Officials hold up tarps to shield the horse from the public after it collapsed and died on Sunday evening. (CBC)

A rider is in hospital after her horse suffered a suspected heart attack and fell on her during a Calgary Stampede event.

Amy Carver was competing in the team cattle penning event on Sunday evening when her horse collapsed, causing her to fall and strike her head. She was then pinned under the animal for a few moments.

Carver is in intensive care in a Calgary hospital with a traumatic head injury and a broken shoulder blade, said a statement released by her family on Monday.

In team penning, three riders on horseback have 60 seconds to separate three kinds of cattle from a herd of 30 and place them into a pen at the opposite end of the arena. The event calls for speed and teamwork.

Amy Carver suffered a traumatic head injury and a broken shoulder blade after falling from her horse. (Courtesy Chinook Team Penning Association)

Carver was competing with her father and brother at the time of the accident.

"The family is guardedly optimistic of a full recovery although with injuries of this nature it is much to early to tell. The family wishes to express thanks for all the support," they said.

Veterinarian Dennis Rach said the animal, which was 10 to 15 years old, died instantly which probably spared its rider from further injury.

Rach said the horse was otherwise healthy and whatever led to its demise would not have been caught in a standard pre-event examination.

"You wouldn't pick this up with an electrocardiogram even before. This is usually related to a rupture of the pulmonary artery or an electro-cardiovascular event," he told CBC News.

The Calgary Humane Society is waiting for a final report on the horse's death and will see if anything could have been done differently, said a spokesperson.

With files from the CBC's Alison Myers