Heart disease is common in both cats and dogs. Diseases can either develop over time—generally as the result of age-related degenerative changes—or may be present at birth.
Diseases present at birth or related to your pet’s breed are known as congenital heart diseases. Many of these diseases may manifest with similar symptoms, though small detectable changes can help delineate one disease from the next.
Congenital heart disease is a serious condition. If your pet is an at-risk breed, or shows signs of slowing down, coughing, exercise intolerance or collapse, seek veterinary attention. If your veterinarian hears a heart murmur, especially at a young age, request a referral to a veterinary cardiologist.
Congenital heart disease can affect up to 17 percent of dogs, and up to 5 percent of cats. Here, we’ll review some of the most common conditions:
Subaortic Stenosis (SAS)
The most common congenital heart disease in dogs is subaortic stenosis (SAS). This disease manifests as a narrowing of the outflow tract involving the aorta, the body’s largest blood vessel tasked with delivering blood to the abdominal organs. SAS is very common in Newfoundlands.
Similar to other congenital heart diseases, a heart murmur may be detected over the left side of your pet’s heart, specifically near the top of the heart. The louder the heart murmur, the worse the disease. A diagnosis is usually achieved via ultrasound of the heart, though radiographs of the heart and lungs can be suggestive.
Treatment reduces clinical signs—such as weakness, exercise intolerance and fainting—associated with the disease. This usually involves medical therapy to prevent arrhythmias and slow the heart rate down.
Other treatments, such a surgical excision, are sometimes possible if extra tissue surrounding the aorta is present. Additionally, valvuloplasty—entering a balloon into the heart and stretching the narrowed vessel—may be considered.
Pulmonic Stenosis
Although rarely seen in cats, pulmonic stenosis is the third most common congenital heart disease in dogs. It involves a narrowing of the main pulmonary artery or pulmonic valve that is responsible for delivering blood from the heart to the lungs.
On a physical examination, your veterinarian may hear a heart murmur (an abnormal “swoosh”) over the left side of your pet’s heart, near the top where the pulmonic valve sits. A diagnosis is usually achieved with an ultrasound of the heart.
Treatment can be pursued with valvuloplasty, and medication may also be required. More than 50% of dogs will experience improvement in their clinical signs.
Ventricular Septal Defect (VSD)
Ventricular septal defect (VSD) is one of the most common congenital heart issues in cats. Although rare in most dogs, it’s seen frequently in English Springer Spaniels.
Essentially, there is a defect in the heart that allows passage and mixture of blood between chambers. The most common clinical finding is a murmur, similar to a washing machine sound. An ultrasound of the heart usually provides a more specific diagnosis in terms of location, as well as its severity.
Medical therapy is used for patients experiencing symptoms and those who develop heart failure.
Patent Ductus Arteriosus (PDA)
Patent ductus arteriosus (PDA) is a result of an abnormal blood vessel that should “close” while a pet is in the mother’s womb. When it fails to close, blood is prevented from entering the lungs and becoming oxygenated.
PDA is commonly seen in dogs, particularly Maltese, Poodles and Pomeranians. It is occasionally observed in cats.
Some PDA patients will not thrive or grow and may be considered “runts” of the litter. A continuous murmur may be detected on physical examination, and some pets may develop congestive heart failure. Ultrasound of the heart is typically required for a definitive diagnosis.
Surgically correcting the defect is one of the most common methods of treatments. Non-invasive catheterization with a device that blocks the vessel (and then allows it to regress) is also an option.
Mitral Valve Dysplasia
Mitral valve dysplasia is a malformation in one of the valves that connects the upper and lower chambers of the heart.
On physical examination, your pet may have a heart murmur over the right side or left side of the heart. X-rays of the chest may provide evidence of an enlarged heart. Ultrasound of the heart usually provides a definitive diagnosis.
Dogs can develop heart failure as a result; medical therapy may be instituted prior to or at the start of heart failure. Although valve replacement is an option in human patients, it’s extremely rare in animals.