Observational Angiographic Study of the Anatomical Variations of the Left Internal Mammary Artery and its Surgical Significance

Objective: The objective of this study was to study the presence and incidence of anatomical variations of the left internal mammary artery (LIMA) by angiogram and its surgical relevance. Materials and Methods: In patients with coronary artery disease, who were referred for coronary artery bypass grafting (CABG), we evaluated the LIMA while performing coronary angiogram. The study involved evaluation of differences in origin, course, branches, and level and type of termination of the LIMA. Results: LIMA was assessed angiographically in 500 patients who underwent CABG surgery. Anatomical variations were observed in 150 patients (30%). Ectopic origin of LIMA from the third part of the Subclavian artery was seen in 3 patients (0.6%). Eighteen patients (3.6%) had common origin of LIMA from thyrocervical trunk. LIMA had a tortuous course with loops and bends in 65 cases (13%). A large lateral costal branch from the proximal part of LIMA supplying the lateral chest wall was seen in 60 cases (12%). In all patients, LIMA was found to terminate as a bifurcation at or beyond the 6 th rib. Conclusion: Angiographic evaluation of the LIMA can highlight the anatomical variations of the LIMA thereby forewarns and enables the surgeon to make a safe harvest of the LIMA. LIMA is the primary conduit of choice for CABG operations due to the longevity of the conduit. If a prominent lateral costal branch is left unclipped, it may cause internal mammary artery steal. Ectopic origin and tortuous course can endanger the LIMA during harvest. Prior knowledge of the LIMA variations visualized during angiogram will enable the surgeon to anticipate and take adequate precautions for a safe LIMA harvest.