Reoperations are more complicated than primary operations. The specific technical challenges that surgeons must recognize and solve that are unique to or more common during coronary reoperation are
The overall problem of myocardial protection is more difficult during reoperations, with perioperative myocardial infarction still being the most common cause of in-hospital death.3,6 The metabolic concepts of myocardial protection in use today are valid, but the reasons that myocardial protection sometimes fails during reoperation are related to anatomical causes of myocardial infarction. These anatomical causes of perioperative myocardial infarction include injury to bypass grafts, atherosclerotic embolization from vein grafts or the aorta to distal coronary arteries, myocardial devascularization secondary to graft removal, hypoperfusion through new grafts, failure to deliver cardioplegic solution, early vein graft thrombosis, incomplete revascularization, diffuse air embolization, and technical error.3,38–42 To be consistently successful, coronary reoperations must be designed to avoid these causes of myocardial infarction.
A complete understanding of the patient's native coronary and bypass graft anatomy is essential. Achieving this goal is sometimes not as easy as it sounds, particularly if the patient has had multiple previous coronary operations. If bypass grafts, venous or arterial, are not demonstrated by a preoperative coronary angiogram, it usually means that they are occluded, but it is also possible that the angiogram simply has failed to demonstrate their location. Examination of old angiograms performed before previous operations and review of previous operative records often help to illustrate the patient's coronary anatomy.
It is also important to know that graftable stenotic coronary arteries supply viable myocardium. Myocardial scar and viability can be differentiated by thallium scanning, positron-emission tomography, and stress (exercise or dobutamine) echocardiography. The intricacies of establishing myocardial viability are beyond this discussion, but it is an important issue. Before embarking on a reoperation, it makes sense to be reasonably sure that there is a matchup between the patient's graftable arteries and some viable myocardium such that grafting those arteries will provide some long-term benefits.
It is also wise to have a preoperative plan for bypass conduit selection and to document that potential bypass conduits are available. ITA angiography often is helpful. Venous Doppler studies can be used to assess the presence of greater and lesser saphenous vein segments, and arterial Doppler studies can assess the radial and inferior epigastric arteries and establish the adequacy of flow to the digits during radial artery occlusion.
Median Sternotomy Incision, Conduit Preparation, and Cannulation
Most coronary reoperations are performed through a median sternotomy. Situations associated with increased risk during a repeat median sternotomy include right ventricular or aortic enlargement, a patent vein graft to the right coronary artery, an in situ right ITA graft patent to a left coronary artery branch, an in situ left ITA graft that curls under the sternum, multiple previous operations, and difficulty reopening the sternum during a previous reoperation. In such situations, vessels for arterial (via the femoral or axillary artery) and venous access for cardiopulmonary bypass are dissected out before sternal reentry. All bypass grafts except for the internal thoracic arteries may be prepared before sternal reentry. Preparation of radial artery and greater and lesser saphenous vein segments can be carried out simultaneously. The most common structure injured during reentry is a bypass graft.4
When reopening a median sternotomy, the incision is made to the level of the sternal wires; the wires are cut anteriorly and bent back but are not removed (Fig. 26-9). An oscillating saw is used to divide the anterior table of the sternum. When the anterior table has been divided, ventilation is stopped, and the assistants elevate each side of the sternum with rake retractors while the posterior table of the sternum is divided in a caudal-cranial direction. The sternal wires that have been left in place posterior to the sternum help to protect underlying structures. Once the posterior table of the sternum has been divided with the saw, the wires are removed, and sharp dissection with scissors is used to separate each side of the sternum from underlying structures. Once the sternum has been divided, it is important that the assistants retract in an upward direction, not laterally. The right ventricle is injured more often by lateral retraction while it is still adherent to the underside of the sternum than it is by a direct saw injury.
Leaving the sternal wires in place posteriorly helps to protect underlying structures while the posterior table of the sternum is divided with an oscillating saw. The direction of retraction with rake retractors should be anterior, not lateral.
