Dilated Cardiomyopathy is an inherited disorder of the heart affecting several breeds of dog. This disease shows Incomplete Penetrance, meaning that not all dogs at risk (those with one or two copies of the Mutation) will develop the disease. In affected dogs, the heart muscle is weak and the chambers become dilated with thin walls. These enlarged hearts have poor contractility and are prone to arrhythmias. Affected dogs present with clinical signs of poor heart function between 1 to 8 years of age. Affected dogs develop clinical signs as they age ranging from mild exercise intolerance to sudden death or congestive heart failure. Signs of heart disease include exercise intolerance, fatigue, coughing, difficulty breathing, rapid breathing, fainting and sudden death. Affected dogs that don’t die suddenly from arrhythmias usually die from congestive heart failure around 7 years of age. Different disease genes and environmental factors play a role in the development of dilated cardiomyopathy in dogs. Therefore not all dogs with this disease will have the same genetic mutation.