Improvement of flow capacity of the left internal thoracic artery graft assessed by using a pressure wire

Objective: We sought to evaluate improvement of flow capacity in a left internal thoracic artery graft by means of pressure measurement. Methods: Eighteen patients who received a left internal thoracic artery graft to the left anterior descending coronary artery were studied. Angiography and pressure measurement at the proximal and distal portions of the left internal thoracic artery graft during maximal hyperemia with a pressure guide wire were performed at 1 month (early study) and 6 months (late study) after surgical intervention. Results: There are no significant differences between the early and late studies in resting mean aortic pressure, left ventricular end-diastolic pressure, left ventricular ejection fraction, and percentage diameter stenosis of the recipient left anterior descending coronary artery. There was no stenosis in the anastomosis site of the left internal thoracic artery graft and the distal left anterior descending coronary artery, as determined by means of angiography, in the early and late studies. The mean diameter of the distal left internal thoracic artery graft was significantly increased in the late study (1.6 ± 0.2 vs. 1.8 ± 0.2 mm, P = .011). There was a significant difference between the early and late studies in the pressure gradient through the graft (15 ± 4 vs 13 ± 3 mm Hg, P = .036). The ratio of distal to proximal pressure within the left internal thoracic artery graft in the late study was significantly increased from that in the early study (0.80 ± 0.04 to 0.84 ± 0.03, P = .0003). Conclusions: The pressure ratio within the left internal thoracic artery graft became higher as the left internal thoracic artery graft adapted itself to the myocardial circulation. This finding might relate to decreasing the resistance of the left internal thoracic artery graft.