Heart Murmur Heart Disease Screening in Dogs

Dr. Woody Dudley, DVM

What is a heart murmur?

Heart murmurs are exaggerated heart sounds heard with a stethoscope. The sound of a heart murmur is detected due to turbulent blood flow in the heart often caused by valve abnormalities. There are 4 chambers to the heart, right atrium, right ventricle, left atrium, left ventricle. There are valves between the heart chambers along with the pulmonic and aortic valves. The valves are designed to move blood in one direction. When they don’t close completely, and “leak” in the opposite direction, an unusual sound is heard with the stethoscope. Sometimes the valves such as the aortic and pulmonic can be too small in diameter and cause murmur sounds as well.

The most common cause of a heart murmur in adult dogs is due to mitral regurgitation (leaky valve). This is a defective valve between the left upper chamber (left atrium) and left lower chamber (left ventricle). This is commonly seen in small breed dogs and Cavalier King Charles Spaniels. We can also hear heart murmurs in our large breed dogs such as Doberman Pinschers and Boxers that have a heart condition called Dilated Cardiomyopathy, a heart that doesn’t contract as well as it should. Loud heart murmurs in puppies and young growing dogs may need a Cardiologist’s opinion since they can be caused by congenital defects.

What should be done if my dog has a heart murmur?

First, don’t panic. Heart murmurs are often found early before any symptoms are present.

Early detection of heart murmurs and heart disease is important for lengthening your pet’s lifespan, quality of life, and planning for the future. Early detection leads to early diagnosis, early treatment, and better outcomes, as well as a way of reducing anesthetic risk for procedures such as teeth cleaning or surgery.

Heart murmurs are frequently detected before symptoms of heart disease occur. An inexpensive ultrasound screening should be done when a heart murmur is detected. The ultrasound will determine if heart disease is present. Ultrasound will also determine the stage of heart disease. Heart disease often gets worse with age. The valves often become leakier and the murmur gets louder. Over time the heart starts to enlarge to compensate for the extra work required with the leaky valve. The structure and size of the heart can be seen with ultrasound. If enlargement is obvious on ultrasound, such as enlargement of the Left Atrium, X-rays may be recommended as well. When the heart becomes significantly enlarged, medication can be given to improve heart contractions and delay heart failure.

Once Heart Disease has been diagnosed, we recommend an Ultrasound Screening every year to follow the progression of heart disease. In addition, an Electrocardiogram screening every year will help detect abnormal heart rates as well as irregular heartbeats that can occur in heart disease even though symptoms are not obvious.

How can we monitor Heart Disease at home?

Early symptoms of Heart Disease include tiring easily after exercise and coughing especially at night. The respiratory or breathing rates may increase as well. Monitoring sleeping respiratory rate at home is a good early test of heart disease and heart failure. If the sleeping respiratory rate is greater than 30, your dog should be brought into the Animal Hospital for a Heart Disease Evaluation, which includes a physical exam, ultrasound, and electrocardiogram. Chest X-rays may also be needed.


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