We know that Usher's wife (Tameka Foster) was to have an operation in South America recently and it was aborted due to cardiac arrest. This has been referred to as botched plastic surgery although we do not know if any plastic surgery occurred.
I serve as an expert reviewer on California's Medical Board for plastic surgery cases. In the really rare event that cardiac arrest occurs in any elective surgery case, it is frequently an issue of hypoxia, meaning adequate oxygen wasn't getting to the patient's tissues. This is more likely when the center in which the procedure is being performed is not "up to snuff" on equipment and staff.
Was this the cause in Mrs Foster's case? I don't know. Furthermore, I do not know what the procedure is for investigating such an incident outside of the State of California. As I have said before there are risks to "Surgical Tourism."
Hopefully Mrs Foster will recover well for this unfortunate event. It is my understanding that she had returned to the US at this point.