IS INTERNAL THORACIC ARTERY GRAFTING SUITABLE FOR A MODERATELY STENOTIC CORONARY-ARTERY

Grafting an internal thoracic artery to a coronary artery with moderat e stenosis remains controversial. Competitive how from the native coro nary artery has been proposed as the cause of distal narrowing and ult imate failure of the internal thoracic artery graft. We investigated i ntraoperative phasic blood flow in internal thoracic arteries grafted to coronary arteries with various degrees of stenosis and the influenc e of stenosis on postoperative angiographic findings. One hundred pati ents who underwent coronary artery bypass grafting of an internal thor acic artery to the left anterior descending coronary artery were divid ed into three groups according to degree of coronary stenosis. Group 1 included 39 patients who had 75% or less stenosis, group 2 included 3 4 patients with stenosis from 76% to 90%, and group 3 included 27 pati ents with stenosis greater than 90%. Mean flow and peak systolic flow of internal thoracic artery graft in group 1 were lower than those in group 2 (p < 0.01, p < 0.05). Peak diastolic flow in group 1 showed no difference from flows in groups 2 and 3, In eight patients in group 1 , internal thoracic artery flow showed a predominant diastole peak wit h characteristic systolic reversal as a result of competitive flow fro m the native coronary artery. Angiography at 1 month showed that the i nternal thoracic artery graft was patent in every case, Relative contr ibutions of native coronary artery and internal thoracic artery flow t o distal perfusion differed among the three groups (p < 0.001). In gro up 1, 15% of patients showed native-dominant how, 62% showed balanced flow, and 23% showed internal thoracic artery-dependent flow. In group 2, 9% of patients showed native-dominant flow, 29% showed balanced ho w, and 62% showed internal thoracic artery-dependent how. In group 3, 96% of patients showed internal thoracic artery- dependent flow. Strin g sign of the internal thoracic artery graft developed in only three p atients; in two of these patients internal thoracic arteries were graf ted to coronary arteries with stenosis of 50% or less and in the other patient there was competitive flow from a diagonal vein graft. Eleven of 13 internal thoracic arteries grafted to coronary arteries with st enosis of 50% or less did not show string sign. Competitive flow from a moderately stenotic coronary artery did not predispose the patient t oward string sign of the internal thoracic artery graft in the presenc e of substantial diastolic internal thoracic artery flow. We conclude that internal thoracic artery grafting is acceptable for a moderately stenotic coronary artery.