Heart Murmurs in Dogs and Cats
What is a Heart Murmur?
A heart murmur is an extra or unusual sound heard during a heartbeat. Murmurs range from very faint to very loud. They sometimes sound like a whooshing or swishing noise. Normal heartbeats make a “lub-DUPP” or “lub-DUB” sound. This is the sound of the heart valves closing as blood moves through the heart. Veterinarians can hear these sounds and heart murmurs using a stethoscope.
There are two types of heart murmurs: innocent (harmless) and pathologic (abnormal).
Animals that have innocent heart murmurs have normal hearts. They usually have no other signs or symptoms of heart problems and are more common in puppies and kittens under 6 months of age. We also see innocent murmurs in adult cats.
Animals that have pathologic murmurs may have other signs or symptoms of heart problems such as coughing, decreased activity, elevated or labored breathing. Most abnormal murmurs in puppies and kittens are due to congenital heart defects. These are heart defects that are present at birth. In adults, abnormal murmurs are most often due to heart valve problems caused by infection, disease, or aging.
About Innocent Heart Murmurs
Innocent heart murmurs are sounds heard when blood flows through a normal heart. These murmurs may occur when blood flows faster than normal through the heart and its attached blood vessels. Illnesses or conditions that may cause this to happen include fever, anemia (uh-NEE-me-eh), and hyperthyroidism (too much thyroid hormone in the body). Changes to the heart that result from aging also may cause some innocent heart murmurs.
About Abnormal Heart Murmurs
The most common cause of abnormal murmurs in puppies and kittens are congenital heart defects. These are problems with the heart’s structure that are present at birth.
These defects can involve the interior walls of the heart, the valves inside the heart, or the arteries and veins that carry blood to the heart or out to the body. Heart valve defects and septal defects (also called holes in the heart) are common heart defects that cause abnormal heart murmurs. Valve defects may include narrow valves that limit blood flow or leaky valves that don’t close properly.
Septal defects are holes in the heart muscle that separates the right and left sides of the heart. A hole in the muscle between the heart’s two upper chambers is called an atrial septal defect (ASD). A hole in the muscle between the heart’s two lower chambers is called a ventricular septal defect (VSD).
How is a Heart Murmur Diagnosed?
Veterinarians use a stethoscope to listen to heart sounds and hear heart murmurs. They often notice heart murmurs during routine checkups or physical exams. Once a murmur is noted the patients is usually referred to a veterinary cardiologist for further care and testing.
How is a Heart Murmur treated?
Some heart murmurs don’t need treatment because either the heart is normal or the impact of the heart disease is not significant at that time. If treatment is recommended the type of therapy recommended will depend on the underlying cause if the heart disease. For example, treatment for a congenital heart defect depends on the type and severity of the defect and may include medicine or surgery.
When an infection or disease causes a heart murmur, treatment depends on the type, amount, and severity of the heart disease.