When a horse runs badly, lameness or respiratory disease tends to immediately spring to mind, and indeed these are the most common causes—in that order. The heart comes in third, albeit quite a way behind these other body systems. If sudden death occurs in an equine athlete, a heart problem is usually the first thing that’s suspected. A new study, published in The Equine Veterinary Journal, provides significant insights on the cardiac rhythm abnormalities that can develop during and after racing in Standardbreds.