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Technical aspects of double-skeletonized internal mammary artery grafting
Technical Aspects of Double-Skeletonized Internal Mammary Artery Grafting Jacob Gurevitch, MD, Amir Kramer, MD, Chaim Locker, MD, Itzhak Shapira, MD, Yosef Paz, MD, Menachem Matsa, MD, and Rephael Mohr, MD Department of Thoracic and Cardiovascular Surgery, Tel Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, Tel-Aviv, Israel
Background. Bilateral internal mammary artery (IMA) grafting is performed to provide complete arterial myocardial revascularization with the intention of decreasing postoperative return of angina and the need for reoperation. We present here technical views of doubleskeletonized IMA grafting, and evaluate its clinical outcome. Methods. Skeletonized IMA is harvested gently with scissors and silver clips, without use of cauterization, and embedded in a small syringe filled with papaverine. Three strategies for arterial revascularization were employed in 762 consecutive patients: (1) the cross arrangement (242 patients, 32%), where the in situ right internal mammary artery (RIMA) is used for the left anterior descending artery (LAD), in situ left internal mammary artery (LIMA) to circumflex marginal branches and the gastroepiploic artery for the right coronary artery (RCA); (2) the composite arrangement (476 patients, 62%), where
free IMA is attached end-to-side to the other in situ IMA; and (3) the natural arrangement (44 patients, 6%), where the in situ RIMA is connected to the RCA and in situ LIMA to LAD. Mean age was 66 years (range 30 to 92). Two hundred ninety-two patients (38%) were older than 70, and 229 (30%) were diabetic. Results. Operative mortality was 2.5% (n ⴝ 19). The mortality of urgent and elective cases was 1.2% (8 of 663), and that of emergency operation was 11% (11 of 99). There were 9 (1.2%) perioperative myocardial infarctions, and 10 patients (1.3%) sustained strokes. Sternal wound infection occurred in 14 (1.8%). Conclusions. The three strategies described here provide the surgeon with the versatility required for arterial revascularization with bilateral IMAs in most patients referred for coronary artery bypass grafting. (Ann Thorac Surg 2000;69:841– 6) © 2000 by The Society of Thoracic Surgeons
T
technical experience of double-skeletonized IMA harvesting and grafting in 762 patients.
he internal mammary artery (IMA) is usually isolated from the chest wall as a pedicle, together with vein, muscle, fat, and accompanying endothoracic fascia [1–3]. A surgical technique was recently developed, where the IMA is dissected as a skeletonized vessel [4, 5]. The skeletonized artery is isolated gently with scissors and silver clips, without the use of cauterization (Fig 1A, B). The advantage is that the dissected artery is particularly long, and its spontaneous blood flow is greater than in a pedicled IMA [6], allowing the use of both IMAs as grafts to practically all coronary vessels requiring surgical revascularization. Another advantage of using the skeletonized IMA, is the preservation of collateral blood supply to the sternum (Fig 2), enabling more rapid healing, and decreasing the risk of infection [7, 8]. We have adopted bilateral skeletonized IMA grafting as our preferred method for myocardial revascularization. Daily use of this IMA-harvesting technique has enabled the surgeons to acquire the dexterity required for dissecting the skeletonized IMA. We report here our Accepted for publication Sept 17, 1999. Address reprint requests to Dr Mohr, Department of Thoracic and Cardiovascular Surgery, Tel-Aviv Sourasky Medical Center, 6 Weizman St, Tel Aviv 64239, Israel.
© 2000 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
Material and Methods Harvesting and Preparing the Skeletonized IMA In our harvesting technique, we basically follow instructions and recommendations given before by Cunningham and associates [5], and add our experience. A standard median sternotomy incision is used with only rare application of bone wax. Later dissection of the IMA is easier if meticulous hemostasis is obtained on the sternal edges to avoid accumulation of blood in the field. The IMAs are dissected as skeletonized arteries [3], before heparin administration, to decrease the risk of damage and hematoma formation in the region of the side branches during dissection. We favor elective opening of pleura before IMA dissection, to facilitate exposure. Though it is possible to completely skeletonize the IMA from its origin to its distal bifurcation without opening the pleura, dissection of proximal IMA with its anterior and pericardial branches is easier and safer when the pleura is open. To avoid thermal injury to the IMA, it is extremely important to keep the cautery setting on low, throughout the dissection. Cautery is used to cut the endothoracic fascia 0003-4975/00/$20.00 PII S0003-4975(99)01407-1
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Fig 1. (A) The pedicled internal mammary artery (IMA) (A), the skeletonized IMA (B), and skeletonized IMA embedded in papaverine solution (jacuzzi) (C). (B) The left skeletonized IMA during harvesting. (C) The skeletonized IMA after harvesting inside a jacuzzi.
and expose the underlying IMA. Using scissors or the tip of the cold cautery as dissectors, the artery can be gently separated from the chest wall, leaving the accompanying veins, fascia, and adipose tissue in place. Forceps should never grasp the artery itself, but may hold the small remnants of soft tissue that cling to the adventitia of the
Fig 2. Collateral blood flow to the sternum is preserved after division of internal mammary artery side branches.
