Off-Pump Coronary Artery Bypass Grafting
◆ The ability to perform coronary artery bypass grafting (CABG) competently without the use of cardiopulmonary bypass is an important skill for all cardiac surgeons. There are cases in which a safe coronary revascularization procedure can only be performed as an off-pump procedure. Although off-pump coronary artery bypass (OPCAB) has a steeper learning curve than on-pump revascularization, there are clear benefits to it.
◆ After an initial surge in popularity following its widespread adoption, the frequency of OPCAB has declined. In 2012, only 17% of all coronary artery bypass surgery was performed as an off-pump procedure.1 Much of this decline could be attributed to the results of several cohort studies and clinical trials, which showed no survival benefit for off-pump surgery.2,3 Despite this, OPCAB has consistently been shown to decrease blood transfusions and lower the risks of postoperative bleeding and renal and respiratory failure. OPCAB performed with the aorta no–touch technique also seems to lower the risk of postoperative stroke.4
◆ The results of the initial large trials have also highlighted potential pitfalls of OPCAB. Results suggested a higher proportion of incomplete revascularization with off-pump cases and a lower graft patency rate.5,6 This reinforces the notion that this procedure has a significant learning curve, and surgeons must ensure that the choice to use an off-pump approach does not affect the overall quality of the surgical revascularization.
◆ Understanding when an off-pump approach is not in the patient’s best interest is also critical; severe ventricular dysfunction, left main disease, ongoing ischemia, and pulmonary hypertension are associated with poorer outcomes and the need to convert to on-pump procedures.7
◆ To perform OPCAB, a keen understanding of cardiac physiology is essential, because it allows more careful positioning of the heart to visualize the targets without affecting hemodynamics.
◆ In this chapter, we describe a systematic, step by step approach to performing complete myocardial revascularization using an OPCAB technique. We discuss and illustrate key maneuvers, major pitfalls, and important strategic considerations for off-pump coronary revascularization. We also highlight the importance of total arterial revascularization and strategies to decrease aortic manipulation.
◆ The benefits of complete revascularization are well established, and surgeons should bypass all vessels 1.5 mm or larger with stenosis of 70% or more. The off-pump approach should never jeopardize the ability to perform complete revascularization. Careful OPCAB planning should have a composite goal of a safe, complete revascularization without the use of cardio- pulmonary bypass.
◆ Planning an OPCAB begins at the time of the preoperative assessment. Patients presenting for isolated CABG should be carefully and thoroughly examined and undergo a complete diagnostic imaging workup. Particular attention should be paid to congenital anomalies of the chest, such as pectus excavatum, which may affect the feasibility of the operation.
◆ A comprehensive preoperative assessment and diagnostic imaging workup should be carried out, as with any cardiac operation.
◆ A noncontrast computed tomography (CT) of the chest to rule out aortic calcification is recom- mended for patients with advanced age (> 75 years), chronic renal disease, severe vasculopathy, and a history of heavy smoking. Ascending aorta calcification might make cross-clamping the aorta inadvisable or, in the case of a porcelain aorta, impossible.
◆ Aortic manipulation likely increases the risk of stroke,8-10 and an off-pump approach allows myocardial revascularization without aortic manipulation. The aortic no–touch technique should be strongly considered for patients at increased risk for stroke.
◆ Aortic calcification is one of the more common reasons to choose OPCAB, but there are other indications. Patients who decline blood transfusions (e.g., Jehovah’s Witnesses), and have borderline kidney and respiratory dysfunction likely benefit from OPCAB.
◆ Just as some preoperative findings might make OPCAB the preferred choice, other findings, such as severe left ventricular dysfunction, ongoing ischemia, pulmonary hypertension, and valvular heart diseases will strongly suggest an on-pump approach to surgical revascularization. On-pump CABG is the safest approach in these scenarios.
◆ With any surgical coronary revascularization, the choice of conduits should be tailored to the patient. In the case of OPCAB, careful consideration of the patient’s coronary anatomy, targets to be grafted, and availability of conduits is required.
◆ The use of the left internal thoracic artery (LITA) to graft the left anterior descending (LAD) territory has long been the standard of care for surgical revascularization. For patients with multivessel coronary artery disease, the remaining targets may be grafted with either arterial or venous grafts.
