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Heart Testing in Dogs: a Note for Owners

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Aims

  • To identify dogs free from any cardiac abnormality at the invitation of the breed club involved
  • To ascertain the prevalence of heart murmurs, abnormal rhythms or specific heart defects in specific breeds, at the invitation of the breed club involved
  • To confirm the cause of heart murmurs or abnormal rhythms by further investigation of affected animals
  • To collate data for investigation of a possible genetic basis to a specific heart problem in a given breed by a breed club nominated person, geneticist or veterinary surgeon
  • To advise the owner, breeder and dog's veterinary surgeon when an abnormality has been identified and recommendations about any further investigation, if indicated

Methods of heart testing

  1. Auscultation: examination with a stethoscope
    This is an essential part of examining the animals' heart and circulation. Any heart murmurs are identified, timed, localised and graded (grade 0 - 6). Careful note of the heart rhythm is made.

    Heart murmurs are a feature of most congenital heart defects (CHD) and mitral valve disease (MVD). Some common forms of CHD include aortic stenosis (AS), patent ductus arteriosus (PDA) and pulmonic stenosis (PS). Abnormal heart rhythms may occur without murmurs in dilated cardiomyopathy (DCM). It may be difficult for the veterinary surgeon to detect a quiet murmur in a noisy room or in a dog which fidgets. Auscultation may also have decreased sensitivity in dogs with broad chests or thick hair coats. Some murmurs may increase or alter at different heart rates, after exercise or excitement.

    If a significant murmur is detected, the veterinary surgeon may advise that the condition should be investigated further. Auscultation does not provide a conclusive diagnosis; further investigations are required. Although all veterinary surgeons will check your dog's heart, most breed club schemes will use a veterinary cardiologist, who has received training, has passed post-graduate examinations and is able to grade heart murmurs in a way which is consistent with other cardiologists.

  2. Electrocardiogram (ECG)
    This is always indicated if an abnormal heart rhythm is detected. It is most often used to screen certain breeds of dogs for DCM. It is less sensitive at identifying CHD or MVD.
  3. Echocardiogram (with Doppler)
    Two-dimensional echocardiography allows visualisation of a "slice" through the heart in real-time. M-mode echocardiography allows measurements to be taken and compared with normal values for breed or size of dog. Severe CHD, MVD or DCM are usually evident using these techniques. However, Doppler echocardiography (spectral, with or without colour flow mapping) is required to confirm the diagnosis of the specific type of CHD, and to identify mildly affected animals. It will confirm whether or not there is a significant cause of the heart murmur or whether it is "innocent". In some cases, it is difficult to be certain whether a dog has mild disease or an "innocent" murmur.

    Doppler will allow the cardiologist to give a prognosis about the severity of any disease. Veterinary cardiologists normally carry out Doppler examinations, as this is a very skilled technique which requires considerable expertise and experience.

Further information
If you have questions about the conditions screened for in your breed of dog, you should consult the relevant person in your breed club or the cardiologist attached to the breed club. The cardiologist testing your dog will be willing to discuss the results of the tests with you, which are summarised on the certificate of heart testing.

Heart testing is carried out at the invitation of breed clubs and with the agreement of the RCVS. Information provided by The Veterinary Cardiovascular Society