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Coronary artery bypass graft


Coronary artery bypass graft operations are effective in the treatment of ischemic heart disease. Although these operations have become quite standard, there seems to be an infinite variety of presentations of atherosclerotic disease and combinations of operations to revascularize the ischemic myocardium.

Figure 36-1

  • Combinations for Saphenous Vein Bypass Grafts

  • A

    Sequential grafts conserve the amount of saphenous vein required for complete revascularization. A number of combinations and sequences can be used. One common sequence is that used in the left anterior descending coronary artery system. The graft is anastomosed side-to-side to the diagonal branch and end-to-side to the left anterior descending coronary artery.

  • B

    Another common sequence is anastomosis to the marginal branches of the circumflex coronary artery. The vein graft is anastomosed to the proximal marginal branches in a side-to-side fashion and to the most distal marginal branch in an end-to-side fashion.

  • C

    Posterior sequential grafts to the circumflex marginal branches can be continued to include branches of the right coronary artery, such as its posterior lateral or posterior descending branch.

  • D

    The right posterior descending coronary artery and a left ventricular branch of the distal right coronary artery can be used in sequence.

  • E

    Posterior sequential grafts that include both the right coronary artery and branches of the circumflex coronary artery eliminate the requirement for one proximal anastomosis. The direction is chosen based on the premise that placing the largest coronary artery branch at the end of the sequence will provide runoff that is greatest to the end of the graft.

  • Combinations for Internal Mammary Artery Bypass Grafts

  • F

    The left internal mammary artery is commonly used for bypass to the left anterior descending artery. Sequential graft techniques may include the diagonal branch of the left anterior descending artery. The right internal mammary artery can be used for bypass to the right coronary artery.

  • G

    The left internal mammary artery can be anastomosed to the obtuse marginal branch of the circumflex coronary artery. The right internal mammary artery can be brought across the midline to the left anterior descending coronary artery; however, most surgeons avoid this configuration because the right internal mammary artery is placed in proximity to the sternotomy increasing the hazard of re-entry.

  • H

    When extensive revascularization of the posterior surface of the heart is required, a posterior sequential vein graft in combination with a left internal mammary artery graft to the left anterior descending coronary artery is usually performed.

  • I

    The radial artery can be used to sequentially bypass arteries on the posterior surface of the heart. The radial artery is anastomosed to the left internal mammary artery, which is used to revascularize the anterior circulation.

  • J

    Visceral arteries, such as the right gastroepiploic artery or the splenic artery, can be used for posterior revascularization. Combined with a left internal mammary artery bypass graft for anterior revascularization, this achieves total artery revascularization.

Preparation of saphenous vein graft

Figure 36-2, A While the midsternal incision is made and preparations for cardiopulmonary bypass are under way, a simultaneous incision is made in the left leg over the course of the greater saphenous vein. The leg is abducted and rotated laterally by placing a roll under the knee. The foot is draped so that the ankle is exposed. With the leg in the dependent position, the vein becomes distended, allowing its course to be easily marked on the skin with a fine needle or marking pen before making the incision. The skin is opened sharply down to the level of the saphenous vein. Beginning at the ankle—to ensure a constant location anterior to the medial malleolus and easy identification of the vein—the connective tissue overlying the vein is removed. Curved Mayo scissors are ideal for this dissection. These scissors can be placed easily and safely into the plane between the connective tissue and adventitia of the saphenous vein, allowing the plane to be opened without injuring the vein. The scissors are opened perpendicular to the vein to lift the connective tissue from the top of the vein. Lateral blunt dissection should be avoided to prevent tearing of the side branches. The dissection must be limited to tissues directly over the vein. The scissors are then used to divide the connective tissue and expose the vein. Most of the side branches of the vein come into view without any lateral dissection. The entire length of the vein should be exposed before attempting to remove any of it. For a single segment of vein graft, the incision extends from the ankle to the midportion of the leg below the knee. For two grafts, the vein from the ankle to just below the knee is sufficient; for three or more grafts, the vein should be exposed to the midportion of the leg above the knee. B The saphenous vein is ligated at the ankle over the medial malleolus. The vein is divided, and an angled peripheral vascular clamp is applied to the end to serve as a handle for retraction. For ease of dissection, firm upward retraction is applied to expose the posterior connective tissue and the side branches of the vein as they are encountered. Connective tissue must be cleanly removed from each branch’s junction with the main vein so that the branch can be accurately ligated. A ligature of 4/0 silk is passed on a curved hemostat around the branch. The branch is tied precisely on the side of the saphenous vein. A small hemoclip is applied to the branch at the tissue level, and the vein branch is divided. Ligatures placed too close to the saphenous vein or that include any connective tissue not completely removed from the junction will distort and narrow the saphenous vein as its adventitia is drawn into the ligature. If the ligatures are placed away from the side of the vein, thereby leaving a length of branch between the vein and the ligatures, there is the potential for thrombus formation where stasis occurs. These errors in technique should be avoided. C The desired length of saphenous vein is removed and prepared for bypass grafting by gentle distension using heparinized isotonic electrolyte solution. Some surgeons prefer to use the patient’s blood to distend the vein. The addition of papaverine to the solution is optional. A Dietrich vascular clamp is placed on the distal end of the saphenous vein as a matter of routine to ensure proper orientation of the valves. As the vein is distended, side branches that have not been ligated are identified. A small hemostat can be applied, and the branch can simply be ligated with 4/0 silk suture or a hemoclip. D When the branch consists of a hole in the vein, the site is closed by a double-loop stitch of 7/0 polypropylene. This technique provides the most accurate and secure closure of the vein perforation and results in the least chance of vein distortion by the pulling in of adventitial connective tissue. The right coronary system, anterior descending coronary system, and circumflex coronary system can be bypassed using individual grafts for each system. When more than one anastomosis is required in any of the three systems, sequential graft techniques are used. Alternatively, various combinations of graft sequences can be employed to conserve the length of vein required to accomplish complete revascularization of the coronary arteries.