◆ For patients younger than 75 years, the literature has demonstrated a survival benefit for multiarterial revascularization.11-13 In general, high-grade stenosis (> 80%) will be the preferred target for either radial or gastroepiploic arteries due to their susceptibility to competitive flow.14
◆ The internal thoracic arteries are less prone to competitive flow and can be considered for stenosis of 60% to 80%.
◆ Venous grafts will tolerate almost any degree of stenosis, although their suboptimal durability and patency remain a major drawback, particularly in younger patients.
◆ A composite graft of a LITA with a radial artery grafting seems to confer the same benefits as for a bilateral internal thoracic artery (BITA) and may be preferable in diabetic patients, who may be at greater risk for sternal wound complications.15-17
Step 3. Operative Steps
◆ OPCAB is a team effort. The anesthesia team should be engaged prior to surgery for better support of the patient’s hemodynamics during induction and conduit harvesting and at the time of grafting.
◆ The operating room should be kept warm during these operations, similar to the practice in pediatric operating rooms. If this is not done, the patient’s temperature can drop to a dangerous level, where spontaneous, malignant ventricular arrhythmias, such as ventricular fibrillation and ventricular tachycardia, could occur.
◆The availability of pacing wires, atrial and ventricular, can help maintain normal hemodynamics in patients with heart block or extreme bradycardia.
◆ Both the surgical and anesthesia teams should carefully monitor hemodynamic changes during heart positioning. If inadequate hemodynamics are observed, the best course of action is to return the heart into the pericardium for optimal functioning. The surgeon should then consult with the anesthesia team while the heart is allowed to recover. Once hemodynamics stabilizes, an attempt may be made to carefully reattempt the required positioning.
◆ Off-pump CABG has been made possible by the development of many specialized tools. Two of the most important tools are vacuum-based devices that are used to position the heart or stabilize the segment of coronary artery to be anastomosed. For the purposes of this text, the former will be referred to as positioning devices, and the latter will be referred to as stabilization devices. In addition to adequately placed pericardial sutures, these allow for optimal exposure of the target vessels.
◆ Enhanced visualization devices, such as the Blower/Mister (Clear View Misted Blower; Medtronic, Minneapolis), have also been adopted, and they allow a safe construction of the anastomosis. We routinely use a Blower/Mister to optimize visualization. It delivers a jet of CO2 under pressure in the middle of a jet of a pH-balanced saline solution, resulting in atomization of the liquid. The resulting stream of mist and CO2, when directed over the arteriotomy, clears the blood from the anastomosis without resulting in air embolism because the CO2 is rapidly resorbed. The device does not prevent blood loss but improves visualization during the anastomosis.
◆ Table tilt maneuvers can aid with visualization and allow adequate filling of the heart. If table tilting is not sufficient to correct preload, fluid infusion should be initiated by anesthesia. The Trendelenburg position and rotating the operating table toward the surgeon may also optimize lateral wall visualization. Changes to the operating table should be performed slowly and incrementally to allow the heart to adapt to different loading conditions.
◆ Most OPCAB procedures are performed through the standard median sternotomy.
◆ An extensive inverted-T pericardial incision is usually required. The opening should reach the cardiac apex on the left side and reach the pericardial reflection on the right side (Fig. 4.1). This allows heart positioning without any compressions or deformity.
◆When harvesting the internal thoracic arteries, we strongly recommend complete skeletonization. This approach decreases the rate of pleural effusions postoperatively and decreases the incidence of ischemic injury to the chest wall and subsequent mediastinitis. This is particularly important during BITA harvesting.
◆ The lie of the conducts is critical to avoid kinking and compression by the lungs. An incision is made on the pericardium to accommodate the internal thoracic artery (ITA). This pericardial incision starts at the edge and is located at the level of the base of the left appendage for the LITA and at the level of the transverse sinus for the right internal thoracic artery (RITA). It is posteriorly directed toward the phrenic nerve. At 1 cm anterior to the phrenic nerve, the incision extends 2 cm superiorly and inferiorly, creating a T-inverted incision. This trench accommodates the in situ ITAs where they enter the pericardium.