IMA. The initial cut in the endothoracic fascia is extended inferiorly until the terminal bifurcation of the IMA, into its lateral musculophrenic and medial superior epigastric branches, is visualized. Terminal bifurcation usually occurs at the sixth intercostal space. These terminal branches are left intact to allow blood flow through the IMA, until it is ready for use. Branches are divided between two silver clips using scissors. Once branches are controlled, scissors or low cautery are used to divide remaining medial and lateral soft tissue attachments. After the distal portion of the artery is freed, an additional cautery cut in the endothoracic fascia is made to allow dissection superiorly. The proximal third of the IMA occasionally has large anterior perforating branches that may initially seem too short to allow satisfactory clip application. With careful dissection, proximal and distal to the branch, suitable length can usually be obtained. Excessive traction should not be applied to the IMA, as these branches can tear easily, causing serious bleeding or hematomas. If insufficient branch length precludes safe application of two clips, it is sometimes best to apply a clip to the IMA side of the branch. The branch is then cut, and cautery used to obtain hemostasis on the chest wall. Meticulous technique is essential to avoid tearing of
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these branches, or worse, avulsing them from the IMA itself. Should a tear or avulsion occur, small atraumatic vascular clamps are applied proximally and distally following systemic administration of 5000 IU of heparin, thus allowing adequate visualization. Precise 8-0 polypropylene sutures can then be placed without compromising the IMA lumen. Throughout the dissection, the IMA is sprayed with warm diluted papaverine solution to minimize spasm and prevent dessication. Care is taken to keep cautery well away from the IMA when using it, even in the low setting. As the origin of the IMA is approached, pericardial branches are identified and divided. Lowering the table facilitates exposure of collaterals in this portion of the IMA. To obtain maximal IMA length, diameter, and flow, it might be necessary to divide the internal mammary vein, to obtain satisfactory exposure of these most proximal collateral branches. While the retractor is still in place and exposure is good, the superomedial pleural reflection is divided with cautery. This maneuver increases the usable length of the artery as it allows the IMA to drop into a groove established between the pleura and pericardium. A vertical incision is made in the lateral pericardium, from its free edge up to the phrenic nerve. The LIMA is mobilized through this incision, and penetrates the pericardial cavity anterior to the phrenic nerve. This maneuver also allows the IMA to lie medial and posterior to the lung, thus ventilation does not produce any notable stretch or distortion of the artery. Additionally, the artery is somewhat protected from injury, should resternotomy be required. The vessel is then carefully inspected for any signs of inadequate hemostasis or wall trauma. Bleeding points are controlled with a clip or fine suture. It is not unusual to notice small areas of adventitial blood staining at clip application points. Occasionally, a clip can partially cut through a branch, causing bleeding and localized hematoma. It is extremely important to minimize adventitial blood staining by applying another clip if possible. When necessary, one can momentarily occlude the IMA to allow placement of a suture. These small, well-localized areas of staining do not preclude use of the IMA. However, longer areas of wall hematoma or wall discoloration are distressing, as they might be associated with intimal tears or dissection. The distal portion of the IMA should be discarded when distal dissection is suspected. Heparin is administered before distal IMA division. Medium sized hemoclips are used to secure the distal stumps of both IMAs and the proximal stump of the RIMA when this conduit is being used as a free graft. Hemoclips are used to block the distal IMA, thus enabling hydraulic distention of the skeletonized artery by pulsations of arterial pressure wave against the walls of the blocked artery. The skeletonized pedicle is then put in a small syringe filled with a 1 to 30 papaverine saline solution (Figure 1A, C). This bath of warm papaverine (jacuzzi) is good enough to relax any spasm produced during dissection
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without the risk of endothelial damage caused by other antispastic maneuvers, such as intraluminar papaverine injection or mechanical dilatation. Hence, arguments in favor of opening the pleura are: facilitated exposure, and this is of paramount importance during proximal IMA harvesting; as the route of the IMA now becomes medial, and somewhat posterior to the anterior segment of the upper lobe of the lung (when the pleura is kept open), ventilation does not produce any tension on the artery, which runs straight towards the heart. Additionally, the artery is somewhat protected from injury should resternotomy be required. Finally, there is now room for the harvested IMA, vertically embedded in the jacuzzi in the open pleural cavity. Both IMA grafts are palpated after 5 to 10 minutes in the papaverine jacuzzi. The pulse should be strong, and spontaneous free flow is almost always greater than 150 mL/ minute.
Strategies of Complete Arterial Revascularization THE CROSS TECHNIQUE. We prefer the use of bilateral IMA as in situ grafts for myocardial revascularization. The two IMAs in combination with the right gastroepiploic artery give us three sources of blood supply. We believe that more blood sources are associated with improved longterm outcome. The cross arrangement (Fig 3A) is based on the assumption that patency rates of the right internal mammary artery (RIMA) on the left anterior descending coronary artery (LAD) is similar to that of the left internal mammary artery (LIMA) on the LAD [9, 10]. To improve late survival, every effort should be made to use both IMA grafts for the left system [11–13]. We do not use the cross technique in cases with short RIMA, very long ascending aorta, enlarged right ventricle, too distal or unpredictable LAD anastomotic site, and in cases with high probability of future reoperations (for example, combined aortic valve replacement and coronary artery bypass grafting [CABG]). We always try to avoid the use of the IMA distal to its bifurcation. This portion of the IMA is very delicate, and prone to spasm. A major concern of surgeons using bilateral IMA is the risk of damage to an artery crossing the midline (RIMA) in case of future reoperation. The extra length obtained by skeletonizing dissection very often enables the surgeon to move the RIMA superiorly, above the origin of the innominate artery, and secure it under the pericardial fat and thymic remnants before chest closure. This maneuver decreases the risk of damage to the artery during potential resternotomy, and avoids kinking of the RIMA when this artery is too long.
