The 1973 Triple Crown winner, Secretariat, had a reputation of running just fast enough to beat his competition. After the racehorse’s death, it was discovered during the necropsy that Secretariat’s heart was perfect, no problems with it, but weighed between 21-22 pounds. [An average horse has a heart weight of about nine pounds.] Not to be forgotten is Secretariat’s key rival, Sham. He was a fantastic racehorse who not so surprisedly also had a big heart with a weight of…..