Trainer Mitch Beer has been forced to send stable star Redouble for an immediate spell.
Redouble pulled up with atrial fibrillation after finishing at the tail of the field in the $1m The Hunter, (1300m) at Newcastle on Saturday.
Beer said it's not the first time Redouble had suffered from the complaint which is not uncommon in gallopers.
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"It's a disappointing result but the main thing is he will bounce back from it," Beer said.
"He's had it before and then came out and won his next start so it's not career threatening.
"It's not uncommon with horses.
"He will have to trial to the satisfaction of stewards before he will be able to race again.
"But it was a long way to go for such a disappointing result.
"The kid (Tom Sherry) had him in a lovely spot and I was excited when they got to the top of the home straight because I thought he was going to be right in the finish."