Joan Rivers was frightened by her heart condition.

The 81-year-old comedienne, who passed away last week following surgical complications, admitted in a previous interview that she suffered from heart arrhythmia, a condition which causes the heart to unexpectedly beat out of sync, and undergoing surgery could make it ''go out of kilter.''

Speaking to Joan Lunden on 'Good Morning America' in 1985, she said: ''All of a sudden you'll be on stage and hear 'tha-thud!' ... It scares the hell out of me.

''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.''

The 'Fashion Police' host died last Thursday (04.09.14), a week after she was placed in a medically-induced coma at Mount Sinai hospital, following a cardiac and respiratory arrest while undergoing a routine operation on her vocal cords at a private clinic.

However, the New York Medical Examiner's Office have completed a physical examination of Joan's body but could not find a clear ''cause and manner of death.''

Further tests will be carried out on the star's remains to determine exactly how she died, including toxicology testing, and the clinic's medical team will also be interviewed about the throat procedure she was undergoing when she stopped breathing on August 28.

A private funeral is scheduled to take place tomorrow (07.09.14) at Temple Emanu-El in Manhattan.