Congenital Heart Surgery: Expected Versus Observed Surgical Performance According to the Aristotle Complexity Score

Abstract

Background: The Aristotle score quantifies the complexity involved in congenital heart surgery. It defines surgical performance as complexity score times hospital survival. We studied how expected and observed surgical performance evolved over time. Methods: 2312 main procedures carried out between 2006 and 2010 were analyzed. The Aristotle basic score, corresponding hospital survival and related observed surgical performance were estimated. Expected survival was based on the mortality risks published by O'Brien and coauthors. Observed performance divided by expected performance was called the standardized ratio of performance. This should trend towards a figure above 100 %. Survival rates and performance are given with 95 % confidence intervals. Results: The mean Aristotle basic score was 7.88 ± 2.68. 51 patients died: observed hospital survival was 97.8 % (97.1 % – 98.3 %). 115 deaths were anticipated: expected survival was 95.2 % (93.5 % – 96.3 %). Observed and expected surgical performance reached 7.71 (7.65–7.75) and 7.49 (7.37–7.59), respectively. Therefore the overall standardized ratio of performance was 102.94 %. The ratio increased from 2006 (ratio = 101.60 %) to 2009 (103.92 %) and was 103.42 % in 2010. Performance was high for the repair of congenital corrected transposition of the great arteries and ventricular septal defect (VSD) by atrial switch and Rastelli procedure, the Norwood procedure, repair of truncus arteriosus, aortic arch repair and VSD closure, and the Ross-Konno procedure, with corresponding standardized ratios of 123.30 %, 116.83 %, 112.99 %, 110.86 % and 110.38 %, respectively. With a ratio of 82.87 %, performance was low for repair of Ebstein's anomaly. Conclusion: The standardized ratio of surgical performance integrates three factors into a single value: procedure complexity, postoperative observed survival, and comparison with expected survival. It constitutes an excellent instrument for quality monitoring of congenital heart surgery programs over time. It allows an accurate comparison of surgical performance across institutions with different case mixes.

Key words

congenital heart disease - CHD - outcomes (includes mortality - morbidity) - quality assessment - risk adjusted method

References

• 1 Lacour-Gayet F, Clarke D, Jacobs J et al. The Aristotle score: a complexity-adjusted method to evaluate surgical results.  Eur J Cardiothorac Surg. 2004;  25 911-924
• 2 O'Brien S M, Clarke D R, Jacobs J P et al. An empirically based tool for analyzing mortality associated with congenital heart surgery.  J Thorac Cardiovasc Surg. 2009;  138 1139-1153
• 3 Welke K F, Diggs B S, Karamlou T, Ungerleider R M. Comparison of pediatric cardiac surgical mortality rates from national administrative data to contemporary clinical standards.  Ann Thorac Surg. 2009;  87 216-222
• 4 Jacobs J P, Lacour-Gayet F G, Jacobs M L et al. Initial application in the STS congenital database of complexity adjustment to evaluate surgical case mix and results.  Ann Thorac Surg. 2005;  79 1635-1649
• 5 O'Brien S M, Jacobs J P, Clarke D R et al. Accuracy of the Aristotle basic complexity score for classifying the mortality and morbidity potential of congenital heart surgery operations.  Ann Thorac Surg. 2007;  84 2027-2037
• 6 Heinrichs J, Sinzobahamvya N, Arenz C et al. Surgical management of congenital heart disease: evaluation according to Aristotle score.  Eur J Cardiothorac Surg. 2010;  37 210-217
• 7 Kang N, Tsang T V, Elliott M J, de Leval M R, Cole T J. Does the Aristotle score predict outcome in congenital heart surgery?.  Eur J Cardiothorac Surg. 2006;  29 986-990
• 8 Macé L, Bertrand S, Lucron H et al. Paediatric cardiac surgery and autoevaluation: risk score and graphic analysis.  Arch Mal Coeur. 2005;  98 477-484
• 9 DeCampli W M, Burke R P. Interinstitutional comparison of risk-adjusted mortality and length of stay in congenital heart surgery.  Ann Thorac Surg. 2009;  88 151-157
• 10 Sinzobahamvya N, Kopp T, Photiadis J et al. Surgical management of congenital heart disease: correlation between hospital costs and the Aristotle complexity score.  Thorac Cardiovasc Surg. 2010;  58 322-327
• 11 Sinzobahamvya N, Photiadis J, Arenz C et al. Applicability of hospital reimbursement according to German diagnosis-related groups system in conformity with the Aristotle complexity score.  Thorac Cardiovasc Surg. 2010;  58 328-332

1 Both authors contributed equally to this work (see acknowledgement).