 days, and then you can go to every 9-12 months. These tests shouldn't be terribly expensive - I pay $60 for chest x-ray (two views) and $75 for an Antech superchem and CBC. In six months or so (depending on how the dog responds to the meds) you'll want to do another chest x-ray to see if his heart has continued to enlarge or if it seems the same size. This is when you'll know more about the prognosis.
A vet may decide to start the dog on two frequently used heart medications, enalapril and furosemide/frusemide (Lasix). He will get quick relief with these drugs. I started most of mine on enalapril as soon as heart enlargement was evident and there was significant regurgitation of blood back into the lungs. (This was under supervision of a cardiologist. Mine believes in not waiting until there are overt signs of CHF such as coughing or fainting, etc.) When mine have "imminent CHF" I start them on lasix. The cardiologist (and I agree) feels that this can prevent a CHF "crash" in many cases. When CHF does begin despite these drugs, there are many other heart meds to add (digoxin, Pimobendan, hydralazine, spironolactone, etc.) which can keep them stable for more decent quality time. The good news is that all of these meds are pretty inexpensive, and most have generic versions. Most Cavaliers tolerate these drugs with no or few side effects. Your vet will do blood chemistry to check kidney values about 10 days after starting a drug, and then after about 30 days, and then every 3-12 months.
Important -- if you purchase enalapril (Enacard) at the vet's office, you might pay $1.00 per pill. Ridiculous! I purchase generic enalapril at Walmart and pay $22 for 100 5 mg. tablets (cost is same for 100 10 mg. tablets). The pills are scored, and I split them to save even more money. Furosemide is also a very cheap drug - I also get this at the pharmacy. (Actually, I get all my dog meds at Walmart.) Your vet will give you a prescription. If he/she doesn't, then I'd consider another vet because you will be spending plenty of money there and you don't need to be ripped off.
I keep copies of all blood chemistry and the actual x-rays at home so that I have them to take to cardiologist appts or in case there is a crisis and I have to go to ER in the middle of the night or something. That way, I have info to give which helps in figuring out what is going on.
Other things to read about and consider:
WEIGHT - KEEP HIM THIN, THIN, THIN. This is really important and can make a world of difference. Many longtime cavalier breeders believe keepoing a dog in good weight can delay onset of MVD by several years and add several years to a cavalier's life. For more on feeding and how to tell if your cavalier is overweight, see: http://www.roycroftcavaliers.com/manualfeeding.htm
Supplements - I'm a big believer. Some to consider are CoQ10, omega 3 fish oil caps, vitamin E, vitamin B complex. Also glucosamine/chondroitin for joint disease/arthritis and probiotics to help in digestion. There are also combinations such as standard process cardio-support. (I prefer giving single supplements rather than combos.) I absolutely believe my Cavaliers are so old in part due to years of supplements.
Limited Vaccinations - long, long topic. I stopped vaccinating middle aged and seniors in 1997. You can do three year rabies and still be legal, and many think that lifelong immunity to parvo and distemper is acheived after receiving puppy vaccs and a couple of boosters as young to middle aged adults. At a minimum, consider vaccinating every three years instead of yearly. It's a huge hit on the immune system.
Diet - try to feed the best possible diet you can. This might be higher quality commercial which are NOT found in grocery stores or big superpet stores. Or it could be home prepared - raw or cooked (a good deal of research to do). I currently feed a high quality commercial dry with added home cooked or raw items (cooked eggs, boiled chicken, pumpkin). There is new thinking that senior dogs and those with chronic disease (heart, kidney) actually need 50% more protein than average adult dogs. BUT they need a higher bioavailable source of protein not found in commercial food (such as egg whites, chicken, tripe, etc.). This is a huge topic that I won't even try to get into here. But you can research this.
Consider subscribing to Whole Dog Journal ( http://www.whole-dog-journal.com/
) -- you will learn so much about health, diet, vaccinations, supplements, herbs, etc etc.