They weaken, losing their ability to contract with enough strength to adequately pump the blood to the body tissue. Heart Valve Disease - The primary function of heart valves is to prevent blood from flowing backwards once it is pumped through the valves. This maintains a forward flow. When heart valve disease is present, blood may backflow causing excessive pressure on the vales and heart muscle. Infectious Myocarditis - An infection in the heart muscle is termed myocarditis.
Parvovirus is probably the best-known organism to infect the heart of a dog.
Canine Heartworm Disease - Heartworm disease in dogs is one of the most common ailments affecting the heart. A parasite called Dirofilaria Immitis is the causative agent and requires a mosquito to transmit the disease. The heartworm begins as an infectious parasite inside a mosquito. The larva lives inside the mosquito for about two weeks, where it grows and molts into the third larval stage. This stage migrates into the mosquito's salivary glands.