J Thorac Cardiovasc Surg 2001;122:404
© 2001 The American Association for Thoracic Surgery
Effect of flow competition on internal thoracic artery: Postoperative velocimetric and angiographic study
Kenzo Yasuura, MD,
Hiroshi Okamoto, MD,
Akio Matsuura, MD
Department of Thoracic Surgery, Komaki City Hospital, Jobushi 1-20, Komaki City, Aichi 485-8520, Japan
To the Editor:
We read with interest the article by Shimizu and colleagues,
1 describing the flow competition of internal thoracic artery (ITA) graft. Arterial grafts such as the ITA and the right gastroepiploic artery vary widely in diameter and length among patients. We 2 previously reported that the diameters of both the arterial graft and the target coronary artery, as well as the degree of proximal stenosis, were main factors in determining the flow ratio of the graft flow to the distal coronary artery. In our study, when the inner diameters of the arterial graft are 0.5 mm larger than that of the target coronary artery, the graft can carry more than 50% of the total flow of the coronary artery distal to the anastomosis, even with 64% cross-sectional stenosis equivalent to 40% reduction in luminal diameter. If the diameters of both the graft and the target vessel are the same, the graft flow can be dominant in the range of more than 75% cross-sectional stenosis, equivalent to 50% stenosis in the luminal diameter in most cases. In the article reported by Shimizu and colleagues, diameter stenosis of 80% or more could not produce the string sign of the ITA graft, and the string sign would rarely develop in patients with more than 60% stenosis. Although their report did not take the diameter of both the graft and the target vessel into consideration, their results are consistent with our theoretical analysis in respect to the proximal stenosis. To prevent ITA graft failure in the long term period, the relation of the diameter of both the graft and target vessel and the degree of proximal stenosis should be accurately estimated. Theoretical analysis based on Poiseuille's law suggested an appropriate application of the arterial graft to coronary revascularization.
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References
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Shimizu T, Hirayama T, Seusada H, Ikeda K, Ito S, Ishimaru S. Effect of flow competition on internal thoracic artery graft: postoperative velocimetric and angiographic study. J Thorac Cardiovasc Surg. 2000;120:459-65.[Abstract/Free Full Text]
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Yasuura K, Takagi Y, Ohara Y, Takami Y, Matsuura A, Okamoto H. Theoretical analysis of right gastroepiploic artery grafting to right coronary artery. Ann Thorac Surg. 2000;69:728-31.[Abstract/Free Full Text]
