Risk and pediatric cardiac surgery

There is always risk involved in pediatric cardiac surgery. Various attempts have been made to estimate the level of risk associated with surgically treating each of the known pediatric congenital heart lesions.

During the course of 1994, parents in Winnipeg were given estimates by the doctors involved as to how many patients were likely to survive a particular procedure. At the time, there was no single book or list of percentages that contained a definitive estimation of the risk for each procedure, although information was available from pediatric cardiac surgeons and cardiologists working in other centres. Risk depends on many factors, including the specifics of the patient's condition, the skills and experience of the team, available technology and the overall growth of medical knowledge. One variable that recent research has focused attention on is the relationship between the numbers of cases a hospital deals with and results as measured by mortality.

Two academic articles presented to this Inquest examined this question. The articles were "In-Hospital Mortality for Surgical Repair of Congenital Heart Defects: Preliminary Observations of Variation by Hospital Caseload," by Kathy J. Jenkins MD MPH, Jane W. Newburger MD MPH, James E. Lock MD, Roger B. Davis ScD, Gerald A. Coffman MSc and Lisa I. Iezzoni MD MSc, published in the journal Pediatrics (Volume 95, Number 3 (March 1995), pages 323-330) and "Pediatric Cardiac Surgery: The Effect of Hospital and Surgeon Volume on In-Hospital Mortality," by Edward L. Hannan PhD, Michael Racz MS, Rae-Ellen Kavey MD, Jan M. Quaegebeur MD PhD and Roberta Williams MD, published in the journal Pediatrics (Volume 101, Number 6 (June 1998), pages 963-969).

Both articles came to similar conclusions. The Jenkins study made the following comment:

In our study population, the risk of dying in-hospital was much less for children who underwent surgical correction of a congenital heart defect at institutions with the highest volume of such patients, in comparison with lower volume centres. Outcomes at the highest volume institutions appeared clearly different than those for other institutions; below 300 cases annually, no consistent trends in mortality by annual case volume were observed. (Jenkins et al, pages 327-328)

The Hannan study commented:

Findings of the study were that annual hospital volume and annual surgeon volume were both significantly related to inpatient mortality rates, even after controlling for patient age and several clinical risk factors in addition to procedure complexity. The maximal differentiation in mortality rates between high and low-volume providers was 100 procedures annually for hospital and 75 procedures annually for surgeons. (Hannan et al, page 968)

This issue of the relationship between the number of procedures carried out in a pediatric cardiac surgery program and the mortality rate is one that will be returned to later in this report.