She suffered cardiac arrest, not a heart attacks.
The entire history is here, the Wolfson report which is generally considered the most comprehensive history of the entire matter. He was one of her four guardian ad litems and was trusted by both parties.
http://freerepublic.com/focus/f-backroom/1370047/posts?page=1264#1264
Is this the same Wolfson that I read about on another thread with all the connections to the hospice Terri is in?