Histology and morphology of 59 internal thoracic artery grafts and their distal anastomoses

Background. The left internal thoracic artery (LITA) is accepted as a superior graft for the left coronary system because of its better long-term patency rate than saphenous grafts. The postsurgical histomorphometric changes at the distal anastomsis of LITA grafts are not well documented. Methods. The cellular changes within the intima of 59 LITA grafts were analyzed by light microscopy. Results. Grafts implanted 1 week or less (n = 34) showed no postsurgical tissue proliferation. Of the 7 grafts implanted 1 to 8 weeks, only the suture sites exhibited intimal thickening (6 of 7 grafts, 0.08 ± 0.07 mm). The remaining grafts (n = 18), aged 2 months to 10 years, showed significant intimal thickening at the suture sites (0.39 ± 0.17 mm) and on the hood (0.29 ± 0.25 mm), with variable thickening on the floor (10 of 18 left anterior descending coronary arteries, 0.11 ± 0.12 mm). The graft body showed insignificant intimal changes (10 of 18, 0.03 ± 0.04 mm), with mild focal atherosclerotic lesions in 2 of 18 late LITA grafts. Conclusions. Left internal thoracic artery grafts develop fibromuscular intimal hyperplasia primarily around the anastomotosis. The response on the hood appears to be a hemodynamic response, secondary to that of the suture sites.