Mitral Insufficiency sound (Murmur) This murmur is heard best over the mitral valve area (left apical area). The murmur quality is plateau shaped and can vary in its intensity depending on the severity of the mitral regurgitation. The murmur intensity increases with the degree of valvular incompetency. In chronic mitral regurgitation, the murmur begins in systole and continues as long as the left ventricular pressure exceeds left atrial pressure. Therefore, the murmur begins with S1 and may extend into S2. Mild mitral regurgitation (MR) caused by chronic valve disease has a low intensity holosystolic murmur. The first (S1) and second heart sound (S2) are normal in their intensity. Moderate MR is a holosystolic murmur of moderate intensity. S1 is often pronounced and the intensity of S2 is decreased. Severe MR produces an intense (grade 5or 6) systolic murmur that may extend through S2.