What is heart failure?
Heart failure is the inability of the heart to pump enough blood to meet the dog's body needs.
A bit of anatomy to better understand
The dog's heart is made up of 4 cavities:
- On the left, we find: the left atrium (or left atrium) which receives blood from the lungs and the left ventricle which expels blood from the left atrium into the general blood circulation. The left atrium is separated from the left ventricle by the mitral valve, which prevents blood reflux in the opposite direction, and the left ventricle is separated from the aorta, the artery that opens at its exit, by the aortic valve.
- On the right: there is the right atrium (or right atrium) which receives blood from the rest of the body and the right ventricle which expels blood from the right atrium to the lungs. The right atrium is separated from the right ventricle by the tricuspid valve and the right ventricle is separated from the pulmonary artery by the pulmonary valve.
Depending on which side of the heart is causing the heart failure, we usually distinguish:
- right heart failure which leads to a slowdown in general blood circulation,
- left heart failure which leads to blood stasis in the lungs.
In rare cases, it happens that both parts of the heart, right and left, are affected at the same time. This is called right and left heart failure.
Causes of heart failure in dogs
Various conditions present from the birth of the dog or acquired can be the cause of right or left heart failure in dogs.
Congenital conditions causing left heart failure in dogs
Aortic stenosis
This is a narrowing of the aortic valve, this valve located at the exit of the left ventricle of the heart and the aorta, a large artery that carries oxygenated blood from the heart to all parts of the the organism. A narrowing at this level prevents the correct passage of blood and causes the left ventricle of the heart to dilate.
Several breeds of dogs are predisposed to it, such as the Boxer, the German Shepherd, the Dogue de Bordeaux, the Newfoundland, the Rottweiler or even the Golden Retriever.
Mitral dysplasia
Mitral dysplasia is a malformation of the mitral valve, the valve that normally prevents blood reflux between the left atrium and the left ventricle.These valve regurgitations cause dilation of the left atrium with hypertrophy of the left ventricle.
This type of malformation mainly concerns the following dog breeds: the Great Dane, the German Shepherd, the Bull Terrier, the Dalmatian, the Golden Retriever, the Mastiff, the Newfoundland and the Rottweiler.
The persistence of the arterial duct
This is an absence of closure of an arterial duct at the birth of the dog which joins the aorta and the pulmonary artery during the animal's fetal life. It causes an increase in pulmonary arterial pressure and, ultimately, dilation of the left and then right heart chambers, causing heart failure.
The Chihuahua, the German Shepherd, the Poodle, the Bichon Frisé, the Bichon M altese, the Shetland Shepherd, the Spitz, the Newfoundland or even the Yorkshire would be predisposed to this heart defect.
Interventricular communication
This heart defect consists of the presence of an orifice in the wall that separates the two heart ventricles, allowing the abnormal passage of oxygenated blood from the left ventricle to the right ventricle. The blood from the left ventricle which must go to vascularize the whole body is therefore in reduced quantity while the blood flow which leaves the right ventricle to go to the lung is increased causing an excess of blood in the lungs.
The Beagle, the Akita, the German Shepherd, the French Bulldog, the Basset Hound, the Westie, the Pinscher and the Shih Tzu would be predisposed to this fairly common heart defect in dogs.
Acquired heart conditions causing left heart failure in dogs
Several acquired heart conditions can cause left heart failure in dogs, such as:
- mitral endocardiosis, a degenerative disease of the mitral valve in dogs, this condition leads to a lack of tightness of the mitral valve which then no longer prevents the blood from flowing back against the current. Gradually, this condition tires the heart and leads to heart failure.
- mitral or aortic endocarditis, an inflammation of the wall of the heart valves, this condition is most often due to a bacterium which circulates in the blood of the animal and which comes from an infection located in another part of the dog's body (abscess, pyometra, urinary tract infection). It can also be favored by chronic diseases such as diabetes,
- dilated cardiomyopathy, a condition of the heart muscle that results in dilation of its cavities,
- high blood pressure,
- hypertrophic cardiomyopathy (also called hypertrophic obstructive cardiomyopathy), a relatively rare disease in dogs characterized by thickening of the interventricular wall and the free wall of the left ventricle,
- the presence of a heart tumour,
- pericardial effusion, in other words the accumulation of fluid in the pericardium (envelope that surrounds the heart),
- a myocardial infarction,
- pulmonary thromboembolism, an obstruction of one or more arteries supplying the lung.
Congenital conditions causing right heart failure in dogs
Pulmonary stenosis
Pulmonary stenosis refers to the narrowing of the outflow tract from the right ventricle of the heart to the pulmonary artery. This anomaly eventually leads to a thickening of the walls of the right ventricle of the heart, causing right heart failure.
The Tetralogy of Fallot
Tetralogy of Fallot in dogs is a congenital heart defect that combines four anomalies: pulmonary stenosis, interventricular communication, thickening of the walls of the right ventricle and anomalous position of the aorta.
Dog breeds known to be predisposed to Tetralogy of Fallot include Spitz, Miniature Schnauzer, Bulldog, Beagle, Border Collie, Poodle, Wirehaired Fox, and Shetland Sheepdog.
The persistence of the arterial duct
See above
Acquired heart conditions causing right heart failure in dogs
Several acquired heart conditions can cause left heart failure in dogs, such as:
- dilated cardiomyopathy,
- various chronic lung conditions that lead to pulmonary hypertension,
- the presence of a heart tumour,
- pericardial effusion,
- heartworm disease, i.e. the presence of worms in the dog's heart,
- pulmonary thromboembolism,
- constrictive pericarditis, a thickening of the envelope that surrounds the heart, thus hindering the expansion of the heart chambers and their proper filling.
Heart conditions causing right and left heart failure in dogs
More rarely, heart failure in dogs can affect the right and left heart in case:
- thyrotoxicosis, a disorder linked to an excess of thyroid hormones in target tissues,
- dilated cardiomyopathy,
- inflammatory damage to the heart muscle, called myocarditis,
- chronic anemia.
Dog heart failure: symptoms
In case of dog heart failure, we can notice in all cases:
- unusual fatigue and intolerance to effort, that is to say the inability for the dog to provide an effort, regardless of the circumstances, and to maintain this effort over time,
- difficulty breathing (dyspnea) and increased respiratory rate (tachypnea).
If the dog suffers from right heart failure, other symptoms may be added such as:
- abdominal distension: the dog may then have a big belly, a sign of ascites, that is to say an effusion of liquid in his abdomen,
- distension of the jugular veins,
- peripheral edema, i.e. swelling of the dog's paws.
Left heart failure can manifest as:
- increased breathing difficulties when lying down (orthopnea),
- cough, potentially caused by pulmonary edema, one of the most serious complications of heart failure.
Other clinical signs may appear such as loss of appetite, weight loss or even syncope.
Diagnosis and treatment of heart failure in dogs
Heart failure can be confirmed by various tests such as chest and/or abdominal x-rays, echocardiography, electrocardiogram and blood tests.
There is not just one treatment for heart failure but treatments for heart failure. These treatments differ according to the stage of evolution of the disease and the pathology which is at its origin. These treatments are generally accompanied by the administration of a low-sodium diet (low in sodium) and by a limitation of intense and/or prolonged physical exercise.
A dog suffering from heart failure must be regularly monitored by a veterinarian to monitor the progress of his disease, which is likely to worsen over time.