Client Information Sheet Copyright Bilton Veterinary Centre 2016. All rights Reserved
Congestive Heart Failure and Valvular Insufficiency The heart is a complex organ, and essentially has two major purposes: 1. To receive “used” deoxygenated blood from the rest of the body and pump it to the lungs ready to be oxygenated again. 2. To receive freshly oxygenated blood from the lungs and pump it around the rest of the body. Now in order to fulfill both the major purposes explained above, the heart is divided into two distinct areas, the left and the right side. Both sides essentially are a self-contained unit and so it is best to think of the heart as having two separate pumps.
The RIGHT SIDE (deoxygenated blood)
Right atrium – receives “used” deoxygenated blood from the rest of the body. When it contracts it pushes blood through the tricuspid valve into the right ventricle. Right ventricle –receives blood from the right atrium and when it contracts, it pushes blood out of the heart to the lungs, via the pulmonary artery. Tricuspid valve –prevents flow back from the right ventricle into the right atrium. For more information, visit: www.biltonvets.co.uk/advice.html Page 1 of 5
Client Information Sheet Copyright Bilton Veterinary Centre 2016. All rights Reserved
The LEFT SIDE (oxygenated blood)
Left atrium – receives freshly oxygenated blood from the lungs. It contracts and pushes blood through the mitral valve into the left ventricle Left ventricle – receives blood from the left atrium. A highly muscular part of the heart, this is responsible for contracting and pushing oxygenated blood around the whole body, via the aorta. Mitral valve – prevents flow back from the left ventricle into the left atrium.
The Pulmonary Artery and Aorta also have valves in them, to prevent blood flowing back into ventricles after a contraction. These are called the Semi-lunar valves.
What is valvular insufficiency? Valvular insufficiency occurs when either the tricuspid valve (on the right side), or more commonly the mitral valve (on the left side) become diseased and no longer become watertight. This means that when the ventricle contracts, a proportion of blood is allowed back through the faulty valve in the atria again, rather than being pushed out of the correct vessel to either the lungs (right side) or rest of body (left side). Essentially the one-way system in the heart is disrupted. Valvular can occur for a number of reasons including:
Normal degenerative processes (this is most common and tends to occur in middle-age to older dogs). Inherited or genetic weakness or predisposition. Heart valve infections (called endocarditis). This type of infection usually occurs due to a blood borne infection, often from another infective source – such as dental disease. Cancer. What this disruption of blood flow means is that the atria have to work extra hard as they do not only have to pump their normal load of blood, but they have to cope with the extra blood which has leaked back from the ventricle. This increased load on the atria tends to have two effects: 1. The atria start to stretch due to the extra blood. This causes the heart to get bigger and is why we talk about cardiac enlargement. 2. The atria get weaker as they are having to work extra hard to pump the additional blood load. For more information, visit: www.biltonvets.co.uk/advice.html Page 2 of 5
Client Information Sheet Copyright Bilton Veterinary Centre 2016. All rights Reserved
What are the signs of valvular insufficiency? The signs will vary from each animal, and also depends a lot as to which valve it primarily affects. Signs may include:
Heart murmur. This is often the first time a problem is noticed. The abnormal blood flowing backwards through the damaged valve causes the murmur. Heart murmurs are graded on a scale from 1 (very mild) through to 6 (very severe), and your vet will often use this scale to help monitor any deterioration of the condition. (Note: not all heart murmurs are caused by valvular insufficiency.)
Coughing. This may be particularly at night-time but can progress to day time as well. Retching and nonproductive gagging may follow the cough. This is due to fluid building up on the lungs and/or the enlarged heart pressing on the windpipe. You may also notice increased panting and heavier breathing.
Exercise intolerance. If the heart is not pumping enough blood around the rest of the body, you may find your pet tires easily or becomes quite lethargic.
Fainting. This may occur if a sudden increase in heart output is required which the body can’t manage. For example running up the stairs, or during exercise.
Fluid retention. This often occurs in the abdomen, giving the animal a “pot-bellied” appearance. This is called Ascites.
Rhythm disturbances. The heart enlargement that takes place is more of a stretching action rather than physical growth. This means the physical mass of the heart stays the same and so all the links between each cell/tissue etc are put under extreme pressure. This reduces the contact between each part of the heart and so the electrical activity that is required to coordinate each heartbeat can sometimes become faulty. This means that some animals can have very erratic or random heart beats.
