Congestive Heart Failure in Dogs
Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS
Table of Contents
The heart contains four chambers, which work to pump deoxygenated blood from the body towards the lungs, and oxygenated blood from the lungs back around the body. Heart disease reduces the heart’s ability to pump blood effectively, usually due to the chambers becoming enlarged and weaker. Sometimes the heart’s rhythm is also affected, known as an arrhythmia. Eventually, changes become severe enough that the dog enters congestive heart failure (CHF).
When the heart is not pushing enough blood out around the body, the pressure within the heart increases. When the left side of the heart is affected, congestion develops in the blood vessels within the lungs, as they are unable to empty into the main vessels entering the heart. Fluid leaks from the blood vessels into the lung tissue; this is known as pulmonary oedema.
Less commonly, the right side of the heart is affected. This causes congestion in the veins in the abdomen, and can lead to fluid accumulation in the abdomen (called ascites) and in the chest cavity around the lungs (known as pleural effusion). It is uncommon for left and right sided heart failure to develop at the same time, though if severe enough, one can lead to the other.
Symptoms of left-sided CHF are due to pulmonary oedema, which affects the breathing. Symptoms include:
- reduced ability to exercise
- faster or laboured breathing
- excessive panting
- weight loss
- collapse (sometimes).
Dogs may have low blood pressure due to reduced cardiac output, making them weak, lethargic or off their food. Some dogs may cough, but this is more often related to enlargement of the heart and is not a reliable sign of pulmonary oedema.
The most noticeable symptom of right-sided CHF is distension of the abdomen due to ascites. Other than in very thin dogs, there usually has to be quite a large amount of fluid build-up before swelling is noticeable. Ascites creates pressure in the abdomen, so you may see a reduced appetite, difficulty getting comfortable, or more frequent need to urinate. If there is also a pleural effusion, dogs may find it harder to breathe or exercise, similar to with pulmonary oedema.
For many dogs who develop CHF we are already aware of a heart problem, either from previous diagnostics (such as ultrasound), or the presence of an audible murmur at routine checks. In these cases, compatible symptoms and clinical examination findings can make us very suspicious of a diagnosis, but do not confirm it.
Pulmonary oedema and pleural effusion can be diagnosed using ultrasound or x-rays of the chest. Ascites is diagnosed using ultrasound. In all cases, an ultrasound scan of the heart (known as echocardiography, or an “echo”) may be recommended to assess the underlying heart disease. If an arrhythmia is identified or suspect, an ECG may be advised to diagnose this. These investigations often need to be carried out by a vet with further training in cardiology to get a complete diagnosis.
Often blood tests to look at general organ health and specific cardiac enzymes are performed as a baseline before starting treatment, and to screen for other underlying conditions. Blood pressure measurement is advised as abnormal blood pressure may require additional treatment.
Dogs in congestive heart failure always require treatment, which is lifelong. It is not uncommon for dogs in heart failure to be on multiple medications every day. In large dogs especially, this can be costly.
The mainstay of treatment is diuretic therapy, which works to reduce fluid accumulation. This is most commonly a drug called Furosemide, which can be given by injection or as a tablet. Diuretic drugs cause increased thirst and urination, especially in the early stages of treatment. They can also affect electrolytes, such as potassium, and kidney enzyme levels, so periodic blood tests are recommended.
Other medication may be prescribed, depending on the underlying heart disease present. This may include additional diuretic drugs, medication to improve heart function (e.g. Pimobendan), or a category of drugs called ACE-inhibitors which help protect the rest of the body from the effects of heart failure (e.g. Benazepril).
Symptoms of CHF can develop rapidly, and may require immediate veterinary attention. For dogs who are very unwell at the time of diagnosis, often a short period of hospitalisation for intensive care is advisable. This allows medication doses and intervals to be tailored to the individual dog’s response, and drugs can be given by injection. The majority of cases will respond to treatment, but will need to continue taking oral medication at home for the rest of their life.
The prognosis for dogs in congestive heart failure is fairly guarded as the condition is progressive. Although some dogs will remain stable on medication for the rest of their life, others may stop responding to treatment, known as refractory congestive heart failure. The average survival time for dogs with CHF is around one year from diagnosis. This means that some will live longer than this, but others less. All dogs in congestive heart failure will need regular check-ups, and may need their medication doses adjusting over time.
One of the best measurements of congestive heart failure is an increase in respiratory (breathing) rate. Counting the respiratory rate is an easy way to monitor your pet at home. When your dog is calm and relaxed, count how many breaths they take in 15 seconds (in and out is one breath). Multiply this by four to get a respiration rate per minute. Normal dogs take less than 30 breaths per minute; if you repeatedly count over 40, or see a steady increase over several days, contact your vet. The smartphone app “Cardalis” can help with monitoring and recording respiratory rates.
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Page last reviewed: 16th January 2024
Next review due: 16th January 2026