Heart-rending problems in pets

This week concludes the series looking at heart disease in our pets. Having discussed the clinical signs, examination and diagnostic tests, we finish by considering a few of the most common heart problems.

Heart disease can be broadly separated into two categories; congenital (something the animal is born with) or acquired (something that develops). With congenital heart disease, it is not uncommon in both dogs and cats for multiple defects to be found. Today we will start by briefly discussing a condition called aortic stenosis, to which several dog breeds, including boxers, golden retrievers, German shepherds, Newfoundlands and rottweilers, are predisposed.

The textbook case of aortic stenosis would involve a boxer with a history of fainting. Examination would find a murmur and the ventricle on the left side of the heart (the part that pumps blood) being enlarged and thickened. The term aortic stenosis means narrowing of the aorta (the large artery that carries the oxygenated blood away from the heart). In mild cases, no treatment may be necessary but moderate or severe cases do require medication and, occasionally, surgery to reduce the narrowing.

The next two conditions are both acquired. The first is called endocardiosis and is seen in dogs, classically the cavalier King Charles spaniel. Other dogs, including cocker spaniels, poodles, terriers, dachshunds and Irish setters are also predisposed to it, with a higher prevalence in males. You would expect the dog to have a history of coughing and reduced exercise tolerance. Sometimes, however, there are no clinical signs and a murmur may be picked up as an incidental finding at their routine vaccination. The murmur will often intensify as the disease progresses.

Endocardiosis refers to the degeneration and thickening of the valve or valves between the top chambers of the heart (atrium/atria) and the bottom ones (ventricle/s). Depending on which valve is affected (there is one on each side) determines which side of the heart is enlarged. In long-standing disease both valves will be affected, so both sides of the heart will be enlarged. Endocardiosis is a progressive disease and most cases are likely to need medication.

Finally, hypertrophic cardiomyopathy (HCM) is commonly seen in cats. With this disease you get an increase in the muscular tissue of the heart. This condition can occur without an obvious cause but is often secondary to increased blood pressure or the thyroid gland being overactive. Classically HCM is seen in middle-aged or older cats and more in males. When signs are seen they can be dramatic, such as breathing difficulties or the cat going off its back legs due to a blood clot. In addition to further heart tests, the blood pressure and thyroid and kidney function are usually checked to see if they are potentially responsible for HCM. Treatment includes reducing/stopping any factor that started the HCM as well as dealing with the heart itself. Sometimes medication to prevent blood clots is needed.

It’s important to remember that not all murmurs are significant: many pets have them their whole life with no consequence. However, as these conditions illustrate if a new murmur is found, your vet may advise getting further tests done, and if you start seeing any unusual signs speak to them promptly for advice.