When the distal RIMA bifurcation (Fig 3B) cannot loosely reach the LAD, we use the RIMA as a free graft, and a T-shaped [3], or if more suitable, a Y-shaped anastomosis at the level of the main pulmonary artery, is prepared before connection to cardiopulmonary bypass (CPB) (Fig 4). The proximal composite anastomosis of free RIMA on the LIMA might, at times, be performed on bypass, after constructing all distal and sequential RIMA anastomoses.
THE COMPOSITE TECHNIQUE.
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When the composite anastomosis is constructed before CPB, preventing the compromise of LIMA, flow to LAD might be achieved by constructing the most proximal sequential anastomosis (diagonal or obtuse marginal) of RIMA before constructing the more distal anastomoses (circumflex marginals and RCA). If the free RIMA is too short to reach the PDA or posterolateral branches of RCA, we use the right gastroepiploic artery or vein grafts to bypass these branches. Despite the extra length obtained with skeletonization, in some cases the LIMA is not long enough to reach a very distally located anastomotic site on the LAD. In this situation, extra length might be obtained by anastomosing the free RIMA to the LAD and LIMA to circumflex marginal branches. THE IN SITU SEQUENCE. When a graft to the posterior wall of the heart is not necessary (the circumflex region), the LIMA is grafted to the left anterior descending and the RIMA to the right coronary artery or its posterior de-
Fig 3. (A) The cross arrangement: left internal mammary artery (LIMA) anastomoses the first marginal circumflex coronary artery, right internal mammary artery (RIMA) anastomoses the left anterior descending coronary artery (LAD), and the right gastroepiploic artery to the right posterior descending coronary artery. (B) The composite arrangement: in situ LIMA to LAD, and free RIMA (proximally attached end-to-side to LIMA) to first and the second circumflex marginals.
This is the safest way to precisely determine the location of the composite anastomosis without compromise to LIMA flow to LAD.
Fig 4. The composite T-shape anastomosis was preformed here before cardiopulmonary bypass. Free right internal mammary artery was attached to in situ left internal mammary artery (A ⫽ scheme, B ⫽ photograph).
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scending branch. The RIMA grafted on the right coronary artery has a low patency rate [14]. In fact, the right coronary artery is often calcified or severely fibrotic, and therefore the edges of the arteriotomy are not able to remain separated from each other after the incision. We therefore prefer the RIMA to posterior descending artery (PDA) anastomosis. The shortest route on the right side into the posterior pericardial space and the PDA lies along the posterolateral aspect of the subclavian vein and the superior vena cava (SVC). After the thymic tissue and fat have been cleared from the anterior aspect of these vessels, the pathway is developed by reflecting the parietal pleura laterally, carrying the phrenic nerve with it. The pathway into the right posterior pericardial space is opened widely by incising the parietal pericardium in the midline over the SVC. It should be noted that, in most cases, it is impossible to reach the PDA with the IMA graft when employing the regular technique of isolating the pedicled IMA. A skeletonized RIMA, however, is longer and can usually reach the better quality distal PDA.
Sequential Grafting With Skeletonized IMA Sequential grafting is essential only if IMAs are used for complete arterial myocardial revascularization. The economic approach of sequential grafting using diamondshaped side-to-side anastomosis and terminal T-shaped anastomosis for branches of the circumflex and RCA is our preferred approach. It carries the advantage of sparing IMA length using the shortest possible IMA segments between anastomoses. By using short arteriotomies (2 to 3 mm) potential kinking of the graft in the anastomotic region is prevented. To prevent tension between anastomoses after filling the ventricle, the length of the IMA segment between anastomoses should be 5 to 10 mm longer than the actual distance between coronary arteriotomies. Side-to-side parallel anastomosis is often used for sequential LAD diagonal grafting with the LIMA. The skeletonized artery length increases sometimes after harvesting. A common pitfall in this LAD diagonal arrangement is kinking when the IMA segment between anastomoses is too long. This problem, which is not observed when using the pedicled IMA, can be solved by using the Y-graft (mini-composite) technique or by using the RIMA for the diagonal in cases of RIMA on LIMA composite graft. The parallel side-to-side anastomosis is preferred for the intramyocardial coronary artery or for vessels buried inside a deep layer of epicardial fat. Constructing a diamond-shaped anastomosis exposes the IMA to the risk of seagull-wing kinking [15].
Results We prospectively evaluated the use of doubleskeletonized IMA in 762 patients between April 1996 and April 1998. Mean age was 66 years, range 30 to 92 years, 595 (78%) were men, and 167 (22%) women. Two hundred
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ninety-two (38%) were older than 70, 229 (30%) were diabetic, and 141 (18%) had left ventricular dysfunction. Myocardial preservation technique was intermittent anterograde warm blood cardioplegia. Mean bypass time was 102 minutes, and cross-clamp time was 85 minutes. Average number of grafts was 3.1 per patient (2 to 6). The gastroepiploic artery was used in 182 patients (24%). The composite technique was performed in 476 patients (62%), the cross technique in 242 (32%), and in situ arrangement in 44 (5.7%). Operative mortality was 2.5% (n ⫽ 19). The mortality of urgent and elective cases was 1.2% (8 of 663) and that of emergency operation was 11% (11 of 99). There were 9 (1.2%) perioperative myocardial infarctions, and 10 (1.3%) patients sustained strokes. Sternal wound infection occurred in 14 (1.8%). Neither diabetes nor advanced age (⬎ 70) were independent predictors of untoward events. Chronic lung disease was found to be the only independent predictor of sternal infection (chronic obstructive pulmonary disease, odds ratio 7.1; 95% confidence interval, 2.1 to 197). Postoperative follow-up (12 to 45 months) was available in 747 (98%) patients. One and 3 years actuarial survival were 95.5% and 93% respectively. Only 22 of the surviving patients (2.9%) reported return of angina. Forty-one patients underwent postoperative cardiac catheterization during the follow-up period: 22 due to chest pain, 4 had positive thalium-spect scan, and the remainder consented to elective catheterization within the framework of learning to use the composite technique. Seventy-seven of the IMAs were patent and 5 were occluded (patency rate of 94%). Nine patients (1.2%) underwent postoperative percutaneus transluminal coronary angioplasty, and 4 (0.5%) underwent reoperations. There were 12 new cases (1.2%) of congestive heart failure. Ninety-four percent of the surviving patients were well and angina-free at the time of last follow-up.
