It will be at least two months before the midfielder is fit enough to play for his Premier League team again, a surgeon said.
An automatic defribilator was installed in Fadiga's chest on Friday to regulate his heart-beat, the surgeon, Pedro Brugada, told a news conference with Fadiga on Monday.
Fadiga, who underwent surgery to correct an abnormal heartbeat in May, collapsed during the warm-up before Bolton's 4-3 defeat by Tottenham Hotspur.
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The 29-year-old has made only one substitute appearance for Bolton since joining them in September.
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