Final answer:
The continuous-wave Doppler maximum velocity of the regurgitant jet in patients with severe acute mitral regurgitation is increased due to the high pressure gradient created by the backward flow of blood.
Step-by-step explanation:
In patients with severe acute mitral regurgitation, the continuous-wave Doppler maximum velocity of the regurgitant jet is increased. This is because mitral regurgitation allows blood to flow backward from the left ventricle into the left atrium, leading to a higher velocity flow through the insufficient valve during systole. Left ventricular function may influence the amount of regurgitation, but the Doppler maximum velocity is specifically affected by the pressure gradient between the left ventricle and the left atrium, which is elevated during acute mitral regurgitation, leading to a higher velocity jet.