Comment This report focuses on technical aspects of bilateral skeletonized IMA grafting. The technical experience we gathered with the first 762 patients operated upon is detailed above. The patients here are typical for an urban population (relatively old), and this technique was used in 71% of the patients who underwent CABG in our institution, including those older than 70 years of age and diabetic patients, over a relatively short period of time (3 years). The only important contraindication for the use of IMA grafts was in emergency operations with hemodynamic instability requiring rapid connection to a cardiopulmonary bypass. The immediate operative results are comparable to those described in procedures in which one IMA was used [16]. The report confers significant clinical approval of the basic assumption concerning the skeletonized IMA technique; that it probably causes less damage to the sternal blood flow [7– 8, 17–19], and therefore rates of sternal infections and complications are in the lower range of those reported by others.
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Diabetes mellitus is generally considered to be a major risk factor for sternal complications, especially when bilateral IMA grafting is used. The risk in these circumstances was estimated to be five times more than in other patients [20]. We found no evidence of this relationship in those receiving bilateral skeletonized IMA. Our results are even more conclusive, taking into account the fact that 30% of the patients were diabetics. Routine use of bilateral skeletonized IMAs seems to be a safe technique for patients undergoing CABG, not only in terms of morbidity and mortality, but also regarding sternal complications and infections. However, in the patients with chronic lung disease the risk of sternal infection is still unacceptably high, and in these cases we advocate the use of single IMA plus SVGs instead of bilateral IMAs.
References 1. 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– 6. 2. Barner HB, Standeven JW, Reese J. Twelve-year experience with internal mammary artery for coronary artery bypass. J Thorac Cardiovasc Surg 1985;90:668–75. 3. Tector AJ, Kress DC, Downey FX, Schmahl TM. Complete revascularization with internal mammary artery grafts. Semin Thorac Cardiovasc Surg 1996;8:29– 41. 4. Sauvage LR. Extensive myocardial revascularization using only internal thoracic arteries for grafting the anterior descending, circumflex, and right systems. Cardiac surgery: state of the art reviews. 1992:397– 419. 5. Cunningham JM, Gharavi MA, Fardin R, Meek RA. Considerations in the skeletonization technique of internal mammary artery dissection. Ann Thorac Surg 1992;54:947–50. 6. Choi JB, Lee SY. Skeletonized and pedicled internal thoracic artery grafts: effects on free flow during bypass. Ann Thorac Surg 1996;61:909–13. 7. Parish MA, Asai T, Grossi EA, et al. The effects of different
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8. 9. 10. 11. 12. 13.
14.
15. 16. 17. 18. 19. 20.
techniques of internal mammary artery harvesting on sternal blood flow. J Thorac Cardiovasc Surg 1992;104:1303–7. Carrier M, Gregoire J, Tronc F, Cartier R, Leclerc Y, Pelletier LC. Effect of internal mammary artery dissection on sternal vascularization. Ann Thorac Surg 1992;53:115–9. Calafiore AM, Di Giammarco G. Complete revascularization with three or more arterial conduits. Semin Thorac Cardiovasc Surg 1996;8:15–23. Dion R, Etienne, PY, Verhelst GK, et al. Bilateral mammary grafting. Eur J Cardiothorac Surg 1993;7:287–94. Pick AW, Orszulak TA, Anderson BJ, Schaff HV. Single versus bilateral internal mammary artery grafts: 10-year outcome analysis. Ann Thorac Surg 1997;64:599 – 605. Schmidt SE, Jones JW, Thornby JI, Miller CC, Beall AC Jr. Improved survival with multiple left-sided bilateral internal mammary artery grafts. Ann Thorac Surg 1997;64:9–14. Sergeant P, Flameng W, Suy R. The sequential internal mammary artery graft. Long term results of a consecutive series of 364 patients. J Cardiovasc Surg (Torino) 1988;29: 596 – 600. Dion R, Verhelst R, Goenen R, et al. Sequential mammary artery grafts in one hundred and twenty consecutive patients: indications, operative technique, 6 months postoperative functional and angiographic controls. J Cardiovasc Surg 1989;30:635– 42. Grondin CM, Limer R. Sequential anastomoses in coronary artery grafting: technical aspects and early and late angiographic results. Ann Thorac Surg 1977;23:1– 8. Lytle BW, Cosgrove DM. Coronary artery bypass surgery. Curr Probl Surg 1992;29:733– 807. Arnold M. The surgical anatomy of sternal blood supply. J Thorac Cardiovasc Surg 1972;64:596 – 610. Carrier M, Gregoire J, Tronc F, Cartier R, Leclerc Y, Pelletier LC. Effect of internal bilateral artery dissection on sternal vascularization. Ann Thorac Surg 1993;55:803– 4. Galbut DL, Traad EA, Dorman MJ, et al. Twelve-year experience with bilateral internal mammary artery grafts. Ann Thorac Surg 1985;40:264–70. Lytle BW, Cosgrove DM, Loop FD, Borsh J, Goormastic M, Taylor PC. Perioperative risk of bilateral internal mammary artery grafting: analysis of 500 cases from 1971 to 1984; Circulation 1986;74(Suppl):III37– 41.
