HEART DISEASE IN DOGS
The heart is a unique organ, different from any other in the dog’s body. It consists of 4 chambers, all of which contain blood and are responsible for sending blood that is low in oxygen to the lungs to receive more oxygen, then sending this oxygen-rich blood throughout the body to all the tissues in need. A series of valves in the heart separate these 4 chambers, preventing blood from flowing where it shouldn’t.
For dogs suffering heart disease it is generally the valves of the heart that become affected rather than the heart muscle. The four chambers in the heart are divided into right and left sides, each with its own set of valves. In some breeds of dogs — Poodles, Cocker Spaniels, Yorkshire Terriers — there is a predisposition, possibly genetic, towards developing problems with the heart valves although any breed can be affected.
The heart valve itself becomes blunted, or rounded, and fails to close properly, leading to ‘back-flow’ of blood, which results in an overload of blood in the chamber receiving the back-flow. Over time, this overload of blood can stretch the receiving chamber, causing it to enlarge. Chamber enlargement may put pressure on the main airway in the lungs (the trachea or windpipe), resulting in a dry, hacking cough. Stretching of the chamber may also disturb the heart’s rhythm, resulting in an arrhythmia.
Disease of the heart muscle is much less common than that of heart valve disease. Heart muscle disease can be inherited, and is often seen n Cocker Spaniels, Boxers, Great Danes, and Doberman pincers. Other breeds can also be affected.
For dogs affected by this form of heart disease, the heart muscle shrinks, or atrophies. This reduces the effective pump of each heart beat, meaning the weakened heart muscles fail to pump blood adequately to the tissues of the body.
SEVERITY: Chronic. Treatable with appropriate medication
A cough is often the first sign of heart disease. Over time, the overload of blood in the chamber can stretch the receiving chamber, causing it to enlarge and resulting in dry, hacking cough. Stretching of the chamber may also disturb the heart’s rhythm, resulting in an arrhythmia.
Most commonly, the overflow of blood can also back up into the lungs, resulting in a ‘wet,’ productive sounding cough.
Patients can also become weak, stop eating, or eat less or much more slowly, and sleep a good portion of the day. Sometimes they will collapse, showing signs of stiffness in the legs and arching back their head. During these collapsing episodes, the patient may also lose control of their bladder, bowels, or both. Clients often refer to these episodes as ‘seizures,’ although technically they are not. When this occurs, the patient is considered to be in heart failure and both owner and vet will be faced with an emergency. Much better to bring in your dog for an examination if or when you see the earlier telltale signs. Diseased heart muscles can cause similar signs to those seen in heart valve disease — weakness, decreased appetite and cough.
Diagnosis is by physical examination, X-rays, and auscultation, which, in larger animals, helps us to pinpoint the affected valve (PAM on the left and Tricuspid on the right side of the chest).
If the condition is non responsive to medication, or a more definitive diagnosis is required we will refer the patient to a veterinary cardiologist, who may use an electrocardiogram (ECG) or ultrasound of the heart. Specific tests are then used to determine what form of heart disease exists.
Appropriate treatment is aimed at reducing the backflow of blood, reducing the size of the heart if enlarged, strengthening the heartbeat itself, correcting abnormal heart rhythms, and clearing fluid back-up in the lungs. We have a number of medications available to us that have been specifically designed to treat these conditions, either singly, or in combinations with other drugs.
In some cases of heart muscle disease nutrient supplements may be used. L-carnitine, and Taurine are two essential amino acids that are often found to be deficient in some cases of heart muscle disease in dogs, which has prompted the development of specialised cardiac diets designed to help dogs and cats with heart disease. These can be very helpful in controlling symptoms.
These days most canine heart disease can be successfully treated with long term medication but surgery is sometimes an option in some cases.