Heart surgery. Gloved hands of surgeons attaching a valve sewing ring to an incompetent heart valve during coronary artery bypass surgery. The fabric ring provides support for the valve, which normally prevents blood from flowing back into the heart chamber from which it is pumped. This stops the valve from leaking. During a coronary artery bypass, lengths of vein are taken from the legs and attached to the heart to bypass narrowed or blocked coronary arteries. The coronary arteries supply the heart muscle with oxygenated blood and nutrients. Photographed at The Royal Infirmary, Edinburgh, Scotland.