Go Between, a winner of three $1 million races including the 2008 Pacific Classic, died following a Monday workout at the Payson Park training center in Indiantown, Fla.\nTrainer Bill Mott said Tuesday that after Go Between worked six furlongs in 1:17.80 over the deep Payson surface, the horse began to experience heart problems.\n"I guess you could say he died of cardiac arrest," said Mott. "He had put in a subpar work, which was very unusual for him, and came off the track blowing pretty hard."\nMott said that Dr. Jim Pendergast quickly attended to Go Between, a 6-year-old horse, "and the horse just wasn't recovering very well. His heart rate was so fast you couldn't even count the beats. We tried to get his heart rate down for about two hours . . . then he just expired. It was a very sad thing to watch. Everybody was here in the barn, and when a horse has been around that long . . . he had a lot of friends around the stable. It was hard for everybody.\n"I guess that most horses that that happens to, they don't even make it back from the track," Mott continued. "They just die right there. One of the sad things is we had absolutely no indication that something was wrong. Before the work, it seemed like he was better than he'd ever been."\nBred and owned by Peter Vegso, Go Between was a Florida-bred by Point Given. His 27-race career was highlighted by wins in three $1 million races: the Virginia Derby in 2006, and the Sunshine Millions Classic and Pacific Classic in 2008.\nGo Between's racing career was given a substantial lift by the proliferation of synthetic tracks in North America in recent years. He began his career competing primarily on turf, collecting wins in the Palm Beach Stakes and the Virginia Derby at 3, but it wasn't until after he won the Grade 3 Fayette Stakes on the Polytrack surface at Keeneland in October 2007 that his profile became even more nationally recognized. From seven overall starts on synthetics, he posted 3 wins and 3 seconds, earning $1,748,000, accounting for well more than half his lifetime bankroll of $2,908,880 from 27 starts.\nGo Between was being pointed to the Jan. 24 Sunshine Millions Classic on the dirt at Gulfstream Park. In what was his final career start, he finished fifth with traffic trouble in the Oct. 25 Breeders' Cup Classic at Santa Anita.