Ann Thorac Surg 2004;77:1072-1074
© 2004 The Society of Thoracic Surgeons
Case report
Right internal thoracic artery remodeling 18 years after circumflex system grafting
Luiz B. Puig, MDa*,
Paulo R. Soares, MDa,
Fernando Platania, MDa,
Luís A. O. Dallan, MDa,
Luiz A. F. Lisboa, MDa,
Luiz J. Kajita, MDa,
José A. F. Ramires, MDa,
Sérgio A. Oliveira, MDa
a Heart Institute, Medical School, University of São Paulo,São Paulo, Brazil
Accepted for publication April 18, 2003.
* Address reprint requests to Dr Puig, Av. Dr. Eneas de Carvalho Aguiar, 44 2° andar bl. 2, s/11, Cerqueira Cesar 05403-000, São Paulo, SP Brazil
e-mail: lpuig{at}incor.usp.br
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Abstract
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A 64-year-old man with left main coronary artery disease underwent myocardial revascularization. The left internal thoracic artery (LITA) was sutured to the left anterior descending artery, and the right internal thoracic artery (RITA) was sutured to the obtuse marginal artery. Eighteen years later, angina reoccurred. Catheterization revealed that both the coronary and the left subclavian arteries were occluded and that a patent RITA graft was maintaining the cardiac blood supply. The RITA graft evaluation revealed increased lumen diameters, suggestive of remodeling. The LITA was subsequently disconnected and sutured to the aorta as a free graft in order to restore appropriate myocardial blood flow. This case emphasizes the benefits of using a live graft for left coronary system grafting, which include long-term patency and flow-dependent remodeling.
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Introduction
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The internal thoracic artery is the graft of choice for myocardial revascularization, based on 10-year patency rates. It is a live conduit with the potential for remodeling. The growth of this graft provides adaptability when it is subjected to increased blood flow demands. The use of both internal thoracic arteries emphasizes the benefits of grafting the left coronary system.
A 64-year-old man presented with angina pectoris and high-grade stenosis of the left main coronary artery (LMCA). He underwent revascularization in 1984, in which the left internal thoracic artery (LITA) was grafted to the left anterior descending artery (LAD), and the right internal thoracic artery (RITA) was grafted to the obtuse marginal artery through the transverse sinus. His clinical course was uneventful for 16 years.
After 16 years, the patient experienced a recurrence of angina pectoris. Catheterization revealed occlusion of the right coronary and left subclavian arteries, 90% stenosis of the LMCA, retrograde flow from the LAD to the LITA (steal syndrome), and a patent RITA perfusing the obtuse marginal (Fig 1). After 12 months, the symptoms intensified. Repeat cardiac catheterization showed occlusion of the LMCA.
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Fig 1. Angiogram 16 years after the initial operation. (A) Visible through the left coronary artery are the left main coronary artery (with 90% stenosis) and the anterior interventricular and left internal thoracic (steal flow) arteries (LITA). (B) Only the circumflex system is visible through the right internal thoracic artery (RITA). (LAD = left anterior descending coronary artery; OM = obtuse marginal artery.)
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The patient underwent revascularization in which a Dacron graft was used to connect the left subclavian artery to the left carotid artery. Eighteen months later, the angina pectoris returned at rest. A third cardiac catheterization demonstrated occlusion of the Dacron graft. The left internal carotid artery was occluded. Through the RITA, there was perfusion of the obtuse marginal, circumflex, LAD, LITA, and branches of the right coronary artery (Fig 2). Remodeling of the RITA was observed by comparing the diameter in 3 consecutive catheterizations, after intervals of 12 and 18 months, with the Cardiovascular Angiographic Analysis System (CAAS II Version 5v1x, 1996) (Pie Medical Imaging BV, Maastricht, Netherlands). Increases in diameters in three segments of the RITA were observed: proximal—2.27, 2.48, 2.60 mm; intermediate—2.19, 2.39, 2.50 mm; and distal—2.15, 2.36, 2.47 mm.
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Fig 2. Angiogram 18 years after the initial operation. The increase in the diameter of the right internal thoracic artery (RITA) (graft remodeling) is evident. Also visible are the main coronary arteries and the end of the left internal thoracic artery (LITA) (steal flow). (LAD = left anterior descending coronary artery.)
