Gazette Vet: Heart Disease

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By John Andersen, DVM

Heart disease is one area where human and veterinary medicine are pretty different.  Although people can get the types of heart problems that dogs and cats get, our pets do not get the most common type of human heart disease, coronary artery disease (CAD). CAD is when cholesterol plaques build up inside the walls of the coronary arteries, vessels that supply blood to the heart muscle itself. This buildup eventually reduces or even blocks blood flow to the heart muscle and causes the dreaded “heart attack.”

It is widely accepted that dogs and cats do not get coronary heart disease. We simply never see it and do not see “heart attacks.”

Interestingly, there is not good information as to why they do not. One of the obvious reasons is that they simply don’t live long enough to develop significant plaque accumulation in their coronary arteries. Ever heard of a 12-year-old kid with clogged arteries?

Another explanation is probably in diet. The most notable difference in pet foods vs. our typical western diet for humans is the absence of sugar in pet foods and the ridiculous prevalence of sugar in our human western diets. Although fat intake is classically blamed for causing CAD, it is now known that sugar intake is an important risk factor as well.

Lastly, dogs and cats don’t smoke or drink alcohol (hopefully). A dog’s life is generally a good life.

Despite the total absence of CAD in our pets, we are constantly evaluating animals for heart disease.  Here are a few examples of the most common heart disease we see in pets:

Chronic valvular disease (CVD) in dogs:

Jimbo was a 12-year-old Dachshund who presented to me with a bad cough for the past week. Jimbo has had a heart murmur for the past four years with no clinical signs. A murmur is an extra “whoosh” sound we hear when blood is flowing with some turbulence somewhere in the heart. In older, smaller dogs, there is a 90 percent chance that a murmur is from CVD, a condition where the valves in the heart become thickened and knobby on the ends and don’t close all the way. This causes some blood to sneak through the closed valve and leads to increased pressure in some chambers of the heart. Over hundreds of thousands of heartbeats, the extra pressure causes the heart muscle to stretch and weaken. Initially, this is not a problem, but eventually the heart becomes so weak that it cannot do its job as “the pump.” This leads to fluid buildup in the lungs or belly, also known as congestive heart failure (CHF). X-rays and a stethoscope proved that CHF was the cause of Jimbo’s coughing.

Initially, Jimbo responded well to medication and went on to live for another six months.  Eventually no amount of medicine could keep the fluid out of his lungs and he was peacefully euthanized (put to sleep).

Occult (hidden) heart disease and blood clots in cats:

“Charlie” is an 11-year-old cat who came in on emergency in a lot of pain and unable to use her rear legs. She had just had a complete physical exam and even blood work three months ago and looked great—no heart murmur, no breathing issues, and no abnormal heart beats. Unfortunately, her presentation is classic for a “saddle thrombus” due to heart disease. A saddle thrombus is a large blood clot that traveled from the heart down the entire aorta and got lodged where the aorta splits into two arteries that supply blood to the left and right rear legs.

Dogs do not often get strokes or blood clots, but cats – like people – most certainly do.  The classic cause for a blood clot to form in the heart is a dilated heart chamber. Like CVD in dogs, the end-stage of heart disease in older cats is often a dilated, weakened heart. When a heart chamber is dilated in a cat however, blood can start to just swirl around and eventually may form a clot, or a congealed glob of blood.  At some point, these blood clots will leave the heart and go…. somewhere. Charlie’s blood clot went to her rear legs and cut off the blood supply. This is extremely painful and causes the rear legs to stop working. Clots can also go to the brain (stroke) and to the lungs (pulmonary emboli).

Cats are very tricky creatures to care for and it is relatively common for them to have severe heart disease without any obvious clinical signs until it is too late. Charlie’s owners, despite her pain and poor prognosis, did not want to give up on her. So we treated her with pain medication and some heart medications and, wouldn’t you know it, that cat went on to regain function in her rear legs (although always pretty wobbly) and lived another two months. We think she succumbed to a major stroke because the owners came home from work one day to find her passed away on their bed.

Congenital heart disease (birth defects):  

It is always difficult to tell the new owners of a sweet eight-week-old puppy that their dog was born with a terrible birth defect in its heart, but that is what I had to do with “Max.” The owners could probably see the change in my face from enthusiasm to disappointment and I wasted no time delivering the bad news.

Max had a loud heart murmur, and in a Golden Retriever, this is almost always due to a narrowed entrance to one of the major vessels leaving the heart. This eventually leads to increased pressures and a dilation of the heart or major vessels. These dogs do not have a good prognosis and often die young of sudden unexpected death.

Max’s owners taught their kids a good life lesson that day–don’t give up some something you love just because it’s damaged or not what you expected. They took him to Virginia Tech and had some risky and expensive procedures to help open up the narrowing. He is still alive eight months later, but he frequently collapses when he gets excited from an abnormal heart rhythm. Sadly, Max’s prognosis is grave, but his owners are enjoying their limited time with him.

There are many more types of heart disease; these are just a few examples.  Although there is a huge disparity in the treatments given to people vs. pets, we can often successfully manage heart disease at least temporarily. If your pet is coughing, having trouble breathing, or it’s been a while since the old gal has been brought in, bring her to your veterinarian for an evaluation.