Paediatric heart transplant surgery. This close- up shows the tiny defective heart, the size of a walnut, held next to the transplanted heart. The patient, a 6 week old boy, was suffering from a life-threatening congenital heart defect. Throughout the operation, the functions of the heart & lungs were taken over by a machine, & his body temperature cooled to 15 degrees C. The defective heart was replaced with a donor organ; connections to blood vessels were made using sutures 1/3 the width of a human hair. With the heart in place, body temperature was gradually restored to normal and the new heart induced to beat.