We previously reported that the frequency of the T allele of the ACTN3 R577X variant is underreported in elite AF [75,76], reflecting the results of Massidda, Bachis, Corrias, Piras, Scorcu, Culigioni, Masala, and Calo [76] who found no significance in ACTN3 polymorphism distribution in Italian team sports athletes, endurance athletes, and healthy controls. This evidence concerns the gene ACTN3 and atrial fibrillation.