Quantification of operational learning in off-pump coronary bypass

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The use of off-pump coronary artery bypass grafting (OPCAB) has been associated with similar or even worse results vs on-pump coronary artery bypass graft (CABG). Different production processes demand re-engineering, operational learning and quality loops to study and reduce negative learning curves. This analysis studies and quantifies the impact of these processes on the early mortality of continued re-engineering and quality loops within the OPCAB patient group.


We re-engineered CABG towards OPCAB in October 1999. A consecutive cohort of 3054 patients, representing 92.3% (ranging from 90% in 2000 to 99% in 2001 and later) of all primary and redo isolated CABG from that same period, was divided into three consecutive cohorts of 1018 patients. An anniversary follow-up at 3 months was complete for 100% of the patients. The 1- and 3-month survivals are studied using saturated propensity score matching and stratification for cohort variability (area under the curve = 0.82).


Despite a progressively worsening risk profile (history of vascular disease, stroke and diabetes; main stem stenosis; left ventricular dysfunction), a survival improvement was shown between the consecutive cohorts. This improvement remained valid after the propensity stratification and propensity matching at 1 (97.6 vs 99.3%, P < 0.001) and at 3 months (96.7 vs 98.8%, P < 0.001).


OPCAB re-engineering, followed by operational learning, improved the early survival even in the presence of a worsening risk profile.

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