Association of center volume with outcomes: analysis of verified data of European Association for Cardio-Thoracic Surgery Congenital Database.

BACKGROUND

The relation between surgical volumes and outcome in congenital heart surgery (CHS) was investigated with no clear conclusions. We sought to quantify the relationship between surgical volume and surgical performance defined as the relation between outcome and Society of Thoracic Surgeons-European Association for Cardio-Thoracic Surgery Congenital Heart Surgery (STAT) Mortality Score and The Society of Thoracic Surgeons (STS) Morbidity Score.

METHODS

We have used only the verified data of the European Association for Cardio-Thoracic Surgery Congenital Database. The verified dataset consists of 17,861 procedures performed in 23 congenital heart surgery centers between 2003 and 2011. The centers were divided into 4 volume-related groups with annual caseload of below 150, 150 to 250, 250 to 350, and over 350. Stepwise logistic regression was used to calculate the ratio between volume and mortality, as well as between volume and onset of complications. The relations between volume and STAT Mortality Score, and STS Morbidity Score were evaluated using the analysis of variance test. The performance was calculated as the following: 100 - observed mortality/STAT Mortality Score; and 100 - observed complications/STS Morbidity Score.

RESULTS

The study showed no relation between volume and raw mortality (p = 0.94) and between volume and complications (p = 0.6). The STAT Mortality Score and STS Morbidity Score were higher in larger volume centers (p < 0.001). Surgical performances measured as related to mortality and morbidity were higher at high-volume centers (R(2) = 0.95 and R(2) = 0.92).

CONCLUSIONS

Our analysis suggests that after adjustment for case mix higher programmatic volume is associated with lower rates of mortality and morbidity. The small- and medium-volume centers have higher rates of major complications. When complications occurred the chance of rescue is higher in large-volume centers.