Joan Rivers’ final cause of death has been determined, the New York City Office of Chief Medical Examiner told FOX411 on Thursday.

The comedian died on Sept. 4 at the age of 81 after “a predictable complication” during a medical procedure resulted in a loss of oxygen that led to brain damage, the statement on her cause of death revealed.

“The classification of a death as a therapeutic complication means that the death resulted from a predictable complication of medical therapy,” the Office of Chief Medical Examiner explained.

The statement further revealed that Rivers visited Yorkville Endoscopy on Aug. 28 for a laryngoscopy and an upper gastrointestinal endoscopy, and she was put under propofol sedation to evaluate changes to her voice.

At the New York City clinic, Rivers went into cardiac arrest and had to be rushed to Mount Sinai Hospital where she was put on life support. She died several days later.

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The State Department of Health launched an investigation into Yorkville Endoscopy following Rivers' death. The clinic parted ways with its medical director, Dr. Lawrence Cohen, shortly after the star died there. 

Reps for Yorkville Endoscopy declined comment to Fox411, citing laws against disclosing patient information.

Rivers was a trailblazer for all comics—especially for women. The raspy-voiced blonde with the brash New York accent was a TV talk show host, stage, film and TV actress, author, fashion critic, and she sold a line of jewelry.

In her book, Rivers joked that dying of natural causes was boring. "It's the grand finale, act three, the eleven o'clock number — make it count. If you're going to die, die interesting! Is there anything worse than a boring death? I think not."

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The Associated Press contributed to this report.