Mid-systolic ejection murmurs are often heard with a rising then falling intensity. This is called a crescendo-decrescendo murmur. The murmur sound is due to blood flowing through the semilunar valves.
Late systolic murmurs can be best auscultated over the heart's apex. Clicks will often proceed a late systolic murmur because of mitral valve prolapse. Significant (severe) mitral valve prolapse can cause mitral regurgitation.
Holosystolic murmurs begin at the first heart sound (S1) and continue to the second heart sound (S2). They are usually high-pitched and are caused by ventricular septal defect, mitral regurgitation or tricuspid regurgitation.