A harsh holosystolic murmur heard best at the left lower sternal border is most consistent with which defect?

• A. Fixed splitting of S2
• B. Continuous machinery murmur
• C. Harsh holosystolic murmur at left lower sternal border
• D. Cyanosis

Answer: (C)

A harsh holosystolic murmur heard best at the left lower sternal border points to a ventricular septal defect. During systole, blood shunts from the left ventricle to the right ventricle through the septal defect, producing a murmur that lasts the entire systole. The harsh quality reflects high-velocity flow through a relatively small defect, and the left-to-right shunt can cause pulmonary overcirculation.

This pattern helps distinguish it from fixed splitting of S2, which suggests an atrial septal defect, and from a continuous machinery murmur of a patent ductus arteriosus; cyanosis is a broader clue for cyanotic defects and is not a specific murmur description.