Heart surgery. Image 7 of 24. Surgeon attaching a patient to a heart-lung machine during heart surgery. A metal retractor is keeping the chest open. The tubes will join the patient's arteries and veins to the heart-lung machine, which maintains the patient's circulation while the heart is temporarily stopped. The heart is being prepared for heart valve replacement surgery. For a sequence showing the operation, see images M560/494 to M560/517.