Redo coronary artery bypass grafting
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Redo coronary artery bypass grafting (CABG) can be one of the most technically challenging operations in cardiac surgery. The coronary disease is more advanced, and the coronary targets may be suboptimal. In addition, the patients are typically older and sicker compared to those undergoing primary CABG.
A literature review focused on the epidemiology, operative techniques, and outcomes associated with redo CABG.
The frequency of redo CABG relative to total CABG procedures has been decreasing over time. From 2000 to 2009, redo CABG decreased from 6.0 to 3.4% of all CABG procedures reported to the STS Adult Cardiac Surgery Database (STS ACSD) and currently stands at 2%. Risks associated with reoperations include diabetes and renal dialysis. Perioperative mortality for redo CABG is reported to be as high as three times that of primary CABG, but this risk is reduced with experience. Careful preoperative planning including quality imaging and precise surgical technique coupled with meticulous myocardial protection contributes to good outcomes. Experience is important in optimizing outcomes.
Redo CABG is a complicated operation and surgical experience, and appropriate perioperative strategies are essential for achieving optimal outcomes.
KeywordsRedo Reoperation CABG
Redo coronary artery bypass grafting (CABG) occurs when patients who previously underwent CABG develop progression of their native coronary artery disease or graft occlusion that requires another surgical revascularization. Redo CABG poses many more difficulties than primary CABG, including a harder technical operation, shortage of conduits, and often sicker patients, but there are operative strategies and techniques that can help avoid adverse outcomes.
Incidence and patients’ risk profile
A Society of Thoracic Surgeons (STS) study of 723,134 patients age 65 years or older who underwent CABG between 2001 and 2007 reported cumulative incidences of repeat revascularization of 2, 7, 13, and 16% at 1, 5, 10, and 18 years after surgery, respectively . Most of the revascularization procedures were percutaneous coronary interventions (PCI); the prevalence of redo CABG was quite low at all these time points (0.1, 0.6, 1.3, and 1.7%, respectively). Female sex, disease severity, preoperative dialysis, and partial revascularization were strongly associated with a higher prevalence of revascularization, whereas advanced age, left main disease, and smoking were associated with a lower prevalence. In addition, increasing the extent of arterial grafting performed at primary operation decreased the likelihood of coronary reintervention .
Patients who undergo redo CABG tend to be older and have more comorbidities, with a greater burden of coronary atherosclerosis and poorer ventricular function than those undergoing primary CABG . In addition, nationally, the patient risk profile has worsened over time as more patients present with myocardial infarction, heart failure, and previous PCI, and are in need of urgent or emergency surgery. They also have a greater prevalence of other comorbidities, such as obesity, diabetes, hypertension, renal failure, and cerebrovascular disease.
Indications for redo CABG
Because, in general, redo CABG is associated with greater risk than primary CABG, indications for redo CABG are stricter and based on careful assessment of the risk–benefit ratio. Patients being considered for redo CABG should have one or more important coronary arteries suitable for grafting and supplying a viable myocardium. For some patients, PCI may be preferable.
Patients with suspected early graft failure who have clinical or biochemical manifestations of significant myocardial ischemia or infarction should undergo coronary angiography and possible PCI. The preferred target for PCI is the native vessel or internal thoracic artery (ITA) graft, not the freshly occluded saphenous vein graft. If the native artery appears unsuitable for PCI or if several important grafts are occluded, redo CABG is recommended over PCI .
Patients who have late graft failure with extensive myocardial ischemia or severe symptoms despite optimal medical therapy should undergo redo CABG or PCI. PCI should be considered in those with a patent LITA and amenable anatomy, and redo CABG in those with several diseased grafts, reduced left ventricular function, or absence of a patent ITA .
Patients with patent LITA-to-LAD grafts who develop non-LAD-territory compromise derive no survival benefit from reintervention (PCI or CABG), but intervention may be considered for relief of symptoms after careful discussion .
Preoperative evaluation and patient selection
Patients with LAD disease with or without an occluded LAD graft stand to benefit the most from redo CABG, especially if a LITA is available and the distal LAD is graftable. Because patients with patent LITA-to-LAD grafts who develop non-LAD-territory disease derive no survival benefit from reintervention, nuclear imaging to verify a substantial non-LAD territory at jeopardy helps in decision-making.
