String-Sign in Left Internal Thoracic Artery Is Associated With Regression in Left Main Trunk Stenosis After Coronary Artery Bypass

The left internal thoracic artery (LITA) is the conduit of choice for coronary artery bypass (CABG) due to favorable long-term patency. Uncommonly, diffuse narrowing like a string without significant stenosis of an anastomosis is observed in the LITA graft (called “string sign”). Isolated left main trunk (LMT) diseases were reported to regress in some cases. However, the relationship between “string sign” and the regression of solitary LMT disease remains unknown. We retrospectively studied 40 consecutive patients with isolated LMT stenosis who underwent CABG using LITA and who underwent angiography before and after operation (31 males, 9 females, mean age, 65.0 years). The patients were divided into 2 groups according to the postoperative angiographic outcomes of the LITA graft: one group included patients with “string sign” (6 patients), the other group consisted of patients with a patent LITA graft (34 patients). There were no significant differences in clinical backgrounds between the two groups. The 2 groups showed similar quantitative % coronary artery stenosis of the LMT before operation (77.5% versus 76.8%) and the observation period was similar in both groups. Coronary angiography after CABG revealed that % stenosis of the LMT in patients with “string sign” was significantly less than that in patients with a patent LITA graft (41.7 ± 26% versus 82.5 ± 11%, P < 0.001). Regression in LMT was significantly more frequently observed in the “string sign group”. Furthermore, ostial stenosis was more frequent in patients with “string sign”. “String phenomenon” of the LITA graft is one of the signs related to the regression of LMT stenosis, and especially in ostial stenosis of the LMT.