The challenge of departmental quality control in the reengineering towards off-pump coronary artery bypass grafting

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Abstract
Objective: Off pump coronary surgery is a major reengineering effort of the surgical systems. There are no perfect tools available to guide every centre in the confrontation with the complete spectrum of risk and the limited number of events. This study analyses the use of a hospital mortality risk-stratifying system in the complete shift towards off-pump CABG. Methods: All 535 off-pump CABG patients from January 1997 till September 2000 underwent a comparison of their hospital mortality versus the EuroSCORE predictions. The mean risk predicted by the EuroSCORE was 4.5±3% (range 0–14) and the mean age was 65±10 years (range 36–89). The series includes 23 repeat procedures, also 77 patients with per oral or insulin-treated diabetes. The number of distal anastomoses was 2.5±1 and of arterial grafts 1.3±0.6. Results: The observed hospital mortality was 15 patients, 2.8% (Fisher exact test P=0.19 versus the EuroSCORE). The 1 and 3 month Kaplan–Meier survival, irrespective from hospital discharge, was 97.4±0.7 and 97.2±0.7%, respectively. A cumulative risk-adjusted mortality plot is constructed. The area under the ROC curve was 0.886. A stepwise sampling of patients according to increasing risk identified the difference between the EuroSCORE-predicted and observed hospital mortality for the complete spectrum of risk. The P value of this difference was 0.06 for the grouping including all patients from 0–5% risk (78% reduction), 0.04 for the grouping 0–8% risk (61% reduction), and 0.05 for the grouping 0–11% risk (52% reduction of risk). The loss of statistical significant difference was due to the inclusion of the patients at extremely high risk. Conclusion: A hospital mortality risk-stratifying system can provide guidance but different and in depth approaches are mandatory to improve the insight, certainly in the presence of a large spectrum of risk.