"Michael started to feel light headed during his meeting so he walked outside, and that's when he collapsed," a source close to the Lohan patriarch told RadarOnline.com.
"He was taken in an ambulance to Palm Beach Gardens Hospital where doctors found another blood clot in his lung."
The source said that Michael was given medication to break down the clot and the 51-year-old was given CAT scans and an MRI to make sure the clot hadn't spread to his brain.
Since Michael's October arrest when he tried to flee police by jumping out a third-story window because he'd violated a restraining order put in place after his ex-girlfriend Kate Major cried domestic violence, he's been in a 120-day court appointed rehab stint in Florida -- and in and out of the hospital.
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As RadarOnline.com first reported, Michael had surgery to unclog his artery and repair blockage in his heart in early December, only to be rushed back to the hospital almost immediately with a staph infection.
"Michael's still waiting on the test results and we're not sure when he'll be released from the hospital," the source said.
When he's released, Michael will be sent back to rehab, again.
Michael Lohan Checks Out Of Hospital But Is Rushed Back With Staph Infection
Michael Lohan Has Emergency Heart Surgery!