Dilated cardiomyopathy (DCM) is a disease of the heart muscle in which the left ventricle (the heart's main pumping chamber) becomes dilated and enlarged, causing the heart to weaken and fail to pump blood effectively.
A variant of the phospholamban gene has been found to be associated with symptoms of DCM in the Welsh Springer Spaniel breed, and a DNA test is now available from Laboklin. Phospholamban plays an important role in the regulation of intracellular calcium concentration and therefore in the contraction and relaxation of the heart. Left ventricular dilatation, poor systolic function, arrhythmia and sudden cardiac death are typical symptoms seen in affected dogs. Symptoms usually become apparent by 20 months of age. The disease is inherited as an autosomal dominant trait with variable penetrance. Compared to other canine heart diseases, dilated cardiomyopathy in the Welsh Springer Spaniel has a high penetrance, which means that dogs carrying the variant are very likely to develop the disease when they reach the age of onset.
In Manchester Terrier, the disease is known as Juvenile Dilated Cardiomyopathy (JDCM) and it is found to be associated with an autosomal recessive variant in the cardiac ATP-sensitive potassium channel gene (ABCC9 gene).
DCM can lead to sudden death of the affected dog, usually before the age of 2 years, typically by 6 months. In the acute form, the heart is macroscopically normal, and histopathology shows acute multifocal myocardial degeneration and necrosis without inflammation. In the chronic form, clinical signs such as mild cardiomegaly, left ventricular dilatation, left ventricular wall thickening and left atrial enlargement are common. Other histopathological findings include myocardial degeneration, myocardial fibrosis, mild inflammation and sometimes myocardial mineralisation. The disease is inherited as an autosomal recessive trait. Dogs appear healthy prior to sudden death, with reports of anaesthesia or exercise preceding death in some cases.
In Nova Scotia Duck Tolling Retrievers (NSDTR) the disease is caused by another variant that has recently been identified. In this breed DCM is characterized by decreased systolic function and dilation of one or both ventricles, often leading to heart failure or sudden death
