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Is internal thoracic artery grafting suitable for a moderately stenotic coronary artery?
M Kawasuji1, N Sakakibara, H Takemura
1Department of Surgery (I), Kanazawa University School of Medicine, Japan.
Insights
Internal thoracic artery grafting is safe for moderately stenotic coronary arteries. Competitive flow does not increase graft failure, supporting its use in coronary artery bypass grafting.
Area of Science:
- Cardiovascular Surgery
- Vascular Biology
- Interventional Cardiology
Background:
- Grafting internal thoracic artery (ITA) to coronary arteries with moderate stenosis is debated.
- Competitive flow from native coronary arteries is suspected to cause graft failure.
Purpose of the Study:
- To investigate intraoperative blood flow in ITA grafts to coronary arteries with varying stenosis.
- To assess the impact of stenosis degree on postoperative graft patency and angiographic findings.
Main Methods:
- 100 patients undergoing ITA to left anterior descending coronary artery bypass grafting were grouped by coronary stenosis severity (≤75%, 76-90%, >90%).
- Intraoperative phasic blood flow in ITA grafts was measured.
- Postoperative angiography was performed at 1 month.
Main Results:
- ITA graft flow was lower in grafts to less stenotic arteries (≤75%) compared to moderately stenotic ones (76-90%).
- Despite competitive flow in some cases, all ITA grafts were patent at 1 month.
- Graft dependence on ITA flow increased with stenosis severity, with 96% dependence in the >90% stenosis group.
Conclusions:
- Internal thoracic artery grafting is acceptable for moderately stenotic coronary arteries.
- Competitive flow does not predispose ITA grafts to string sign when diastolic flow is adequate.
- ITA grafting demonstrates favorable outcomes regardless of coronary artery stenosis degree.
Abstract:
Grafting an internal thoracic artery to a coronary artery with moderate stenosis remains controversial. Competitive flow from the native coronary artery has been proposed as the cause of distal narrowing and ultimate failure of the internal thoracic artery graft. We investigated intraoperative phasic blood flow in internal thoracic arteries grafted to coronary arteries with various degrees of stenosis and the influence of stenosis on postoperative angiographic findings. One hundred patients who underwent coronary artery bypass grafting of an internal thoracic artery to the left anterior descending coronary artery were divided into three groups according to degree of coronary stenosis. Group 1 included 39 patients who had 75% or less stenosis, group 2 included 34 patients with stenosis from 76% to 90%, and group 3 included 27 patients 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 diastolic peak with characteristic systolic reversal as a result of competitive flow from the native coronary artery. Angiography at 1 month showed that the internal thoracic artery graft was patent in every case. Relative contributions of native coronary artery and internal thoracic artery flow to distal perfusion differed among the three groups (p < 0.001). In group 1, 15% of patients showed native-dominant flow, 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 flow, and 62% showed internal thoracic artery-dependent flow. In group 3, 96% of patients showed internal thoracic artery-dependent flow. String sign of the internal thoracic artery graft developed in only three patients; in two of these patients internal thoracic arteries were grafted 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 stenosis of 50% or less did not show string sign. Competitive flow from a moderately stenotic coronary artery did not predispose the patient toward string sign of the internal thoracic artery graft in the presence of substantial diastolic internal thoracic artery flow. We conclude that internal thoracic artery grafting is acceptable for a moderately stenotic coronary artery.