Background. Bilateral internal mammary artery (IMA) grafting is performed to provide complete arterial myocardial revascularization with the intention of decreasing postoperative return of angina and the need for reoperation. We present here technical views of doubleskeletonized IMA grafting, and evaluate its clinical outcome. Methods. Skeletonized IMA is harvested gently with scissors and silver clips, without use of cauterization, and embedded in a small syringe filled with papaverine. Three strategies for arterial revascularization were employed in 762 consecutive patients: (1) the cross arrangement (242 patients, 32%), where the in situ right internal mammary artery (RIMA) is used for the left anterior descending artery (LAD), in situ left internal mammary artery (LIMA) to circumflex marginal branches and the gastroepiploic artery for the right coronary artery (RCA); (2) the composite arrangement (476 patients, 62%), where
free IMA is attached end-to-side to the other in situ IMA; and (3) the natural arrangement (44 patients, 6%), where the in situ RIMA is connected to the RCA and in situ LIMA to LAD. Mean age was 66 years (range 30 to 92). Two hundred ninety-two patients (38%) were older than 70, and 229 (30%) were diabetic. Results. Operative mortality was 2.5% (n ⴝ 19). The mortality of urgent and elective cases was 1.2% (8 of 663), and that of emergency operation was 11% (11 of 99). There were 9 (1.2%) perioperative myocardial infarctions, and 10 patients (1.3%) sustained strokes. Sternal wound infection occurred in 14 (1.8%). Conclusions. The three strategies described here provide the surgeon with the versatility required for arterial revascularization with bilateral IMAs in most patients referred for coronary artery bypass grafting. (Ann Thorac Surg 2000;69:841– 6) © 2000 by The Society of Thoracic Surgeons
T
technical experience of double-skeletonized IMA harvesting and grafting in 762 patients.
he internal mammary artery (IMA) is usually isolated from the chest wall as a pedicle, together with vein, muscle, fat, and accompanying endothoracic fascia [1–3]. A surgical technique was recently developed, where the IMA is dissected as a skeletonized vessel [4, 5]. The skeletonized artery is isolated gently with scissors and silver clips, without the use of cauterization (Fig 1A, B). The advantage is that the dissected artery is particularly long, and its spontaneous blood flow is greater than in a pedicled IMA [6], allowing the use of both IMAs as grafts to practically all coronary vessels requiring surgical revascularization. Another advantage of using the skeletonized IMA, is the preservation of collateral blood supply to the sternum (Fig 2), enabling more rapid healing, and decreasing the risk of infection [7, 8]. We have adopted bilateral skeletonized IMA grafting as our preferred method for myocardial revascularization. Daily use of this IMA-harvesting technique has enabled the surgeons to acquire the dexterity required for dissecting the skeletonized IMA. We report here our Accepted for publication Sept 17, 1999. Address reprint requests to Dr Mohr, Department of Thoracic and Cardiovascular Surgery, Tel-Aviv Sourasky Medical Center, 6 Weizman St, Tel Aviv 64239, Israel.
© 2000 by The Society of Thoracic Surgeons Published by Elsevier Science Inc
Material and Methods Harvesting and Preparing the Skeletonized IMA In our harvesting technique, we basically follow instructions and recommendations given before by Cunningham and associates [5], and add our experience. A standard median sternotomy incision is used with only rare application of bone wax. Later dissection of the IMA is easier if meticulous hemostasis is obtained on the sternal edges to avoid accumulation of blood in the field. The IMAs are dissected as skeletonized arteries [3], before heparin administration, to decrease the risk of damage and hematoma formation in the region of the side branches during dissection. We favor elective opening of pleura before IMA dissection, to facilitate exposure. Though it is possible to completely skeletonize the IMA from its origin to its distal bifurcation without opening the pleura, dissection of proximal IMA with its anterior and pericardial branches is easier and safer when the pleura is open. To avoid thermal injury to the IMA, it is extremely important to keep the cautery setting on low, throughout the dissection. Cautery is used to cut the endothoracic fascia 0003-4975/00/$20.00 PII S0003-4975(99)01407-1
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Fig 1. (A) The pedicled internal mammary artery (IMA) (A), the skeletonized IMA (B), and skeletonized IMA embedded in papaverine solution (jacuzzi) (C). (B) The left skeletonized IMA during harvesting. (C) The skeletonized IMA after harvesting inside a jacuzzi.
and expose the underlying IMA. Using scissors or the tip of the cold cautery as dissectors, the artery can be gently separated from the chest wall, leaving the accompanying veins, fascia, and adipose tissue in place. Forceps should never grasp the artery itself, but may hold the small remnants of soft tissue that cling to the adventitia of the
Fig 2. Collateral blood flow to the sternum is preserved after division of internal mammary artery side branches.
