American swim star Kate Ledecky was fastest in the heats for the Olympic 800 metres women’s freestyle on Friday as she bids for history in Saturday’s final. The 27-year-old is aiming to become the first woman to win the same Olympic event four times in a row, a ninth career gold would tie her with Soviet gymnast Larisa Latynina for most women’s golds overall at the Games, and would take her past Jenny Thompson for the most ever golds for a women’s swimmer. Ledecky, the Tokyo champion, swam 8 minutes 16.62 seconds ahead of fellow American Paige Madden. Ariarne Titmus of Australia, the 400m gold…