Secretariat's Heart Weighed Three Times More Than a Normal Horse's

When Secretariat died in 1989, veterinary pathologist Dr. Thomas Swerczek performed a necropsy and made a startling discovery. By examining the heart of Secretariat's rival Sham, which weighed 18 pounds, he estimated Secretariat's heart at an astonishing 22 pounds. The average Thoroughbred heart weighs only 8.5 pounds. This anatomical anomaly, often called the 'X-factor,' is believed to have been inherited from his dam Somethingroyal. Interestingly, while none of Secretariat's sons inherited his massive heart, some of his daughters did. All 19 entrants in the 2023 Kentucky Derby were descendants of this remarkable champion.