In high-risk situations, it can be helpful to perform a small anterolateral right thoracotomy (Fig. 26-10) before the repeat median sternotomy. Underlying structures, such as the aorta, patent bypass grafts, and the right atrium and ventricle, can be dissected away from the sternum via this approach, and thus, with the surgeon's hand placed behind the sternum, reentry is safe. This small additional incision contributes little morbidity.
A small anterolateral right thoracotomy allows dissection of substernal structures such as patent grafts and the right ventricle or aorta away from the sternum under direct vision. While the sternum is being divided, the surgeon may place a hand behind the sternum for further safety.
Another technique for sternal reentry in high-risk patients is to heparinize, cannulate, and initiate cardiopulmonary bypass before median sternotomy. The advantages of this strategy are that the heart can be emptied and allowed to fall away from the sternum, and cardiopulmonary bypass already has been initiated for protection if an injury does occur. The disadvantages of this approach are that extensive mediastinal dissection must be carried out in a heparinized patient, including dissection of the right internal thoracic artery if that is to be used. We rarely employ this approach except in situations in which adherence of an aortic aneurysm to the sternum or a patent right ITA-to-LAD graft creates a specific danger.
Once the sternum has been divided, the pleural cavities are entered. A general principle of dissection during reoperation is that starting at the level of the diaphragm and proceeding in a cranial direction is usually the safest approach. At the level of the diaphragm, few critical structures are injured if the wrong plane is entered. Therefore, at this point in the operation we usually dissect along the level of the diaphragm to the patient's right side until we enter the pleural cavity and then detach the pleural reflection from the chest wall in a cranial direction to the level of the innominate vein. The innominate vein is dissected away from both sides of the sternum with scissors, a maneuver that prevents a "stretch" injury to that vein.
Once the right side of the sternum is separated from the cardiac structures, it is usually possible to prepare a right ITA graft. Because of parietal pleural thickening, it is often more difficult to obtain length on ITA grafts during reoperation than it is during primary procedures, and the right ITA frequently is used as a "free" graft. Once the right ITA dissection is completed to the superior border of the first rib, an incision is made in the parietal pleura to separate the proximal ITA from the area of the phrenic nerve. Thus, if the right ITA needs to be converted to a "free" graft during aortic cross-clamping, it makes division at that point easier because the proximal ITA is clearly identifiable. Although intrapericardial dissection of the left side of the heart is left until later, freeing the left side of the anterior chest wall from the underlying structures (which may include a patent ITA graft) is undertaken now. This is difficult only if there is a patent ITA graft that is densely adherent to the chest wall. Again, it is best to enter the left pleural cavity at the level of the diaphragm and proceed in a cranial direction.
The most difficult point of dissection is usually at the level of the sternal angle, where a patent ITA graft may approach the midline and be adherent to the sternum or the aorta. There are no tricks for dissecting out a patent ITA graft except for being careful. The danger to a patent left ITA graft during sternal reentry and mediastinal dissection is entirely related to the location of the graft at the time of the primary operation. Ideally, the pericardium should be divided at a primary operation, and the left ITA graft should be allowed to run posterior to the lung through the incision in the pericardium and to the LAD or circumflex artery (Fig. 26-11). When this is done, the lung will lay anterior to the left ITA, and that graft will not become adherent to the aorta or to the chest wall.
A patent left ITA-to-LAD graft should not pose a threat during reoperation. At a primary operation, the pericardium should be divided in a posterior direction, and the ITA graft should be placed in that incision. The ITA graft then will lie posterior to the lung and will not be pushed toward the midline by the lung or become adherent to the sternum.
