**11. Redo CABG for graft failure**

Redo CABG is considered when revascularization of the LAD or a large area of the myocar‐ dium is required. Redo CABG is also preferred in patients with prior CABG with no patent grafts present but left main disease or 3-vessel disease, and in those with disabling angina, despite optimal non-surgical therapy, including lesions unsuitable for PCI. [217]

Surgeons are posed with a number of challenges in patients requiring redo CABG, including a higher likelihood of technical complications, incomplete revascularization, inadequate myocardial preservation, lack of suitable conduits, neurologic complications including major disabling stroke, renal failure, peri-operative bleeding and ischemia. [218,219] To help decrease the risks associated with redo CABG, a number of technical advances have been introduced in the surgical arena. The first challenge, safe sternal re-entry without damaging coronary bypass grafts and other retrosternal structures, has been described to be safely performed when using an oscillating or micro-oscillating saw. [220,221] Periodic deflating of the lungs will help prevent injury to the pulmonary parenchyme during re-entry. When a mammary artery was used in the first surgery, there are generally four types of mammary artery to sternal relation‐ ships that can be encountered. [219] The first: LIMA and RIMA are both used with the LIMA supplying the LAD and the RIMA reaching to the RCA or its branches. In this case, the risk of injury is relatively low, because the IMA grafts are parallel to the body of the sternum at a deeper plane and go through the pericardium (which is therefore open) directly away from the midline toward the target vessels. In a second situation, a pedicle LIMA graft crosses in front of the pleura, curves around and goes back laterally to reach the LAD, which is typically seen as a C-shaped curve on the angiogram. This type of LIMA grafting is particularly prone to injury during sternotomy because of its close proximity to the sternal body. In the third scenario, the RIMA graft is used and comes in front of the aorta across the midline and reaches the LAD. Although the graft crosses the midline the risk of injury is relatively low due to the close proximity to the aorta which lies deeper in the thorax and can be easily identified. Finally, the RIMA may go behind the aorta through the transverse sinus to reach the marginal branches of the Cx artery, which is very far away from the sternal re-entry area and poses therefore minimal risk for potential injury. The proximity of vein grafts to the sternum varies signifi‐ cantly due to the large number of options for proximal as well as distal anastomosis sites. Careful review of the coronary angiogram or even cardiac/thoracic imaging to assess the relationship to the sternum and other anatomic structures is therefore warranted. Other structures at risk for injury during sternal re-entry include perforation of the right ventricle, and innominate vein. This is particularly true in patients where the pericardium was not closed. After sternal access, subsequent exposure of the heart can be completed by fibrosis which can be significant especially after pericarditis or radiation exposure. In patients requiring posterior vessel bypass, the entire heart should be cleared of fibrosis to allow surgical manipulation.

troponin elevations. Patients with a SVG culprit also suffered higher rates of mortality at 30 days (14.3% vs. 8.4%) and MACE at 1 year (36.8% vs. 24.5%). Finally, in the APEX-AMI trial, STEMI patients with prior CABG exhibited a smaller baseline territory at risk as measured by 12-lead ECG and had less myocardial necrosis. Moreover, in these patients receiving primary PCI, TIMI flow grade 3 was less frequently achieved and ST-segment resolution was less common but they have more frequent clinical comorbidities and increased 90-day clinical events including mortality. Risk factors for mortality were prior heart failure and age.

In conclusion, in patients with prior CABG presenting with ACS, PCI improves clinical outcomes compared to medical therapy alone. Redo CABG does not seem to further improve

Redo CABG is considered when revascularization of the LAD or a large area of the myocar‐ dium is required. Redo CABG is also preferred in patients with prior CABG with no patent grafts present but left main disease or 3-vessel disease, and in those with disabling angina,

