Joan Rivers Joan Rivers appears at the 2010 Sundance Film Festival in Park City, Utah. The longtime comedian died at the age of 81 in New York Thursday. Photo: Reuters

A newly unearthed interview with Joan Rivers indicates the late comedian’s long-standing heart condition may have been a factor in her cardiac arrest during a nonsurgical procedure last week. In the 1985 interview, Rivers, who died at the age of 81 Thursday after several days on life support, admitted to suffering from heart arrhythmia, a condition she said scared her.

“The term ‘arrhythmia’ refers to any change from the normal sequence of electrical impulses. The electrical impulses may happen too fast, too slowly, or erratically -- causing the heart to beat too fast, too slowly, or erratically,” according to the American Heart Association.

“All of a sudden, you’ll be on stage and hear ‘Tha-thud!’ ... It scares the hell out of me,” Rivers said of her health issue, which she classified as a “ladies problem” during an appearance on “Good Morning America” (via People). Rivers went on to say that the condition was especially dangerous during surgical procedures. “When you go under, say for plastic surgery or something like that, that’s when your heart can go out of kilter,” she said. “So I’m always very careful.”

Despite speculation that Rivers’ heart condition may have played a role in her passing, her official cause of death remains unknown. The New York medical examiner’s office said Friday Rivers’ autopsy results were inconclusive, pending further study, TMZ reported.

Rivers was undergoing a throat procedure at Yorkville Endoscopy in New York Aug. 28 when she stopped breathing and went into cardiac arrest. She was removed from life support at Mount Sinai Hospital in the city Thursday. “My mother’s greatest joy in life was to make people laugh,” Rivers’ daughter, fellow television star Melissa Rivers, said of the mother’s passing in a statement Thursday. “Although that is difficult to do right now, I know her final wish would be that we return to laughing soon.”

Her funeral, including a red carpet for guests, will be held at Temple Emanu-El in New York Sunday. Melissa and her son, Edgar Cooper Endicott, 13, were seen leaving a private service for Rivers at the Frank E. Campbell funeral home Saturday, the New York Post reported.

The clinic responsible for treating Joan Rivers is currently under investigation by the New York State Health Department. A source told ABC News the clinic is not suspected of any “wrongdoing.”

Rivers first made her mark in TV on the “The Tonight Show With Johnny Carson” in 1965, later earning the role of a permanent guest host on the late-night series in 1983. After years of working the standup comedy scene, she scored her own program, “The Joan Rivers Show.” To younger audiences, she is best known for her recent work hosting E’s “Fashion Police.”