Once the left side of the chest wall is free, the left IMA is prepared (if it has not been used at a previous operation), the sternal spreader is inserted, and the intrapericardial dissection of the aorta and right atrium is accomplished. Again, in most cases it is safest to find the correct dissection plane at the level of the diaphragm and then to continue around the right atrium to the aorta. The one situation in which this strategy may be dangerous is if an atherosclerotic vein graft to the right coronary artery lies over the right atrium. Manipulation of atherosclerotic vein grafts can cause embolization of atherosclerotic debris into coronary arteries, and it is best to employ a "no touch" technique with such grafts. If a vein graft to the right coronary artery lies in an awkward position over the right atrium, it is best to leave the right atrium alone and use the femoral vein and superior vena cava cannulation to establish venous drainage (Fig. 26-12). Once cardiopulmonary bypass has been established, the aorta has been cross-clamped, and cardioplegia has been given, the atherosclerotic vein graft then can be disconnected.
Manipulation of patent but atherosclerotic vein grafts should be avoided. If an atherosclerotic right coronary vein graft blocks access to the right atrium, femoral vein, and direct superior vena cava, cannulation is safer than mobilizing the vein graft so as to achieve right atrial cannulation.
The goal of dissection of the ascending aorta is to obtain enough length for cannulation and cross-clamping and to avoid the most common error, aortic subadventitial dissection. The correct level of dissection on the aorta usually is found either by following the right atrium to the aorta in a caudal-to-cranial direction or by identifying the innominate vein and leaving all the tissue beneath the innominate vein on the aorta. At the level of the innominate vein, the pericardial reflection on each side of the aorta will be identifiable. Division of the pericardial reflection on the left side in a posterior direction will lead to the plane between the aorta and the pulmonary artery. Once the left side of the aorta is identified, the surgeon then may dissect posteriorly on the medial aspect of the left lung toward the hilum. The segment of tissue between these two dissection planes usually will include a patent left ITA graft, if present, and clamping that tissue will produce occlusion of the ITA graft.
When the aorta has been dissected out, heparin is given, and cannulation is undertaken. Cannulation of an atherosclerotic ascending aorta may cause atherosclerotic embolization leading to stroke, myocardial infarction, or multiorgan failure, so the ascending aorta should be studied with palpation and echocardiography to detect atherosclerosis before cannulation. Although the most widely used alternative arterial cannulation site is the femoral artery, arteriopathic patients often have severe femoral artery atherosclerosis. The axillary artery is an alternative arterial cannulation site that we have used with increasing frequency because atherosclerotic disease is usually not present in that vessel, and its cannulation allows antegrade perfusion44 (Fig. 26-13). If atherosclerotic disease or calcification of the aorta makes any aortic occlusion hazardous, the options are off-pump bypass surgery (see Other Options) or replacement of the aorta with axillary artery cannulation, hypothermia, and circulatory arrest. Venous cannulation usually is accomplished with a single two-stage right atrial cannula. A transatrial coronary sinus cardioplegia cannula is inserted via a right atrial purse string with the aid of a stylet, and a needle is placed in the ascending aorta for delivery of antegrade cardioplegia and for use as a vent (Fig. 26-14).
The axillary artery is an important alternative arterial cannulation site for patients with aortic and femoral artery atherosclerosis. A 21-gauge cannula will fit the axillary artery in most patients.
Standard cannulation for coronary artery reoperation includes aortic arterial cannulation, an aortic needle for antegrade delivery of cardioplegia and aortic root venting, a single two-stage venous cannula, and a transatrial coronary sinus catheter with a self-inflating balloon for delivery of retrograde cardioplegia. Cannulation is accomplished before dissection of the left ventricle.
