Comparison of UK paediatric cardiac surgical performance by analysis of routinely collected data 1984–96: was Bristol an outlier?

Summary

Background

Reports of high mortality after paediatric cardiac surgery at the Bristol Royal Infirmary, UK, led to the establishment of an independent public inquiry. A key question was whether or not the mortality statistics in Bristol were unusual compared with other specialist centres. To answer this question, we did a retrospective analysis of mortality in the UK using two datasets.

Methods

Data from the UK Cardiac Surgical Register (CSR; January, 1984, to March, 1996) and Hospital Episode Statistics (HES; April, 1991, to December, 1995) were obtained for all 12 major centres in which paediatric cardiac surgery is done in the UK. The main outcome measure was mortality within 30 days of a cardiac surgical procedure. We estimated excess deaths in Bristol using a random-effects model derived from the remaining 11 centres. Additionally, a sensitivity analysis was done and case-mix examined.

Findings

For children younger than 1 year, in open operations, the mortality rate in Bristol was around double that of the other centres during 1991–95: within the CSR, there were 19·0 excess deaths (95% interval 2–32) among 43 deaths; and in HES, there were 24·1 excess deaths (12–34) among 41 deaths recorded. There was no strong evidence for excess mortality in Bristol for closed operations or for open operations in children older than 1 year.

Interpretation

Our results suggest that Bristol was an outlier, and we do not believe that statistical variation, systematic bias in data collection, case-mix, or data quality can explain a divergence in performance of this size.

Introduction

Reports of high mortality within paediatric cardiac surgery units at the Bristol Royal Infirmary, UK, led to the establishment of an independent public inquiry.¹ One of the key questions was whether or not the mortality statistics in Bristol were unusual compared with other specialist centres. This paper presents an analysis of data on paediatric cardiac surgery carried out at Bristol and 11 other major centres in England.

We have previously shown that, within Bristol, levels of activity (numbers of cases and deaths) recorded in seven available datasets held for purposes of clinical audit or management (and, in one case, collated specifically for the Inquiry) were broadly similar, with no large discrepancies that could not be accounted for.2, 3, 4, 5, 6 Of these datasets, two were national: Hospital Episode Statistics (HES) and the UK Cardiac Surgical Register (CSR). Despite the limitations of routine data, national comparisons with these two sets of data could be undertaken.

Although our study concerns outcome of paediatric cardiac surgery, its approach and methodology is applicable more generally to comparison of performance across a wide range of specialties.