Internal mammary artery anomalies.

The internal mammary arteries (IMA) are considered to be the superior conduit in coronary bypass grafting (CABG). Anomalies of an IMA can influence the surgical technique and results; their true incidence is not well known. The IMA's were visualised angiographically in 262 consecutive patients undergoing cardiac catheterisation prior to CABG. Satisfactory visualisation was possible of 459/524 IMA's studied (88%). A total of 118/459 (26%) surgically significant anomalies was observed in 79/262 patients (30%): common origin of another large artery in 48/459 (11%), large side branches in 41/459 (9%), tortuosity in 21/459 (5%), atypical course or origin in 5/459 (1%), atherosclerotic lesions in 2/459 (0.4%) and spasticity of an IMA in 1/459 (0.2%). Angiographic visualisation of the IMA's resulted in modification of surgical strategy in 11/262 patients (4%); meticulous preparation because of difficult or atypical IMA anatomy was necessary in 68/262 patients (26%). These results demonstrate that significant anomalies of the IMA which might--when unrecognized--jeopardize IMA-flow after CABG are relatively common; they might escape detection during IMA take-down but can be diagnosed by angiography during catheterisation.