Mother-of-three June Blacker lay helpless on the operating table as she felt a surgeon's scalpel cut into her stomach.
She suffered a heart attack 15 minutes after the operation to sterilise her began.
Her two-year legal battle has ended with Bro Taf, the health authority concerned admitting liability. The amount of compensation is yet to be decided.
Mrs Blacker told yesterday how doctors failed to notice the anaesthetic had not taken effect. But she was unable to raise the alarm because she had been given muscle-relaxing drugs.
The 45-year-old catering worker, who suffers from post-traumatic stress disorder, said: "It was every patient's worse nightmare."
Mrs Blacker, of Aberdare, Glamorgan, was admitted to Prince Charles Hospital, Merthyr Tydfil, South Wales, for the operation.
She spent two days in intensive care before being allowed home.