Visiting Veterinarian : Precious has a heart murmur, and now a guarded prognosis
The first time I met Precious, the Maine coon cat, he was a handsome two-year-old presenting for a routine exam which, of course, included listening to his heart. Although Maine coons are known to occasionally have an inherited cardiac disease called familial hypertrophic cardiomyopathy, the condition is uncommon so I wasn't expecting trouble.
I put my stethoscope to Precious's chest. "He's got a little murmur," I murmured.
Heart murmurs are audible vibrations caused by disturbed blood flow. They are graded on a scale from one to six. A grade one murmur is barely audible. In vet school we said if the professor can hear it but the student can't, that's grade one. Grade six is the loudest — you can actually hear it without a stethoscope. We also assess other parameters. During what part of the be-lub-dub does the murmur occur? Where on the chest is it loudest? What is the quality? Musical, gravelly, harsh? Does it get louder or softer? Certain sounds suggest certain diagnoses. For example, patent ductus arteriousus is a condition in young animals in which a fetal blood vessel connecting the aorta and pulmonary artery in utero fails to close as it should at birth. These animals have distinctive "washing machine"murmurs. But most murmurs just tell us something is not right and further evaluation is indicated.
"Precious has a grade two heart murmur," I told his mom, then suggested a cardiac work-up.
"His heart is slightly enlarged," I explained when I saw his x-rays. "But radiographs only show us the silhouette of his heart. They don't tell us precisely what's going on inside."
Next we ran an electrocardiogram, transmitting it by telephone to a cardiologist who confirmed that the results were highly suspicious of familial hypertrophic cardiomyopathy. An ultrasound would be the next step to further define heart structure and function. Since Precious seemed perfectly happy and healthy, his mom opted to hold off on further testing and started him on the medications suggested by the cardiologist.
Cardiomyopathy. "Cardio" means heart. "Myo" means muscle. "Pathy"comes from the Greek patheia, for suffering or feeling, and in this context means disease. So cardiomyopathy just means heart muscle disease. There are several forms in cats, including hypertrophic, dilated, restrictive, and unclassified — terms that refer to heart size as well as the thickness of the muscle. For example, in dilated cardiomyopathy (DCM) the heart is very big, but with very thin walls. The attenuated muscle cannot pump efficiently, eventually leading to congestive heart failure.
Back when I was a student, feline DCM was a common disease. Then we discovered the underlying cause was often a nutritional deficiency of the amino acid taurine. The pet food industry corrected taurine levels in all their products and, poof, DCM became a rare disease. We still see occasional cases unrelated to nutrition, or in cats being fed taurine-deficient home-cooked diets.
Nowadays, hypertrophic cardiomyopathy (HCM) is the more common heart disease. In HCM the heart may appear normal in silhouette, but if you were to slice it in half, you would see extremely thickened walls leaving little room inside the chambers for normal blood flow. Although typically seen in middle-age or older cats, HCM can occur at any age and in any breed.
"He certainly doesn't seem sick," Precious's mom would comment year after year as he returned for his annual visits.
Clinical symptoms of HCM can vary widely. Many cats show no signs at all. Others may have subtle signs like increased breathing rate. Sometimes the first sign is a life-threatening blood clot or even sudden death. I have seen cats die within weeks of initial diagnosis and others live for a decade.
Four years after his presumptive diagnosis of HCM, at the age of six, Precious's murmur was a little louder, maybe a grade four. We repeated the radiographs. His heart was marginally larger, but without stethoscope and X-ray machine, you'd never know anything was wrong. He was still taking the same two medications every day, but I had been doing some reading.
"A lot of the specialists are now questioning how useful these drugs are," I told his mom. "But, frankly, I'm so happy he is doing well, I'm afraid to stop them."
After some discussion, we agreed that an informed decision about treatment would best be made based on an ultrasound and cardiology consult. I sent them off to see my favorite heart guy, Dr. Brad Moses over on the South Shore. He confirmed the original diagnosis and advised continuing the medications. "He said the prognosis was good for now, but that could change at any moment," the owner reported.
Years passed. I saw Precious every December like clockwork. He always looked fabulous. Then came this year. Now nine years old, Precious sat quietly on my exam table while his mom and I chatted.
"We haven't checked blood work in a while," I commented. "We should be monitoring his kidney function, considering his age, his heart, and his medications."
His owner agreed, but I was distracted, watching the way Precious was expanding his abdomen when inhaling, like a kitty doing yoga belly breathes. "Has he been breathing like that at home?" I asked. It was subtle but he was definitely working just a little extra hard to breathe.
"Now that you mention it, I have seen him do that a bit recently," she replied. New radiographs revealed a massively enlarged heart.
"That could be fluid in the sac around the heart, or it could be worsening cardiomyopathy," I sighed.
We sent Precious off to the cardiologist who did an ultrasound, tapped 20 milliliters of fluid from his pericardial sac, and prescribed multiple new medications.
"[This] could easily be called "unclassified cardiomyopathy," Dr. Moses said, "but calling it advanced HCM will do... Prognosis is quite guarded, but I have had similar cats live over a year."
So now we give Precious his medicine, watch and wait, and hope he has at least a few of his nine lives left to live.