Dilated cardiomyopathy (DCM)

General description

Dilated cardiomyopathy is a disease of the heart muscle. Due to the disease, the left ventricle (the heart‘s main pumping chamber) is enlarged, dilated and weak, so that the heart is not able to pump the blood effectively. The disease usually develops at a young age (depending on the breed, between 6 months and 3 years) and can lead to sudden death without any prior warning signs.

Breeds

English Toy Terrier, Manchester Terrier, Nova Scotia Duck Tolling Retriever, Welsh Springer Spaniel

Dilated cardiomyopathy (DCM) - Manchaster Terrier, English Toy Terrier

In the breeds Manchester Terrier and English Toy Terrier, an autosomal recessive variant in the cardiac ABCC9 (ATP-sensitive potassium channel) gene was found to be associated with DCM. DCM can lead to sudden death of the affected dog, which happens before 2 years of age, typically by 6 months.

In the acute form, the heart is macroscopically normal, a histopathological examination shows of acute multifocal myocardial degeneration and necrosis without inflammation. In the chronic form, clinical signs like a mild cardiomegaly, left ventricle dilation, left ventricular wall thickening, and left auricle enlargement are common. Additional histopathological findings are myocardial degeneration, myocardial fibrosis, mild inflammation, and sometimes also myocardial mineralization.

The dogs appear healthy prior to sudden death, with reports of anaesthetic events or exercise preceding death in some cases.

Dilated cardiomyopathy (DCM) - Nova Scotia Duck Tolling Retriever

In the breed Nova Scotia Duck Tolling Retriever, an autosomal recessive variant in the LMNA gene has been identified that is associated with dilated cardiomyopathy (DCM). An alternative term for this condition is cardiac laminopathy (CLAM).

The disease can lead to sudden episodes of accelerated heart activity (paroxysmal ventricular tachycardia). In addition, signs of a malformation (dysplasia) of the mitral valve and tissue changes of the heart muscle (myocardial fibrosis) may be present.

The age of onset of the disease varies from case to case. DCM can lead to sudden death at a young age (10–15 months).

Dilated cardiomyopathy (DCM) - Welsh Springer Spaniel

In the breed Welsh Springer Spaniel, a genetic variant of the phospholamban (PLN) gene has been found to be associated with DCM. Phospholamban plays an important role in regulating the intracellular calcium concentration and therefore the cardiac contraction and relaxation.

Left ventricular dilation, poor systolic function, arrhythmia and sudden cardiac death are typical symptoms of affected dogs. Usually, the symptoms become visible until the age of 20 months.

The disease is inherited in an autosomal dominant manner with variable penetrance. Compared to other canine cardiac diseases, the dilated cardiomyopathy in the Welsh Springer Spaniel has a high penetrance. This means, that almost every dog carrying the variant shows symptoms at the relevant age.