Surgeons are posed with a number of challenges in patients requiring redo CABG, including a higher likelihood of technical complications, incomplete revascularization, inadequate myocardial preservation, lack of suitable conduits, neurologic complications including major disabling stroke, renal failure, peri-operative bleeding and ischemia. [218,219] To help decrease the risks associated with redo CABG, a number of technical advances have been introduced in the surgical arena. The first challenge, safe sternal re-entry without damaging coronary bypass grafts and other retrosternal structures, has been described to be safely performed when using an oscillating or micro-oscillating saw. [220,221] Periodic deflating of the lungs will help prevent injury to the pulmonary parenchyme during re-entry. When a mammary artery was used in the first surgery, there are generally four types of mammary artery to sternal relation‐ ships that can be encountered. [219] The first: LIMA and RIMA are both used with the LIMA supplying the LAD and the RIMA reaching to the RCA or its branches. In this case, the risk of injury is relatively low, because the IMA grafts are parallel to the body of the sternum at a deeper plane and go through the pericardium (which is therefore open) directly away from the midline toward the target vessels. In a second situation, a pedicle LIMA graft crosses in front of the pleura, curves around and goes back laterally to reach the LAD, which is typically seen as a C-shaped curve on the angiogram. This type of LIMA grafting is particularly prone to injury during sternotomy because of its close proximity to the sternal body. In the third scenario, the RIMA graft is used and comes in front of the aorta across the midline and reaches the LAD. Although the graft crosses the midline the risk of injury is relatively low due to the close proximity to the aorta which lies deeper in the thorax and can be easily identified. Finally, the RIMA may go behind the aorta through the transverse sinus to reach the marginal branches of the Cx artery, which is very far away from the sternal re-entry area and poses therefore minimal risk for potential injury. The proximity of vein grafts to the sternum varies signifi‐

despite optimal non-surgical therapy, including lesions unsuitable for PCI. [217]

clinical outcomes.

214 Artery Bypass

**11. Redo CABG for graft failure**

After sternal entry and inspection of the coronary vessels and branches, the second challenge is to assure adequate revascularization. Diffuse coronary artery disease poses a major problem in finding a suitable and satisfactory area for anastomosis. Thick plaque build-up and calcified coronary artery branches as well as calcification of the aortic arch make distal and proximal anastomosis of coronary bypass grafts hard and increase the chances of graft failure. [219] Additionally, the lack of satisfactory bypass conduits is common, because many patients undergoing redo CABG have very thin and dilated varicose veins, and small and calcified radial arteries. Risk factors for poor saphenous vein quality are age, obesity and diabetes, which are all more prominent in patients requiring redo CABG. In those patients the IMA may be small or even atherosclerotic.

Inadequate myocardial protection is an important cause of failure to wean patients off cardiopulmonary bypass. In the presence of degenerative old vein grafts, delivery of cardio‐ plegia solution is considered safer through retrograde coronary sinus perfusion than anterog‐ rade delivery of cardioplegic solution because of the risk of atheromatous embolization from atherosclerotic vein grafts which can lead to acute occlusion of coronary artery branches. [222] Additional measures include a no touch approach regarding diseased vein grafts to minimalize the chance of distal embolization due to manipulation. [223] To assure a constant temperature in an attempt to minimize haematological abnormalities and tissue edema, some surgeons also occlude the IMA with a bulldog clamp to prevent the delivery of warm blood into the myocardium. In such a way, the entire myocardium is provided with continuous, cold cardioplegic solution through coronary sinus perfusion. [224,225] After placement of newly constructed coronary artery bypass grafts, anterograde cardioplegic solution can also be given.

Neurological complications and bleedings are common following redo CABG. Several techniques are used to decrease the risk of neurological complications. Most common are ischemic stroke or TIA due to cerebral embolization from a calcified ascending aorta, athe‐ romatous plaques on the ascending aorta, and embolization from a jet phenomenon from aortic cannulation. Other causes for cerebal dysfunction are systemic inflammatory processes in response to cardiopulmonary bypass and gaseous microemboli. [226] Soft flow aortic cannu‐ lae, heparin-coated circuits, and administration of adenosine have proposed as techniques to lower neurological complications, but adequate studies and therefore evidence are lacking. [227-229] Bleeding is associated with an increased morbidity and mortality. Bleedings can be largely avoided by meticulous surgical dissection and careful catherization. Some studies using the application of fibrin glue suggest that this may help minimize peri-operative bleeding. [230] Intraoperative blood loss is a major cause of post-operative bleeding from depleted coagulation factors and hemodilution. Consideration should be given to preoperative antiplatelet therapy including aspirin and clopidogrel. A low platelet count and other medical conditions that adversely affect the coagulation process should be carefully investigated.

