The dicrotic notch on the aoic pressure curve is caused by-
Closure of the pulmonary valve
Rapid filling of the left ventricle
Closure of the aoic valve
Contraction of the atria
dichrotic notch is a small dip in the graph of aoic pressure throughout the cardiaccycle corresponding to the closure of aoic valve Ref Harrison 20th edition pg 1445
C.V.S