The CABG surgery volume-outcome relationship: temporal trends and selection effects in California, 1998-2004.

In California, where no state regulations support regionalization of CABG surgeries, a weak volume-outcome relationship was present from 1998 to 2002, but was absent in 2003 and 2004. The disappearance of the volume-outcome association was temporally related to the implementation of a statewide mandatory CABG surgery reporting program.