What physical exam finding is often associated with a patent ductus arteriosus (PDA)?

A continuous "machinery" murmur is a hallmark finding associated with a patent ductus arteriosus (PDA). This type of murmur has a distinct quality that resembles the sound of machinery, hence the name. The murmur occurs due to the continuous flow of blood through the ductus arteriosus, which remains patent after birth. In a normal scenario, the ductus arteriosus closes shortly after birth, but when it remains open (or patent), it allows blood to flow abnormally from the aorta to the pulmonary artery during both systole and diastole.

The unique nature of this murmur helps distinguish PDA from other cardiac conditions. While other murmurs, such as a diastolic murmur or systolic ejection murmur, may be present in different cardiovascular abnormalities, the continuous nature of the "machinery" murmur specifically indicates the presence of a PDA. Splitting of heart sounds can occur in various conditions and is not exclusive to PDA, making the continuous murmur the definitive physical exam finding that points towards this particular condition.