So basically I’m just going to thumb through my notes from the American College of Veterinary Internal Medicine (ACVIM) Forum and try to pick out things that are interesting to you, the general public, and any interested DVMs/vet students out there. Now granted, the students may already know this stuff, since they are in the heart of the land where the new things are being discovered.
Today’s edition involves things I learned about screening for hypertrophic cardiomyopathy in cats and pulmonary (lung) disease in dogs.
Hypertrophic Cardiomyopathy (HCM) Screening in Cats
This disease is very vexing to me because in general, it’s totally clinically silent. The cats show no signs that they have it, usually until they drop dead, go into fulminating heart failure or throw a clot — ending up paralyzed and then euthanized in most cases. Most of these cats end up dead, either by dropping dead as I just mentioned or via euthanasia. Thus, I’d love to hear what, if anything can be done to pick up some of these cats before they die.
In vet school I was taught that heart murmurs are rare in cats, and are usually associated with bad things. The problem in practice is I hear (what I think are) a lot of murmurs, and see very few of those cats go on to develop a problem. The HCM cats that die usually don’t seem to have murmurs (at least in my experience).
Well, according to the study mentioned in this lecture, 34 percent of the "normal" cats they looked at had murmurs; 50 percent of those cats had no heart disease. Thus, a good percentage of cats have murmurs that don’t go on to become a problem (just like I suspected).
Echocardiogram is supposed to be the gold standard for diagnosing these guys. However, in my world of dealing with the average Joe, they are pretty cost-prohibitive ($400-500). She pointed out, however that there is a 1mm difference between "normal" and “abnormal” on an echo. So there is a pretty heavy burden of subjectivity on the person doing the echo. Pretty easy to measure the wrong spot or mistake a bundle of tendonous stuff for part of the heart wall, and maybe call a healthy cat sick.
Genetic testing isn’t the answer yet because they really haven’t isolated the gene (in cats) that causes the problem. Incidentally, they have isolated the human mutation (HCM affects 1 in 500 humans), and they looked at the same spot on the cat’s DNA, but the mutation isn’t there in HCM cats.
The moral of the story in this lecture was there is no true "gold standard" for diagnosing HCM in cats. This, in a way, makes me feel a little bit better, to know that I’m doing the best that I can with what I have at my disposal to identify these guys.
Interstitial Lung Disease in Dogs/Pulmonary Fibrosis
- CT scans are shaping up to be an excellent way to evaluate lung disease in pets. Granted, not so practical now, but ten years ago, the thought of digital radiography in my practice was a total pipe dream. Now film X-rays are a quaint relic of the past.
- This is a disease I really wasn’t familiar with. Westies are the prototype, but I really think a little poodle that passed away last year at our clinic may have had this.
- Happy dogs pant and breathe about 300 breaths per minute vs. dyspneic dogs who are stressed and sad and breathe about 100-120 breaths per minute (you can mix the two up sometimes).
- When a client says their dog is slowing down on walks, don’t just think orthopedic problems (arthritis). It is a very early sign of respiratory disease, too.
- Humans do a six minute walk test. Normal healthy people generally walk a specific distance in six minutes. Those with pulmonary disease walk a shorter distance in the same time. It’s kind of a poor man’s way to tell if your lungs are working right. In the study mentioned in this lecture (in which they said their intern did countless laps with dogs in the hallway of the university), a normal dog can walk around 522 meters in six minutes, while a dog with respiratory dysfunction walked around 340 meters. (This is based on what I wrote in my notes, I could have written the units down wrong.)
- You can use Viagra to treat pulmonary hypertension in dogs. Have fun getting that one at the pharmacy for "your dog." ;-)
- The 4 P’s of lung irritants: pollens, pollution, perfume and puppies. Puppies carry diseases to older dogs that can trigger infections, kennel cough complex, etc.
Stay tuned for future installments — unless of course you don’t share my fascination with this stuff, in which case I can tell you more about my favorite bands, or something ;-)
Dr. Vivian Cardoso-Carroll