In a Hall of Fame career that spanned 32 years, Jerry Bailey could remember only a couple of times that a horse he was riding suffered what could be generically described as a heart attack.\n"Both of them were in training, and neither one was at a dead run," Bailey said this week, not long after hearing about the death of 2008 Pacific Classic winner Go Between on Monday from some kind of cardiac event. "They give you a very lethargic feel, like going down to second gear or a car running out of gas, then they seem to lose all coordination."\nBailey vividly recalls the first time it happened to him, even though it was a long time ago and he had no idea what was happening at the time. There is good reason.\n"It was actually my father's horse," Bailey said. "I was a bug boy, at Oaklawn Park, and it was the best horse he ever had. I'd never ridden him, and I was working him at Hot Springs when he had a heart attack. The phone call to my father was worse than anything."\nHoly Stone, owned by Dr. James Bailey of El Paso, was a stakes winner back in New Mexico, among them the 1972 Billy the Kid Handicap. At the time of his death, at age 6, he had run 86 races and won 14 of them.\n"My father took it well," Bailey added. "But I had never won a race for him. There I was on the best horse he'd ever owned, and the sonofagun drops dead on me."\nAny romantic notions of the Thoroughbred heart get parked by the side of the road when a horse like Go Between is stricken. Here was a genuinely fine 6-year-old athlete who embodied class at a very high level. His narrow victory over Well Armed in the Pacific Classic for trainer Bill Mott could not have been achieved without "heart," as racetrackers so often put it.\nThe factors that can lead to heart-related deaths in racehorses are complicated by their incredible cardiovascular machinery. During a race, the equine heart can oxygenate and circulate nearly 80 gallons of blood per minute. At rest, a Thoroughbred heart beats 20-30 times per minute, then increases to 240 beats per minute while racing. It has been reported that Go Between's pulse while at rest became so erratic that his heart was beating 200 times per minute. At that rate, he couldn't last long.\n"If you look at the geriatric population of horses, heart disease is probably 2 percent," said Dr. Doug Herthel, who runs the Alamo Pintado Equine Medical Center in California's Santa Ynez Valley. "What is it in humans - 80 percent? That's why in horses a coronary occlusion - a blockage - is very rare."\nHerthel noted that horses can have too much heart, in the literal sense.\n"We're talking about the heart muscle getting too big, not the volume of the chambers," Herthel noted. "Secretariat, for instance, probably had huge chambers, with more capacity to pump blood. But he didn't have what we would call an enlarged cardiomyopic heart, where the muscles are too big, and the walls are too thick to function properly."\nCardiomyopia can be hereditary in humans. In horses, who knows? Such a study might be helpful, but the samples would be rare. That leaves the inexact science of training on the front line to interpret any outward signs of subtle internal changes.\n"There's not a guy who takes better care of his horses than Mott," Bailey noted. "I mean, he's in the stalls all the time. Whatever happened to his horse wasn't something that could have been prevented, that's for sure."\nThe same can be said about trainer Greg Gilchrist, who suffered through the decline and merciful death of champion Lost in the Fog in September of 2006 after the colt had been diagnosed with malignant spinal tumors. Reached at Golden Gate, Gilchrist was especially empathetic with Mott just now. On Tuesday, the former Gilchrist-trained filly Indyanne was euthanized in Kentucky as a result of injuries suffered while running in the La Brea Stakes at Santa Anita on Dec. 27. It has been a bad week for good horses.\n"I had a nice 2-year-old once who won something like two out of his first three races and looked like a real promising horse," Gilchrist said. "One day he ran terrible, and as I watched him back at the barn cooling out he just didn't look right. I checked him, and his heartbeat was all over the place.\n"After that, we put him on heart medicine, and monitored him all the time," Gilchrist went on. "He was perfectly regular. In the morning, he'd work faster than they ran in the afternoon. But when he raced, and got stressed or in a bad situation, he would never put out. I became convinced it was like he was saying, 'You can beat on me all you want, but I'll lay down before I let that other thing happen to me again.' "\nSuch a Thoroughbred would be cruelly accused by the uninformed of lacking heart, placing him at the opposite end of the behavioral spectrum from the brave Go Between. Gilchrist, though, preferred to call him "one very smart horse." It would be heartless to think otherwise.