The cart-wheel appearance of the tympanic membrane in ASOM is due to
In the stage of pre suppuration of ASOM, there is congestion of pars tensa. 
A leash of blood vessels appears along the handle of malleus and at the periphery of tympanic membrane imparting it a cart-wheel appearance.
Perforation of tympanic membrane
Edema of tympanic membrane
Granulation tissue on tympanic membrane
Congested blood vessels along malleus