USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which heart condition leads to a widened pulse pressure, known as a water hammer pulse?

1. Coarctation of the aorta

2. Patent ductus arteriosus

3. Aortic regurgitation

4. Mitral stenosis

The correct answer is: Aortic regurgitation

Aortic regurgitation is the heart condition associated with a widened pulse pressure and a characteristic water-hammer pulse. This occurs due to the backflow of blood from the aorta into the left ventricle during diastole, leading to a high stroke volume and a rapid drop in diastolic pressure. The resulting hemodynamic changes create a large difference between systolic and diastolic blood pressures, hence a widened pulse pressure. The "water-hammer" pulse describes the bounding, forceful pulse felt in aortic regurgitation, reflecting the rapid rise and fall of the arterial pressure waveform due to the significant stroke volume and the low diastolic pressure. Other conditions, while they may involve differences in pulse pressure, do not produce this specific combination of findings. For instance, coarctation of the aorta typically leads to hypertension in the upper body and hypotension in the lower body, resulting in different clinical manifestations. Patent ductus arteriosus can also produce increased pulses but does not lead to the specific water-hammer type pulse characteristic of aortic regurgitation. Mitral stenosis is associated with a different set of hemodynamics, primarily affecting the left atrium and pulmonary circulation, and does