ejection sound

The first heart sound may be followed by a sharp ejection sound ("ejection click") best heard at the lower left sternal border and the apex, and, thus, appear to be "split".

The ejection sound, caused by the impact of left ventricular outflow against the partially fused aortic valve leaflets, is more commonly associated with a mobile bicuspid aortic valve than an immobile calcified aortic valve.