Introduction
A heart murmur is an abnormal heart sound produced when the blood flow into and/or out of the heart becomes turbulent. Heart murmurs in dogs can occur for a variety of reasons, and the signs of murmurs are not always evident or easy to detect. In many cases, dogs with heart murmurs show no clinical signs at all, and the murmur is only detected during a routine physical examination or when the pet is taken to the veterinarian for a supposedly unrelated problem. In other cases, a murmur can reflect serious heart disease.
Symptoms of Heart Murmurs in Dogs
When heart murmurs do accompany clinical cardiac symptoms, generally there is something serious going on with the animal’s heart, and the murmur probably is a consequence of an underlying illness or disorder. The signs of heart disease are nonspecific and can include one or more of the following:
- Exercise intolerance
- Decreased activity level
- Panting (even at rest)
- Respiratory distress; difficulty breathing (even at rest)
- Agitation
- Pale mucous membranes
- Coughing
- Pot-bellied appearance; abdominal distension (from fluid retention)
- Fainting spells; collapse
In some cases, heart disease or disorders (suggested by heart murmurs) are associated with fainting spells or other periods of sudden collapse. This can happen when oxygen is not distributed properly to body tissues through normal blood circulation. If a dog’s gums become pale, owners should be suspicious of inadequate oxygen supply and take their dog to a veterinarian immediately. This is cause for serious concern.
Dogs at Increased Risk
Puppies commonly have benign heart murmurs, which disappear by roughly 6 months of age. These puppy murmurs typically are not cause for concern.
Certain breeds are at increased risk of having particular types of heart disease, but murmurs alone are not diagnostic of those conditions. Chronic valvular disease is more common in toy and small breed dogs, especially the Cavalier King Charles Spaniel, Miniature and Toy Poodle, Chihuahua, Lhasa Apso, Yorkshire Terrier, Schnauzer and Cocker Spaniel. Large and giant breeds are more predisposed to dilated cardiomyopathy, which is especially prevalent in the Boxer, Doberman Pinscher, Springer Spaniel, Cocker Spaniel, German Shepherd, Great Dane, Old English Sheepdog, St. Bernard and Schnauzer.