Just as humans can have various heart anomalies, so can dogs. One such abnormality is the canine heart murmur, which is an anomalous sound that your vet hears when listening to your dog's heart through the stethoscope. While a heart murmur is, itself, not a disease, it can be a symptom of an underlying illness.
Dogs with heart murmurs may be asymptomatic, or they may present with some common symptoms. According to VetInfo, common symptoms include:
- A consistent, hacking cough
- The sound of an irregular heartbeat
- Low energy
- Weakness or fainting
- Excessive panting, even at rest
- Labored breathing
- Poor appetite
- Water retention
- A bluish cast to the gums or tongue
Diagnosing Heart Murmur
Only a veterinary professional can diagnose heart murmurs, and they can be difficult to verify simply by listening to the heartbeat. Heartbeat irregularities in puppies are sometimes detected at birth. With an older dog, murmurs can sometimes show up during annual checkups.
The process of diagnosing a dog's heart murmur isn't that different from confirming the presence or absence of the same problem in a human. The initial examination will involve listening to the heart with a stethoscope. If a murmur is present, the heartbeat will make a softer, longer sound than the steady, short thump of a normal canine heartbeat. However, in many cases murmurs are very faint and can't be confirmed without further testing.
When your vet suspects a heart murmur, he will typically follow up a general exam by running an electrocardiogram (ECG) to determine if there is a problem with the dog's heart. If necessary, the ECG may be followed up with an echocardiogram and chest x-rays to determine the extent of the problem and/or damage that it may have caused. Your vet may use multiple tests to detect a heart murmur, including:
- Electrocardiogram: ECG tests can reveal if there is a problem with your dog's heart. This test allows the vet to measure the heart rate and determine whether or not there are abnormal heart rhythms.
- Echocardiogram: This procedure allows the veterinary professional to determine if there are problems with the valves of your dog's heart and to determine how well the heart if functioning. This test helps the vet decide if your pet needs treatment for his or her heart condition.
- X-Ray: Viewing radiographic images of your dog's heart allows the veterinarian to see if there seem to be any abnormalities of the cardiopulmonary system related to heart problems.
Grades of Murmurs
Once detected, all murmurs are assigned one of six different grades:
- Grades one and two: These are typically minor murmurs that don't require immediate medical intervention. Most vets will ask you to keep an eye on your dog as time goes on, and report right away if your dog develops a habitual cough or lethargy. These could be signs that the murmur is getting worse and may now require treatment.
- Grades three and four: These murmurs are a bit more serious than grades one and two, so they are cause for more concern. At grade three or four, you may notice your dog tires quickly after exercise, and there may be a persistent cough that indicates some extra fluid is collecting in the lungs. Murmurs of these grades usually require medication to help regulate them.
- Grades five and six: These are the most serious grades of murmurs. Dogs diagnosed at a five or six will require medication, and may also need surgery to try to repair the defect. Murmurs at this level may eventually develop into congestive heart failure.
Treating Your Dog's Heart Murmur
When puppies are born with murmurs, treatment is not recommended right away unless there are signs of significant health problems associated with the murmur. As with human children, congenital heart murmurs often disappear with age. In most cases, it will take a few years to determine if a canine heart murmur is a serious problem or one that is self-correcting. In many cases, no treatment is necessary. Depending on the overall health and age of the affected dog, many heart murmur problems that do not go away without treatment can be corrected via surgical procedures to repair or replace the mitral valve. Medication or dietary changes may also help treat underlying conditions causing the murmur.
Causes of Heart Murmurs in Dogs
There are several possible causes of murmurs. If diagnostic testing reveals that your dog has a heart murmur, the next step toward determining the best course of action is to identify both the severity of the problem and its underlying cause.
Some puppies are born with heart murmurs. These types of murmurs are considered congenital birth defects.
Murmurs in dogs can also be caused by anemia. In such cases, the best course of action is to figure out what is causing the dog to experience anemia. Dog parasites, for example, can cause anemia. In such situations, getting rid of the parasites may cure the anemia and eliminate the heart murmur.
Heart Valve Disease
In some cases, murmurs in dogs are caused by mitral valve disease. With age, or as a result of high blood pressure or other cardiac disease conditions, the mitral valves weaken and blood leaks from them into the heart's atrium instead of being pumped out as it should. This leakage results in the audible murmur sound. This problem is more common in older dogs than younger ones, and represents the most serious form of a heart murmur.
A number of other conditions may also cause heart murmurs, including:
- Inflammatory conditions
- Stenosis (narrowing) of blood vessels near the heart
Health Implications of Heart Murmurs in Dogs
For some dogs, having a heart murmur doesn't have significant health consequences. Many dogs that develop murmurs never develop heart health problems that impact their quality of life or longevity. For others, the condition can be severe and can cause a wide variety of health problems. Dogs that are diagnosed with any type of hereditary heart problem should not be bred in order to avoid passing on congenital heart health problems to future generations.