Congestive heart failure (CHF) is a failure of the heart to distribute an adequate amount of blood to the body. The heart is nothing more than a sophisticated pump that consists of two smaller chambers called atriums and two larger ones placed underneath called ventricles. They communicate through the valves that allow movement of blood in one direction only.
The left side of the heart shifts the blood that comes from the lungs to the periphery of the body and consists of left atrium, bicuspid (mitral) valve and left ventricle. The left ventricle pumps the blood into the aorta and from there the blood vessels become smaller and smaller.
The right side of the heart receives blood from the periphery of the body and delivers it to the lungs where oxygen gets absorbed and the blood ends up in the left side of the heart. The right atrium, tricuspid valve and right ventricle make up the right side of the heart.
What are the risk factors for CHF?
CHF is a common problem in a small animal practice and usually affects middle age to older dogs and cats. It may occur at a younger age as well if toxins or congenital problems are involved. Small breeds appear to be affected more frequently and there is a proof that some congenital disorders have a genetic component. Pre-existing conditions such as a chronic chough, hyperthyroidism, anaemia (low blood cell count), pregnancy and lack of heartworm prevention can cause or contribute to congestive heart failure.
What causes CHF in dogs and cats?
There are many things that can go wrong inside or outside of the heart and can lead to CHF. Both sides of the heart can be affected with similar problems that can be grouped into:
• Heart muscle failure (dilated heart e.g. dilated cardiomyopathy)
• Pressure overload of the heart (hypertension, heartworm disease or birth defect)
• Volume overload (chronic damage to valves)
• Reduced filling of the heart ( presence of fluid or tumour around the heart e.g. pericardial effusion and thickened heart muscle )
• Problems with heart rhythm (skipped heart beat, slow heart beat, rapid heart beat)
It is important to remember that although the problem can involve one side of the heart initially, in the end both sides of the heart can become affected.
How do I know that there is a problem?
Exercise intolerance, pale mucous membranes, difficulties breathing and coughing especially at night are common symptoms. Cats usually do not cough as a result of CHF. Other symptoms that can be seen are abnormal heart rhythm, muffled heart sounds, heart murmurs, enlarged liver and free fluid in the abdominal cavity. The latter two are usually not seen in cats.
Are the symptoms enough to diagnose congestive heart failure?
The simple answer is no. The symptoms may help us make provisional diagnosis but additional tests are needed. Early stages of heart failure may be confused with respiratory disease which has different treatments.
The additional tests that are useful in diagnosing or assessment of the patients with CHF are;
1. Blood tests (full bloods and proBNP). A full blood profile tells us about the general body condition and if other concurrent problems are present such as kidney failure, electrolyte imbalance or anaemia. ProBNP is the latest blood test that can detect early heart problems. It tests for a special peptide (type of protein) released by a diseased heart muscle.
2. X rays are a very useful tool for assessing the size and shape of the heart. Heart shape can give us an indication of the cause of the problem. Also it gives us an opportunity to check the lungs for any abnormalities or to look for tumours.
3. Heart ultrasound looks into the heart and its structures, anomalies, issues with heart valves or to assess the thickness of the ventricles.
4. ECG can help us reveal abnormalities in the conduction of the impulse through the heart muscle.
How can I help my pet?
Congestive heart failure can often be managed by an early diagnosis. Many dogs will be treated as outpatients but the initial assessment is crucial. Your vet must know exactly how severe your pet’s condition is in order to treat it successfully.
The basics of the treatment are:
1. Remove excessive fluid from the lungs and make it easier for the patient to breathe.
This is usually achieved by medications called diuretics. The most common drug used is furosemide that makes the body lose excessive fluid through the kidneys.
2. Support the heart muscle by either improving the contractions of the heart or dilating the blood vessels to make it easier for the heart to pump the blood out. Pimobendan (Vetmedin) and benazepril (Fortecor) are two frequently used. Pimodenan does both while Benazepril dilates blood vessels only.
3. Correct heart arrhythmias. There are many different types of heart arrhythmias and the treatment can be pretty complex.
4. Supportive treatment (low salt diet, oxygen).
5. Restricted exercise. It is important to remember that strenuous exercise puts an enormous pressure on the heart and should be avoided. Only leash walks are recommended for pets with moderate to severe heart failure.
6. Surgical intervention. Tapping the chest and abdomen to remove excessive fluid can be done successfully in general practice and improves the effectiveness of the treatment.
Correction of certain congenital deformities is possible however some surgeries need a high degree of skill and are performed at specialist centres only.
Every pet with heart disease is a different story. While some can be treated with a simple combination of drugs and six monthly check ups, others need much more. It is virtually impossible to predict how quickly the disease may progress and this is why regular checkups are important. Our vets will develop a treatment plan depending on each individual case. Regular checkups give us an opportunity to see if the treatment is working and how your pet is responding to it. Blood tests to monitor kidney function and electrolytes are always recommended.