A leaky pulmonary valve can be problematic if it is severe. If the pulmonary valve begins to allow significant amounts of blood to leak back into the heart, then the heart’s right pumping chamber (the right ventricle) must begin to work harder to pump more blood - both the backward-flowing leaked blood and the incoming blood from the heart’s right upper chamber (the atrium). The more blood the valve allows to back into the heart, the more work the right ventricle must do. Over time, the extra work can fatigue the heart and make the pumping chamber enlarge significantly. Its ability to pump blood may deteriorate, leading to heart failure.