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Objective: Although the safety and efficacy of minimally invasive coronary artery bypass grafting (MICS CABG) have been reported, the procedure is still limited to a few experienced surgeons because specialized techniques are required. This study examined the effects of learning curve on clinical outcomes and operation time in MICS CABG.
Methods: Logistic regression analysis was performed to investigate the relationship between 1-year clinical outcomes (bleeding, myocardial infarction, revascularization, mortality) and the number of MICS CABG performed by a surgeon. Curve regression analysis was performed to assess the correlation between operation time and number of MICS CABG performed. Follow-up beyond the first postoperative year was 100% complete. Also, a cumulative summation (CUSUM) technique was performed to evaluate learning curves.
Results: MICS CABG was performed in 200 consecutive patients by the same surgeon [3 cardiopulmonary bypass (CPB)- assisted single vessel small thoracotomy (SVST), 82 off-pump SVST, 50 CPB-assisted multivessel small thoracotomy (MVST) and 65 off-pump MVST]. There was no perioperative mortality, and 5 patients (2.5%) underwent reopening for perioperative bleeding. No complications occurred as a result of CPB assistance. At 1 year follow-up, 1 patient had a myocardial infarction, 1 patient had a percutaneous coronary intervention, and there were 2 non-cardiac deaths. Logistic regression analysis revealed that experience was not associated with adverse events; however, in off-pump SVST and off-pump MVST, experience numbers correlated with operation time (mean duration 124±31 and 241±80 minutes, respectively; R² = 0.16 and R²=0.38; P<0.001 and P<0.001). Conversely, experience was not associated with operation time in pump-assisted MVST (mean duration 254±42 minutes; R² < 0.001; P=0.9) (Figure 1). By using a CUSUM analysis, the learning period for off-pump MVST to reach optimization was calculated to be 45 cases..
Conclusions: MICS CABG can be safely initiated, with a very low 1-year cardiac event risk. Pump assistance is safe and may be a good strategy to alleviate some of the learning curve when initiating a multi-vessel MICS CABG program.