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The patient underwent off-pump myocardial revascularization during which the LITA was disconnected near the left subclavian artery and sutured to the ascending aorta (Fig 3). The patient has remained in New York Heart Association functional class I.
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Fig 3. The left internal thoracic artery in situ is disconnected and sutured as a free graft to the ascending aorta.
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Comment
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In 1983 we proposed using the RITA, routed through the transverse sinus, to graft the circumflex system and leaving the LITA to graft the LAD [1]. The aim of this technique was to revascularize the entire left coronary system with arterial grafts. In 1986 Spencer stated: "If one patent internal mammary artery can improve longevity a decade later, exciting possibilities are raised by the fact that bilateral mammary-artery grafts, perhaps combined with sequential anastomoses, are now clinically possible" [2]. Consistent with this, survival benefits have been observed with use of both LITA and RITA grafts in the left coronary system [3]. Use of these grafts has been gradually increasing, based on 10-year patency rates of nearly 90%. In our experience with 50 patients who were followed up for a mean of 61.9 months, the RITA, LITA, and SV grafts were patent in 92%, 96%, and 67.5% of patients, respectively [4]. Other surgeons have reported similar results [5, 6].
The RITA is a viable graft, thus contributing to long-term graft patency [7]. In addition, the graft diameter increases over time. The spatially smooth location of the in situ RITA allows it to reach the circumflex and its branches, without placing tension on the graft. This characteristic would favor less turbulent blood flow and better distribution of shear stress at the endothelial surface of the anastomosis, where the frictional force of the fluid on the endothelium becomes manifest [8].
The large diameter of the RITA suggests remodeling of the graft. The patient underwent a repeat revascularization by which the LITA was detached at its origin and sutured on the aorta as a free graft. This case emphasizes the benefits of grafting the left coronary system with a live graft not only by the long-term patency but also for its remodeling ability when subjected to increased blood flow demands. Although the remodeling of the RITA supplied blood to the heart, it was not enough, thus explaining our patient's late symptoms.
The strategy of routing the RITA behind the aorta facilitates a safe reoperation that avoids the risk of graft damage. The change of the LITA from an in situ graft to a free graft is also safe and represents an alternative approach to the treatment of steal syndrome. The remodeling of this live graft provided the opportunity, 18 years later, to perform revascularization in a patient who had a well-preserved left ventricle.
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References
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- Puig L.B., Neto L.F., Rati M., et al. A technique of anastomosis of the right internal mammary artery to the circumflex artery and its branches. Ann Thorac Surg 1984;38:533-534.[Abstract]
- Spencer F.C. The internal mammary artery: the ideal coronary bypass graft?. N Engl J Med 1986;314:50-51.[Medline]
- Buxton B.F., Ruengsakulrach P., Fuller J., et al. The right internal thoracic artery graft—benefits of grafting the left coronary system and native vessels with a high grade stenosis. Eur J Cardiothorac Surg 2000;18:255-261.[Abstract/Free Full Text]
- Puig L.B., Papanikolau C.G., Najar M.P. The use of the left and right internal thoracic arteries grafts for revascularization of the left coronary artery. Arq Bras Cardiol 1997;68:437-442.[Medline]
- Buche M., Schroeder E., Chenu P., et al. Revascularization of the circumflex artery with the pedicled right internal thoracic artery: clinical functional and angiographic midterm results. J Thorac Cardiovasc Surg 1995;110:1338-1343.[Abstract/Free Full Text]
- Ura M., Sakata R., Nakayama Y., et al. Long-term patency rate of right internal thoracic artery bypass via the transverse sinus. Circulation 1998;98:2043-2048.[Abstract/Free Full Text]
- Kitamura S., Seki T., Kawachi K., et al. Excellent patency and growth potential of internal mammary artery grafts in pediatric coronary artery bypass surgery. Circulation 1988;78(3 Pt 2):I129-139.
- Nerem R.M., Levesque M.J., Cornhill J.F. Vascular endothelial morphology as an indicator of the pattern of blood flow. J Biomech Eng August 1981;103:172-176.
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Abstract
Introduction
