The symptoms of a PDA can vary depending upon the defect's size and the patient's age. The larger the size of a PDA and the longer it is present, the greater the blood volume traveling through the lungs and back to the left side of the heart. Over time, typically within 12 - 18 months of life, the left side of the heart may not be able to keep up with the increased blood volume needing to be pumped, and left-sided congestive heart failure (L-CHF) can develop. This results in fluid retention within the lungs and associated symptoms such as coughing, labored breathing, and severe lethargy.
Unfortunately, L-CHF is a progressive disorder that affected patients ultimately succumb to. Rarely, a PDA can cause blood flow in the opposite direction (from the pulmonary artery to the aorta) due to the development of a condition referred to as pulmonary hypertension. In this case, sufficient blood never reaches the lungs to pick up oxygen and signs of systemic hypoxemia develop with severe weakness, lethargy, intolerance to exercise, and episodes of collapse (particularly with activity).