IMA. The initial cut in the endothoracic fascia is extended inferiorly until the terminal bifurcation of the IMA, into its lateral musculophrenic and medial superior epigastric branches, is visualized. Terminal bifurcation usually occurs at the sixth intercostal space. These terminal branches are left intact to allow blood flow through the IMA, until it is ready for use. Branches are divided between two silver clips using scissors. Once branches are controlled, scissors or low cautery are used to divide remaining medial and lateral soft tissue attachments. After the distal portion of the artery is freed, an additional cautery cut in the endothoracic fascia is made to allow dissection superiorly. The proximal third of the IMA occasionally has large anterior perforating branches that may initially seem too short to allow satisfactory clip application. With careful dissection, proximal and distal to the branch, suitable length can usually be obtained. Excessive traction should not be applied to the IMA, as these branches can tear easily, causing serious bleeding or hematomas. If insufficient branch length precludes safe application of two clips, it is sometimes best to apply a clip to the IMA side of the branch. The branch is then cut, and cautery used to obtain hemostasis on the chest wall. Meticulous technique is essential to avoid tearing of
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these branches, or worse, avulsing them from the IMA itself. Should a tear or avulsion occur, small atraumatic vascular clamps are applied proximally and distally following systemic administration of 5000 IU of heparin, thus allowing adequate visualization. Precise 8-0 polypropylene sutures can then be placed without compromising the IMA lumen. Throughout the dissection, the IMA is sprayed with warm diluted papaverine solution to minimize spasm and prevent dessication. Care is taken to keep cautery well away from the IMA when using it, even in the low setting. As the origin of the IMA is approached, pericardial branches are identified and divided. Lowering the table facilitates exposure of collaterals in this portion of the IMA. To obtain maximal IMA length, diameter, and flow, it might be necessary to divide the internal mammary vein, to obtain satisfactory exposure of these most proximal collateral branches. While the retractor is still in place and exposure is good, the superomedial pleural reflection is divided with cautery. This maneuver increases the usable length of the artery as it allows the IMA to drop into a groove established between the pleura and pericardium. A vertical incision is made in the lateral pericardium, from its free edge up to the phrenic nerve. The LIMA is mobilized through this incision, and penetrates the pericardial cavity anterior to the phrenic nerve. This maneuver also allows the IMA to lie medial and posterior to the lung, thus ventilation does not produce any notable stretch or distortion of the artery. Additionally, the artery is somewhat protected from injury, should resternotomy be required. The vessel is then carefully inspected for any signs of inadequate hemostasis or wall trauma. Bleeding points are controlled with a clip or fine suture. It is not unusual to notice small areas of adventitial blood staining at clip application points. Occasionally, a clip can partially cut through a branch, causing bleeding and localized hematoma. It is extremely important to minimize adventitial blood staining by applying another clip if possible. When necessary, one can momentarily occlude the IMA to allow placement of a suture. These small, well-localized areas of staining do not preclude use of the IMA. However, longer areas of wall hematoma or wall discoloration are distressing, as they might be associated with intimal tears or dissection. The distal portion of the IMA should be discarded when distal dissection is suspected. Heparin is administered before distal IMA division. Medium sized hemoclips are used to secure the distal stumps of both IMAs and the proximal stump of the RIMA when this conduit is being used as a free graft. Hemoclips are used to block the distal IMA, thus enabling hydraulic distention of the skeletonized artery by pulsations of arterial pressure wave against the walls of the blocked artery. The skeletonized pedicle is then put in a small syringe filled with a 1 to 30 papaverine saline solution (Figure 1A, C). This bath of warm papaverine (jacuzzi) is good enough to relax any spasm produced during dissection
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without the risk of endothelial damage caused by other antispastic maneuvers, such as intraluminar papaverine injection or mechanical dilatation. Hence, arguments in favor of opening the pleura are: facilitated exposure, and this is of paramount importance during proximal IMA harvesting; as the route of the IMA now becomes medial, and somewhat posterior to the anterior segment of the upper lobe of the lung (when the pleura is kept open), ventilation does not produce any tension on the artery, which runs straight towards the heart. Additionally, the artery is somewhat protected from injury should resternotomy be required. Finally, there is now room for the harvested IMA, vertically embedded in the jacuzzi in the open pleural cavity. Both IMA grafts are palpated after 5 to 10 minutes in the papaverine jacuzzi. The pulse should be strong, and spontaneous free flow is almost always greater than 150 mL/ minute.
Strategies of Complete Arterial Revascularization THE CROSS TECHNIQUE. We prefer the use of bilateral IMA as in situ grafts for myocardial revascularization. The two IMAs in combination with the right gastroepiploic artery give us three sources of blood supply. We believe that more blood sources are associated with improved longterm outcome. The cross arrangement (Fig 3A) is based on the assumption that patency rates of the right internal mammary artery (RIMA) on the left anterior descending coronary artery (LAD) is similar to that of the left internal mammary artery (LIMA) on the LAD [9, 10]. To improve late survival, every effort should be made to use both IMA grafts for the left system [11–13]. We do not use the cross technique in cases with short RIMA, very long ascending aorta, enlarged right ventricle, too distal or unpredictable LAD anastomotic site, and in cases with high probability of future reoperations (for example, combined aortic valve replacement and coronary artery bypass grafting [CABG]). We always try to avoid the use of the IMA distal to its bifurcation. This portion of the IMA is very delicate, and prone to spasm. A major concern of surgeons using bilateral IMA is the risk of damage to an artery crossing the midline (RIMA) in case of future reoperation. The extra length obtained by skeletonizing dissection very often enables the surgeon to move the RIMA superiorly, above the origin of the innominate artery, and secure it under the pericardial fat and thymic remnants before chest closure. This maneuver decreases the risk of damage to the artery during potential resternotomy, and avoids kinking of the RIMA when this artery is too long.
When the distal RIMA bifurcation (Fig 3B) cannot loosely reach the LAD, we use the RIMA as a free graft, and a T-shaped [3], or if more suitable, a Y-shaped anastomosis at the level of the main pulmonary artery, is prepared before connection to cardiopulmonary bypass (CPB) (Fig 4). The proximal composite anastomosis of free RIMA on the LIMA might, at times, be performed on bypass, after constructing all distal and sequential RIMA anastomoses.
