LONDON (AP) -- Sprinter Sacre, one of Britain's top horses, will undergo heart tests after pulling up during his seasonal debut this week.
The 7-year-old steeplechaser's trainer, Nicky Henderson, said Saturday that "the only thing we know at the moment is that he did have an irregular heartbeat and that is what we're concentrating on. It's the only explanation."
Sprinter Sacre was described by his jockey Barry Geraghty as horse racing's version of football great Pele after winning his first 10 races over fences. However, he withdrew halfway through a race at Kempton on Friday to lose his unbeaten record.
He was being assessed Saturday by Celia Marr, a specialist in equine internal medicine and cardiology who worked on Denman after the former Cheltenham Gold Cup winner had a similar complaint.