Patent ductus arteriosus can lead to left heart failure. This occurs because of a left-to-right shunt, which increases blood flow to the pulmonary circulation, thereby increasing the workload on the left heart and leading to its enlargement and consequently, left heart failure. In cases of patent ductus arteriosus where the shunt is small, there may be no symptoms. With moderate shunting, common symptoms include fatigue, palpitations after exertion, and breathlessness with chest tightness. A prominent sign is a continuous machinery-like murmur heard at the second intercostal space along the left sternal border and below the left clavicle, often accompanied by a palpable thrill that can be widely transmitted. In severe cases with large shunting, there is often associated severe secondary pulmonary hypertension, leading to a right-to-left shunt, often manifesting as cyanosis and severe clinical symptoms. Once diagnosed, patent ductus arteriosus must be treated.