THE COMPOSITE TECHNIQUE.
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When the composite anastomosis is constructed before CPB, preventing the compromise of LIMA, flow to LAD might be achieved by constructing the most proximal sequential anastomosis (diagonal or obtuse marginal) of RIMA before constructing the more distal anastomoses (circumflex marginals and RCA). If the free RIMA is too short to reach the PDA or posterolateral branches of RCA, we use the right gastroepiploic artery or vein grafts to bypass these branches. Despite the extra length obtained with skeletonization, in some cases the LIMA is not long enough to reach a very distally located anastomotic site on the LAD. In this situation, extra length might be obtained by anastomosing the free RIMA to the LAD and LIMA to circumflex marginal branches. THE IN SITU SEQUENCE. When a graft to the posterior wall of the heart is not necessary (the circumflex region), the LIMA is grafted to the left anterior descending and the RIMA to the right coronary artery or its posterior de-
Fig 3. (A) The cross arrangement: left internal mammary artery (LIMA) anastomoses the first marginal circumflex coronary artery, right internal mammary artery (RIMA) anastomoses the left anterior descending coronary artery (LAD), and the right gastroepiploic artery to the right posterior descending coronary artery. (B) The composite arrangement: in situ LIMA to LAD, and free RIMA (proximally attached end-to-side to LIMA) to first and the second circumflex marginals.
This is the safest way to precisely determine the location of the composite anastomosis without compromise to LIMA flow to LAD.
Fig 4. The composite T-shape anastomosis was preformed here before cardiopulmonary bypass. Free right internal mammary artery was attached to in situ left internal mammary artery (A ⫽ scheme, B ⫽ photograph).
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scending branch. The RIMA grafted on the right coronary artery has a low patency rate [14]. In fact, the right coronary artery is often calcified or severely fibrotic, and therefore the edges of the arteriotomy are not able to remain separated from each other after the incision. We therefore prefer the RIMA to posterior descending artery (PDA) anastomosis. The shortest route on the right side into the posterior pericardial space and the PDA lies along the posterolateral aspect of the subclavian vein and the superior vena cava (SVC). After the thymic tissue and fat have been cleared from the anterior aspect of these vessels, the pathway is developed by reflecting the parietal pleura laterally, carrying the phrenic nerve with it. The pathway into the right posterior pericardial space is opened widely by incising the parietal pericardium in the midline over the SVC. It should be noted that, in most cases, it is impossible to reach the PDA with the IMA graft when employing the regular technique of isolating the pedicled IMA. A skeletonized RIMA, however, is longer and can usually reach the better quality distal PDA.
Sequential Grafting With Skeletonized IMA Sequential grafting is essential only if IMAs are used for complete arterial myocardial revascularization. The economic approach of sequential grafting using diamondshaped side-to-side anastomosis and terminal T-shaped anastomosis for branches of the circumflex and RCA is our preferred approach. It carries the advantage of sparing IMA length using the shortest possible IMA segments between anastomoses. By using short arteriotomies (2 to 3 mm) potential kinking of the graft in the anastomotic region is prevented. To prevent tension between anastomoses after filling the ventricle, the length of the IMA segment between anastomoses should be 5 to 10 mm longer than the actual distance between coronary arteriotomies. Side-to-side parallel anastomosis is often used for sequential LAD diagonal grafting with the LIMA. The skeletonized artery length increases sometimes after harvesting. A common pitfall in this LAD diagonal arrangement is kinking when the IMA segment between anastomoses is too long. This problem, which is not observed when using the pedicled IMA, can be solved by using the Y-graft (mini-composite) technique or by using the RIMA for the diagonal in cases of RIMA on LIMA composite graft. The parallel side-to-side anastomosis is preferred for the intramyocardial coronary artery or for vessels buried inside a deep layer of epicardial fat. Constructing a diamond-shaped anastomosis exposes the IMA to the risk of seagull-wing kinking [15].
Results We prospectively evaluated the use of doubleskeletonized IMA in 762 patients between April 1996 and April 1998. Mean age was 66 years, range 30 to 92 years, 595 (78%) were men, and 167 (22%) women. Two hundred
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ninety-two (38%) were older than 70, 229 (30%) were diabetic, and 141 (18%) had left ventricular dysfunction. Myocardial preservation technique was intermittent anterograde warm blood cardioplegia. Mean bypass time was 102 minutes, and cross-clamp time was 85 minutes. Average number of grafts was 3.1 per patient (2 to 6). The gastroepiploic artery was used in 182 patients (24%). The composite technique was performed in 476 patients (62%), the cross technique in 242 (32%), and in situ arrangement in 44 (5.7%). Operative mortality was 2.5% (n ⫽ 19). The mortality of urgent and elective cases was 1.2% (8 of 663) and that of emergency operation was 11% (11 of 99). There were 9 (1.2%) perioperative myocardial infarctions, and 10 (1.3%) patients sustained strokes. Sternal wound infection occurred in 14 (1.8%). Neither diabetes nor advanced age (⬎ 70) were independent predictors of untoward events. Chronic lung disease was found to be the only independent predictor of sternal infection (chronic obstructive pulmonary disease, odds ratio 7.1; 95% confidence interval, 2.1 to 197). Postoperative follow-up (12 to 45 months) was available in 747 (98%) patients. One and 3 years actuarial survival were 95.5% and 93% respectively. Only 22 of the surviving patients (2.9%) reported return of angina. Forty-one patients underwent postoperative cardiac catheterization during the follow-up period: 22 due to chest pain, 4 had positive thalium-spect scan, and the remainder consented to elective catheterization within the framework of learning to use the composite technique. Seventy-seven of the IMAs were patent and 5 were occluded (patency rate of 94%). Nine patients (1.2%) underwent postoperative percutaneus transluminal coronary angioplasty, and 4 (0.5%) underwent reoperations. There were 12 new cases (1.2%) of congestive heart failure. Ninety-four percent of the surviving patients were well and angina-free at the time of last follow-up.
