What is a key physical exam finding for patent ductus arteriosus (PDA)?

A continuous machinery murmur is a hallmark finding for patent ductus arteriosus (PDA). This characteristic sound is produced due to the continuous flow of blood from the aorta to the pulmonary artery through the ductus arteriosus during both systole and diastole. The presence of this murmur is significant because it helps in distinguishing PDA from other types of cardiac conditions, where murmurs may only occur during systole or diastole. Detecting the continuous machinery murmur is crucial for diagnosing PDA and indicates the abnormal connection between the two major blood vessels.

Other findings and symptoms can accompany PDA, but they are not specific enough to be used as key indicators. For instance, bilateral lower limb edema is more suggestive of systemic issues or heart failure; hypotension in the upper extremities might point toward coarctation of the aorta; and pulmonary rales are indicative of pulmonary congestion rather than PDA itself. Thus, the continuous machinery murmur stands out as the distinctive physical exam finding associated with patent ductus arteriosus.