Michael Clarke Duncan is a rather large man, as is evidenced in the role that most people remember him by; John Coffey in "The Green Mile". Because of his stature--around 6'5"--his heart will always be at risk in proportion to his weight. Officials aren't sure what caused the incident that almost killed him early this morning, but that could be a factor.
Around two a.m., Duncan's girlfriend, Omarosa Stallworth, found him going into cardiac arrest at home. Rather than panic, Stallworth performed CPR on her man and was able to resuscitate him while waiting on paramedics to arrive.
Omarosa is best known for her appearance on the Donald Trump-helmed "The Apprentice", where she became embroiled in battles with other contestants and was famously outspoken. Perhaps now her reputation will become a bit more gilded.