Comment This report focuses on technical aspects of bilateral skeletonized IMA grafting. The technical experience we gathered with the first 762 patients operated upon is detailed above. The patients here are typical for an urban population (relatively old), and this technique was used in 71% of the patients who underwent CABG in our institution, including those older than 70 years of age and diabetic patients, over a relatively short period of time (3 years). The only important contraindication for the use of IMA grafts was in emergency operations with hemodynamic instability requiring rapid connection to a cardiopulmonary bypass. The immediate operative results are comparable to those described in procedures in which one IMA was used [16]. The report confers significant clinical approval of the basic assumption concerning the skeletonized IMA technique; that it probably causes less damage to the sternal blood flow [7– 8, 17–19], and therefore rates of sternal infections and complications are in the lower range of those reported by others.
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Diabetes mellitus is generally considered to be a major risk factor for sternal complications, especially when bilateral IMA grafting is used. The risk in these circumstances was estimated to be five times more than in other patients [20]. We found no evidence of this relationship in those receiving bilateral skeletonized IMA. Our results are even more conclusive, taking into account the fact that 30% of the patients were diabetics. Routine use of bilateral skeletonized IMAs seems to be a safe technique for patients undergoing CABG, not only in terms of morbidity and mortality, but also regarding sternal complications and infections. However, in the patients with chronic lung disease the risk of sternal infection is still unacceptably high, and in these cases we advocate the use of single IMA plus SVGs instead of bilateral IMAs.
References 1. 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– 6. 2. Barner HB, Standeven JW, Reese J. Twelve-year experience with internal mammary artery for coronary artery bypass. J Thorac Cardiovasc Surg 1985;90:668–75. 3. Tector AJ, Kress DC, Downey FX, Schmahl TM. Complete revascularization with internal mammary artery grafts. Semin Thorac Cardiovasc Surg 1996;8:29– 41. 4. Sauvage LR. Extensive myocardial revascularization using only internal thoracic arteries for grafting the anterior descending, circumflex, and right systems. Cardiac surgery: state of the art reviews. 1992:397– 419. 5. Cunningham JM, Gharavi MA, Fardin R, Meek RA. Considerations in the skeletonization technique of internal mammary artery dissection. Ann Thorac Surg 1992;54:947–50. 6. Choi JB, Lee SY. Skeletonized and pedicled internal thoracic artery grafts: effects on free flow during bypass. Ann Thorac Surg 1996;61:909–13. 7. Parish MA, Asai T, Grossi EA, et al. The effects of different
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8. 9. 10. 11. 12. 13.
14.
15. 16. 17. 18. 19. 20.
techniques of internal mammary artery harvesting on sternal blood flow. J Thorac Cardiovasc Surg 1992;104:1303–7. Carrier M, Gregoire J, Tronc F, Cartier R, Leclerc Y, Pelletier LC. Effect of internal mammary artery dissection on sternal vascularization. Ann Thorac Surg 1992;53:115–9. Calafiore AM, Di Giammarco G. Complete revascularization with three or more arterial conduits. Semin Thorac Cardiovasc Surg 1996;8:15–23. Dion R, Etienne, PY, Verhelst GK, et al. Bilateral mammary grafting. Eur J Cardiothorac Surg 1993;7:287–94. Pick AW, Orszulak TA, Anderson BJ, Schaff HV. Single versus bilateral internal mammary artery grafts: 10-year outcome analysis. Ann Thorac Surg 1997;64:599 – 605. Schmidt SE, Jones JW, Thornby JI, Miller CC, Beall AC Jr. Improved survival with multiple left-sided bilateral internal mammary artery grafts. Ann Thorac Surg 1997;64:9–14. Sergeant P, Flameng W, Suy R. The sequential internal mammary artery graft. Long term results of a consecutive series of 364 patients. J Cardiovasc Surg (Torino) 1988;29: 596 – 600. Dion R, Verhelst R, Goenen R, et al. Sequential mammary artery grafts in one hundred and twenty consecutive patients: indications, operative technique, 6 months postoperative functional and angiographic controls. J Cardiovasc Surg 1989;30:635– 42. Grondin CM, Limer R. Sequential anastomoses in coronary artery grafting: technical aspects and early and late angiographic results. Ann Thorac Surg 1977;23:1– 8. Lytle BW, Cosgrove DM. Coronary artery bypass surgery. Curr Probl Surg 1992;29:733– 807. Arnold M. The surgical anatomy of sternal blood supply. J Thorac Cardiovasc Surg 1972;64:596 – 610. Carrier M, Gregoire J, Tronc F, Cartier R, Leclerc Y, Pelletier LC. Effect of internal bilateral artery dissection on sternal vascularization. Ann Thorac Surg 1993;55:803– 4. Galbut DL, Traad EA, Dorman MJ, et al. Twelve-year experience with bilateral internal mammary artery grafts. Ann Thorac Surg 1985;40:264–70. Lytle BW, Cosgrove DM, Loop FD, Borsh J, Goormastic M, Taylor PC. Perioperative risk of bilateral internal mammary artery grafting: analysis of 500 cases from 1971 to 1984; Circulation 1986;74(Suppl):III37– 41.