Physiological Murmurs in Dogs

Physiological murmurs are common in puppies, but most resolve on their own.
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Your new puppy has been active and playful, and gazing into his eyes makes your heart melt. Now, his first checkup has the veterinarian taking an intense and lengthy listen to your puppy’s heart. The doctor concludes this auscultation with the pronouncement that your puppy has a heart murmur. Before you feel your own heart sink with dread, it is important to understand how common, and often harmless, a puppy’s heart murmur is.

The Telltale Whoosh

A heart murmur is an abnormal heart sound. Instead of the normal “lub-dub” sound of each heartbeat, a veterinarian will hear a whooshing sound in between the “lub” and the “dub.” This whooshing sound is the murmur, and it is caused by turbulent blood flow through the heart. In some cases, a murmur indicates an anatomical defect in the valves or chambers of the heart. If a valve does not open or close and seal properly, the blood flow is disrupted. Leaky mitral valves are one of the most common reasons for these types of murmurs in dogs. In other cases, a heart murmur is referred to as a benign, innocent or physiological murmur. These murmurs are not the result of any apparent defect or disease. Physiological murmurs are commonly detected in puppies. They also occur in dogs who are excited and panting heavily during their examinations.

Grading the Murmur

As your veterinarian listens to your dog’s heart, he is also grading the murmur based on its intensity. Heart murmurs are graded on a scale from one to six. A grade one is assigned to the lowest intensity, and a grade six indicates the loudest, most pronounced intensity. A low grade may only be heard intermittently, while a high grade can be heard easily throughout the chest. If a veterinarian places his hand on the chest, be can sometimes feel a high grade murmur. The sensation is similar to that of a splash of water hitting your fabric coat. Physiological murmurs usually fall into a category of grade one or two.

He May Outgrow It

Physiological murmurs are commonly heard in puppies younger than 6 months of age, especially in larger breeds. This is simply a result of your puppy growing so quickly and his heart increasing the blood flow to accommodate. These murmurs usually appear around the age of 6 to 8 weeks, and they disappear between 4 and 6 months of age. These benign murmurs are understandably concerning for new puppy owners. More often than not, they vanish without incident. Your veterinarian will listen closely each time your puppy returns for a vaccination booster.

Confirmation Through Further Evaluation

If there is no change in your puppy’s murmur by the last vaccination booster visit, your veterinarian may schedule an additional examination to listen to the murmur a few weeks later. By this time, the murmur may be gone completely and no further investigation is warranted. If the murmur is still present, your veterinarian may recommend an echo cardiogram, which is a simple, noninvasive type of ultrasound that evaluates the heart’s structure and function. This diagnostic procedure is quick and performed without anesthesia. The result will confirm if there is underlying heart disease that is causing a murmur. If no such defects are found, your veterinarian will pay close attention to the murmur throughout your dog’s life to make sure that it remains physiological. Many dogs with these murmurs go on to live out full, normal lives.