Congenital heart disease in dogs
Congenital heart diseases are heart malformations present from the birth of the animal. They affect 0.5% of dogs in general, and reach a little less than 1% of purebred dogs. What are these heart defects, what do they cause and how can they be treated?
A congenital disease means present from birth, but it is not necessarily hereditary. It results from a defect in embryonic development and can therefore be due to an infection, a toxic substance, a trauma during gestation or be transmitted by a parent (hereditary).
What are the main congenital heart diseases in dogs?
Heart valves can be abnormal in shape (too narrow, malformed), in location (too low, too high) and can then prevent the heart from properly sending blood flow into the vessels when it contracts.
- Pulmonary stenosis is quite common. The pulmonary valve that separates the right ventricle from the pulmonary trunk (the large vessel that exits the heart towards the lungs) is abnormally thickened, fibrous and diminishes and impedes the passage of blood. The right ventricle must therefore force blood out of the heart abnormally and right heart failure ensues. This leads to the symptoms of fatigue, syncope, ascites (accumulation of liquid in the abdomen).
- Aortic stenosis is also relatively common. The narrowing is in the aorta that leaves the left ventricle to distribute blood to all other organs of the body. This narrowing can be due to a malformed aortic valve or to a fibrous subaortic flange. The left ventricle has to work harder to send blood to the general circulation, which causes a left heart failure. The symptoms are fatigue on exertion, syncope, and complications such as pulmonary edema.
- Tricuspid dysplasia affects the tricuspid valve (which lies between the atrium and the right ventricle). There is usually a dilatation of the right atrium and the right ventricle, heart rhythm disorders... This anomaly is rarer.
- Mitral dysplasia affects the mitral valve (which is located between the atrium and the left ventricle) and is also very rare.
Abnormal communications between the chambers of the heart or vessels leaving the heart
The persistence of the ductus arteriosus is the 3rd most frequent anomaly after pulmonary and aortic stenosis. The ductus arteriosus is a communication between two vessels that normally closes in 4 to 5 days when the baby is born and starts to breathe. It shunts blood to the lung while the fetus is in the uterus and receives oxygenated blood from the placenta. If the ductus arteriosus persists, this leads to poor oxygenation and therefore to significant fatigue. Heart failure develops.
Ventricular septal defect: there is a hole in the wall between the two ventricles, which makes the right heart communicate with the left heart.
The inter-atrial communication
More complex malformations or several malformations combined
Tetralogy of Fallot combines 4 anomalies: pulmonary stenosis, ventricular septal defect, malposition of the aorta, and right ventricular hypertrophy.
The triatrial heart.
How can congenital heart disease in dogs be treated?
For a precise diagnosis of these malformations an echocardiography with doppler is essential. On auscultation a murmur can be heard but without imaging it is impossible to tell which malformation it is.
As these heart diseases are mainly malformations, a surgical correction is often necessary.
However, surgery is not always affordable and sometimes technically impossible... In any case risky.
Some malformations are operable and can be cured after surgery (e.g. persistent ductus arteriosus).
The medical treatment is that of cardiac insufficiency if it is present, i.e. signs of decompensation of the heart: oedema, breathlessness, etc...
Of course it is necessary to limit the physical exercise of dogs affected by these malformations.