Final answer:
In patients with significant mitral regurgitation, the isovolumic relaxation time may be increased. This phase is characterized by the closure of the semilunar valves to prevent backflow into the heart, but the atrioventricular valves remain closed as well.
Step-by-step explanation:
In patients with significant mitral regurgitation, the isovolumic relaxation time may be increased. During the isovolumic ventricular relaxation phase, the ventricular muscle relaxes and there is no change in the volume of blood in the ventricle. This phase is characterized by the closure of the semilunar valves to prevent backflow into the heart, but the atrioventricular valves remain closed as well. The isovolumic relaxation time can be affected by various factors, including mitral regurgitation.