**9. Guidelines on revascularization in patients with prior CABG**

with PCI, prehospital use of antiplatelet therapy compared with patients not using antiplatelets was associated with lower occurrence of major adverse cardiac events after SVG intervention. [102] Also, DAPT did not improved outcomes when compared to single antiplatelet therapy.

*Warfarin* – Conflicting evidence is reported whether warfarin in addition to aspirin is beneficial in patients post CABG. In an extended follow-up of 7.5 years of the post CABG trial, low-dose anticoagulation compared with placebo reduced the rate of death by 35%, deaths or myocardial infarction (MI) by 31%, and the composite clinical endpoint of death, MI, stroke, CABG, or angioplasty by 17%. [103] However, in a smaller randomized trial, moderate-intensity oral anticoagulation alone or combined with low-dose aspirin was not superior to low-dose aspirin in the prevention of recurrent ischemic events in patients with non-ST-elevation ACS and previous CABG. [104] Currently, the American College of Chest Physicians (ACCP) Evidence-Based Clinical Practice Guidelines recommended that oral anticoagulation in addition to

*Lipid lowering therapy* – Clinical trials have shown that lipid lowering therapy (in particular statins) is beneficial in patients who have undergone CABG. [103,106-110] Besides the lipid lowering effect, statins also exert a number of pleiotropic effects on the vascular wall which may effect SVG in a similar way. In SVG, statins have shown to reduce vascular oxidative stress, improve NO bioavailability and reduce vascular inflammation, all critical components of SVG failure. [111] Subsequently, statins have systemic antithrombotic and anti-inflamma‐ tory effects and their administration may prevent acute SVG failure post CABG. [112] Ag‐ gressive lipid lowering therapy may be beneficial for long-term patency of grafts. In the randomized Post CABG trial, patients who had undergone bypass surgery 1 to 11 years before base line with elevated serum LDL-cholesterol concentrations (130 to 175 mg/dL / 3.4 to 4.5 mmol/L) were assigned to receive either aggressive lipid lowering therapy with lovastatin and, if needed, cholestyramine (target LDL-cholesterol <100 mg/dL / 2.6 mmol/L) or to moderate therapy (target LDL-cholesterol of approximately 134 mg/dL / 3.5 mmol/L). [106] Compared to a moderate strategy, aggressive lipid lowering therapy was associated with a delay in the progression of graft disease at an average of 4.3 years as assessed by angiography. Moreover, after clinical follow-up of 7.5 years, a 30% reduction in revascularization procedures and a 24% reduction in the composite endpoint of cardiovascular death, MI, stroke, CABG, or angioplasty were seen. [103] Similar findings were observed in a post hoc analysis from the TNT trial. In patients with previous CABG, simvastatine 80 mg compared to simvastatine 10 mg, was significantly more effective in reducing the rate of a combined cardiovascular endpoint at a median follow-up of 4.9 years (9.7% versus 13.0%). [110] Repeat revascularization with either CABG or PCI was also significantly reduced in patients assigned to the higher dose (11.3%

Antiplatelet agents and statin therapy are the only modalities with proven efficacy for the prevention of SVG stenosis. The routine use of beta blockers, calcium channel blockers, angiotensin converting enzyme (ACE) inhibitors, or nitrates post CABG is not supported by data, however, many of these patients require beta blockers and ACE inhibitors for preexistent

heart failure or MI according to the ACC/AHA guideline recommendations. [113,114]

aspirin can be considered only when it is indicated for other reasons. [105]

versus 15.9%).

202 Artery Bypass

In the European Society of Cardiology (ESC)/ European Association for Cardio-Thoracic Surgery (EACTS) guidelines on myocardial revascularization [116] published in 2010 states that in acute post-operative graft failure PCI may be an alternative to re-operation with acceptable results and fewer complications. [117] 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. When multiple grafts are occluded or the graft or native coronary artery appears unsuitable for PCI, surgery should be favoured. In asymptomatic patients, redo CABG or PCI should only be considered if the graft or coronary artery is of good size, severely narrowed and supplies a large territory of myocardium. Redo CABG or PCI should be decided by the Heart Team.

Repeat revascularization in patients with late graft failure is indicated in the presence of severe anginal symptoms despite anti-anginal medication. In patients with mild or no symptoms repeat revascularization is dependent on risk stratification by non-invasive testing. [118,119] In patients with previous CABG, PCI has worse acute and long-term outcomes than in patients without prior CABG. Redo CABG has a two- to four-fold higher mortality than the first procedure which is mainly driven by comorbidity and less by the re-operation itself. [120,121] There is limited data comparing the efficacy of PCI with redo CABG in patients with previous CABG. In a propensity analysis of long-term survival after redo CABG or PCI in patients with multivessel disease and high-risk features, short-term outcome was very favourable, with nearly identical survival at 1 and 5 years. [118] However, in the AWESOME RCT and registry the overall in-hospital mortality was higher in the redo CABG group compared to the PCI group. [17,122] Because of the initial higher mortality of redo CABG and comparable longterm mortality, the guidelines state that PCI is the preferred revascularization strategy in patients with LIMA or amenable anatomy. Redo CABG is preferred in patients with more diseased or occluded grafts, reduced systolic function, total occlusions of native coronary arteries or in the absence of a patent arterial graft. [118] If possible, the IMA is the conduit of choice when performing redo CABG. [123]

