Ann Thorac Surg 1997;63:1183-1185
© 1997 The Society of Thoracic Surgeons
How To Do It
A Technique to Protect the Left Internal Thoracic Artery
Michael A. Wait, MD
Parkland Memorial Hospital and Zale Lipshy University Hospital, Dallas, Texas
Accepted for publication October 17, 1996.
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Abstract
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The natural tendency of the harvested in-situ left internal thoracic artery is to assume a position near the anterior midline of the mediastinum, adjacent to the posterior sternal table. This repositioning of the left internal thoracic artery makes sternal reentry for redo myocardial revascularization (or other open cardiac procedures) hazardous. A technique of posterior and lateral repositioning of the mobilized in-situ left internal thoracic artery by creating a thymic flap and a pleuromediastinal groove is presented.
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Introduction
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Myocardial r evascularization strategies that use the in-situ left internal thoracic artery (LITA) to perfuse the left anterior descending coronary artery have resulted in prolonged graft patency, reoperation-free survival, and patient survival, as well as decreased perioperative mortality when compared with techniques that use only saphenous vein grafts [1]. In the 1990s redo myocardial revascularization operations comprise a higher percentage of total coronary artery bypass grafting (CABG) procedures than in the past decade. The native LITA occupies a position that is 1 to 2 cm lateral to the lateral sternal margin; once harvested, the in-situ LITA assumes a medial anterior position due to the "tenting" effect of the inflated left lung. Often this fixes the LITA in a position that is directly retrosternal midline and at jeopardy during traditional transsternal reentry on redo CABG procedures. This can be presumed when examination of the lateral chest roentgenogram demonstrates that the LITA clips are situated immediately retrosternal, or in viewing the true lateral projection of the coronary arteriogram during the LITA injection (Fig 1
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Fig 1. . True lateral coronary arteriogram during left internal thoracic artery injection. Note the immediate medial substernal course of the unprotected harvested left internal thoracic artery, making it vulnerable to injury during subsequent redo sternotomy.
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Technical considerations inherent in transsternal redo CABG procedures involve preservation of functioning grafts and dissection of mediastinal adhesions. In a 1984 series reported by Baillot and associates [2] of 100 patients undergoing redo CABG with a patent LITA graft, 8 LITA pedicles (8%) were damaged during or after sternal reentry; a subsequent report from the same institution in 1994 reviewed 36 patients with previous bilateral LITA grafting undergoing redo CABG, with 2 LITA injuries (5.6%). Coltharp and colleagues [3] reported an LITA graft injury rate of 9% (5 of 54 LITAs at risk) with one death. Some authors have suggested protecting the LITA with a polytetrafluoroethylene membrane to facilitate LITA dissection in redo CABG cases; others have recommended wide intrapleural routing [4] or the use of complex pleuropericardial advancement and rotation flaps [5]. Herein is described a simple technique of protecting the harvested in-situ LITA.
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Technique
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A median sternotomy is used to expose the LITA, which is dissected in an extrapleural manner from its cephalad course posterior to the left subclavian vein to its caudad bifurcation. After heparinization, the divided LITA is controlled with an atraumatic bulldog clamp. As the lungs are gently hyperinflated, the medial mediastinal pleural reflection is bluntly dissected (without the use of the cautery current) laterally away from the great vessels, thymus, and pericardium exposing a potential space, thus creating a medial pleuromediastinal groove (Fig 2). This allows the LITA to course posteriorly to the cupola of the lung. The pericardial cradle is created by dividing the pericardium in the midline, and the left lobe of the thymus is dissected off the pericardium, thus creating a thymic flap. The distal LITA anastomosis is created during cardioplegic arrest. An oblique pericardial incision is fashioned in the left lateral pericardium, and the LITA body is then coursed posteriorly in the pleuromediastinal groove, and is covered anteriorly by the thymic flap (Fig 3). If necessary the thymic flap is secured to the intact left mediastinal pleura, anterior to the LITA. Before sternal closure, the mediastinum is drained with a midline silicone drain. A similar procedure may be carried out on the in-situ right internal thoracic artery.
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Fig 2. . Creation of the medial pleuromediastinal groove, a potential space between the mediastinal pleural reflection laterally and the thymus/great vessels medially. (Note: although a cautery pencil is depicted in this figure, it should be used without current when dissecting near the phrenic nerve.)
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Fig 3. . The protected left internal thoracic artery rests medial to the cupola, posterior to the thymic flap within the pleuromediastinal groove.
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Comment
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The avoidance of internal thoracic artery graft injury at sternal reentry is established at the index CABG procedure by a thoughtful, careful, limited mediastinal dissection. This technique has been demonstrated on subsequent true lateral coronary angiograms to reliably secure the LITA body in a posterior, lateral position (Fig 4). In this position, the patent LITA is not at undue risk of injury during sternal reentry and mediastinal dissection for redo CABG procedures. This technique is simple, adds only a few minutes to the operative procedure, uses readily available native tissues in their anatomic location, and avoids heterologous biological membranes (such as bovine pericardium) or foreign bodies (such as polytetrafluoroethylene) and their added cost and inherent risk of inflammatory foreign body reaction, calcification, and infection. Intrapleural routing of the in-situ LITA has been advocated by some [4]; however, the advantages of an extrapleural internal thoracic artery route as advocated by Noera and colleagues [6] seem prudent to strive for.
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Fig 4. . True lateral coronary arteriogram during left internal thoracic artery injection. The harvested in-situ left internal thoracic artery is posterior to the posterior sternal table, and not at risk of injury during subsequent redo sternotomy.
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I have used this technique in more than 600 myocardial revascularization procedures. There have been no instances of phrenic nerve injury or paralysis of the left hemidiaphragm directly attributable to this technique, although that is one of the primary concerns one should consider when adopting this procedure. Although none of these patients have had to return for redo revascularization, 6 patients have returned for sternal rewiring (due to sternal fractures from osteoporosis, diabetes, or other causes), and in each instance there has not been any difficulty with inadvertent reencounter with the harvested LITA graft.
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Footnotes
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Address reprint requests to Dr Wait, Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Texas Southwestern Medical Center, 5161 Harry Hines Blvd, Suite 7.506, Dallas, TX 75235.
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References
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- Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internal mammary artery graft on 10-year survival and other cardiac events. N Engl J Med 1986;314:1–8.[Medline]
- Baillot RG, Loop FD, Lytle BW, et al. Reoperation after previous grafting with the internal mammary artery: technique and early results. Ann Thorac Surg 1985;40:271–3.[Abstract/Free Full Text]
- Coltharp WH, Decker MD, Stoney WS, et al. Internal mammary artery graft at reoperation: risks, benefits, and methods of preservation. Ann Thorac Surg 1991;52:225–9.[Abstract/Free Full Text]
- Pacifico AD, Sears NJ, Burogs C. Harvesting, routing and anastomosing the left internal mammary artery graft. Ann Thorac Surg 1986;42:708–10.[Abstract/Free Full Text]
- DiMarco DB, Jurado RA. The DiMarco-Jurado pleuropericardioplasties: complete closure of the pericardial space with advancement/rotation flaps after adult primary cardiac operations. J Cardiac Surg 1993;8:641–9.[Medline]
- Noera G, Pensa PM, Guelfi P, Biagi B, Lodi R, Carbone C. Extrapleural takedown of the internal mammary artery as a pedicle. Ann Thorac Surg 1991;52:1292–4.[Abstract/Free Full Text]
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Abstract
Introduction
