Dilated cardiomyopathy (DCM) is an inherited disorder of heart muscle affecting dogs. Affected dogs present with clinical signs of poor heart function before 3 years of age. Affected male dogs typically develop disease earlier than affected females, at around 1.5 years old versus 2.4 years old. Development of progressive cardiac muscle weakness, dilation of heart chambers, and thinning of heart walls result in poor contractility and makes affected dogs prone to potentially fatal arrhythmias. Affected dogs develop clinical signs ranging from exercise intolerance, fatigue, coughing, difficulty breathing, rapid breathing, fainting, collapse, and sudden death. Affected dogs that do not die suddenly from arrhythmias usually die from congestive heart failure when heart muscle becomes too weak to adequately pump blood. Different disease genes and environmental factors play a role the development of dilated cardiomyopathy in dogs. Therefore, not all dogs with this disease will have the same genetic Mutation.