was no significant difference in mortality between groups (redo CABG 74% vs. PCI 68%). Noteworthy, the available comparative studies were, however, conducted before the use of aggressive dual antiplatelet therapy with aspirin and clopidogrel after PCI with stenting and

Treatment of Coronary Artery Bypass Graft Failure

http://dx.doi.org/10.5772/54928

217

In a recently published retrospective study, in which patients were prescribed aggressive dual antiplatelet therapy, 287 consecutive patients with graft failure were assigned by the heart-team to PCI or redo CABG. [235] A total of 243 patients underwent PCI (82% treat‐ ed with BMS, 18% treated with DES) and 44 redo CABG. Patient selection was present as patients undergoing PCI more frequently presented with STEMI, multivessel disease, SVG failure, a history of MI, and shorter time-to-graft failure. At 5 year, the rate of com‐ posite all-cause death, MI or target vessel revascularization was comparable, 57.6% after PCI and 51% after redo CABG. Target lesion revascularization was 21.3% after PCI, and 3.2% following redo CABG. In the PCI group, BMS was associated with significantly higher rates of target lesion revascularization (24.8% vs. 7.6%), but the rate of death or MI compared with DES was similar. Independent predictors for the composite outcome were creatinine and peak creatine kinase MB. These results have to be confirmed in larg‐

Patients with prior CABG remain at risk for future cardiac events, including graft failure. Stable patients with recurrence of angina following CABG can be treated medically for their symp‐ toms and risk factor reduction. In all patients with coronary heart disease aggressive risk factor reduction is recommended which includes aspirin, treatment for hypertension and serum lipids, avoidance of smoking, and controlling serum glucose in diabetic patients. Evaluation for ischemia is as in other patients with stable angina without prior CABG. However, early diagnostic angiography is suggested as the different anatomic possibilities, i.e. graft stenosis or progression of native vessel disease in nonbypassed vessels can lead to recurrent ischemia. Revascularization of graft failure either by PCI or redo CABG is associated with worse acute and long-term outcomes compared to patients without prior CABG. The choice of treatment modality is influenced by clinical and angiographic characteristics. When multiple grafts are occluded or the graft or native coronary artery appears unsuitable for PCI, surgery should be favoured. The target for PCI is the body of the coronary artery of the arterial graft while freshly occluded SVG or the anastomosis itself should be targeted due to the risk of embolization or perforation. Whether specific stent platforms, polymers or drugs are more appropriate in SVG and arterial graft lesions has not been addressed at this time. Moreover, the role of various surgical techniques for graft revascularization, such as off-pump and minimal invasive CABG also remain unclear. Finally, factors including disease status of the native vessel, and patient characteristics such as left ventricular function, renal failure, diabetes and advanced age, as shown in our multivariate analysis are of influence on outcomes. Future prospective studies in the medical and invasive treatment of graft failure are therefore warranted. Those studies together with our growing understanding of the pathobiology of arterial and vein grafts will

aggressive lipid-lowering with statins for secondary prevention.

er studies before definite conclusion can be drawn.

