Patent ductus arteriosus (PDA) is a congenital heart disease.
The ductus arteriosus is a normal structure that is present in the fetal heart. Its an opening that diverts blood from the pulmonary artery (the vessel that brings blood from the heart to the lungs for oxygenation) directly to the aorta (the vessel that delivers blood from the heart to the rest of the body). Therefore, the ductus arteriosus is present in the fetal heart to allow the majority of fetal blood to flow around rather than through the lungs. This is necessary because the fetus lives in the fluid environment of the mother's uterus, receiving oxygen from its mother's bloodstream. The ductus arteriosus normally closes at the time of birth when the young animal begins to breath, oxygen is obtained by the lungs and normal circulation is established. The problem occurs when the ductus arteriosus does not close causing abnormal blood flow through the heart and lungs. The result is a connecting vessel that allows blood to travel in a circular fashion from the left side of heart through the lungs and immediately back to the left side of the heart. The heart must work much harder to maintain a normal amount of blood flow to the rest of the body. This extra workload eventually causes the heart to fail.
Clinical symptoms of the disease include: coughing, reduced tolerance of exercise, loss of weight, and eventually, congestive heart failure. Affected puppies initially appear normal although they are usually smaller and play less vigorously than their littermates. Typically, there are no clinical signs until congestive heart failure develops. This leads to fluid accumulation in the lungs that causes the previously described clinical symptoms. In most cases, clinical signs develop and progress rapidly. Most of the affected dogs will die within a year without surgical treatment.
The majority of cases are first diagnosed upon the initial visit to a veterinarian when the characteristic heart murmur is detected on routine physical examination.
When caught early and following treatment with successful closure of the PDA, most dogs live a normal life. Unless there are complications from other heart defects or heart failure has already developed, there is rarely any future need for medication.