◆ The radial artery can be harvested endoscopically or using an open approach, and either pedicled or skeletonized, depending on the surgeon’s preferences. The gastroepiploic artery should be harvested in a skeletonized manner for better patency. Veins can be harvested endoscopically or using an open approach. Veins harvested through an endoscopic approach have shown lower patency rates than those harvested in an open manner.18,19
◆ There are several possibilities for graft configuration, and the approach should be tailored to the number and location of targets to be grafted:
1. In situ grafts do not require aortic anastomosis, but they offer fewer distal anastomoses, and their length is constrained.
2. Free grafts are less constrained by length but require aortic manipulation for the inflow creation.
3. Composite grafts pair an in situ graft, usually a LITA, with another conduit branching in a Y or T fashion. Composite grafts offer greater length and flexibility for grafting. In all cases, the graft configuration should be planned to take into consideration the availability of conduits and degree of stenosis in the target vessel.
§ For a full arterial revascularization in a patient with multivessel coronary artery disease, the plan should almost always include composite grafts due to the limited length of arterial conduits.
◆ Once the surgical plan has been made, conduits harvested, and the pericardium prepared, graft inflows should be considered.
◆ Lateral pericardial sutures should be placed on each edge of the pericardium. These should be attached to the drapes using hemostats to keep the lungs away from the operative field and to expose the aorta for proximal anastomosis.
◆ Side-biting clamping is safe for aortas with a wall thickness less than 3 mm throughout the clamp length and the anastomotic site. Plaques that are more than 3 mm in thickness increase the risk of adverse neurologic events during aortic manipulaton20-22 (Table 4.1). We recommend the use of epiaortic scanning to assess the quality of the ascending aorta.22,23
◆ When manipulation of the ascending aorta is not advisable, the use of proximal anastomosis sealing devices, such as the Heartstring Proximal Seal System (Maquet Cardiovascular, Wayne, NJ), is recommended. They allow for minimal manipulation of a severely diseased aorta.
◆ In patients for whom this is not an option, and an aortic no–touch technique is the only possible course of action, composite grafting allows for multiple anastomoses.
◆ When the aorta can be manipulated without concern, the standard sequence of events is as follows: (1) blood pressure is brought below 90 mm Hg; (2) an atraumatic side-biting clamp is applied; (3) small aortotomies are made with an aortic punch, followed by direct anastomosis of each of the free grafts to the ascending aorta; and (4) the partial clamp to fill the graft is released, avoiding a purse-string effect of the proximal anastomosis as one ties the suture.
◆ If the surgeon plans to use a composite graft approach, the ideal site of the Y- or T-graft anastomosis is 1 cm distal the point of entry of the LITA into the pericardial sac, at the level of the left atrial appendage. This can be constructed in a Y or a T configuration, depending on which sequential anastomosis will be constructed first. For high proximal branches, such as a high diagonal (diagonal-LAD angle ≥ 90 degrees), ramus intermedius, or high marginal, a T approach is ideal because it allows an optimal lie of conduct once it is anastomosed in a diamond shape on those vessels (Fig. 4.2A). For more distal branches of the circumflex and right coronary artery, either a Y or a T graft will suffice, depending on the length of the available conduit (see Fig. 4.2B).23
◆ Skillful heart positioning is vital to maintaining stable hemodynamics while still allowing visualization of target arteries. The heart should move freely inside the pericardial sac and should not be squeezed or compressed against taut pleurae and the sternal borders. This can be achieved by releasing some of the pericardial sutures that hold the pericardial cradle up, specifically the right-sided sutures.
◆ The heart can be elevated using three methods: (1) pericardial stitches (Lima stitch); (2) the deep stitch–sling technique; and (3) the use of suction-driven positioning devices.
|Figure 4.2 T and Y configurations of the composite graft.|
◆ Posterior pericardial stitches (Lima stitches) can be used to enucleate the heart; the number of stitches and location is a matter of surgeon preference. We place three sutures to the posterior pericardium. The first suture is placed anterior to the left superior pulmonary vein (LSPV) and below the phrenic nerve, the second is anterior to the left inferior pulmonary vein (LIPV) and inferior to the phrenic nerve, and the third suture is placed on the medial aspect of the inferior vena cava (IVC; Fig. 4.3). A Rummel tourniquet is then passed through each of these sutures to avoid injury to the epicardium. If each tourniquet is sequentially put under tension, the heart will lift incrementally and rotate medially. This will cause a broad posterior pericardial ridge, which helps herniate the heart from the pericardial sac, with its apex pointing to the ceiling. In most cases, these sutures allow for complete elevation of the heart without hemodynamic consequences.