Endoscopic saphenous vein harvest

Endoscopic dissection and excision of the saphenous vein have the advantages of requiring smaller skin incisions, which heal better; produce less postoperative pain and patient discomfort; and reduce the incidence of infection of the leg incision. Minimally invasive harvest of the greater saphenous vein also improves cosmesis. Nearly the entire saphenous vein can be removed with this technique, using just a few small incisions.

Figure 36-3, A A small incision is made on the medial aspect of the knee. Direct or endoscopic visualization is used to locate the greater saphenous vein, which can be encircled with a vascular snare if necessary. Prior to inserting the endoscopic system, intravenous heparin is administered to prevent intraluminal clot. B The endoscopic port is inserted into the incision. The balloon on the port is inflated to maintain the seal if necessary. Continuous carbon dioxide insufflation is used to expand the tunnel and subcutaneous tissues for better visualization. C A tunnel is created along the course of the saphenous vein in the thigh by gradually advancing the cone of the dissector under videoscopic guidance. The vein and side branches are freed from the subcutaneous tissue anteriorly, posteriorly, and bilaterally. The side branches are then cauterized and divided to free the vein within the tunnel in the thigh. D A similar tunnel is created along the course of the saphenous vein in the calf by reversing the direction of the endoscopic system within the primary incision. The vein and side branches are freed from the subcutaneous tissue, and the side branches are divided to free the vein within the tunnel in the lower leg. E Using videoscopic guidance, a small stab wound is made through the skin and into the tunnel above the vein at both the proximal and distal ends of the tunnel. The vein is gently retrieved through the stab incision and divided under direct vision. Alternatively, an endoloop can be used to ligate the proximal and distal ends; the vein is then divided with electrocautery. F The entire saphenous vein is removed through the knee incision. The remnants of the side branches are reinforced with fine silk ligatures. A pressure dressing is applied to the leg.

