A Guide to the Significance of Heart Murmurs in Cavaliers
So, you have done the right thing and taken your dog to a cardiologist for heart testing. Unfortunately, a murmur has been discovered. What should you do now? The answer may depend on the age of your dog and the loudness of the murmur.
Dogs under 5 years
  1. Low grade (quiet) murmurs
    For dogs under 5 years of age, the discovery of a murmur is potentially more serious as it may have consequences on a breeding program. Without further investigations, it is impossible to be absolutely certain that the murmur discovered represents degenerative mitral valve disease (DMVD). However, the location of the murmur can be suggestive and the cardiologist will advise on this. In addition, the loudness of the murmur can be helpful in assessing the severity. Loud murmurs usually represent significant disease but subtle murmurs may be more difficult to interpret. Remember, a heart murmur just indicates that there is turbulent (non-laminar), usually high speed blood flow in the heart. As a result, it would be inadvisable to make a breeding decision based on one examination on what can be a stressful day for your dog. If this murmur truly represents DMVD, then the murmur will be present all the time. As a result a second examination with a Specialist Cardiologist 1-2 months later will confirm the result and breeding should be avoided. If a murmur is not confirmed, this result will be used for the database. This may change slightly with the new BVA/KC/VCS scheme. The rules in the new scheme state that if the second cardiologist agrees with the first, the murmur stands. However if the second cardiologist disagrees and thinks no murmur is present, the case is referred to a senior panellist. This is similar to the appeals procedure in the eye scheme and will apply to dogs of all ages.
  2. High grade (loud) murmurs
    In young dogs, this either indicates significant mitral valve disease or a congenital heart defect. Referral to a Specialist Cardiologist for further evaluation including an echocardiogram to make a specific diagnosis would be indicated. Whatever the cause, it is recommended that these dogs are not used for breeding.
Dogs over 5 years

If your dog is over 5 years old and already has a heart test clear over 5, then you probably do not need to do anything. There is no evidence that treatment at this stage before signs of heart failure develop delays the onset of heart failure. These signs include exercise intolerance, breathlessness, weight loss, poor appetite and a cough often at night. Heart failure may never develop but if it does, on average, it takes 2-3 years. Chest radiographs or echocardiography may be useful to document progressive heart enlargement. Repeat examination can also be helpful as the discovery of a louder murmur indicates the disease is worsening.
Simon Swift
Hon Member
Cardiology adviser to the CKCS Club
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Material Copyright © 2011 The Cavalier King Charles Spaniel Club