Initial application in the STS congenital database of complexity adjustment to evaluate surgical case mix and results

Background. The analysis of the second harvest (19982001) of the Society of Thoracic Surgeons Congenital Heart Surgery Database included the first attempt by the STS to apply a complexity-adjustment method to evaluate congenital heart surgery results. Methods. This data harvest represents the first STS multiinstitutional experience with software utilizing the international nomenclature and database specifications adopted by the STS and the European Association for Cardio-Thoracic Surgery (April 2000 Annals of Thoracic Surgery) and the first STS Congenital Database Report incorporating a methodology facilitating complexity adjustment. This methodology, allowing for complexity adjustment, gives each operation a basic complexity score (1.5 to 15) and level (1 to 4) based upon the work of the EACTS-STS Aristotle Committee, a panel of 50 expert surgeons. The complexity scoring, based on the primary procedure (from the EACTS-STS International Nomenclature Procedures Short List), estimates complexity through three factors: mortality potential, morbidity potential, and technical difficulty. Results. This STS harvest includes data from 16 centers reporting 12,787 cases, with discharge mortality known for 10,246 cases. The basic complexity score has been applied to the outcomes analysis of these cases and a new equation has been proposed to evaluate one aspect of performance: Aristotle Performance Index = Outcome X Complexity = (Survival) X (Mean Complexity Score). Conclusions. The complexity analysis represents a basic complexity-adjustment method to evaluate surgical results. Complexity is a constant precise value for a given patient at a given point in time; performance varies between centers. Future STS congenital data harvests will incorporate a second step, the Comprehensive Aristotle Score, utilizing additional patient specific complexity modifiers to allow a more precise complexity adjustment. © 2005 by The Society of Thoracic Surgeons.