**12. Conclusion**

Redo CABG for coronary bypass graft failure is not favoured by cardiologists and surgeons alike, due to the higher morbidity and mortality compared with primary CABG. Reported intraoperative mortality rates are 5.8-9.6%. [231] Other major complications include stroke (1.4-3.2%), non-fatal MI (3.0-9.6%), renal failure (2.4-11%) and post-operative bleeding (2.7-4.4%). [217,223] Following redo CABG, survival is 75–90% and 55–75% at 5- and 10-year follow-up, respectively. [231]

*Redo CABG versus PCI -* Available data comparing the outcomes of PCI to redo CABG in patients with prior CABG is limited. Initial studies evaluating BA versus CABG noted comparable long-term results except for a much higher rate of repeat revascularization in the BA group (BA 64% vs. redo CABG 8%). [232] Multivariate analysis identified age > 70 years, left ventricular ejection fraction < 40%, unstable angina, number of diseased vessels and diabetes mellitus as independent correlates of mortality for the entire group. Direct compari‐ son between redo CABG and PCI was performed in the AWESOME trial. A total of 142 patients with refractory post-CABG ischemia and at least one of five high-risk features (i.e. prior openheart surgery, age >70 years, left ventricular ejection fraction <35%, MI within seven days or intraaortic balloon pump required) amandable for either PCI or redo CABG were randomized. [17] Arterial grafts were used in 75% of redo CABG procedures and stents in 54% of PCI (approximately one-half with BMS). In-hospital mortality was higher after redo CABG (8% vs. 0%). At 3 years, there was no significant difference in overall patient survival (redo CABG 71% vs. PCI 77%), but there was a nonsignificant increase in survival free of unstable angina in the CABG group (65% vs. 48%). In the much larger retrospective observational study from the Cleveland Clinic of 2191 patients with prior CABG who underwent multivessel revasculari‐ zation between 1995 and 2000 were evaluated. [233] A total of 1487 had redo CABG and 704 underwent PCI (77% with at least one stent). No difference was observed in 30-day mortality with redo CABG compared to PCI (2.8% vs. 1.7%) but as expected periprocedural Q wave MI occurred more often after redo CABG (1.4% vs. 0.3%). At 5-years follow-up, cumulative survival was similar with redo CABG and PCI (79.5% vs. 75.3%). After adjustment, PCI was associated with a nonsignificant increase in mortality risk (hazard ratio 1.47, 95% CI 0.94-2.28). The major predictors of mortality were higher age and lower LVEF, not the method of revascularization. Importantly, the choice of treatment strategy was largely determined by coronary anatomy wherein the most important factors to perform redo CABG were: 1) more diseased or occluded grafts, 2) absence of a prior MI, 3) lower left ventricular ejection fraction, 4) longer interval from first CABG (15 vs. 6 years), 5) more total occlusions in native coronary arteries, and 6) the absence of a patent mammary artery graft.

In diabetic patients with post-CABG angina, the outcomes after repeat revascularization were evaluated in an observational study in which 1123 such patients underwent PCI (75% BA, 25% stent palcement) and 598 underwent redo CABG. [234] Redo CABG was associated with increased in-hospital mortality (11.2% vs. 1.6%) and stroke (4.7% vs. 0.1%). At 10 years, there was no significant difference in mortality between groups (redo CABG 74% vs. PCI 68%). Noteworthy, the available comparative studies were, however, conducted before the use of aggressive dual antiplatelet therapy with aspirin and clopidogrel after PCI with stenting and aggressive lipid-lowering with statins for secondary prevention.

In a recently published retrospective study, in which patients were prescribed aggressive dual antiplatelet therapy, 287 consecutive patients with graft failure were assigned by the heart-team to PCI or redo CABG. [235] A total of 243 patients underwent PCI (82% treat‐ ed with BMS, 18% treated with DES) and 44 redo CABG. Patient selection was present as patients undergoing PCI more frequently presented with STEMI, multivessel disease, SVG failure, a history of MI, and shorter time-to-graft failure. At 5 year, the rate of com‐ posite all-cause death, MI or target vessel revascularization was comparable, 57.6% after PCI and 51% after redo CABG. Target lesion revascularization was 21.3% after PCI, and 3.2% following redo CABG. In the PCI group, BMS was associated with significantly higher rates of target lesion revascularization (24.8% vs. 7.6%), but the rate of death or MI compared with DES was similar. Independent predictors for the composite outcome were creatinine and peak creatine kinase MB. These results have to be confirmed in larg‐ er studies before definite conclusion can be drawn.
