A healthy heart is essential to successful performance for any athlete and this is certainly true of canine competitors. Heart disease in dogs may be present since birth (congenital conditions) or may be acquired later in life. Dogs can develop abnormalities of the heart valves or heart muscle, as well as structural deformities. Clinical signs of heart disease in dogs include exercise intolerance, fatigue, shortness of breath, fainting, discoloration of the gums, coughing and restlessness, particularly at night. Upon physical examination, a veterinarian may detect abnormalities such as a heart murmur, an abnormal heart rhythm, or a rapid or slow heart rate. If heart disease is suspected, a consultation with a veterinary cardiologist is strongly recommended in order to further define the extent of the problem. This is particularly important with working dogs and those that are actively involved in competition. A thorough cardiac evaluation is also recommended for young dogs that are about to enter into competition for the first time.
Cardiac evaluation begins with a complete physical examination and auscultation of the heart with a stethoscope. Further assessment is performed using a series of specialized diagnostic tests. These include thoracic radiographs (chest x-rays), an electrocardiogram (ECG), and an ultrasound examination of the heart, referred to as echocardiography. These tests provide different pieces of information about the overall health of a dog's heart.
Chest x-rays provide direct information regarding the size of the heart and the condition of the lungs. The larger vessels entering and leaving the heart can also be evaluated. In cases of heart failure, fluid accumulation can be detected. When x-rays are repeated over a period of time, they can help judge the effectiveness of treatment.
An electrocardiogram is a test used to record the electrical activity of the heart and to detect abnormal heart rhythms called arrhythmias. The ECG can also provide information regarding enlargement of specific chambers of the heart and the position of the heart in the chest cavity.
Echocardiography is a highly specialized, non-invasive test that allows the veterinary cardiologist to "see" inside the heart using a form of sonogram. An ultrasound probe is placed on the chest and sound waves are used to assess heart structure, chamber size, and heart valves. The ultrasound exam allows for evaluation of functional abnormalities such as weak heart muscle contractions or incompetent heart valves. A specialized test called "color flow Doppler" provides greater detail about the blood flow through the heart. This test is discussed in more detail elsewhere in this issue (see page 5).
When these tests are performed on a canine athlete, they provide complete information regarding the dog's heart. If no abnormalities are detected, the dog is cleared of any limitations due to cardiac disease. In cases where one or several tests are abnormal, the veterinary cardiologist will interpret the information and formulate a treatment plan.