Assessment of a congenital heart surgery programme: a reappraisal

To assess our practice according to the Society of Thoracic Surgeons and the European Association for Cardio-Thoracic Surgery (STS-EACTS) Mortality Score and to the new concept of unit performance.

All main procedures carried out in the years 2012-2016 were analysed. The STS-EACTS model-based mortality risk procedure was used to calculate expected mortality. Surgical performance was estimated as the Aristotle complexity score multiplied by hospital survival. Unit performance was defined as surgical performance multiplied by the number of procedures.

In total, 2435 procedures were analysed. One hundred and two deaths (95% confidence interval 71-135 deaths) were expected; 43 patients died after operation. Observed mortality divided by expected mortality was 0.42. The ratio ranged from 0.23 (year 2014) to 0.59 (year 2013) and was <0.6 in all STS-EACTS mortality categories. The difference between observed and expected mortality was highly significant: 1.8% vs 4.2% (P-value <0.0001). Observed surgical and unit performances were, higher than expected performances every year. Achieved surgical performance was the highest in year 2012 (7.28 ± 2.54) and the lowest in year 2014 (7.04 ± 2.52). The highest figure of unit performance was achieved in year 2016: 3980 points.

The STS-EACTS score, currently recognized as a sound instrument to assess mortality after congenital heart surgery, overestimated postoperative mortality. If these results are confirmed by other centres, the model should be recalibrated to match the current surgical practice. Although surgical performance can evaluate outcome quality, it does not include case volume activity. Unit performance provides this information, and it integrates quality and quantity into a single value.