The Incidance of Side Branch on Left Internal Mammary Artery (LIMA) and The Effect of Side Branch on Flow Rate

OBJECTIVES
The left internal mammarian artery (LIMA) is the most commonly used arterial graft for coronary artery bypass grafting (CABG) and occlusion of LIMA side branches during surgery is important for avoiding myocardial ischemia. In this study, we investigated the incidence of patent LIMA side branches in patients undergoing CABG and evaluated changes in LIMA flow with the use of TIMI frame count in patients with and without LIMA side branches.

STUDY DESIGN
The study included 38 patients (27 males, 11 females) who underwent coronary angiography due to symptoms and complaints that appeared after CABG. In all the patients, a LIMA graft was used for revascularization of the left anterior descending artery. Coronary angiographies were performed after a mean of four years following CABG. Angiograms were examined with respect to the presence of LIMA side branches and LIMI flow was assessed by the TIMI frame count method.

RESULTS
Patent LIMA side branches were detected in seven patients (18.4%). The mean TIMI frame counts were 27.3±3.4 and 15.7±2.3 in patients with and without a LIMA side branch, respectively (p<0.0001). In all the patients, the side branch was at the level of the proximal third of the LIMA, having the same diameter (3.1±0.2 mm). Fourteen patients were evaluated by myocardial perfusion scintigraphy, six of whom had anterior ischemia. The incidence of anterior ischemia was 30% (3/10) for those without a side branch, and 75% (3/4) for those with a side branch.

CONCLUSION
We suggest that, in the presence of a LIMA side branch, LIMA flow may be used in assessing myocardial ischemia, and TIMI frame count is an objective means of measuring LIMA flow.