Defining the learning curve of multi-vessel MIDCAB using CUSUM analysis

Abstract

Background

Minimally invasive direct coronary artery bypass (MIDCAB) has emerged as an alternative to conventional coronary artery bypass grafting; however, its adoption remains limited due to technical complexity and a steep learning curve, particularly in patients requiring multi-vessel revascularization. Objective data defining the learning curve of multi-vessel MIDCAB are scarce.

Methods

This retrospective study included consecutive patients who underwent multi-vessel MIDCAB between January 2020 and December 2025. Patients requiring single-vessel revascularization were intentionally excluded to ensure procedural homogeneity. The learning curve was evaluated using cumulative sum (CUSUM) analysis, and cases were stratified into three phases based on CUSUM inflection points. Perioperative and postoperative outcomes were compared across learning curve phases.

Results

A total of 169 patients were analyzed. CUSUM analysis identified three distinct learning phases: an initial learning phase (cases 1–48), a transition phase (cases 49–107), and a proficiency phase (cases 108–169). With increasing surgical experience, cardiopulmonary bypass time, aortic cross-clamp time, and total operative duration decreased significantly. The rate of conversion to open surgery declined markedly across learning phases, whereas in-hospital mortality and major postoperative complications remained low and comparable. These findings indicate improved procedural efficiency without compromising early clinical outcomes.

Conclusions

Multi-vessel MIDCAB is associated with a substantial learning curve that can be objectively characterized using CUSUM analysis. Surgical proficiency is achieved only after a considerable number of cases, emphasizing the importance of adequate case volume and structured performance monitoring. These results provide a practical benchmark for centers aiming to adopt or expand multi-vessel MIDCAB programs.