Where is a patent ductus arteriosus murmur best auscultated?

• A. Lower left sternal border
• B. Upper left sternal border
• C. Upper right sternal border
• D. Lower right sternal border

Answer: (B)

A patent ductus arteriosus murmur is best heard where the turbulent flow from the aorta to the pulmonary artery is closest to the chest wall: along the left upper sternal border, typically at the second intercostal space. The ductus runs on the left side near the aortic arch, so the continuous “machinery-like” murmur produced by blood flowing through it is loudest there and may radiate toward the back or left shoulder. This location helps distinguish it from murmurs of other lesions, which tend to be heard best in different areas (for example, some right-sided or aortic valve murmurs).