Bilateral Internal Thoracic Artery Grafting in Coronary Surgery: A Three-Tier Decision Framework

Abstract

The left internal mammary artery grafted to the left anterior descending artery (LAD) is the main determinant of survival in coronary artery bypass grafting, but the choice of the second graft remains controversial. The use of both mammary arteries offers a greater long-term survival benefit compared with a single mammary artery graft; however, this advantage is delayed and diminished when compared with a single mammary artery graft plus a radial artery graft. Furthermore, this approach is associated with a higher risk of sternal complications and, via mechanisms of competitive flow and steal phenomenon, of perioperative coronary malperfusion. This article proposes organising the clinical decision-making process according to three hierarchical levels: (1) absolute contraindications based on the patient’s medical history that preclude the use of a particular graft (thoracic irradiation, subclavian artery disease, acute aortic dissection); (2) the haemodynamic adequacy of the graft for the target coronary territory; (3) the assessment of the risk of delayed sternal healing in the individual patient, where skeletonization has reduced the historical significance of diabetes. Overlaying these is a transversal variable represented by the harvesting technique (pedicled mammary artery vs. skeletonized mammary artery, together with the surgeon’s learning curve), which re-interprets apparently unfavourable results and distinguishes the risk associated with the graft itself from that of the surgical procedure. The model aims to rationalise patient selection and reduce the persistent underutilisation of bilateral mammary artery grafting. It should be noted at the outset that this survival advantage rests largely on observational and propensity-matched evidence and has not been confirmed on an intention-to-treat basis by the only adequately powered randomised trial, so that the model proposed here is offered as a framework for selection rather than as a claim of established superiority.