How Dilated Cardiomyopathy is Diagnosed
Dilated cardiomyopathy (DCM) often goes undiagnosed, even for many years. Unfortunately, it frequently is only discovered when an affected dog suddenly dies for no apparent reason. Sometimes, DCM is an incidental finding during an otherwise routine physical examination, or when a veterinarian is taking chest radiographs (X-rays) for some other reason and notices an abnormally large cardiac silhouette. The attending veterinarian may hear abnormal heart or lung sounds when listening to the chest of a dog with dilated cardiomyopathy during an annual veterinary examination, depending upon the severity of the particular dog’s disease. When a veterinarian (or a human doctor, for that matter) listens to heart and lung sounds through a stethoscope, the process is referred to as “auscultation.”
The results of a urinalysis and routine blood work (a complete blood count and serum biochemistry profile) typically are unremarkable in dogs with DCM, unless kidney function has been significantly compromised. Thoracic radiographs (chest X-rays) may or may not disclose an enlarged heart or fluid build-up around the heart and lungs – referred to as pleural effusion and pulmonary edema - which are consistent with congestive heart failure. Frequently, the left ventricle and atrium are the most obviously enlarged heart chambers visible on chest radiographs, especially in the early stages of disease. Doberman Pinschers in particular usually have marked enlargement of their left atrium with patchy, diffuse radiographic evidence of pulmonary edema. Liver enlargement (hepatomegaly) may be identified on radiographs taken of the abdomen.
The gold standard for diagnosing DCM is echocardiography, which essentially is a highly sophisticated ultrasound of the heart. This is a completely noninvasive procedure, but it does usually require some degree of sedation so that the animal remains quiet and still. This technology is usually not available in a general veterinary practice; specialized referral centers and veterinary teaching hospitals usually have veterinary cardiologists on staff with the training and equipment necessary to perform an echocardiogram. An echocardiogram can reveal ventricular and atrial enlargement (dilation), as well as abnormal regurgitation of blood through the valves that separate the four heart chambers. An electrocardiogram can also identify erratic heart rhythms (arrhythmias). Atrial fibrillation and ventricular tachycardia are extremely common arrhythmias in Doberman Pinschers. Boxers more commonly have isolated ventricular arrhythmias that can be seen using echocardiography.
In most cases, canine dilated cardiomyopathy is a progressive disease that worsens with time. It is not particularly difficult to diagnose. Unfortunately, it cannot be cured and almost always is fatal.