Hi, thanks for the query. As per your description, there are 2 possibilities. 1. During process of putting a stent, small blood clots called as emboli may get dislodged & get inside blood vessels supplying the brain. If any such blood vessel supplying a particular area of brain gets blocked due to an embolus; symptoms specific to the particular area blocked appear (memory problems of sudden origin in case of your father). Alternatively second explanation is there is a post stent/post operative condition known as delirium or acute confusional state characterized by fluctuating state of consciousness, alertness, misidentification, sleep disturbances, extreme apathy or aggression etc. delirium is a medical emergency & we aggressively need to do certain blood investigations to ascertain electrolytes levels, blood parameters, ruling out infection etc. Depending upon his prominent symptoms, low dose antipsychotics like haloperidol, olanzapine etc. will treat his condition. Do consult your cardiologist to rule out these 2 conditions. Hope this helps. Good Luck