What is the hallmark feature of a ventricular septal defect on physical examination?

The hallmark feature of a ventricular septal defect (VSD) on physical examination is a harsh holosystolic murmur. This type of murmur occurs throughout the entire systolic phase of the cardiac cycle and is caused by the high-pressure flow of blood from the left ventricle to the right ventricle due to the defect. The sound is often best heard at the left lower sternal border, and its intensity can vary depending on the size of the VSD and the overall hemodynamic status of the patient. The harsh quality of the murmur reflects the turbulent blood flow that occurs when blood mixes inappropriately across the septal defect.

This characteristic feature is critical for clinicians in diagnosing VSDs during a physical exam and differentiating them from other cardiac murmurs, which may have different timing, locations, and sounds.