The myocardial protection strategy used by us during most coronary artery reoperations is a combination of antegrade and retrograde delivery of intermittent cold blood cardioplegia combined with a dose of warm reperfusion cardioplegia ("hot shot") given before aortic unclamping, principles developed by Buckberg and colleagues.45 Multiple types of cardioplegic solutions have been described, and most appear to provide a metabolic environment that effectively protects the myocardium. Because of the potential anatomical challenges to cardioplegic myocardial protection during reoperations, the details of how the cardioplegic solution is delivered are very important. In most primary bypass operations, antegrade cardioplegia works well by itself. During reoperations, however, antegrade cardioplegia may not be effective for areas of myocardium that are supplied by patent in situ arterial grafts and may be dangerous because of the risk of embolization of atherosclerotic debris into the coronary arteries from old vein grafts. The delivery of cardioplegia through the coronary sinus and through the cardiac venous system to the myocardium (retrograde cardioplegia) has been a step forward in myocardial protection during reoperations.46,47 Retrograde cardioplegia delivery avoids atheroembolism from vein grafts, can be helpful in removing atherosclerotic debris and air from the coronary artery system, and can deliver cardioplegia to areas supplied by in situ arterial grafts. The biggest disadvantage of retrograde cardioplegia is that it is not always possible to place a catheter in the coronary sinuses that will deliver cardioplegia consistently. It is important to monitor the adequacy of cardioplegia delivery by measuring the pressure in the coronary sinus, noting the distention of cardiac veins with arterial blood, the cooling of the myocardium, and the return of desaturated blood from open coronary arteries.
Cardiopulmonary bypass is begun, the perfusionist empties the heart and produces mild systemic hypothermia (34°C), and the aorta is cross-clamped. We usually initiate cardioplegia induction with aortic root cardioplegia. To induce and maintain cardioplegic protection, it is helpful to be able to occlude patent arterial grafts. If it has not yet been possible to dissect out a patent arterial graft so that it can be clamped, the systemic perfusion temperature is decreased to 25°C until control of the graft is achieved. After antegrade cardioplegia has been given for 2 to 3 minutes, we shift to retrograde induction for another 2 to 3 minutes. Giving any antegrade cardioplegia does risk embolization from atherosclerotic vein grafts, but if these grafts have not yet been manipulated, that danger is relatively small. Once the adequacy of retrograde cardioplegia delivery has been established, it is often possible to use that route predominantly for maintenance doses.
When the heart has been arrested completely, intrapericardial dissection of the left ventricle is undertaken, starting at the diaphragm and extending out to the left of the apex of the heart. After the apex is identified, the surgeon divides the pericardium in a cranial direction on the left side of the LAD artery (Fig. 26-15). A patent LITA-to-LAD graft will be contained within the strip of pericardium that lies over the LAD artery. Dissection of this pedicle from the anterior aspect of the pulmonary artery will allow an atraumatic clamp to be placed across the patent ITA graft and also will allow the passage of new bypass grafts from the aorta underneath the patent ITA graft to left-sided coronary arteries. The advantages of waiting until after aortic clamping and arrest to dissect out the left ventricle are that dissection is more accurate, there is less damage to the epicardium and less bleeding, manipulation of atherosclerotic vein grafts is less likely to cause coronary embolization, and the dissection of patent ITA grafts is safer.
Division of the pericardium along the diaphragm allows the surgeon to reach a point to the left of the cardiac apex. From that point, the pericardium can be divided in a cranial direction to the left of the LAD artery, leaving a patent ITA graft in the strip of tissue overlying the LAD artery. Atherosclerotic vein grafts that are going to be replaced may be divided once a dose of antegrade cardioplegia is given.
After the heart is dissected out completely, the coronary arteries to be grafted can be identified, the lengths that bypass conduits need to reach those vessels may be assessed, and the final operative plan can be established. The old grafts and epicardial scarring that are present during reoperations make the preoperative prediction of the lengths of conduits needed for bypass grafts quite difficult, particularly the lengths of arterial grafts, and it is wise to have some flexibility in the operative plan. Before the construction of the anastomoses, those patent but atherosclerotic vein grafts that are going to be disconnected are identified and are disconnected with a scalpel. The order of anastomosis construction that is used by the authors is: (1) distal vein graft anastomoses; (2) distal free arterial graft anastomoses; (3) distal in situ arterial graft anastomoses; and (4) proximal (aortic) anastomoses.
When should patent or stenotic vein grafts be replaced, and with what should they be replaced? Atherosclerosis in vein grafts is common if those grafts are more than 5 years old, and leaving them in place risks embolization of atherosclerotic debris at the time of reoperation and subsequent development of premature graft stenoses or occlusions after reoperation. On the other hand, replacement of all vein grafts extends the operation and may use up available bypass conduits.
