Here is a wonderful Video  by Mark Russell.
IMO everyone aspiring to horsemanship that is for the horse should have a copy of his book' Lessons in Lightness" A great working guide for all levels .

Nice brief article on Tying Up syndrome in horses.

I have had more questions come in about it this year than I ever recall.

http://www.wisconsinequineclinic.com/uploads/What_Is_Tying_Up.pdf