The United States rider, on board Capital Colnardo Clinch, negotiated the jump-off in Californian capital Sacramento with zero faults and in the quickest time of 39.85 seconds.

Brazil's Eduardo Menezes, riding Catalina, also went round with no faults but had to settle for silver with a slower time of 40.84sec.

Bronze went to Canada's Christopher Surbey and Arezzo, who were timed at 42.47sec and were also faultless.

All eight riders in the jump-off had earlier gone round fault-free to guarantee the extra round of action.

"It feels great - it’s really great to be here, back on home turf," said Coulter, a native of California who won a major competition for the first time.

"I grew up coming to this show all the time, so it’s nice to be back and have a win. 

"I thought it was a well-set course. 

"It was tricky. 

"It all came up very quickly indoors, and it was hard, but we had a great jump-off, and I was really happy with how my horse jumped."

The course at the Murieta Equestrian Center was designed by Brazil's Guilherme Jorge and included two combinations, a double and a triple, bending lines, and short turns off the rail.

Riders needed to maintain a good pace and a defined track to go clear.

"I had coach Harrie Smolders watching on the screen in the warm-up [during the jump off] and he watched people go and said that I could definitely make up time from fence one to two," Coulter added. 

"That was the main place. 

"Then to the double, I went around and turned tight and got a good jump, and we had a good gallop to the last jump."