Drizzle, a cherished polo pony belonging to the Royal Family of Wales, died during a polo match May 8 following a cardiac event, according to several sources.

The 10-year-old dark brown and white spotted mare "could not be saved," said a spokesperson for the Royal Family at the Clarence House in London. Prince Harry of Wales had been riding her for approximately three minutes when he sensed she was unwell and sought veterinary care. The horse then collapsed and died, the spokesperson said.

"She wasn't on the pitch long before (Harry) took her over to the side," said Roddy Wood, polo manager at Coworth Park in Ascot (Berkshire), where the charity match took place.

Veterinarians from Shotter and Byers Equine Veterinary Services, based in Surrey, examined the horse immediately. Sudden cardiac death was the diagnosis given at the scene by the veterinary team, Wood said. The attending veterinarians declined to comment.

"When a horse starts exercising, its heart rate can go from 25 beats per minute to over 200, with the heart pumping out five times as much blood," said Lesley Young, PhD, BVSc, DVA, DVC, DipECEIM, MRCVS, RCVS-recognized specialist in veterinary cardiology, based in Newmarket, England. Fast exercise also results in increased blood pressure and body temperature; at the same time, blood oxygen levels drop while lactic acid accumulates.

"This is a potentially bad environment for any heart, even a healthy one," said Young. "When circumstances conspire, a fatal heart rhythm problem or fatal hemorrhage can occasionally result."

Even so, this type of tragedy remains extremel