Bottom line: Murmurs that are midsystolic and soft (grades 1-3) are usually benign when they occur in an asymptomatic child or young adult without other clinical evidence of heart disease.
Summary: Walsh RA, et al. Chapter 14, the History, Physical Examination, and Cardiac Auscultation. In: Hurst’s the Heart, 13th ed., 2011. AccessMedicine.
Fig. 14-88 is an algorithm distinguishing between benign murmurs and those requiring further follow-up.