<prompt> Answer this question truthfullyHow can standing up or performing the Valsalva maneuver impact the intensity of murmurs caused by mitral regurgitation MR, aortic regurgitation AR, mitral stenosis MS, and aortic stenosis AS?  <response>: <reason> Standing up or performing the Valsalva maneuver can cause a decrease in the intensity of MR, AR, MS, and AS murmurs. 