Mode of intervention was elective in 768 patients, urgent in 185 patients, and emergent in 102 patients (9.7%). The in-hospital mortality rate was 5.1% and ranged from 3% (group 3) to 9% (group 11). The percentage of triple-vessel disease and the mean number of diseased vessels increased over time. The mean number of distal anastomoses increased over time, from 2.64 ± 0.82 in group 1 to 4.13 ± 0.98 in group 11. It reached a plateau of 4.0 at group 7 (cases 600–700). The revascularization index also increased over time, from 1.01 ± 0.20 in group 1 to 1.41 ± 0.28 in group 11. It reached a plateau of 1.4 at group 7 (cases 600–700). The conversion rate in nonemergent cases decreased rapidly as the volume of OPCAB increased, and it reached a baseline of 5% at group 3 (cases 200–300).
Surgical proficiency at performing OPCAB could be evaluated with 2 quality indicators: revascularization index of 1.4 or more and conversion rate in nonemergent cases of 5% or less. The required case number for technical maturation was 200 to 300 for conversion and 600 to 700 for complete revascularization.