◆ An alternative to the three-tourniquet approach described previously is the single deep suture–sling technique, which is placed in the oblique sinus medial to the right inferior pulmonary vein.24 In between the two ends of this suture, an open 4- × 8-inch gauze is passed through the suture loop, and then a Rummel tourniquet is applied, creating a sling. The deep stitch is put under tension by pulling it inferiorly at the patient’s midline. This maneuver creates a pericardial ridge deep in the oblique sinus. The two arms of the 4- × 8-inch gauze work as a sling that rotates and lifts the heart by giving extra support to the base of the heart. Different tension can be applied to either arm of the sling, allowing variable heart exposures (Fig. 4.4).
◆ Suction-driven heart positioning devices allow for complete enucleation of the heart. The heart positioner is clipped onto the chest retractor, and the silicone cup is applied to the epicardium, immobilizing an area of the myocardium approximately 3 × 2 cm in size. Once the cup has been applied, the heart can be slowly displaced. When in the working position, the device arm is tightened, and it becomes immobile. The ideal suction applied by these devices is 100 to 250 mm Hg, and the silicone cup should be placed onto a smooth, fat-free region of the pericardium to avoid epicardial avulsions and unnecessary bleeding.
◆ The operator must never pull the suction cup off the epicardial layer while under negative pressure; this will invariably cause an epicardial avulsion and bleeding. To release the device, support the heart with one hand, and turn the suction off by opening the stopcock to air. Then place the heart gently back into the pericardial sac.
◆ During heart positioning, particular attention should be given to patients with enlarged hearts, decreased ventricular function, and pulmonary hypertension because they are more likely not to tolerate aggressive displacement maneuvers. A common mistake in OPCAB is to occlude inflow to the right-sided chambers due to inadvertent tenting and occlusion of both venae cavae.
◆ Optimal heart positioning can be achieved using more than one method that allows herniation of the heart with normal hemodynamics. We favor a combination of suction devices and pericardial stitches, which, when combined, seems to allow for the maintenance of normal hemodynamics.
◆ In the following, we describe different maneuvers to expose each wall of the heart.
Location of the three Lima stitches. (1) Anterior to the LSPV; (2) anterior to the LIPV; and (3) halfway between the IVC and LIPV.
The deep stitch–sling technique.
◆ These are the most straightforward targets to expose, with minimal rotation of the heart required. This can be easily achieved by applying traction on the first and second Lima stitches. This pericardial traction brings the LAD and diagonal branches anteriorly and superiorly (see Video 4.1 for anterior wall exposure).
◆ Alternatively, one or two lap pads can be placed posteriorly to lift and rotate the heart, moving the LAD toward the midline. Suction devices are not necessary to expose these targets.
◆ Exposure of the lateral wall poses a significant challenge during OPCAB. Proper heart positioning technique is critical to allow optimal visualization without hemodynamic instability. Many OPCAB surgeons advocate the use of a combination of pericardial stitches and positioning device.
◆ The pericardial retention sutures should all be relaxed to allow broad heart mobilization toward the right side. A right pleural opening might be needed to accommodate enlarged hearts.
◆ The pericardial manipulation, in either form described previously, is the cornerstone of this exposure if one seeks to maintain normal hemodynamics. For the sling-aided method, the tourniquet is kept under traction at the midline, attached to the drapes. The right arm of the rolled 4- × 8-inch gauze is put on traction at the midline, and the left side is pulled slowly toward the assistant’s side. This maneuver creates a platform to keep the heart chambers aligned while it lifts the apex and rotates the heart simultaneously, exposing the lateral wall. Once the lateral wall is exposed, the left arm of the gauze is tethered on the drapes under traction (Fig. 4.5; see Video 4.2).
◆ For the pericardial stitches method, the stitches are pulled under maximum traction, allowing the heart to herniate superiorly through the mediastinum. We favor the use of either a small lap pad or unfolded gauzes to protect the heart against injuries when using this technique.
