Repetition Training - Basic Heart Sounds Mitral Regurgitation Lesson Waveform Anatomy play pause Table of Contents 1Third Heart Sound Gallop 2Fourth Heart Sound Gallop 3Aortic Stenosis (Diamond Shaped Systolic Murmur) 4Aortic Regurgitation - Moderate 5Mitral Stenosis (Diastolic Murmur) 6Mitral Regurgitation 7Innocent Murmur Practice Quiz This video is an animation of Mitral Regurgitation A#401 (lesson# 6) within course number 6. The murmur of mitral regurgitation is a mid-frequency, rectangular murmur taking up all of systole. S1 is normal. S2 is single.There is a third heart sound gallop in diastole.Both the left ventricle and the left atrium are enlarged. The murmur is caused by turbulent flow through the incompetent mitral valve leaflets into the left atrium.