In the 2012 appropriateness criteria for coronary revascularization focussed update of the American College of Cardiology Foundation Appropriateness Criteria Task Force (ACCF), Society for Cardiovascular Angiography and Interventions (SCAI), Society of Thoracic Surgeons (STS), American Association for Thoracic Surgery (AATS), American Heart Associ‐ ation (AHA), and the American Society of Nuclear Cardiology (ASNC) it is stated that in patients with prior CABG, the presence of high-risk findings on noninvasive testing, higher severity of symptoms, or an increasing burden of disease in either the bypass grafts or native coronaries tended to increase the likelihood of an appropriate rating. [119] In patients with prior CABG receiving no or minimal anti-ischemic therapy or having low-risk findings on noninvasive testing revascularization was considered inappropriate. No specific recommenda‐ tions are provided on the strategy for revascularization, performing redo CABG or PCI.

graft failure following CABG, emergency PCI may limit the extent of myocardial cellular damage compared with redo CABG. [133] A nonsignifiant numerical difference was observed in in-hospital and 1-year mortality between the PCI group or redo CABG (12.0% and 20.0% in PCI group versus 20.0% and 27% in redo CABG group). Moreover, compared to acute redo-CABG, emergency PCI is quicker and less invasive. Importantly, in this study patent grafts were observed in 25% to 34% of the patients, therefore repeat coronary angiography should be applied when myocardial ischemia due to acute graft failure is suspected. Regarding the type of bypass graft, LIMA graft failure may be responsible for acute ischemic complications

Treatment of Coronary Artery Bypass Graft Failure

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

205

Recurrent angina during the early postoperative period is usually due to a technical problem with a graft or with early graft closure and there is an indication for prompt coronary angiog‐ raphy with percutaneous revascularization. The feasibility of PCI in patients presenting with clinical evidence of ischemia within 90 days of CABG was evaluated in 2 registries. Most patients presented with ACS and the most common cause of graft failure was occlusion or thrombosis. Both registries showed that patients with graft failure can undergo PCI with a

*SVG failure -* Recurrent angina after the first few months after CABG is caused by both graft disease and by progression of atherosclerosis in non-bypassed vessels. Percutaneous inter‐ vention in SVG lesions was evaluated in several randomized studies. The SAVED (Saphenous Vein de Novo) study randomized 200 patients with SVG lesions to placement of Palmaz-Schatz bare metal stent (BMS) or standard balloon angioplasty (BA) and demonstrated that compared to BA, bare metal stents (BMS) were associated with a higher procedural success (92% vs. 69%, p<0.001) but they had more frequent hemorrhagic complications (17% vs. 5 %, p<0.01). [145] At 6 months, a non-significant reduction in angiographic restenosis was observed (36% vs. 47%, p=0.11) and clinical follow-up at 9 months showed that freedom from death, MI, repeated bypass surgery, or revascularization of the target lesion was significantly better in the stent group (73% vs. 58 %, P = 0.03). Based on the results of the SAVED study, the majority of patients with SVG stenosis are treated with stenting. To prevent distal embolization form friable atheroemboli, and in addition may serve as a smooth-muscle cell barrier to decrease restenosis, stents covered with a mesh, most commonly polytetrafluorethylene (PTFE), were evaluated. However, 3 prospective randomized trails have not shown benefit with covered stents with

relatively low risk for in-hospital mortality or nonfatal major complications. [143,144]

respect to major adverse cardiac events nor in preventing restenosis. [146-148]

In native coronary arteries, drug-eluting stents (DES) have demonstrated a marked reduction in in-stent restenosis compared to BMS in the treatment of coronary artery disease. Several DES with different stent platforms, polymers or drugs are available. In the RRISC (Reduction of Restenosis in Saphenous Vein Grafts With Cypher Sirolimus-Eluting Stent) trial, 75 patients were randomized to sirolimus-eluting stent (SES) or BMS. [149] At 6 months follow-up, instent late loss was significantly reduced in SES (0.38 ± 0.51 mm vs. 0.79 ± 0.66 mm in BMS). Target lesion revascularization rate was also significantly reduced (5.3% vs. 21.6%) but no difference in death and MI was observed. Howbeit, a post hoc analysis of RRISC trial at 3 years reported similar rates of target vessel revascularization and while statistically underpowered for clinical outcomes, significantly higher all-cause mortality was reported with SES compared

after CABG in at least a third up to half of the cases. [133,138,142]

Both the ESC/EACTS guidelines on myocardial revascularization and the ACCF/SCAI/STS/ AATS/AHA/ASNC/HFSA/SCCT 2012 appropriate use criteria for coronary revascularization focused update do not provide recommendations for patients with prior CABG presenting with (non) ST segment elevation myocardial infarction (STEMI) or ACS.