In addition to the routine testing primary CABG patients undergo, preoperative testing to assess the availability and quality of conduits is particularly important in redo CABG. Internal thoracic arteries are imaged at the time of diagnostic coronary angiography to verify their integrity and rule out the possibility of injury during previous surgery.
Ultrasonographic vein mapping provides useful information about the size and quality of the greater and lesser saphenous veins available for harvest. Previous endoscopic vein harvesting makes it particularly difficult to determine how much vein is available after a prior harvest. The Allen test or the more sophisticated non-invasive testing is performed to determine if radial arteries could be used. Recent instrumentation for diagnostic coronary angiography precludes safe use of the accessed radial artery.
Routine use of preoperative multidetector computed tomographic angiography (CTA) in redo CABG is recommended to detect high-risk situations, such as proximity of cardiovascular structures and conduits to the posterior table of the sternum (Fig. 1), ascending aorta calcification, and pseudoaneurysms . Adoption of preventive surgical strategies in such risky scenarios can enhance the safety of reoperations and improve outcomes. Contrast is administered if the renal function allows it to enhance vascular imaging resolution.
The importance of a complete and well-performed coronary angiogram cannot be overemphasized. This is critical to identify potential targets that are underfilled or completely missed if the angiographic technique is inadequate.
Careful attention is given to identify preoperative antithrombotic therapy that patients may be receiving and to determine the safety of stopping versus bridging such therapies.
Challenges associated with redo CABG
Redo CABG is technically more challenging than primary CABG for a number of reasons . There may be a shortage of conduits because of their use in previous operation(s). Cardiovascular injury on reentry is always a risk, because the pericardium has been opened and the heart, major vessels, or bypass grafts can be close or adherent to the sternum. Structures that cross the midline, such as a patent right ITA graft, can be vulnerable. The aorta may be diseased and surrounded with scar tissue, leaving limited space to cannulate for cardiopulmonary bypass, clamp, and perform the proximal anastomosis.
Effective delivery of cardioplegia to all areas of the myocardium can be challenging in the presence of occluded coronaries and grafts. A patent ITA to a totally occluded LAD is not an uncommon scenario. According to the STS ACSD, the requirement for an intraoperative intra-aortic balloon pump in redo CABG is more than four times that for primary CABG, probably a reflection of increased difficulties in achieving optimal myocardial protection and complete revascularization .
Finding and controlling patent ITA grafts can be difficult, and the consequences of ITA graft injuries are serious. Gillinov et al. reported that of 655 patients with a patent LITA-to-LAD graft undergoing redo CABG from 1986 to 1997, 35 (5.3%) sustained intraoperative injury to the LITA graft. Of those 35 patients, 14 (40%) had a perioperative myocardial infarction, and 3 (8.6%) died. The 3 patients who died all had stenosis or thrombosis of the graft to the LAD documented at autopsy .
Finding a coronary target can be challenging if the adhesions are dense and the coronaries are deep in fat or myocardium. The quality of targets may be poor, with more diffuse disease and calcification, and more bleeding can occur because of adhesions and an increase in vulnerable raw surfaces. In addition, some patients may be on antithrombotic therapy in the immediate preoperative period, compounding the risk of bleeding.
Vein graft atherosclerosis is an important reason for reoperation between postoperative years 5 and 10 and beyond and poses a significant problem for the surgeon. Partially occluded atherosclerotic veins that have continued antegrade flow are predisposed to embolization that can result in a lethal myocardial infarction .
Redo CABG outcomes
Despite patients presenting with more comorbidities and increasing atherosclerotic burden, according to the STS ACSD the overall prevalence of operative mortality for redo CABG has been decreasing with time, from 6.0% in 2000 to 4.6% in 2009 .The STS risk model informs us that redo CABG is associated with increased perioperative mortality (odds ratio 3.1 for the first reoperation and higher for subsequent reoperations) .Similarly, the incidence of postoperative renal failure, prolonged ventilation, and the composite of major morbidity is also higher in redo than primary CABG .
Ultimately, the two most important factors that determine the outcome of redo CABG are surgical experience and patient risk. With the increase in surgical experience, the risk of redo CABG attributable to a more difficult technical operation has been neutralized. At Cleveland Clinic, reoperation itself is no longer an important risk factor; rather, patient characteristics are the primary determinant of outcome . Contemporary perioperative mortality for redo CABG is less than 2%. Below we share some strategies to improve redo CABG outcomes.
