Deaths among young children undergoing heart surgery are lower in hospitals that carry out a high number of these operations, even when data from Bristol Royal Infirmary are excluded, confirms a study in this week's BMJ. However, this does not explain the high number of deaths at Bristol, despite being a hospital with a low volume of cases.
David Spiegelhalter, a senior scientist at the Institute of Public Health in Cambridge, used data from 12 English hospitals carrying out heart surgery on children from 1991 to 1995. His analysis excluded results from Bristol.
He found strong and consistent evidence that hospitals performing a higher number of open heart operations in children aged under 1 year tended to have a lower death rate. For instance, a hospital carrying out 120 operations per year during this period would be expected to have a 25% lower death rate than a hospital carrying out only 40 such operations.
Including the results from Bristol strengthened this association. Furthermore, only a small proportion (less than a fifth) of the excess deaths seen at the Bristol over this period was due to the hospital's lower volume of surgery, adds the author.
Considerable caution is needed in interpreting these results and the policy implications are unclear, stresses the author. It does not necessary follow that concentrating resources in fewer centres would reduce deaths, he concludes.