In the past, our general rule has been to replace all vein grafts that are more than 5 years old at the time of reoperation, even if those grafts are not diseased angiographically. However, this strategy assumes that conduits are available that can replace these old grafts. Today, many patients have very limited conduits at reoperation because of the large numbers of vein grafts used at primary surgery or because of multiple previous operations. Thus, graft replacement must be individualized. Inspection of vein grafts at reoperation occasionally will identify a graft that looks normal angiographically and does not appear to have any thickening or atherosclerosis on visual inspection. Often such vein grafts will be left alone.
Replacing old vein grafts with new vein grafts may often be accomplished by creating the new vein-to-coronary-artery anastomosis at the site of the previous distal anastomosis, leaving only 1 mm or so of the old vein in place (Fig. 26-16). If significant native-vessel stenoses have developed distal to the old vein graft, it is often best to place a new graft to the distal vessel in addition to replacing the vein graft. Many reoperative candidates have proximal occlusions of the native coronary artery system and multiple stenoses throughout the vessel, and if only new distal grafts are constructed, the proximal segments of coronary arteries and their branches that are supplied by atherosclerotic vein grafts may be jeopardized. More than one graft to a major coronary artery may be desirable during reoperation (Fig. 26-17).
For patients with extensive native coronary atherosclerosis, the distal anastomotic site of an old vein graft is often the best spot for the distal anastomosis of a new graft. Only a small rim of the old graft should be left in place.
Extension of native-vessel coronary artery disease may indicate the placement of new distal grafts as well as replacement of diseased vein grafts supplying proximal coronary artery segments.
Sequential vein grafts often are very helpful during reoperation because they allow more distal anastomoses and fewer proximal anastomoses. Sites for proximal anastomoses are often at a premium in the scarred reoperative aorta.
Artery-to-coronary-artery bypass grafts have many advantages during reoperations. First, they are often available. Second, the tendency of arteries to remain patent even when used as grafts to diffusely diseased coronary arteries makes them particularly applicable to reoperative candidates. Third, in situ arterial grafts do not require a proximal anastomosis. If the left ITA has not been used as a graft at a previous operation, a strong attempt should be made to use it as an in situ graft to the LAD artery. During primary operations, the right ITA usually can be crossed over as an in situ graft to left-sided vessels, but such a plan is more difficult during repeat surgery, so the right ITA is often used as a free graft.
Arterial graft proximal anastomoses are a problem at reoperation because the scarring and thickening of the reoperative aorta often make direct anastomoses of arterial grafts to the aorta unsatisfactory. However, when old vein grafts become occluded, there is usually a "bubble" of the hood of the old vein graft that is not atherosclerotic and that often is a good spot for construction of a free (aorta-to-coronary-artery) arterial graft anastomosis (Fig. 26-18). In addition, if new vein grafts are performed, the hood of that new vein graft represents a favorable location for an arterial graft anastomosis. Late angiographic data regarding this strategy are not available, but the relative freedom of the hood of vein grafts from the development of atherosclerosis means these grafts are likely to be successful.
The hood of new or old vein grafts is often the best spot for the aortic anastomosis of free arterial grafts. Atherosclerosis rarely occurs in that "bubble" of vein.
Another effective strategy is to use either an old arterial graft or a newly constructed arterial graft for the proximal anastomosis of a free arterial graft (Fig. 26-19). Composite arterial grafts, usually using a new in situ left ITA graft at the proximal anastomotic site for a free right ITA graft, have been employed with increasing frequency, and early outcomes have been favorable.48,49 This method is particularly useful during reoperations because it may avoid an aortic anastomosis, and less right ITA graft length is needed to reach distal circumflex arteries. Other advantages of using a previously performed patent ITA graft for the proximal anastomosis of a new arterial graft are that the old left ITA graft often has increased in size, and the preoperative angiogram has demonstrated its integrity. In situations in which the effectiveness of an LITA-to-LAD graft has been jeopardized by a distal LAD lesion, a short segment of a new arterial graft can be used to bridge that stenosis from the old arterial graft to the distal LAD artery (see Fig. 26-18).
