Trends in 30-day mortality rate and case mix for paediatric cardiac surgery in the UK between 2000 and 2010

Abstract

Objectives: To explore changes over time in the 30-day mortality rate for paediatric cardiac surgery and to understand the role of attendant changes in the case mix.

Methods setting and participants: Included were: all mandatory submissions to the National Institute of Cardiovascular Outcomes Research (NICOR) relating to UK cardiac surgery in patients aged <16 years. The χ(2) test for trend was used to retrospectively analyse the proportion of surgical episodes ending in 30-day mortality and with various case mix indicators, in 10 consecutive time periods, from 2000 to 2010. Comparisons were made between two 5-year eras of: 30-day mortality, period prevalence and mean age for 30 groups of specific operations.

Main outcome measure: 30-day mortality for an episode of surgical management.

Results: Our analysis includes 36 641 surgical episodes with an increase from 2283 episodes in 2000 to 3939 in 2009 (p<0.01). The raw national 30-day mortality rate fell over the period of review from 4.3% (95% CI 3.5% to 5.1%) in 2000 to 2.6% (95% CI 2.2% to 3.0%) in 2009/2010 (p<0.01). The case mix became more complex in terms of the percentage of patients <2.5 kg (p=0.05), with functionally univentricular hearts (p<0.01) and higher risk diagnoses (p<0.01). In the later time era, there was significant improvement in 30-day mortality for arterial switch with ventricular septal defect (VSD) repair, patent ductus arteriosus ligation, Fontan-type operation, tetralogy of Fallot and VSD repair, and the mean age of patients fell for a range of operations performed in infancy.

Conclusions: The raw 30-day mortality rate for paediatric cardiac surgery fell over a decade despite a rise in the national case mix complexity, and compares well with international benchmarks. Definitive repair is now more likely at a younger age for selected infants with congenital heart defects.

Keywords: CONGENITAL HEART DISEASE; QUALITY OF CARE AND OUTCOMES.

Figure 1

UK paediatric cardiac surgery mortality rate by year for all cases and total number of procedures performed between 2000 and 2009/2010. Figure shows observed annual paediatric cardiac surgery case numbers for each completed year between 2000 and 2009 (presented as a single year in this instance) and national unadjusted 30-day mortality with 95% CI by year between 2000 and 2009/2010.

Figure 2

UK trends in paediatric cardiac surgery case volume analysed by risk band between 2000 and 2009. Figure shows observed annual paediatric cardiac surgery case numbers for each completed year between 2000 and 2009 (presented as a single year in this instance) divided by the risk band of each surgical episode. Risk band 1—less than 1% estimated risk of death; band 2—cases with estimated risk between 1% and up to 3%; band 3—cases with between 3% and 10% estimated risk and band 4—cases with over 10% estimated risk.

Figure 3

UK trends in paediatric cardiac surgery case mortality rate analysed by risk band between 2000 and 2009/2010. Figure shows the national unadjusted 30-day mortality with 95% CI by year between 2000 and 2009/2010 divided by the risk band of each surgical episode. Risk band 1—less than 1% estimated risk of death; band 2—cases with estimated risk between 1% and up to 3%; band 3—cases with between 3% and 10% estimated risk and band 4—cases with over 10% estimated risk.

Figure 4

UK trends in selected aspects of paediatric cardiac surgery case mix between 2000 and 2009/2010. Figure shows selected aspects of the national case mix related to all paediatric cardiac surgery cases for each year between 2000 and 2009/2010 shown as a proportion with 95% CI. These are operations in patients with functionally univentricular hearts (triangle); operations performed in patients with underlying higher risk congenital heart disease types (diamond), include hypoplastic left heart syndrome, pulmonary atresia with intact septum and interrupted aortic arch; operations in babies weighing <2.5 kg (square) and cases in risk band 4 (circle).

Figure 5

UK paediatric cardiac surgery 30-day mortality rates for individual specific procedures by era (2000–2004 compared with 2005–2010). Figure shows observed 30-day mortality for specific procedure groups in the first era 2000–2004 (circles) and the second era 2005–2010 (crosses) with 95% CI (bars). The vertical lines denote the mean 30-day mortality in the first era (black continuous, representing 3.4%) and the second era (blue dashed, representing 2.9%). Data are ordered in decreasing 30-day mortality for the first era 2000–2004. The low-volume procedure group (n=528, 1.4% of operations performed) includes aortic root replacement (not Ross), aortopulmonary window repair, atrioventricular septal defect and tetralogy repair, cor triatriatum repair, multiple VSD closure, Senning or Mustard procedure, tetralogy with absent pulmonary valve repair, total anomalous pulmonary venous connection repair plus arterial shunt, tricuspid valve replacement and truncus with interrupted aortic arch repair. The ‘not a specific procedure’ group contains all bypass and non-bypass cardiac operations that did not fall into a defined group: 6791 (18.5%) operations performed. VSD, ventricular septal defect; PDA, patent ductus arteriosus; AVR, aortic valve replacement; ASD, atrial septal defect.