My own little Isora has a heart murmur, suggesting MVD
Yesterday, I was running around delivering medications to three patients, and it occurred to me that all three were heart patients. So, I thought I would discuss heart disease in pets with this blog.
Now, we all know how important heart disease is in humans. Well, for people, it is all about the cholesterol plaques. These insidious globs of material gum up the blood vessels, promoting clots (strokes) and choking off the blood supply to the heart itself.
This is not the case in our pets. In fact, the only domestic animal that has a problem with its blood vessels in such a way is the turkey (so, apologies if your pet is a turkey and I have inadvertently excluded it!)
Heart disease that develops in our pets involves either the heart muscle, or the valves of the heart.
Cats:
In cats, the most common form of heart disease is heart muscle disease: the heart muscle becomes thick and stiff, and is unable to contract properly. This is called Hypertrophic Cardiomyopathy (HCM). As the heart’s contractions get less effective, and each beat pumps less blood, the heart has to go faster to make up for it. The problem with this is that the heart muscle itself gets its blood supply delivered in the relaxation between the beats. This means that when it is going fast all the time, it is actually choking off its own blood supply, contributing to the further degeneration of the heart muscle.
The medical treatment of HCM is aimed primarily at slowing down this excessive speed in the heartbeat.
As the body attempts to compensate for the poor contraction of the heart, it may also raise its blood pressure. With pressure, a little squirt from a failing heart can “go further”: picture the effect on a slow-flowing garden hose when you partly cover the opening with your thumb. This form of compensation is OK for a little while, such as in the case of “fight or flight”, but working against this pressure day and night overworks the heart, and wears it out faster. If high blood pressure is a factor in a cat’s condition, then blood pressure medication may be prescribed.
Small Breed Dogs:
The most common form of heart disease that little dogs develop is heart valve disease. It usually involves the Mitral Valve, the valve that separates the left atrium from the left ventricle, and so is called Mitral Valve Disease (MVD).
The flaps of the valve degenerate, becoming thick and stubby. These shorter valve flaps no longer meet in the middle – the valve does not seal tight.
The left side of the heart has the job of receiving nice oxygenated blood from the lungs, and giving it a good strong push to distribute it to all the far corners of the body. The atrium is the receiving chamber; it squeezes the blood through the mitral valve, down into the left ventricle which is the strongest pump chamber of the heart. The mitral valve is meant to be one way – down from the atrium, into the ventricle, then sealed shut when the ventricle is giving its mighty push.
When those valve leaflets don’t meet anymore, they leave a gap – this means that when the left ventricle gives its push, not all the blood heads down the road; some leaks back upstream. The result is that upstream comes to be under too much pressure. Since upstream of the heart are the lungs, the blood pressure in the lungs goes up. Fluid leaks out of the overfull lung vessels, into the lungs’ air spaces. The result is shortness of breath and a wet cough, especially when exercise or excitement increase the demands on the heart.
Treatment of MVD involves decreasing the fluid overload with diuretics (“water pills”), and medications to decrease the back pressure that the heart has to push against, so that there is less tendency for blood to go backwards through the leaky valve.
Some breeds of dogs…:
The other form of acquired heart disease we see is less common – it tends to occur in certain breeds of dogs, as it has a genetic component. It is called Dilated Cardiomyopathy (DCM). Some of the breeds that are predisposed to this condition include Cavalier King Charles Spanial, Boxers, and Doberman Pinschers.
This is the opposite of the heart muscle disease seen in cats – instead of getting thick and stiff, the heart muscle becomes soft and flabby. This damaged muscle just does not have the push it needs to send the blood along.
Treatment is based on reducing fluid overload with diuretics (“water pills”), and medications to boost the “oomph” of the heart muscle.
We can’t cure these heart diseases – we don’t have the means or resources to replace heart valves or do heart transplants in pets. But we can manage them. Medications, along with dietary management and even some supplements, can help keep an affected pet feeling as good as possible for as long as possible.