Total Arterial Revascularization Silvana Marasco  Operative Techniques in Thoracic and Cardiovascular Surgery  Volume 21, Issue 1, Pages 20-30 (March 2016) DOI: 10.1053/j.optechstcvs.2016.08.002 Copyright © 2016 Terms and Conditions

Figure 1 Skeletonized internal thoracic artery. The internal thoracic arterial (ITA) length is maximized by skeletonizing the vessel. Construction of sequential anastomoses is also facilitated by skeletonization as all walls of the conduit are clearly visualized, and thus assists in achieving total arterial vascularization. The ITA arises from the subclavian artery and passes caudally, anterior to the brachiocephalic vein. It passes between the costal cartilages and the pleura, approximately 1cm lateral to the lateral border of the sternum. At the level of the third intercostal space, the artery passes anterior to the transversus thoracic muscle, lying posterior to the intercostal muscles. At approximately the level of the sixth intercostal space, the internal thoracic artery divides into the superior epigastric artery and the musculophrenic artery. Care must be taken with the proximal dissection, where the artery crosses the phrenic nerve, typically on its medial side. Technique for harvesting the ITA involves opening the endothoracic fascia with low energy electrocautery just medial to the internal thoracic vein which accompanies the artery on its medial side. This allows retraction of the fascia, which brings the artery down into view. The electrocautery tip can then be used as a spatula, without heat, to gently tease down the artery along its length, leaving the accompanying veins in situ. As each side branch is encountered it is clipped twice and divided between with scissors. The artery is then gently peeled off the accompanying endothoracic fascia. The advantage of this technique is that the vessel wall is not handled at all. Skeletonization of the ITAs has the added advantage of reducing devascularization of the chest wall compared with the traditional technique of harvesting the ITA with a thick pedicle of surrounding tissue, using predominantly electrocautery. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 2 Allenʼs test. Assessment of the ulnar collateral circulation to the hand is essential before radial artery harvest. This is accomplished by application of the Allen test whereby occlusion of both the ulnar and radial arteries at the level of the wrist is performed until blanching of the hand is noted. Occlusion of the ulnar artery is then released, and if reperfusion is not noted in the thumb, index finger, and thenar eminence by 10 seconds, the test is considered positive (and use of the vessel contraindicated). On the operating table, the test can be performed using the oxygen plethysmography waveform from the index finger, or even during harvesting by transecting distally the radial artery and observing for backflow from the distal segment. However, if performing the test on the operating table, be aware that conditions such as a cold operating room or hypotension associated with anesthesia can lead to a false positive Allenʼs test. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 3 Radial artery harvest. The radial artery arises from the brachial artery in the cubital fossa, having emerged from beneath the bicipital aponeurosis. It then runs distally under the muscle belly of brachioradialis, in close proximity to the superficial radial nerve, which lies lateral. The radial artery becomes more superficial in its distal third lying over pronator quadratus between the tendons of brachioradialis and flexor carpi radialis. It then enters the palm to form the deep palmar arch with the ulnar artery. Harvesting can be accomplished either open or minimally invasively, using low energy electrocautery, harmonic scalpel, or sharp dissection with scissors and clips. The artery is harvested with both venae commitantes. In the more distal portion, the surrounding fascia and fat is more adherent and it is safer to leave those tissues attached to the pedicle. Skeletonization of the artery does not improve length and increases the risk of endothelial damage. Histologically, the radial artery has a thicker medial layer than other arterial conduits making it more prone to spasm. It should, therefore, be stored after harvest in a vasodilating solution such as 1% papaverine in heparinised blood, or verapamil and nitroglycerin solution, until required for grafting. The artery should not be stored in a papaverine solution without blood, as papaverine is quite acidic and needs the buffer action of blood to ensure the radial artery is not adversely affected. Postoperatively, use of calcium channel blockers has been advocated to reduce vasospasm. However, the benchtop studies that showed the vasodilatory effects of calcium channel blockers on radial artery specimens used supra-therapeutic doses. Clinically, the use of vasodilatory drugs as prophylaxis against radial artery spasm has never been proven, and indeed the potential attendant hypotension is probably deleterious to graft flow. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 4 Use of in situ internal thoracic arteries. The in situ RITA can be used to reach the distal right coronary artery or proximal posterior descending artery (PDA), particularly if the PDA has a high take off (A). However, many surgeons prefer to use the in situ RITA to graft the left coronary system (B). (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 4 Use of in situ internal thoracic arteries. The in situ RITA can be used to reach the distal right coronary artery or proximal posterior descending artery (PDA), particularly if the PDA has a high take off (A). However, many surgeons prefer to use the in situ RITA to graft the left coronary system (B). (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 4 (Continued) The right ITA can be brought behind the thymic fat to reach the left anterior descending (LAD) or a proximal diagonal in an anterior crossover position (C). Often the RITA would need to be threaded above its accompanying vein proximally to maximize length, or the accompanying vein can be clipped and divided. The conduit would usually only be long enough to reach the more proximal LAD and the reach can be facilitated by closing the sternal retractor slightly, which increases the apparent length (D). The LITA is then used to graft the circumflex territory. Care needs to be taken with the left pericardial window in this situation to ensure that it is low enough to provide a smooth course for the LITA, but not so low that the phrenic nerve is approached. Alternatively, the RITA can be brought through the transverse sinus to reach an intermediate or high obtuse marginal in a posterior crossover position (E). Care must be taken when bringing the RITA through the transverse sinus not to twist the graft or dislodge clips on side branches, which can be difficult to rectify once the graft is in position. This positioning can also make a redo operation difficult, particularly when placing the aortic cross clamp. