Patent Ductus Arteriosus
Many pituitary dwarf dogs have Patent Ductus Arteriosus which is seen as a slight heart murmur depending on the severity of the condition. Normal German Shepherds are also prone to this condition and is seen quite commonly amongst the breed.
PDA is a birth defect in the heart and is caused by incomplete changes in the heart's circulation when a dog born. The ductus arteriosus is an important blood vessel that ensures that blood does not go to the lungs unnecessarily as the foetus is developing in the uterus. During the first few hours after birth, this blood vessel naturally closes and allows the blood to travel normally through the lungs for oxygenation as the lungs begin to function when the puppy takes its first few breath's. In many dwarf puppies, the ductus arteriosus remains open (patent). This results in changes in the way that the heart pumps blood through the heart and to the rest of the body.
This abnormal link between the aorta and pulmonary artery passes extra volumes of blood into the lungs. The continuous flow of blood into the pulmonary artery causes a continuous heart murmur, increased blood flow into the lungs and an increased return of blood to the left atrium and the left ventricle. Volume overloading of blood on the left side of the heart causes enlargement of the left ventricle. If the overloading gets severe enough, the left atrium also gets enlarged and could cause the mitral valve which separates the left atrium from the left ventricle to become nonfunctional. The final result of the patent ductus arteriosus is heart failure, however in dwarf dogs this is just one of many more serious issues and tends to be overlooked or ignored.