◆ At the conclusion of either maneuver for lateral wall exposure, the base of the heart is exposed, permitting the visualization of the atrioventricular (AV) groove. As the heart is lifted and freely floats within the pericardial sac, the suction positioning device is used to stabilize the most apical aspect of the heart and elongate the cardiac chambers. This prevents inflow disturbances, squeezing of the right ventricle, and bending of the heart. The positioning device must be clipped on the right side of the chest retractor in the most cephalad position. This allows ample manipulation of the heart within the pericardial sac, without disturbing the surgeon’s movements.
◆ The Trendelenburg position and table rotation toward the operators help optimize target visualization and cardiac loading conditions. If positioning does not correct preload, fluid should be initiated by anesthesia.
◆ At this point, the surgeon should be able to see the targets and safely apply the coronary stabilization device.
◆ The targets of the inferior wall can be separated into two areas: (1) the distal right coronary artery (RCA); and (2) the posterior descending artery (PDA) and posterolateral branches (PLB). Each of these requires a fundamentally different exposure.
◆ For the distal RCA, all that is required is tilting the table into the Trendelenburg position and, if the surgeon wishes, use of the suction device to rotate the free wall of the right ventricle. It should be noted that not all surgeons use a suction device to graft this territory. If a suction device is to be used, it should be positioned as cranially as possible on the right side of the retractor. Cranial retraction is applied until the distal RCA is optimally visualized and the working position is obtained. Whether or not a suction device is used, the coronary stabilization device helps exposure. In addition to stabilization of the segment of the coronary artery to be exposed, it retracts the inferior wall superiorly, allowing visualization of the distal RCA.
◆ For the PDA or PL branches, a combination of table positioning, pericardial maneuvers, and use of a positioning device may be required. The first step is to place the patient in the Trendelenburg position. Then, the two arms of the sling or the pericardial sutures are put under traction, toward the patient’s left, to herniate the heart without medial rotation. The inferior wall is then visualized; the positioning device must be applied to gain adequate exposure and stabilization. The positioning device is applied adjacent to the apex, never directly on the apex itself. For optimal epicardial suctioning, the silicone cup fingers should be placed so that the three fingers are on the anterolateral surface. No finger should be placed on the inferior wall because it makes suctioning inefficient. Also, attention should be taken to avoid suctioning on the LAD. Because the sling supports the heart inferiorly, a low suction setting should (≤ 200 mm Hg) suffice. This maneuver allows for elevation of the apex and traction of the heart toward the patient’s head (Fig. 4.6).
◆ Coronary stabilizers have evolved tremendously, from first-generation stabilizers that used compression as the method of stabilization to the latest generation of suction-based stabilizers. Their primary goal is to decrease motion at the anastomotic site.
◆ All coronary stabilizers have flexible prongs in a fork-shaped configuration. Each prong has four small silicone cups, connected to suction, that can be adjusted as necessary. This suction- based stabilization allows OPCAB to be performed with less aggressive fluid administration, which decreases volume overload and reduces the need to open the right pleural cavity. Moreover, the malleable prong allows for different shapes to mold the irregularities of the heart wall.
◆ Once the heart is in the working position, the coronary stabilizer is applied over the anastomotic site. The target coronary artery should lie in between the two prongs. The suction prongs are applied first, and then the mechanical arm of the stabilizer is tightened. The anastomotic site should not be compressed because this might lead to a paradoxic increase in motion.
◆ Once applied, the stabilizer prongs may be spread apart slightly to increase the epicardial tension over the target. This facilitates coronary dissection with a no. 15 blade.
◆ The optimal heart rate during coronary anastomoses is controversial. Although bradycardia leads to decreased visualization of the lateral wall by increasing the heart size during diastole, the lower the heart rate, the more stable the anastomotic site.
◆ Next we will describe different maneuvers to achieve coronary stabilization on each wall of the heart.
Inferior wall exposure for the PDA and PL branches. Note the two arms of the sling toward the left side and the proper position of the silicone cup.
s The stabilizer is positioned on the right side of the chest retractor, usually midway on the retractor arm. The prongs are slightly bent inferiorly to create a convex shape. This allows for optimal adherence of the stabilizer to the epicardium (Figs. 4.7 and 4.8).