Strategies to improve surgical outcomes
Thorough patient evaluation and operative planning are key to minimizing complications and enhancing outcomes . The operating room team should be briefed on the surgical plan and expected actions should an adverse event occur. They must be prepared and the tools readily available for effective execution of any rescue plan.
Careful review of preoperative imaging studies is important. On coronary angiograms, grafts normally move with the heart during the cardiac cycle, but if segments are immobile, that means they are restricted by dense scar tissue. Peeling them off the anterior chest wall is challenging, requiring manipulation, and risk of injury is high. Patent ITAs are particularly valuable and vulnerable. For each previous bypass graft at risk, a rescue plan should injury occur must be part of the planning process. Knowing the availability of conduits for replacement is necessary.
Considerations when reviewing the preoperative CT scan include evaluation of the distance of vital structures from the posterior table of the sternum, and the anatomy and patency of axillary, iliac, and femoral vessels should the need for extrathoracic cannulation arise.
Sternotomy and dissection
Dissection of the aorta and the right side of the heart is typically performed to allow for safe central aortic and venous cannulation. Identifying the pericardial edges and applying the appropriate traction stretches the adhesions and eases the dissection into the right plane. The adhesions may be fleshier and shorter and the planes less well defined if reoperating within 3 weeks to 6 months after a prior operation. Dissection of the left side of the heart and a patent LITA graft may be performed before going on cardiopulmonary bypass if the dissection is easy and safe.
The no-touch method for old venous grafts can help avoid embolization, as can single aortic clamping. Without proper caution, the phrenic nerves may be at risk. Moreover, it is important to secure hemostasis carefully throughout the operation.
Myocardial protection with retrograde cardioplegia delivery is particularly important in redo CABG. We have a low threshold for placing the retrograde cardioplegia under direct vision into the coronary sinus if there are difficulties in insertion by feel. Systemic cooling is used selectively, but not routinely, and giving cardioplegia down new vein grafts is useful. Hypothermic fibrillatory arrest is used rarely in scenarios where the aorta cannot be safely clamped.
If injury or ischemia occurs, the prime objectives are to protect the brain and heart. This often requires emergency cannulation with or without hypothermia. Perfusion or cardioplegia to the injured cardiac territory should be optimized by primary repair of injuries, retrograde delivery of cardioplegia, and control of a patent ITA graft. Cardioplegia should be given down new vein grafts. Primary repair of injured bypass grafts should be backed up with a replacement graft.
Conduit choice and configuration
For patients in whom the LITA has been previously used, harvesting the RITA does not increase the risk of deep sternal wound infection . Radial artery grafting in redo CABG has been associated with improved outcomes , but patency is diminished when RAs are grafted to vessels that are not severely stenosed. Therefore, careful selection of target vessels to avoid competitive flow and enhance radial graft patency is important .
Gastroepiploic arteries are particularly sensitive to competitive flow and pose challenges related to limited graft length, size variation, small distal diameter, and vulnerability to spasm; they are rarely used in North America. We have used this approach selectively to bypass large branches of the right coronary artery. Tavilla and Bruggemans reported good short- and mid-term outcomes in 22 patients presenting with only right coronary artery disease who underwent reoperation using a sternal-sparing transabdominal approach and a skeletonized gastroepiploic artery graft .
Recycling arterial grafts is certainly a useful adjunct in redo CABG when conduit shortage is an issue and the anatomy is conducive. A proximal stenosis in an in situ ITA can be remedied by using it as a free graft off the hood of a radial graft. Composite Y or T grafts can extend the reach of the grafts. For example, a free RITA can be taken off the patent in situ LITA-to-LAD graft to bypass a lateral wall target (Fig. 4).
The off-pump technique in redo CABG offers potential advantages. First, it eliminates cardiopulmonary bypass-induced complications, including coagulopathy, and can avoid aortic manipulation in scenarios where the new grafts are based off the ITA inflows. Second, by using intracoronary shunts, off-pump redo CABG eliminates concerns relating to the effectiveness of cardioplegia.
