Several different tests may be necessary when investigating an animal with heart disease. Each test gives information on different aspects of the disease. Most tests are performed on conscious or lightly sedated animals. They are painless and every effort is made to avoid stress or discomfort to the patient.
Echocardiography is an ultrasound examination of the heart. There are three parts to the examination: M mode – measuring heart dimensions; B mode – looking at the heart beating in real time; and Doppler – looking at blood flow through the heart. Echo gives detailed information on the size, structure and function of the heart. It allows a precise diagnosis to be made. Progression of the disease can be monitored by follow up echo examinations.
An ECG is a recording of the electrical activity of the heart. It measures and records the electrical impulse which causes the heart to beat. ECG examination reveals the exact rate and rhythm of the heart, identifying irregular rhythms and conduction disturbances.
The ultrasound image of the heart (right hand side) shows a dog with a damaged (mitral) heart valve. The left atrium has increased in size weakening its wall, leading to a small tear.
Chest X-rays show the size and shape of the heart and great vessels within the chest. More importantly, X-rays show if the heart is failing (allowing fluid to build up in the lungs or body cavities) requiring urgent medical treatment.
These are often recommended for animals with heart disease. Routine blood tests check whether other organs, such as the liver and kidneys, are affected by the heart disease. Other tests may be helpful in looking for an underlying cause for the heart disease, such as a thyroid problem.
The x-ray (right hand side) is of the same dog. Note the enlarged, dilated heart and the compressed airway (white arrow). This airway compression is the reason dogs cough due to cardiac disease.