◆ The stabilizer is placed on either side of the chest retractor, per surgeon preference. The prongs are left straight and facing down to optimize inferior wall coronary stabilization ig. 4.9).
Distal Right Coronary Artery
s The stabilizer is usually placed on the left side. The arm makes a curve superiorly, and the prongs are kept straight and placed facing leftward (Fig. 4.10).
s During OPCAB, the surgical team must pay extra attention to hemodynamics and myocardial ischemia. Maneuvers to avoid hemodynamic instability have been described previously. Prevention of myocardial ischemia requires careful planning of the sequence of target vessels to be revascularized and the use of ischemia prevention strategies, such as shunts.
◆ The sequence of revascularization is key to a successful OPCAB. It allows optimizing blood supply to the myocardium during challenging heart positions.
◆ We strongly recommend grafting the LAD territory first for a number of reasons. Exposure of the LAD territory requires the least manipulation of the heart. Revascularizing the LAD also protects the largest proportion of myocardium from ischemic damage and improves blood supply to collateral territories in subsequent repositioning. Finally, the LAD offers some of the most technically straightforward anastomoses during OPCAB.
◆ It should be noted, however, that grafting the LAD territory first is not always the best approach; for example, when the LAD feeds occluded vessels through collaterals. In this situ- ation, the choice to graft the LAD first may cause extensive ischemia during the coronary arteriotomy, and it is preferable to graft the occluded vessels before addressing the LAD.
◆ As a general rule, we recommend revascularizing the inferior wall vessel (PDA or PL branch) as the next step. The positioning of the heart required to expose the inferior wall is less likely to induce hemodynamic instability than the lateral wall. This anastomosis is also less technically challenging than those required for more lateral exposures, such as the obtuse marginals (OMs).
◆ After revascularization of the anterior and inferior walls, there is less risk of hemodynamic instability when repositioning the heart to expose the lateral wall. It is of paramount importance, however, to be aware of (and avoid) the tension that may be applied to the LITA to LAD graft during this positioning maneuver.
◆ When constructing composite grafts, the LAD should be grafted first as well. However, the sequence of anastomoses should be the ramus intermedius (RI), OMs, PLB, and finally PDA. This approach precludes the need for intermittent clamping of the graft, allowing immediate and continuous reperfusion of each target vessel.
Coronary stabilizer positioning for the distal RCA. Note the use of positioning device to rotate the right ventricular (RV) free wall.
◆ The use of temporary intracoronary shunts is the most reliable method to prevent myocardial ischemia. These shunts allow distal perfusion of the coronary artery while the anastomosis is being constructed. Shunts also improve the ability to visualize the target and greatly facilitate the construction of anastomoses. We recommend the use of shunts for every anastomosis.
◆ Shunts are flexible, tubelike structures that permit the flow of blood when they are inserted into a coronary artery. Shunts have a short tether attached asymmetrically that can be used to remove the shunt prior to the completion of the anastomosis. The asymmetric placement of the tether creates short and long arms, and the long arm should be introduced into the artery first. Shunts range in size from 1 to 3 mm. We recommend the use of silicone-based shunts, rather than plastic, because they are more flexible and less likely to damage the coronary wall.
◆ Care should be taken not to oversize the shunt. An oversized shunt can damage the coronary endothelium. It also can impair visualization and therefore the construction of the anastomosis.
◆ The shunt should be sized to allow smooth insertion, with minimal loss of blood through the anastomosis. Adequate visualization should be maintained at all times.
◆ Undersizing is less of an issue with shunts. Visualization may be improved with smaller shunts, keeping in mind that an element of benign coronary vasoconstriction will likely occur.
◆ Coronary arteriotomy usually requires proximal control for adequate visualization of the anastomotic site after coronary opening. However, for severely stenotic vessels, proximal control may not be necessary because the amount of blood inside the vessel does not preclude visualization.
◆There are different methods to occlude the coronary artery intermittently before the arteriotomy. We use silicone (Silastic) tapes looped around the coronary artery for blood flow control before opening and shunting the artery. Each arm of the silicone tape is passed through one pledget, which works as an outside occluder. Once the tape is put under tension, the pledget is pushed against and occludes the coronary artery, with minimal trauma (Fig. 4.11).