Saphenous vein–coronary artery (distal) anastomosis

Figure 36-4, A Cardiopulmonary bypass is established using a single cannula (two stage) for venous drainage, with oxygenated blood returned to the ascending aorta through a cannula placed just below the pericardial reflection. The left ventricle is decompressed by a right-angled vent catheter or a pediatric vent catheter passed via the right superior pulmonary vein to the left atrium and left ventricle. The aorta is occluded by a vascular clamp high on the ascending aorta. Revascularization is accomplished during a single aortic occlusion period. Cold cardioplegic solution (blood-based) is injected into the ascending aorta, retrograde through the coronary sinus; alternatively, a combination of antegrade and retrograde perfusion can be used. The myocardium is perfused intermittently during the procedure. Exposure of the coronary arteries for the distal anastomosis of the saphenous vein to the coronary arteries can be accomplished by a number of techniques. The common practice of having an assistant retract the heart under a gauze sponge or with a cotton glove may cause unwanted cardiac trauma. The quality of the exposure depends on the attention of the assistant. Static exposure of the distal right coronary artery and its posterior descending branch can be obtained by placing three or four traction stitches on the acute margin of the heart. One of the stitches should be near the atrioventricular groove. These stitches are held with a hemostat, which is retracted cephalad either by an assistant or by attaching it to a rubber band secured to the drapes. B Exposure of the left coronary branches is accomplished by a net device tied to umbilical tape. The ends of the tape are drawn through the transverse sinus and through an opening below the right inferior pulmonary vein behind the inferior vena cava. The net is placed behind the heart and drawn tight to the atrioventricular groove by right lateral retraction and by securing the tape to hemostats on the right anterior chest wall. Elevating the net and securing the end of it to the left anterior chest wall expose the left anterior descending coronary artery. C By retracting the net to the right and securing it to the right anterior chest wall, the cardiac apex is tipped up, exposing the posterior surface of the left ventricle and providing access to the left circumflex coronary artery. Sections of the net can be removed for improved access to the surface coronary arteries. Incision of the Coronary Artery D The coronary artery is exposed and incised directly through the epicardium, without mobilization. Lateral traction with forceps fixes the coronary artery in place. A No. 15 scalpel is gently stroked on the coronary artery until the lumen is entered. The part of the scalpel blade near the tip is used so that neither the scoring nor the subsequent arteriotomy is too long. Entry of the coronary artery is confirmed by observing cardioplegic solution exiting the artery. Optical magnification (2.5 to 3.5×) is essential for precise and accurate visualization of the coronary artery. E The arteriotomy is extended at each apex using Dietrich coronary artery scissors. The 20- or 45-degree scissors are used to open the artery at the proximal end. The scissors should be placed carefully into the lumen of the artery so that the tips do not damage the intima. The tips of the scissors should never be used to probe the lumen of the coronary artery. The cut should be to the tips of the scissors so that the length of the incision is precisely controlled. Should there be any question about the identification of the actual coronary artery lumen, calibrated coronary probes should be employed judiciously. F The distal end of the arteriotomy is completed in a similar fashion using 130-degree Dietrich scissors. The length of the coronary artery incision should approximate the diameter of the saphenous vein, measuring about 4 to 5 mm. Care should be taken to ensure that the completed arteriotomy extends for the full length of the scoring to avoid potential weakness at the ends of the arteriotomy. End-to-Side Anastomosis: Left-Side Grafts G The distal end of the saphenous vein segment is beveled at a 30- to 45-degree angle, and an adequate length is ensured for its course over the surface of the heart. A 10-stitch anastomosis is constructed using 7/0 polypropylene. Performing the anastomosis in precisely the same fashion in every case ensures a standardized technique and reproducible patency results. Five stitches are taken around the “heel” of the graft: two stitches to the side of the apex of the vein graft and coronary artery, one stitch through the apex, and two stitches on the opposite side of the apex. The graft is held apart from the coronary artery while these stitches are taken. Tension on the suture and retraction of the vein graft to the side provide exposure of the subsequent stitch. The vein graft is held by fine forceps at the side so that the intima at the tip is not injured. Suturing for left-side grafts is performed clockwise on the vein and counterclockwise on the artery. H The suture loops are drawn up, and the suture is pulled straight through to prevent a purse-string effect. The ends of the suture provide lateral traction on the coronary artery for exposure of the distal apex of the coronary arteriotomy. I Five stitches are taken around the “toe” of the graft, with the third stitch placed precisely at the apex of the coronary arteriotomy. Loops of the five sutures are left lax for exposure of the distal portion of the anastomosis. For the proper wagon-wheel effect, the needle direction is changed after the apex stitch is placed. Retraction of the vein graft and opposing traction on the epicardium expose the intima of the coronary artery. The ends of the sutures are tied precisely with tension to approximate the tissue without causing a purse-string effect. End-to-Side Anastomosis: Right-Side Grafts J The arteriotomy in the right coronary artery is generally made in the distal portion near the takeoff of the posterior descending coronary artery or in the posterior descending coronary artery itself as it courses along the posterior aspect of the ventricular septum. With right coronary artery grafts, it is usually easier to place the initial five stitches around the toe of the graft. Careful orientation of the graft prevents confusion. Stitches are placed around the toe of the graft in a counterclockwise fashion and around the distal end of the coronary arteriotomy in a clockwise fashion. The graft is held by fine forceps at the side. Retraction of the graft and suture tension help achieve exposure of the apex of the coronary arteriotomy. Suture loops are drawn up to approximate the graft to the artery and to provide lateral traction on the coronary arteriotomy. K The vein graft is retracted inferiorly with forceps to expose the proximal end of the coronary arteriotomy. Five stitches are placed at the heel in a clockwise fashion to complete the anastomosis. As the apex of the arteriotomy is passed with a suture placed directly in line with the coronary artery, the suture is passed beneath the vein graft. L The final two stitches are placed accurately by retracting the graft laterally and applying opposing traction on the epicardium medially. The suture ends are joined to complete the anastomosis. Sequential Grafts M When more than one graft is required in a coronary artery system, sequential graft techniques are used by creating proximal side-to-side anastomoses and completing the graft as an end-to-side anastomosis. A No. 11 scalpel is used to incise the vein in an appropriate orientation. In most cases a transverse incision is necessary; however, diagonal and longitudinal incisions may be more suitable, depending on the orientation of the graft relative to the coronary artery. As the pointed scalpel perforates the wall of the saphenous vein, the incision through the wall should not exceed one third of the circumference of the vein. N The five stitches placed around the heel of the graft and the coronary arteriotomy are used to provide lateral traction while the five stitches around the toe are placed. It is easiest to work in a counterclockwise fashion around the coronary arteriotomy for the most proximal of the sequential anastomoses. The more distal anastomoses are performed in a clockwise fashion to prevent unnecessary traction on the more proximal anastomoses. This technique of reversing the direction of the continuous suture anastomosis allows the graft to be retracted toward the more proximal anastomoses, providing exposure without exerting any tension on the completed anastomoses. Only four stitches are placed around the proximal end of the arteriotomy because once the suturing has passed the apex, it is no longer possible to retract the vein graft for exposure without pulling on the proximal anastomoses. The vein graft and the arteriotomy are nicely approximated at this point, and the walls of graft and the artery are easily sutured together. O The last anastomosis in a sequential graft is an end-to-side connection of the graft to the coronary artery. This arteriotomy is, of necessity, somewhat larger than those for the side-to-side anastomoses. Suturing proceeds clockwise around the arteriotomy, allowing use of the suture and retraction of the vein graft to provide exposure without distorting the completed proximal anastomoses. Again, it is of no advantage to place more than four stitches around the apex of the arteriotomy before approximating the vein graft and the artery. Determining the length of graft to use between the coronary artery sequences is a simple matter because the distensibility of the vein graft is approximately the same as the expansion of the heart when it is filled. Simply place the graft on the surface of the heart and make the anastomoses where the graft seems to fit. This results in a graft that lies without stretch or excess length when blood distends the graft and the heart.

