Methods of heart testing
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 and can be associated with diseases such as 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.
Murmurs are sometimes ‘innocent’ and not associated with heart disease.
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.
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.
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.