Facts A heart murmur is an abnormal heart sound created by turbulent blood flow into, out of, or through the heart. Not actually a disease or illness in and of itself, a heart murmur is the result of another heart problem that causes the abnormal sounds. They may range from being minor to being indicative of heart disease, and are rated according to several characteristics. These characteristics include intensity, shape, location, timing, quality, pitch, and radiation. There are diastolic murmurs, systolic murmurs, continuous murmurs, and to-and-fro murmurs. The grading scale for intensity is as follows: Grade I is barely audible; Grade II is soft but heard easily with a stethoscope; Grade III is of intermediate loudness (most are, at minimum, Grade III); Grade IV is loud and radiates widely; Grade V is very loud and can be heard with just the edge of the stethoscope touching the chest; and Grade VI is very loud and audible with the stethoscope lifted off the chest. Causes A heart murmur is typically caused by leakage in the heart, which is, in turn, caused by a hole in the heart wall or faulty heart valves. Young dogs will often produce murmur sounds but as they mature, the velocity of the blood flow decreases and the abnormal heart sounds disappear. This is completely normal. Some diseases or structural problems that cause systolic murmurs include anemia, heartworm disease, systolic anterior mitral motion, hyperthyroidism, mitral and tricuspid valve heart failure, dynamic subaortic stenosis, cardiomyopathy and aortic valve insufficiency, aortic stenosis, mitral and tricuspid valve endocarditis, pulmonic stenosis, Tetralogy of Fallot, and atrial and ventricular septal defect. Diastolic murmurs are caused by aortic and pulmonic valve endocarditis, and mitral and tricuspid valve stenosis. Continuous or to-and-fro murmurs may be caused by ventricular septal defect with aortic regurgitation, patent ductus arteriosus, and aorortic stenosis with aortic regurgitation. Prevention It is not possible to prevent murmurs, especially since they are simply a clinical finding related to the root cause of the heart sounds. Once a murmur has been diagnosed, the underlying cause must be determined as soon as possible so treatment may begin. Symptoms A dog with a heart murmur may have no symptoms at all, and the issue itself may be very minor and non-life threatening. On the other hand, dogs with murmurs associated with heart disease may exhibit signs of fainting spells, respiratory distress, coughing (especially at night or at rest), panting (even at rest), exercise intolerance, pale mucous membranes, decreased activity level, agitation, abdominal distension or pot-bellied appearance, or collapse. These symptoms are very non-specific and may not indicate heart disease; however, it’s always a good idea to get your dog checked right away if you notice any of these symptoms. Dogs at Risk Murmurs in puppies usually disappear by the age of six months and generally do not cause any problems. Breeds most likely to develop murmurs related to chronic valvular disease are the Miniature and Toy Poodle, Lhasa Apso, Cavalier King Charles Spaniel, Schnauzer, Cocker Spaniel, and Yorkshire Terrier. Dogs predisposed to murmurs caused by dilated cardiomyopathy are Doberman Pinschers, Springer Spaniels, Boxers, Great Danes, St. Bernards, Cocker Spaniels, Schnauzers, German Shepherds, and Old English Sheepdogs. Testing and Diagnosis Heart murmurs are usually detected during a routine physical exam when the vet listens to the dog’s heart with a stethoscope. Upon detection, the vet should investigate further to try to determine the cause. There are a wide range of tests depending on the type of murmur and its cause – ultrasound, chest x-ray, and echocardiography, for example. Blood and urinalysis may also be helpful in diagnosing the underlying cause. Treatment and Prognosis Murmurs in and of themselves cannot be treated – the underlying cause must be treated. If the dog is suffering from heart failure, it will be admitted and treated to relieve those symptoms and to try to reduce the severity. Severely ill dogs may be given oxygen treatment, IV fluids to restore electrolyte and/or fluid balance, and medications to normalize heart function, if possible. If no heart disease is present, the dog will be treated on an outpatient basis depending upon the grade of the murmur. Minor cases often resolve themselves when the dog is placed on a low-sodium diet. Puppies who exhibit no signs of serious disease should be monitored with the expectation that the murmur will resolve itself as the dog ages. Adult dogs should undergo more advanced testing to determine the cause and to assess the heart’s condition. The prognosis for a dog with a murmur depends upon the severity and type of murmur, and the underlying cause. For dogs with heart disease, the progression of the disease will dictate the prognosis. In dogs with advanced heart disease, sometimes there is nothing that can be done other than to try to make the dog comfortable. In cases where the heart disease is minor, all steps should be taken to try to halt the progression and to heal any damage done to the heart.
Just Us Dogs2017-08-06T00:00:00+00:00