How can I get a screen reader to recognize a state change and read an update alt text????

I have listed a version of this question a couple of weeks ago but suspect I did not provide enough information.  

I have a series objects on a slide and  a learner will click and a slide layer will provide additional information.  In the focus order, I ensure that the object's alt text reads something like, "Clickable button:  (and then the object's label).  For the sighted learner, when they return to the base layer, I have a state change trigger (usually smaller print and color is greyed), letting them know that they have visited that object.  However, the non-sighted learner needs their screen reader to recognize that state change and read the object as visited. How can this be accomplished when there is not another entry to assign a new alt text for the state change to read "this object has been visited" in the focus order?  I have provided a simple example in the attachment.