Aorta–saphenous vein (proximal) anastomosis

Figure 36-5, A Anastomosis of the saphenous vein to the aorta is usually performed after construction of the distal anastomosis to the coronary artery. We favor this technique and use a single period of aortic occlusion and intermittent retrograde perfusion of the myocardium via the coronary sinus for both distal and proximal anastomoses. Alternatively, some surgeons prefer to perform the proximal anastomosis as the initial step to ensure aortic input to the graft and to allow antegrade perfusion of cardioplegia solution through the graft via the aorta as the revascularization proceeds. The pericardial layer covering the aorta is removed over its anterior wall. Small openings (4 to 5 mm in diameter) are made into the ascending aorta using an aortic punch. The opening for the right coronary artery graft is directly anterior to or to the right lateral side of the aorta, whereas openings for left-side grafts are made on the left lateral side. The end of the saphenous vein is cut back longitudinally for a distance of approximately 1 cm. A Cooley infant vascular clamp is placed across the tip of the saphenous vein to flatten it for exposure of the vein’s shorter, beveled end. Five suture loops of 5/0 polypropylene are then placed around the heel of the graft and passed through the aortic wall. Two stitches are placed to the side of the apex, the third stitch is placed precisely through the apex of the incision in the saphenous vein, and the final two stitches are placed on the opposite side of the apex. Traction on both the suture and the vein graft helps expose the edge of the aortic opening for accurate needle placement. Stitches include about 3 to 5 mm of the aortic wall to ensure adequate strength of the anastomosis. B The suture loops are pulled up to approximate the vein graft to the aorta. The anastomosis is completed by placing stitches in a wagon-wheel fashion around the opening in the aorta. The placement of each stitch should be accurately visualized by observing the edge of the vein graft and the intima of the aorta. Retraction of the vein graft with forceps and slight relaxation of suture tension as the needle passes from the graft to the aorta provide exposure. Wide stitches are taken along the lateral edge of the saphenous vein as it is approximated with narrow stitches to the aorta to ensure that the maximal length of saphenous vein is positioned laterally. The completed anastomosis should bulge anteriorly above the aortic wall, achieving a “cobra head” appearance. C Left-side grafts are oriented so that the shorter, beveled end of the saphenous vein graft (the heel) directly faces the left side. The stitches are placed in a clockwise fashion around the heel of the graft and in a counterclockwise fashion around the aortic opening. The right coronary graft is placed so that the heel is oriented caudally; the stitches are placed in a counterclockwise fashion around the heel of the graft and in a clockwise fashion around the aorta.

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