Stephen Sackur talks to leading Cardiac Surgeon Samer Nashef at the Hay literary festival in Wales. There is something special about the human heart. We live with, and by, its constant beat. We invest it with our deepest feelings. So naturally we reserve something like reverence for the surgeons who try to fix it when it is broken. Samer Nashef has chosen to write, with honesty, about the highs, the lows and the limitations of life and death surgery.