Abstract: Bi-leaflet and single occluder heart valves have improved pivot arrangements that create quick valve response to flow reversal and minimize impact. Valve members or occluders, which are slidably and pivotally mounted in a heart valve body, can be aligned precisely parallel to blood flow in the open position. Lugs on the valve members engage surfaces on projections extending radially inward from flat wall sections in the valve body sidewall, and the shape and relationship of these interengaging surfaces provide prompt initial rotation, low wear and reduced impact upon closing. Laterally directed ears engage the valve body arcuate sidewall and assist in defining the path of closing movement.