According to our sources … Lohan, who is currently in a court-ordered treatment center in Florida, was not feeling well last night and complained of chest pains. We’re told he had his blood pressure taken, and when it came back 200/110 … he was immediately taken to the hospital.

After undergoing tests, our sources say doctors decided Lohan needed a stent in his heart and scheduled surgery for today. We’re also told doctors discovered blood clots in one of his lungs.

Lohan underwent surgery back in February to clear blockage in the posterior interventricular artery of his heart.