First Heart Sounds First Heart Sound plus Aortic Ejection Click Lesson Waveform Anatomy play pause Table of Contents 1First Heart Sound - Loud 2First Heart Sound (Minimally Split) 3First Heart Sound (Markedly Split) 4First Heart Sound - Decreased Intensity 5Fourth Heart Sound Plus First Heart Sound 6First Heart Sound plus Aortic Ejection Click Practice Quiz This video is an animation of First Heart Sound plus Aortic Ejection Click A#23 (lesson# 6) within course number 6. A single first heart sound (S1) followed by an aortic ejection click (AEC) can also mimic a split first heart sound. An AEC follows S1 by 50 milliseconds.An aortic ejection click is caused by thickened aortic valve leaflets. This is commonly seen in a bicuspid aortic valve, a congenital abnormality where someone is born with two aortic valve leaflets instead of the normal three.Listen carefully to the second sound of the pair. If it is an AEC it will have a shorter duration and a higher pitch than the first sound of the pair (S1).The AEC is best heard at the Aortic valve area where splitting of S1 is not heard.