Composite arterial grafts can be constructed using a new or old left ITA graft as the inflow source. With its proximal anastomosis to the left ITA, a right ITA graft will easily reach the circumflex branches. Furthermore, a shorter segment of inferior epigastric artery or radial artery can be used to reach the distal LAD artery if intervening native LAD stenoses have limited the effectiveness of an old ITA graft.
Can an ITA graft be used to replace a vein graft during reoperation? When faced with replacing a stenotic or patent vein graft during reoperation, the surgeon has a number of options, all of which have some potential disadvantages:
The surgeon may leave the old vein graft in place and add an arterial graft to the same coronary vessel. The dangers of this approach are that atherosclerotic embolization from the old vein may occur during the reoperation, and competitive flow between the vein graft and the arterial graft may jeopardize the ITA graft after reoperation.
The surgeon may remove the old vein graft and replace it with an ITA graft. This decreases the likelihood of atherosclerotic embolization and competitive flow but risks hypoperfusion during reoperation if the arterial graft cannot supply all the flow that had been generated previously by the vein graft.
The surgeon may replace the old vein graft with a new vein graft. The disadvantage of this approach is a long-term one: The coronary vessel is left dependent on a vein graft.
When we examined these choices in a retrospective study of operations for patients with atherosclerotic vein grafts supplying the LAD artery, we found that the worst outcomes resulted from removing a patent (although stenotic) vein graft and replacing it with only an ITA graft.39 This strategy was associated with a significant incidence of hypoperfusion and severe hemodynamic difficulties during reoperation that were treated effectively only by adding a vein graft to the same coronary artery. The incidence of myocardial infarction associated with leaving a stenotic vein graft in place was low. Thus, atherosclerotic embolization from an atherosclerotic vein graft is a danger, but it appears that with the use of retrograde cardioplegia, it is not commonly a major catastrophe.
Another potential disadvantage of the strategy of adding an ITA graft to a stenotic vein graft is that competition in flow from the stenotic vein graft may lead to failure of the new ITA graft. However, this is unlikely to occur as long as the stenosis in the SVG is severe.50 Our usual approach, therefore, is to remove atherosclerotic vein grafts when replacing them with a new vein graft but leave stenotic vein grafts in place when grafting the same vessel with an arterial graft (Fig. 26-20).
In this example, an atherosclerotic right coronary artery vein graft is disconnected and is replaced with a new vein graft. However, the stenotic vein graft to the LAD artery is left in place to avoid hypoperfusion, and a new ITA graft is added to the LAD artery.
Alternative arterial grafts often are very useful during reoperation. The radial artery has particular advantages during repeat surgery because it is larger and longer than other free arterial grafts. These qualities increase the range of coronary arteries that can be grafted. Early studies of radial artery grafts have shown favorable patency rates, but few long-term data currently exist. If the high patency rates that have been documented by early studies are confirmed by the tests of time, the radial artery will be used extensively during reoperations. The inferior epigastric artery often is too short to function as a separate aorta-to-coronary-artery graft during reoperation but can be extremely useful as a short composite arterial graft, as illustrated in Fig. 26-19.
The right gastroepiploic artery (RGEA) has established a good midterm graft patency rate record and often is useful during reoperation because it is an in situ graft.51 Furthermore, it can be prepared before the median sternotomy. It is effective most often as an in situ graft to the posterior descending branch of the right coronary artery or the distal LAD artery (Fig. 26-21).
Circumflex vessels may be grafted through a left thoracotomy incision without cardiopulmonary bypass.
