The heart is a dual two-stage pump, with inlet and outlet valves working in tandem for each “beat”. Blood enters through separate veins from upper and lower body extremities into the right auricle, from there to the right ventricle and out to the lungs for carbon dioxide removal. It returns, again through the separate veins, from the left and right lungs into the left auricle, and thence to the left ventricle. From here the flow is normally through the aortic valve, but when this valve narrows and tightens blood backwashes into the ventricle, forcing the heart to work harder to remove it. Sometimes the strain is just too much. The Silastic valve relieves this condition by by-passing the damaged valve entirely.

Dow Corning Corporation · [ca. December 1955]

[Information from item housing] Heart + Heart Surgery