by Dr. Jodi Reed

Heart Murmurs in pets don't always need to be cause for concern. Sometimes, when doing a thorough physical exam on a patient, we hear a heart murmur. Often, informing pet parents we are hearing a murmur elicits fear and concern, so I want to shed some light on the subject to help navigate through the good, the bad and the ugly regarding this condition. Basically, hearing a heart murmur is not a diagnosis of any particular type of heart disease; the only thing it means is that there is an abnormal sound made by the heart when listening with a stethoscope. Murmurs are extra heart vibrations created from a disturbance in the blood flow, which produces an abnormal “swooshing” sound between the normal “lub-dub” sounds a beating heart makes.

Hearing a murmur during a physical exam is no reason to panic; it is, however, a reason to have a discussion about heart disease and what it may mean for your pet. Let me start by saying that many dogs and cats with heart murmurs will live long, happy, healthy lives and never need any treatment for their heart disease. For a select few, however, the murmur can be an indication that something more serious is going on. Further testing is warranted to determine whether treatment is recommended.

Types of Heart Murmurs in Pets

The first part of the discussion will focus on the grade of the heart murmur. Murmur grading is simply a way to describe the loudness, the intensity and the number of locations where we hear the murmur. The louder and more intense the murmur and the more locations on the chest (i.e., left side, under side and right side of the chest) in which we hear the murmur, the higher the grade.

Heart murmurs are graded on a scale from 1 to 6, with 1 being very soft and often difficult to hear and 6 being very loud.  A 6 can be heard basically anywhere you put the stethoscope on the animal’s chest and can even be felt as a vibration if you put your hand on your pet’s chest, over the heart.  While higher murmur grades can indicate more cause for concern, it does not always correlate with the severity of the underlying heart disease. For instance, a cat with no murmur or only a grade 1 can have severe heart disease (i.e., cardiomyopathy), while another cat with a grade 5 murmur may have minimal heart abnormalities that would never cause any clinical signs or warrant any kind of heart treatment.


Causes of heart murmurs vary widely and can result from actual damage or changes within the heart, or from causes that are unrelated to primary heart disease.  Since murmurs are caused by turbulent blood flow through the chambers and valves of the heart itself, the actual cause of the abnormal sounds can vary widely.  The heart is designed to pump blood forward through the body (only in one direction). If there are faulty valves, abnormal stretching of the heart muscles, dilated heart chambers, holes in the heart walls, narrowing of the arteries or veins, a tumor in the heart or other structural abnormality of the heart, some of the blood will backflow (go in the wrong direction), creating turbulence of the blood and resulting in the murmur “swooshing” noise.

Non-Heart Related Causes

Sometimes innocent murmurs, which are benign and not associated with heart disease, can occur in a young animal under the age of 15 weeks; in a pet who is overly excited, anxious or panting; or in association with anemia or other non-heart conditions that may cause the heart to speed up temporarily. For example, anemia occurs when there is not enough blood in the body, so the pet’s heart speeds up trying to get more blood through and this can cause a murmur. In this case there is not a problem within the heart itself, but it does have an effect on the heart. These murmurs are usually soft, can be intermittent, and generally resolve as the puppy or kitten grows, once the pet calms down or after the cause is corrected.

Congenital Murmurs

A congenital heart murmur is one that the puppy or kitten is born with, which stems from structural defects within the heart. While most of the time the issue is revealed during the puppy’s or kitten’s exams, sometimes they can only be detected later in life. The severity and causes of congenital murmurs vary widely, but it is always recommended to have some baseline testing performed on puppies or kittens with a heart murmur that is greater than a grade 2 and still present after 5 to 6 months of age.

Acquired Murmurs

An acquired murmur is one that develops later in life. These murmurs can be from a wide variety of causes and can range from being incidental to very serious. It is recommended and worthwhile to have baseline testing performed to investigate every heart murmur, but realistically, a full cardiac workup is not warranted for many cases.

If the murmur is detected on an otherwise normal, routine examination in an otherwise happy, healthy animal, many pet owners will elect to monitor their fur baby for signs that indicate something more serious is going on.

If there are signs that the murmur may already be affecting your pet, a series of tests will be recommended based on your pet’s specific signs and symptoms. Whether or not your pet shows clinical signs for a murmur, there are specific tests that should always be performed prior to scheduling a procedure requiring anesthesia.

Testing for Heart Conditions

To help determine the cause and the severity of the condition causing the heart murmur, there are several recommended tests:

  • A complete blood and urine panel, including a Cardiac ProBNP hormone blood test is a great place to start. This will help us check for anemia, infections, kidney disease, liver disease, thyroid disease and other medical abnormalities that can cause or worsen heart disease.
  • The Cardiac ProBNP is a simple blood test that checks for the presence of a hormone released as the heart muscle stretches, often due to being overworked from structural defect or damage. If there are abnormalities associated with the blood panel or ProBNP test, then further investigation more specific to the heart will be recommended.
  • Simple, non-invasive and relatively inexpensive cardiac tests generally include blood pressure measurement, electrocardiography (ECG or EKG) and chest x-rays. Based on the results of the above tests and your pet’s clinical signs, more advanced testing, such as an echocardiogram (an ultrasound of the heart), Holter monitor and an evaluation by a veterinary cardiologist may be warranted.

The series of tests will shed light on the cause, the severity and the necessity of treatment for your pet, enabling the vet to give you a more accurate prognosis for their quality of life and expected life span.

Treatment Options

Treatment for a heart murmur specifically is not warranted, although treatment for heart disease would be tailored to the pet’s symptoms and cause of the murmur determined by the above-mentioned tests. Medical treatment often consists of a combination of dietary changes, exercise restrictions and medications. In general, recommended treatment for heart disease is based on many factors, including the likelihood of the benefit from treatment, the pet’s acceptance of the treatment, the cost of treatment and the owner’s commitment to providing the level of care recommended.

It is also recommended that any animal with a heart murmur not be bred, due to the risk of exacerbating their heart disease during the stress of breeding or pregnancy, as well as the risk of passing on the heart disease to their offspring. Ideally, animals with heart disease should maintain healthy weights, be monitored closely and taken into a veterinarian at the first sign that something is off, have regular examinations twice a year with basic blood testing and maintain healthy oral hygiene, as inflammation and infection associated with dental disease can and often will exacerbate heart disease.

Long Term Outlook

In summary, diagnosis of a heart murmur in your pet, young or old, can elicit concerns, but it is in no way a death sentence for the majority of pets. The first step is to take a deep breath, then start discussing your pet’s history, symptoms, risks, lifestyle and all of your concerns with your veterinarian. Ideally, some basic tests will be run, but electing to monitor your otherwise seemingly healthy pet is also an option. The key to keeping your pet happy and healthy for as long as possible is close monitoring for outward signs that they may have symptoms of heart disease.

Signs that your pet may have worsening heart disease include exercise intolerance, lethargy, weakness, limping or loss of use of their back legs (cats), decreased appetite, weight loss, increased breathing rates or effort, coughing or anything else that seems unusual for your pet. Noticing any of the above symptoms warrants an immediate trip to your veterinarian or emergency veterinarian if it is after hours.  It is important to know that heart disease can be treated and managed in the vast majority of pets; however, early detection, prevention and treatment are crucial.

Helping your pet have a happy, healthy heart is our commitment to you and your pet!! Happy Valentine’s month from Harmony Animal Hospital!!