TMZ reports that Dr. Gwen Korovin, pictured here in a Facebook photo, was the doctor who was not named. The site revealed Korovin, who has treated some of the biggest celebrities in the world, was not authorized to practice medicine at the center. Investigators believe Joan’s vocal cords began to swell during biopsy, cutting off the flow of oxygen, which caused her to have a heart attack. She was rushed to Mount Sinai Hospital in New York, where she passed away. Neither doctor has been accused of wrongdoing by investigators and the clinic refuses to respond to the allegations due to federal privacy law.