Pacemaker - surgery - effects

  Good day;
  After the pacemaker was implanted in a patient he was complaining of chest pains, unfortunately the doctors did not intervene and sent him home. That night he was sent back to another hospital and had to have his stomach pumped. He was then transferred to the same hospital where his pacemaker was implanted and had some test done.
  He now has lost fifty percent of his sight because of brain damage. Apparently, from the tests done at the second hospital, his brain lacked oxygen and his neurones died.
  Is there any history of this happening ? If so, how do you explain it?Can the pacemaker have malfunctionned or could it be because of the surgery?
  Thank you for your knowledge and response.
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Dear  Denton,
I am sorry to hear of your friends difficulties.  Without knowing the specifics of the case I can