A Canine with a Systolic Heart Murmur

The phrase “systolic heart murmur” can terrify dog owners. However, the murmur is a symptom, not a disease. A heart murmur is either indicative of an underlying heart problem or completely innocent—puppies often develop short-lived murmurs during rapid growth. Understanding murmurs can help relieve the anxiety that accompanies the diagnosis.

A heart murmur is an abnormal heart sound that occurs as the result of a disturbance in blood flow. A systolic murmur, the most common heart murmur found in canines, occurs when the heart muscle contracts and pushes blood through the arteries. The murmur, or whooshing sound heard upon contraction, indicates something may be amiss with you buddy’s heart. Your veterinarian grades the murmur by intensity on a scale of I to VI. A grade I murmur is very quiet and may occur only intermittently, while a grade VI murmur is quite loud, and it’s possible to actually feel it by placing your hand over your dog’s heart.

Puppies are often diagnosed with benign, low-grade systolic heart murmurs that they eventually outgrow by 4 to 5 months of age. These “young murmurs” are the result of rapid muscular growth and the heart trying to “catch up,” so to speak. Systolic murmurs diagnosed in adult dogs are usually the result of structural heart problems, which are either congenital or acquired later in life. Common congenital causes of systolic murmurs include sub-aortic stenosis, pulmonic stenosis and patent ductus arteriosis. The two most commonly acquired causes are mitral valve disease and endocarditis. Extracardiac problems, those occurring away from the heart, can also cause a functional systolic murmur. Anemia, fever, infection and hypoproteinemia (low protein levels in the blood) commonly put strain on the heart and cause functional systolic murmurs.

Certain breeds can be predisposed to congenital heart problems or acquired heart problems, or both. Samoyeds and bulldogs are predisposed to congenital septal defects. Congenital dysplasia affects Great Danes, Labrador retrievers, German shepherds, Weimaraners and bull terriers. Other breeds predisposed to congenital heart disease include Newfoundlands, golden retrievers, Rottweilers, boxers, poodles, Pomeranians, spaniels, beagles and schnauzers. Small breeds under 20 pounds, such as Cavalier King Charles spaniels, cocker spaniels, dachshunds, miniature poodles and Yorkshire terriers are prone to the most prevalent acquired canine heart disease, chronic mitral valve disease.

Systolic heart murmurs are generally diagnosed when your vet hears a whooshing sound during contraction as he listens to your buddy’s heart through a stethoscope. X-rays, an electrocardiogram and an ultrasound of the heart can pinpoint the exact location and cause of the murmur. Treatment for heart murmurs depends on the underlying cause of the murmur and can include specialized diets, medications, supportive care and surgery.

When your dog is diagnosed with a heart murmur, it’s important to recognize and remain vigilant for any signs of heart failure. These include shortness of breath, coughing or wheezing, abdominal swelling, fatigue and pale gums. Rush your dog to the nearest veterinary clinic if he exhibits any signs or symptoms of heart failure.