Calling all heart patients who received a Bjork-Shiley 60-degree convexo-concave implanted valve. Pfizer Inc. is conducting an unprecedented search to warn recipients about rare but often fatal fractures of the implanted heart valve. The valve was implanted in about 82,000 people worldwide between 1979 and November 1986. The search is being run by Medic Alert, a non-profit foundation. For information, call (800) 245-1492.