Heart Murmurs

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It’s annual exam and vaccine time for your dog. He has been doing very well and there have been no problems concerning you, so you are expecting to quickly sail through this exam as usual. Then your veterinarian pauses with the stethoscope over your dog’s heart. She listens a while, then listens some more, then she tells you that he has developed a heart murmur. That news can make a dog owner’s blood run cold. What do you do now?

The appropriate steps to take when a heart murmur is newly discovered in an adult dog depend quite a bit on the rest of the clinical picture. Many different things can cause heart murmurs. Some of those things can be very serious, and some can be inconsequential for the dog in the long run. Finding out the cause for the murmur and the amount that heart function is affected by that cause guides the decision for whether medical treatment is necessary, and if so, what treatments would be most appropriate.

A heart murmur is a whooshing sound that can be heard in association with the regular lub-dub sounds of the heartbeats. It happens when something interferes with the normally smooth flow of blood through the chambers and valves of the heart.

Sometimes an acquired heart murmur can be caused by something that never leads to clinical disease. Many dogs develop small knobs of scar tissue on the edges of their heart valves that keep the valves from sealing completely. The leakage around the seal causes the whooshing sound of the murmur, but if the impairment of the valve is small the dog may never develop problems as a result.

On the other hand, some dogs develop severe problems such as Dilated Cardiomyopathy that results from a weakening and thinning of the heart muscle. The result is rapid degeneration into heart failure, which is the inability of the heart to function well enough to get blood moved through the body like it needs to be moved. We don’t know what causes this particular problem to happen, but we do know that certain breeds are more prone to it than others. Most of the larger breeds are susceptible, but Great Danes, Boxers, and Dobermans are particularly at risk.

The stethoscope doesn’t give very much information about the cause of a murmur or the severity of the problem in the heart. If a dog is showing clinical signs like frequent coughing, exercise intolerance, or fainting an aggressive work-up is warranted. In a dog with no symptoms of heart disease it is sometimes acceptable to be more conservative and just watch closely.

A complete cardiac evaluation involves x-rays of the chest to see if there are any changes in the heart shape or lung involvement, an ECG to assess the electrical activity in the heart, an echocardiogram to look at the structures inside the heart and to assess the function of the heart, and now there is a newly developed blood test that can confirm the presence of heart disease and give a general idea how severely the heart muscle is affected.

There are many different medications that can help hearts that are having difficulty functioning correctly. Each one has a specific effect that is aimed at a particular aspect of dysfunction, so it is important to know exactly what sort of process is causing the problem so appropriate treatment can be selected. We can’t always cure heart disease, but with medical management many dogs that would have had only weeks to live can often have years instead.