Sixty-five years ago this week, on the 2nd September 1952, surgeons at the University of Minnesota, Floyd John Lewis (1916-1993) and Walton Lillehei (1918-1999), made medical history by performing the first successful open heart surgery. It was a milestone in cardiac surgery – as little as 25 years earlier, such an operation would have been seen as practically impossible. What developments in medical practice led to this landmark?