Which finding does peak mitral valve regurgitant Doppler velocity reflect?

The peak Doppler velocity of mitral regurgitation (MR) reflects the instantaneous pressure gradient between the left ventricle (LV) and left atrium (LA) during systole. The higher the velocity, the greater the pressure difference.

However, the velocity itself does not quantify severity directly; severity depends on the size and volume of the regurgitant jet. The mechanism is determined by valve morphology and motion, not velocity. The LV to aorta gradient relates to aortic valve pathology.

This principle is discussed in the "Textbook of Clinical Echocardiography, 6e", Chapter on Mitral Regurgitation and Doppler Evaluation【20:390-395†Textbook of Clinical Echocardiography】.