The aortic anastomoses of the vein and arterial grafts are performed last during the single period of aortic cross-clamping. Sites for aortic anastomoses are often at a premium owing to previous scarring, atherosclerotic disease, or the use of Teflon felt during the primary operation, and often the locations of the previous vein graft proximal anastomoses are the best locations for the new ones. The advantages of constructing aortic anastomoses during a single period of aortic cross-clamping are that it minimizes aortic trauma and allows excellent visualization of the proximal anastomoses. In addition, if patent or stenotic vein grafts have been removed and replaced, reperfusion is not accomplished by aortic declamping until the aortic anastomoses have been completed.
The disadvantage of this approach is that it prolongs the period of aortic cross-clamping. However, our strategies for reoperation are not based on trying to minimize myocardial ischemic time. If cardioplegia can be delivered effectively, its metabolic concepts are valid, and myocardial protection is secure. Failure of myocardial protection usually is caused by anatomical events, not by metabolic failure. Once the proximal anastomosis has been constructed, a "hot shot" of substrate-enhanced blood cardioplegia is given, and the aortic cross-clamp is removed.
Although most reoperations are performed through a median sternotomy with the use of cardiopulmonary bypass, the strategies of small-incision surgery and off-pump surgery that have been gaining increasing use for primary coronary artery operations also can be helpful during reoperations. Reoperations in situations in which a limited area of myocardium needs revascularization often can be accomplished through a limited incision and without the use of cardiopulmonary bypass (known as the minimally invasive direct coronary artery bypass [MIDCAB] operation). The distal LAD artery may be exposed with a small anterior thoracotomy, and the LAD or diagonal artery may be grafted with a left ITA graft. A stabilizing device usually is employed for anastomotic construction, although the intrapericardial adhesions provide some stability during reoperations. If the left ITA is not available, a segment of saphenous vein can be anastomosed to the subclavian artery and routed in a transthoracic path to the LAD artery. If the right ITA is to be used as an in situ graft to the LAD artery, a median sternotomy is indicated, but if this is the only graft, off-pump surgery usually is possible.
The lateral wall of the heart can be exposed through a left lateral thoracotomy (Fig. 26-22), and the circumflex and distal right coronary artery branches can be grafted with this approach. Often the LITA already has been used for a graft, but the descending thoracic aorta may be used as a site for the proximal anastomosis of a vein graft or a radial artery graft using a partial occluding clamp. The disadvantages of this approach are that the right ITA is difficult to use as an in situ graft, and if the circumflex vessels are deeply intramyocardial, they may be difficult to expose and isolate with the off-pump strategy.
An in situ gastroepiploic artery (GEA) graft may be used for an on- or off-pump anastomosis to the distal LAD artery.
In addition to avoiding potential complications of cardiopulmonary bypass, the "limited-area, off-pump" approach also avoids extensive dissection of the heart and possible manipulation of atherosclerotic vein grafts. The disadvantage of this approach is that most patients who are candidates for reoperation need grafts to multiple vessels in multiple myocardial areas.
Use of a median sternotomy and the off-pump strategy to graft multiple myocardial areas is now a standard approach to primary coronary revascularization and also can be used during reoperation. However, because of the need to access all areas, extensive dissection sometimes is necessary for lysis of adhesions to be able to mobilize the heart. If patients have atherosclerotic vein grafts, dissection and manipulation create the dangers of embolization of atherosclerotic debris and myocardial infarction. This problem was encountered during the early years of bypass surgery when the risks of atherosclerotic embolization were less recognized. Another disadvantage of off-pump reoperative strategies is that reoperative candidates often have very distal and diffuse CAD, which leaves intramyocardial segments as the best areas for grafting. These characteristics stress off-pump isolation and immobilization techniques. In addition, the aortic anastomoses of vein or free arterial grafts may be difficult because of aortic atherosclerosis, adhesions, or previous aortic anastomoses that may limit the application of a partial occluding clamp. On the other hand, the use of off-pump techniques may minimize aortic trauma, particularly if in situ arterial grafts can be employed to provide inflow to new grafts.
In an individual case, the disadvantages of off-pump surgery may be important or irrelevant. Surgeons who perform reoperative coronary artery surgery in a wide spectrum of situations will find both on- and off-pump strategies helpful.