The murmur heard at the upper left sternal edge is systolic, short, early peaking, crescendo-decrescendo and mid frequency. Murmurs at the upper left sternal edge that occur early in systole typically result from turbulent flow when the majority of blood is ejected from the right ventricle.
Pressure curves
These simultaneous pulmonary artery and right ventricular pressure curves illustrate the relationship of these hemodynamic events to timing and contour of the murmur. The murmur begins in early systole, after opening of the pulmonary valve as right ventricular pressure minimally exceeds pulmonary artery pressure. Rapid ejection velocity causes turbulence, generating the murmur. The crescendo-decrescendo configuration of the murmur is related to changing blood flow velocity from the right ventricle to the pulmonary artery in systole. The short length of the murmur reflects enhanced blood flow without obstruction. [Sounds]
Differential diagnosis
The differential diagnosis of a systolic, short, early peaking, crescendo-decrescendo murmur at the upper left sternal edge includes: an innocent murmur from normal flow, the obstruction murmur of mild pulmonary stenosis and the murmur from increased pulmonary blood flow due to an atrial level left-to-right shunt. Interpretation of the significance of the murmur depends on its specific characteristics, evaluation of the second heart sound as well as other findings of the cardiovascular examination.