Sub-optimal internal mammary grafts: incidence, timing, and etiology

The left internal mammary (thoracic) artery (LIMA), when used as a pedicle graft at the time of coronary artery bypass grafting, is effective and durable. Data concerning the rate and causes of LIMA failure are scant. The aim of this paper is to explore the modes and frequency of sub-optimal LIMA grafts. We examined all cases of invasive graft angiography performed in our cardiothoracic center 2016–2020 and analyzed the quality of the LIMA graft. Of 551 cases, 323 had undergone isolated coronary artery bypass grafting including a LIMA since 2001; of those, 59 (18%) appeared sub-optimal; 16 (5%) being totally occluded, 26 (8%) exhibiting a “string sign” (i.e., atretic or cord-like), 12 (4%) being focally stenosed, and 5 (1.5%) being patent but placed on a diseased portion of the left anterior descending artery or other vessel. The commonest cause of failure were poor-quality left anterior descending artery target and non-flow-limiting disease. This paper highlights the low rate, and likely modes, of failure of this valuable treatment in contemporary practice.