A 23-year-old woman, who was rushed by ambulance from Tring and District Horse Association show on Sunday, is in the intensive care unit at Wycombe Hospital.
Carla Perotton, 23, who is an instructor and groom at High Herts Riding School, near Hemel Hempstead, collapsed after she completed a showjumping round at the show.
Show secretary Val Evett-Farman told H&H: “She came to the end of the course and just slid off the side of her horse — she didn’t have a fall.
“Our first aider was with her until the ambulance came and she was resuscitated in the ambulance.
“They think she may have a heart condition.”
Carla was taken to Stoke Mandeville Hospital but moved to the intensive care unit at High Wycombe yesterday.