A video clip from 1985 has surfaced in which comedienne Joan Rivers revealed she had concerns about anesthesia because of a heart condition she was living with, People magazine reports. The 81-year-old comic died on Thursday, Sept. 4, one week after being hospitalized for cardiac and respiratory arrest.

In the clip, Rivers had stopped by "Good Morning America" and was asked by host Joan Lunden about heart arrhythmia, a condition where the heart beats out of sync.

"All of sudden you'll be on stage and hear 'tha-thud!'... It scares the hell out of me," Rivers admitted.

The comedienne has always been open about her many plastic surgery procedures but told Lunden in the video that she tries to be extra careful.

"When you go under, say for plastic surgery or something like that, that's when your heart can go out of kilter. So I'm always very careful," Rivers said.

Following her death, the New York State Health Department has launched an investigation into the clinic where Rivers was having an outpatient throat procedure when she suddenly stopped breathing. A source told ABC News that the Health Department has opened a "full investigation" into Yorkville Endoscopy Center but as of now no wrongdoing is suspected. The source said the investigation is strictly "routine."

It was previously reported that Rivers was undergoing minor surgery at the clinic but Deborah Norville, a close friend of Rivers' family, told ABC that the TV personality was at Yorkville for a "diagnostic procedure... [to] see why her voice had gotten raspy."

A source close to the investigation told ABC that Rivers was under general anesthesia when she went into cardiac and respiratory arrest. Upon arrival to Mount Sinai Hospital, she was already on life support, the source claims.

Details surrounding what might have contributed to Rivers' death remains unclear, but a spokesperson for Yorkville Endoscopy Center told ABC that "as a federally and state licensed facility, [we have] the same level of life-saving and resuscitation devices (such as state-of-the-art cardiac defibrillators, airway management equipment, etc.) found in any hospital emergency room or hospital-based operating room."

"Yorkville Endoscopy has performed 18,000 procedures since it opened in February 2013. Yorkville Endoscopy has maintained an exceptional safety record that far exceeds the national average," the spokesperson added.

The New York medical examiner's office completed an autopsy on Rivers but said Friday that no clear cause of death had been determined.