Disease and Illnesses of dogs – Heart Failure


Heart disease is present in around 15% of dogs in the UK. This can progress to heart failure, often called “Congestive heart failure” or CHF. It is a progressive disease which, without veterinary intervention, will slowly worsen; dogs do not have a sudden heart attack as people can.

The heart is a muscular pump with four chambers which pumps blood to the lungs to pick up oxygen and then around the rest of the body to deliver that oxygen and pick up waste products. The heart can compensate for disease for a while but heart failure will follow when the heart cannot compensate any longer and the pump is not sending enough blood around the body. There are a variety of medicines that can be used to support the heart and keep dogs with heart disease comfortable for sometimes quite long periods of time.

What are the symptoms of heart failure in dogs?

Symptoms are mainly related to fluid that has not been effectively pumped by the heart, building up in various areas of the body. These include:

  • Lethargy
  • Weight loss
  • Inappetence
  • Exercise intolerance
  • Coughing due to fluid in the lungs
  • Wheezing or struggling for breath
  • Pale gums
  • Swollen abdomen due to fluid retention – called “Ascities”

If you notice any of these signs then you should have your pet examined by the vet as soon as possible. A history of the above signs will arouse the vet’s suspicion of heart disease and they may also detect things such as weak pulses, an enlarged liver or crackles in the lungs which would all point towards heart failure. A heart murmur is also often heard. This is an abnormal “swoosh” sound that is heard between or during normal heart sounds and is caused by turbulent blood flow.

What causes heart failure in Dogs?

The underlying causes of heart failure can be broadly divided into acquired disease and congenital disease.

Acquired disease

Acquired disease is disease that has developed over the course of the animal’s life, often due to general wear and tear but sometimes as a result of other problems such as infection. Acquired heart disease includes:

  • Valvular disease: There are several sets of valves in the heart, dividing the chambers from each other and from the blood vessels entering and leaving the heart. They can become hard and thickened with age or infection and as a result don’t close properly. Blood can then leak through the valves causing turbulent blood flow and meaning that less blood is being pumped around the body. Predisposed breeds: Usually smaller breeds including Cavalier King Charles Spaniels, Whippets, Miniature Schnauzers, Maltese terriers and Pekinese.
  • Myocardial disease: The myocardium is the heart muscle and if this becomes weakened then the heart pump is ineffective and starts to fail. The most common cause of this in dogs is a disease called Dilated Cardiomyopathy or DCM where the heart muscle becomes thin and the chambers dilate and cannotrelax or contract properly.  Predisposed breeds: Usually larger breeds such as Dobermans, Great Danes, St Bernards, Bernese Mountain dogs and Irish Wolfhounds. It is more common in males and there is probably an inherited component. DCM may also be set off by viral infection or a nutritional deficiency.
  • Pericardial disease: The pericardium is a protective sac around the heart. It can harden or fill with fluid and this will restrict the expansion and contraction of the heart, leading to heart failure. Predisposed breeds: Golden Retrievers
  • Arrhythmias: This is when a disturbance in the electrical conduction of the heart causes an abnormal heart beat. This can be too fast so that the heart doesn’t have time to fill before contracting again or too slow so that not enough blood is circulating in the body. Predisposed breeds:  Cavalier King Charles Spaniels, Boxers, Dobermans and Irish Wolfhounds.

Congenital disease

Congenital disease is a disease that an animal is born with. With heart disease, these are usually anatomical defects and can be detected by a heart murmur.  Congenital heart defects include:

  • Patent Ductus Arteriosis (PDA): A blood vessel which bypasses the lungs in an embryo. It should close but can remain open, leading to heart disease.
  • Pulmonary or Aortic Stenosis (PS/AS): A narrowing of either the Pulmonary Artery (main vessel to the lungs) or Aorta (main artery to the rest of the body) causing resistance to smooth blood flow.
  • Ventricular or Atrial septal defects (VSD/ASD): The muscle wall between the two sides of the heart fails to close properly, leading to a hole in the heart causing mixing of bloods from both side and turbulent blood flow.

How can heart disease in dogs be diagnosed?

The clinical signs and history described above would be very suggestive of heart disease but further tests may be needed. These may include imaging of the heart and lungs, often by chest x-rays or ultrasound of the heart. An electrocardiogram or ECG can also be performed which shows the electrical conduction of the heart. Occasionally other tests such as blood screens will be advised to check things like kidney function.

How can heart failure in dogs be treated?

Angiotensin Converting Enzyme Inhibitors (ACEI): These are drugs that suppress the compensation of the heart which relieves stress on the heart therefore reducing damage. These are drugs such as Fortekor and Benazecare which contain the ACEI benazapril, Vasotop which contains ramipril and Enacard which has the active ingredient enalapril. These are a mainstay of treatment of heart disease and can be given alone or in combination with other drugs.

Diuretics: These are drugs which cause the body to reabsorb fluids from places that it shouldn’t be such as the lungs and abdomen as described above. The fluid is absorbed into the bloodstream then these drugs act on the kidney which produces more urine to get rid of the fluid. There are different diuretics which act on different parts of the kidney. These include Frusemide or Frusecare, frusemide is the active ingredient and also Prilactone which contains spironolactone. These drugs can be used separately or together and your vet may want to monitor kidney function when using these drugs.

Inotropes: An inotrope is a drug which causes the heart muscle to pump more strongly and they are often combined with agents which slow the heart rate, giving it more time to fill fully with blood. Vetmedin is an example of this used in veterinary medicine and this contains the drug pimobendan and can be very helpful when used in combination with the other classes of drugs.

There are other drugs that may be used depending on the specific heart disease that your pet is suffering from such as drugs to control blood pressure or abnormal heart rhythms.

Diet and exercise are also very important. Animals with heart disease are often exercise intolerant but it is important not to let these animals become overweight as this can worsen the heart disease. There are prescription diets specially formulated for animals with heart disease such as Hills h/d and RCWC Cardiac. These diets are low in salt so as not to raise blood pressure which can further damage the heart.

Surgery: In a small number of cases there may be a surgical solution to the heart disease but this is only rarely done and is incredibly specialist surgery. Cases where this may be indicated are in some of the congenital defects that can be fixed surgically, implanting a pacemaker in dogs with dangerously slow heartbeats or in cases of pericardial disease and the protective sac around the heart can be removed if needed.

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