However, off-pump coronary artery grafting also has several potential disadvantages. Exposure of the target vessels may be difficult in large and fatty hearts. Performing revascularization on a beating heart may result in hemodynamic instability. Additionally, off-pump CABG may be associated with compromised graft patency and less effective revascularization , and a meta-analysis found that it was associated with an increased risk of late (1 year or more) mortality .
Although some centers never use off-pump grafting for redo CABG, others use it frequently. In a recent report from a large academic center, cardiopulmonary bypass was used in all redo CABG cases, with a 6% perioperative mortality; half the patients survived to 10 years . On the other hand, the Japan Cardiovascular Surgery Database included 617 patients undergoing redo CABG from 2008 to 2011, with 59% undergoing an off-pump procedure. Patients in the off-pump group had 50% lower 30-day mortality, as well as a significantly lower incidence of major morbidity, prolonged ventilation, and blood transfusion . Furthermore, a meta-analysis of 12 studies from Imperial College London found that the off-pump technique significantly reduced early mortality in selected patients undergoing redo CABG .
At Cleveland Clinic, we use the off-pump technique selectively as part of a versatile strategy based on the patient’s hemodynamics, aorta status, and quality, number, and location of the coronary targets. It is always best to tailor the procedure to the patient’s specific physiologic and anatomic features.
In patients with a patent LITA-to-LAD graft and significant myocardial ischemia in a sizable non-LAD territory not amenable to percutaneous intervention, sternal-sparing alternative surgical strategies with or without cardiopulmonary bypass may be considered. Such strategies can reduce risk of cardiovascular injury and avoid manipulation of the ascending aorta, especially if calcified or diseased. Redo CABG for the circumflex and its branches via a left posterolateral thoracotomy is a useful option in the armamentarium of cardiac surgeons .
After conduit harvesting, the patient is repositioned in a right lateral decubitus position with the pelvis externally rotated (45°) to allow access to the femoral vessels should cannulation for cardiopulmonary bypass become necessary. The left lung is deflated, and an incision is made in the fourth or fifth intercostal space. In the presence of a patent LITA-to-LAD bypass, the anteromedial aspect of the lung is dissected from the pericardium only enough to locate the circumflex target.
The pericardium is opened posterior to the phrenic nerve. Limited dissection is performed to locate the target vessel, tracing old grafts when present. Once the target vessel is identified, attention usually turns to the proximal anastomosis. In addition to preoperative CTA assessment of the descending aorta, the aorta is assessed further by epiaortic echocardiography. Heparin is administered and the activated clotting time maintained at longer than 300 s. The proximal anastomosis is constructed with the aid of a side-biting clamp on the descending aorta or left subclavian artery. Constructing the proximal anastomosis first allows for immediate revascularization once the distal anastomosis is complete.
The distal anastomosis is completed using a proximal snare and an off-pump stabilizing platform. Coronary shunts are not routinely used, but are used selectively if occluding the coronary vessel is not well tolerated of if there are signs of myocardial ischemia. Grafts originating from the left subclavian artery and proximal descending aorta are routed anterior to the pulmonary hilum. Grafts are examined with the lung inflated to ensure a smooth course with no kinking.
As mentioned above, minimally invasive direct CABG for the right coronary artery and its branches using the right gastroepiploic artery via a sternal-sparing approach has been reported to have good outcomes, but experience with this approach is limited.
Immediate postoperative care is identical to that for primary CABG, but with adjustment to account for the higher risk features of redo CABG. Routine post-redo CABG care includes guideline-directed medical therapy and secondary preventive strategies to optimize short- and long-term outcomes.
Redo CABG is a complicated procedure associated with technical challenges. Relative to primary CABG, the frequency of redo CABG operations is decreasing. Mortality associated with redo CABG approaches that of primary CABG in the hands of experienced surgeons at experienced centers. Careful preoperative planning and meticulous surgical technique are important ingredients for successful outcomes.
This review article was funded by the Sheikh Hamdan bin Rashid Al Maktoum Distinguished Chair in Thoracic and Cardiovascular Surgery, held by Dr. Bakaeen, and the Marty and Michelle Weinberg and Family Fund.
Compliance with ethical standards
Conflicts of interest
The authors declare that they have no conflicts of interest.
The manuscript is a review paper and is exempt from IRB.
The manuscript is a review, and there are no relevant informed consent issues.
None of the authors has a relevant relationship with industry to report.
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