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 4 (Continued) The right ITA can be brought behind the thymic fat to reach the left anterior descending (LAD) or a proximal diagonal in an anterior crossover position (C). Often the RITA would need to be threaded above its accompanying vein proximally to maximize length, or the accompanying vein can be clipped and divided. The conduit would usually only be long enough to reach the more proximal LAD and the reach can be facilitated by closing the sternal retractor slightly, which increases the apparent length (D). The LITA is then used to graft the circumflex territory. Care needs to be taken with the left pericardial window in this situation to ensure that it is low enough to provide a smooth course for the LITA, but not so low that the phrenic nerve is approached. Alternatively, the RITA can be brought through the transverse sinus to reach an intermediate or high obtuse marginal in a posterior crossover position (E). Care must be taken when bringing the RITA through the transverse sinus not to twist the graft or dislodge clips on side branches, which can be difficult to rectify once the graft is in position. This positioning can also make a redo operation difficult, particularly when placing the aortic cross clamp. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 5 Construction of composite grafts. Total arterial revascularization can be accomplished using separate grafts for each coronary grafted, for example, by harvesting bilateral ITAs and RAs. However, TAR would often require the construction of composite grafts in the form of T or Y grafts and sequential grafts to ensure efficient use of available conduits, and to reduce the number of conduits harvested. Construction of the Y graft is best positioned at the point where the LITA enters the pericardium leaving all available length of the second conduit within the pericardium for construction of the distal anastomoses. When constructing the Y graft, the 2 vessels can be brought up almost to the level of the sternum for the construction of the actual anastomosis, making it technically easier than trying to do the anastomosis in situ. Construction of the T graft vs Y graft poses a slightly different technique. The T graft tends to mandate a shorter arteriotomy on the LITA with the arteriotomy of the hood of the second vessel also being cut shorter to match. In contrast the arteriotomy of both vessels for construction of a Y graft is longer. The technique of actual construction of the T or Y graft can be determined by the surgeon, but we find the easiest method, particularly when starting this technique is to commence suturing at the furthest point (most proximal part of the arteriotomy on the LITA) and use a forehand stitching technique with each end of the double ended suture coming toward yourself down each side of the anastomosis. Either a 7-0 or 8-0 polypropylene suture can be used. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 6 Sequential grafting. Using a RITA or a RA as a T or Y graft onto the LITA is a frequently constructed composite graft, which allows complete revascularization of the left sided coronary vessels. This strategy is suited to off pump coronary revascularization, facilitating a “no touch” technique of the ascending aorta. If surgery is planned on bypass, the Y graft can be constructed before cannulation, leaving only distal anastomoses to be performed on the left side during the cross-clamp period. The constructed limb of the Y graft can then “skipped” over multiple obtuse marginal branches as required. A radial artery as a Y graft is even long enough to reach the posterior descending branch of the right coronary artery. However, patency rates are significantly worse for this distal anastomosis and so it is best to keep the Y graft off the LITA revascularising only left sided vessels. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions

Figure 7 Sequential anastomoses. Sequential grafting or “skip” grafting also allows conduit conservation in multigraft cases. Sequential grafts can either be constructed as parallel (A) or cruciate grafts, or rotated to lesser degrees. Care is essential, however, to ensure that the vessel lies free of kinks particularly when forming a cruciate anastomosis—too long an arteriotomy in the coronary vessel would play the conduit excessively leading to flattening of the hood at the graft site (B). A shorter arteriotomy in both vessels ensures a more rounded anastomosis, which is less likely to flatten the hood of the conduit (C). Consideration of target vessel size and run off is also needed when planning sequential grafts. If the first touch down of a sequential graft is to a large vessel supplying a large territory, and that vessel is affected by a tight stenosis, then most of the flow through that conduit is likely to go to that target. If the distal touch down is a smaller vessel with less run off, then less flow would go down that part of the conduit. Some investigators have concerns about the patency of the entire length of the conduit in such a situation, whereas others remain confident that autoregulation would determine flow appropriately through the conduit in the same way that it determines flow in the native circulation. It is very difficult to demonstrate this in a clinical study. Computer generated reconstructions have attempted to predict the behavior of conduits in these situations but it is very difficult to accurately recreate the myriad of conditions that affect flow; conduit and native artery size, coronary vessel degree of stenosis; further disease or tandem lesions in the coronary vessel; run off and territory size supplied by the native vessel; viability of myocardium in that territory; size and patency of the actual anastomoses; inflow into the conduit; etc. (Color version of figure is available online at www.optechtcs.com.) Operative Techniques in Thoracic and Cardiovascular Surgery 2016 21, 20-30DOI: (10.1053/j.optechstcvs.2016.08.002) Copyright © 2016 Terms and Conditions