The symptoms above are all a signs of the heart starting to struggle, and this type of heart failure is known as “congestive heart failure”. It is a term used to describe the progressive and insidious deterioration typically seen this with type of disease.
What breeds are affected? In dogs, valvular insufficiency (particularly Mitral Valve Disease) can affect any breed, however it is much more common in small/medium breeds such as Terriers and the Cavalier King Charles Spaniel is very commonly affected. Congestive Heart Failure is seen commonly in the cat but more commonly due to various different type of structural heart disease affecting the heart muscle (called Cardiomyopathies)
Figure 1 - The Cavalier King Charles Spaniel is commonly affected with Mitral Valve Disease and Congestive Heart Failure
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Client Information Sheet Copyright Bilton Veterinary Centre 2016. All rights Reserved
What tests are needed? A good thorough examination is going to be necessary if we are suspicious that your pet may have congestive heart failure. Physical exam may show the following:
Pale mucus membranes (implying poor perfusion)
Reduced Capillary Refill Time (CRT). If you press your fingernail, it goes white initially and then quickly returns to being pink again. In dogs, we test this by pressing on the gums or inside of the lip. Normal should be under 2 seconds to refill.
Checking the pulse rate and quality (often in the groin) Listening to the heart and lung sounds. Measuring the blood pressure.
Further tests may be required if we feel that heart failure is present. These may include:
Ultrasound (echocardiography) can be performed to try to directly visualize the damaged valves and also can be used to measure the degree of heart enlargement. This is usually the test of choice.
Blood tests to check to other underlying conditions or testing for evidence of heart muscle damage.
X-rays to check for heart enlargement or lung disease.
ECG performed to check the electrical activity of the heart. This can often give
Figure 2 - This echocardiogram is from a dog with mitral valve disease. The Atrium is very stretched and dilated and is considerably wider than the ventricle. In normal animals, these measurements should be approximately the same.
clues as to the degree of heart enlargement/insufficiency. Most of these tests can be performed at the Bilton Surgery, but some may require referral to a specialist cardiac vet nearby.
Figure 3 - A dog having an ECG done. Most animals are happy to have the ECG done just lying down. It is very simple and non-invasive.
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Client Information Sheet Copyright Bilton Veterinary Centre 2016. All rights Reserved
What is the treatment? Treatment is entirely medical as currently there are no operations to help manage this condition. With the exception of a valve infection (endocarditis), this condition cannot be cured, and so it is important to realise the treatment involves: “Delaying the inevitable onset of more severe clinical signs, whilst trying to manage any current clinical signs, and improving the quality of life.” A variety of drugs are available to try and achieve this and your vet may decide to use one or more of the following 1. ACE Inhibitors (ACEi Drugs). These are a group of drugs that help lower the body’s blood pressure and controls the amount of water contained in the blood stream. By doing this it reduces the amount of effort/work that the heart has to do in order to pump blood around the body. 2. Diuretics (“Water tablets”). These drugs work by helping the body to eliminate fluid that is accumulating in the lungs or abdominal cavity. They are used to reduce the cough associated with heart failure, and ascites. They do unfortunately make your animal want to drink and urinate a bit more. 3. Positive Inotropes. Can be used to help the heart contract more effectively and therefore pump blood around the body with more efficiency. 4. Anti-dysrhythmic treatment. Are used to try and control any rhythm disturbances that may be present. Rhythm disturbances are caused by abnormal/faulty electrical activity in the heart caused by chamber enlargement and heart muscle damage. 5. Low salt diets. Helps to control the amount of water in the blood and so also helps with blood pressure.
What is the prognosis with this condition? Longevity and quality of life in dogs with this disease vary with the severity of the valve damage and the amount of blood leakage into the upper chambers of the heart. Concurrent medical conditions, age, and the physical status of the pet play a large role in determining the animal’s prognosis. Clinical signs are progressive, and although they may be decreased, they never entirely resolve. Medical therapy can enhance the quality of life of the pet as well as increase life expectancy. Medical treatment will have continued through the animal’s life, and stopping the medication may have a severe and sometimes dramatic deterioration in the animal’s condition. When the clinical signs have progressed to a severe stage, you may find that the symptoms cannot be controlled well enough to allow a good quality of life, and so euthanasia may considered. Although heart attacks can occur, they are rare.
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