◆ The temporary occlusion of the coronary artery allows for a safe arteriotomy and placement of a coronary shunt. After the shunt is inserted, the temporary coronary occlusion should be reversed by the removal of the Silastic tapes or the sutures.
◆ Distal RCA grafting usually requires shunting because its occlusion frequently leads to AV node ischemia and bradycardia. A jumper cable for ventricular pacing is useful to overcome bradycardia should it occur during the temporary RCA occlusion and shunting.
◆ Shunt insertion follows several principles. It is performed using two forceps, with the long arm inserted first, which allows more shunt mobilization during shunt bending. The long arm should be inserted proximally in most cases, which decreases the amount of blood in the anatomic field. After insertion of the long arm proximally, blood control is achieved by pinching the shunt with one forceps. Then the other forceps bend the shunt, and the short arm is inserted distally. Final adjustments may be required (Fig. 4.12; Video 4.3)
Figure 4.11 Coronary occlusion with silicone tape for proximal blood vessel control.
Figure 4.12 Coronary shunt in place.
Step 4. Postoperative Care
◆ Patients who have an uneventful OPCAB are extubated shortly after arrival to the intensive care unit. Some centers even extubate patients in the operating room. Because of less inflam- matory response and less blood loss, patients have a smoother postoperative course, with less fluid and pressor requirements.
◆ Most patients are transferred to the cardiac step-down unit the morning after the surgery.
Step 5. Pearls and Pitfalls
◆The anesthesia and surgical teams should work in close collaboration to anticipate hemodynamic changes during heart positioning.
◆ The pulmonary artery catheter is a useful adjunct to understanding loading conditions and pulmonary pressures during OPCAB.
◆ The combination of the deep stitch–sling technique and the use of suction-based positioning devices allows for less hemodynamic changes during lateral wall exposure. The sling prevents ventricular underfilling, and the suction-based heart positioner elongates the heart, reshaping the cardiac chambers, which improves heart performance.
◆ Common mistakes during heart positioning and coronary stabilization include the following:
1. Not enough opening of the pericardium. The inverted-T pericardiotomy should extend past the apex of the heart.
2. Taut pericardium. The lateral pericardial stay sutures that create the initial pericardial cradle should be taken down before manipulating the heart.
3. Impaired right ventricular filling during lateral wall exposure. Suction devices and deep pericardial sutures should be used to avoid distortion of the inflow of blood to the heart. Do not bend or squeeze the heart. To this effect, the Trendelenburg position and right lateral rotation are helpful maneuvers.
4. Compressing the heart with the stabilizer. This is more common when the heart is underfilled and may paradoxically increase the heart’s mobility. Before applying any compression with a stabilization device, optimization of heart filling pressures should be achieved. Do not push down on the stabilizer; this will avoid impaired filling of the heart and hemodynamic collapse.
◆ The sequence of the revascularization strategy should aim to decrease myocardial ischemia and hemodynamic instability. The LAD territory should be grafted first in most patients.
◆ The use of intracoronary shunts is the safest approach to avoid ischemia and should be used routinely in most cases. For severely stenotic and occluded vessels, shunting may not be necessary. Shunts greatly facilitate the safe completion of any anastomotic off-pump procedure.
◆ Myocardial ischemia should be promptly corrected. If ischemia develops after coronary occlusion, shunting is warranted. When myocardial ischemia secondary to hemodynamic instability occurs, the heart back should be released into the pericardial sac. The heart should be allowed to recover, and manipulation can be reattempted in incremental moves.
◆ The goal of CABG is to achieve complete revascularization with conduits that have good long-term patency. OPCAB should not compromise the overall quality of the revascularization procedure.
◆ Conversion to an on-pump technique is sometimes needed, and the surgeon should perform it electively. Emergency conversion to an on-pump procedure leads to increased morbidity and mortality rates and therefore should be avoided at all costs.
◆ OPCAB requires meticulous planning and evaluation of targets, distances, and angles. If the operator feels that completing the operation will be compromised by the use of a pumpless technique, a strong argument can be made to plan the procedure, from the beginning, as on-pump CABG.
Keywords : OPCAG, coronary artery bypass surgery off-pump surgery surgical technique, Operations for Coronary Artery Disease
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