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Causes of Heart Disease in Dogs

A Summary of the Types of Canine Heart Disease

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Heart disease in dogs can have many different causes.

Heart disease in dogs can have many different causes.
Photo courtesy of epSos.de/Flickr.com

Heart disease is dogs is commonly encountered. There are many potential causes of canine heart disease and, depending on the severity of the disease, any form of heart disease can lead to heart failure.

Types of Canine Heart Disease

Heart disease in dogs can be congenital or acquired.

  • Congenital heart disease is present at birth. It may or may not be inherited from the parents.
  • Acquired heart disease occurs most often because of "wear and tear" on the heart structures but may also occur as a result of injury or infection. Middle-aged to older dogs most often suffer from acquired heart disease.

Causes of Congenital Heart Disease in Dogs

There are several types of heart defects that can cause congenital heart disease.

  • Patent ductus arteriosus (PDA) is the most commonly diagnosed congenital heart defect in dogs. It occurs when the vessel that connects the aorta and pulmonary artery in the developing fetus (known as the ductus arteriosus) does not close properly shortly after birth, as it should.
  • Aortic stenosis (or subaortic stenosis) is most commonly seen in large breed dogs. Aortic stenosis results in a narrowing or partial blockage of the aorta as it leaves the left ventricle of the heart. The aorta is responsible for transporting blood to the rest of the body.
  • Pulmonic stenosis is a narrowing of the valve which allows blood to flow from the heart to the lungs. It is the third most common congenital heart defect seen in dogs.
  • Ventricular septal defects result from an abnormal communication (a "hole") between the right and the left ventricle of the heart.
  • A persistent right aortic arch results from a fetal structure (known as an aortic arch) that does not deteriorate as normal but instead encircles the esophagus, causing abnormalities in the growth and function of the esophagus.
  • Other less commonly encountered canine congenital heart defects include abnormal openings between the right and left atria (atrial septal defects) and malformation of the valves of the heart (mitral and tricuspid dysplasia). Persistent left cranial vena cava and tetralogy of Fallot are also uncommon causes of congenital heart disease in the dog and are both developmental defects of the canine heart.

Causes of Acquired Heart Disease in the Dog

Acquired canine heart disease can take many forms.

  • Valvular disease can affect any breed of dog but is particularly common in small breed dogs. The mitral valve is most commonly affected but other valves of the heart may be affected as well.
  • Myocardial diseases, also known as cardiomyopathies, affect the muscle of the heart. Cardiomyopathies are commonly diagnosed in large breed dogs.
  • Cardiac arrhythmias are abnormal heart beats or heart rhythms. These result from disease that affects the electrical system that regulates the heart and makes it beat properly.
  • Pericardial disease affects the pericardium of the heart, which is the sac that surrounds the heart. When the pericardium becomes diseased, it can restrict the heart and result in the heart being unable to beat properly.
  • Injuries to the heart and infections of the heart (such as heartworm infection or parvovirus infection) can also cause acquired heart disease.

Many of these heart diseases cause similar symptoms. Proper diagnosis is necessary in order to adequately treat any canine heart disease.

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