Myocardial damage following CABG surgery is due to two different causes classified as graft or non-graft related [ 6 , 7 ]. Non-graft-related ischaemia is related to inappropriate myocardial protection, excessive surgical manipulations, and air or plaque embolization [ 8 ].
Graft-related injury is associated with: early graft thrombosis, anastomotic stenosis, bypass kinks, overstretching or tension, significant spasm or incomplete revascularization [ 4 , 7 ]. Hence, discrimination between graft-related ischaemic events from other reasons [ 6 ] must be made rapidly.
Early reintervention has been proposed to allow myocardial rescue to preserve ventricular function after CABG surgery [ 9 ] since MI is associated with congestive heart failure and significant adverse outcomes [ 3 , 8 ]. The primary objective of this study was to describe specific angiographic findings in patients with early graft dysfunction to determine the most appropriate management.
This study was performed as a retrospective analysis. Between January and December , data were collected from consecutive patients who receive isolated CABG surgery. From this group, 39 underwent early coronary angiography for signs of myocardial ischaemia and suspicion of early graft dysfunction at the Montreal Heart Institute MHI. Early graft failure was defined as suspected graft dysfunction occurring within the first 72 h after the CABG procedure. Following angiographic diagnosis, patients were divided in two groups according to the treatment strategy chosen.
The first group consisted of patients with early aggressive treatment of graft dysfunction [return to OR for CABG revision or percutaneous coronary intervention PCI ], while the second group consisted of patients with observation in the ICU. Revascularization strategy was according to surgeon's preferences. The left internal mammary artery was anastomosed to the left anterior descending coronary artery and the right internal mammary artery or a saphenous vein graft were used to complete revascularization.
Patency of grafts was assessed following the last proximal anastomosis with intraoperative Doppler. Transoesophageal echography TEE was routinely performed in the OR by experienced cardiac anaesthesiologists to evaluate myocardial and valvular function. TEE evaluations of regional wall motion abnormalities RWMAs were performed after the anaesthetic induction and after weaning from cardiopulmonary bypass. Measurements were done according to the standard guidelines using a segment model [ 10 ].
These parameters were evaluated every 8 h and daily for 72 h. Intravenous nitroglycerin 1. American Society of Anaesthesiologists mg was administrated orally 6 h after surgery when was controlled. Once the diagnosis of graft dysfunction was made, the treatment strategy was chosen after consultation with an interventional cardiologist and attending cardiac surgeon.
Conservative treatment consisted of aggressive inotropic and intra-aortic balloon pumping support, intravenous heparin, beta-blockers and pain management. When PCI was chosen, the patient underwent immediate revascularization with percutaneous dilatation of the native coronary circulation.
When redo CABG was chosen, the patient was immediately transferred to the OR and the failed graft was repaired or replaced. Postoperative myocardial was evaluated according to the two treatment strategies. In-hospital and day mortality was also recorded for both treatment strategies. Categorical variables are described as percentages, and the Fisher exact test was used to compare groups. The differences were tested by t -test or Wilcoxon rank-sum test when appropriate.
Signs of ongoing ischaemia. Overall, early graft dysfunction was diagnosed in 0. Preoperative baseline characteristics and operative details are summarized for both groups in Tables 1 and 2 , respectively. There were no significant differences between groups. The angiographic findings are presented in Fig. When comparing the two treatment options conservative vs.
The type of conduits failing and myocardial territory with the failing conduit did not differ between the groups Table 3. Myocardial injury following myocardial initial revascularization, as indicated by peak postoperative CKMB and TnT serum levels, was not statistically different between the two groups.
However, there was a trend towards more extensive myocardial injury in the group with conservative treatment: CKMB: In-hospital or day mortality was This was not significant between the two groups Table 4. In the 32 patients with graft failure, 8 patients The aim of this study was to determine the appropriate treatment for patients with early graft dysfunction following CABG surgery.
Two important reports addressing revascularization of patient after angiographic confirmation of early graft failure have been published [ 4 , 5 ]. Thielmann et al. Early PCI can limit the progression towards LCOS and that early aggressive re-revascularization can limit the extent of myocardial cellular damage.
Rasmussen et al. Prevention of postoperative graft failure starts with harvesting vessels for CABG. A special attention must be taken not to injure the endothelium. At the end of the procedure, intraoperative assessment of the technical adequacy of distal graft anastomoses is of paramount importance.
This holds true particularly for off-pump CABG, where technical errors requiring revision for distal anastomoses have been reported in up to 9. Hence, non-permeable graft must be repaired or replaced rapidly when detected in the OR.
The most common method of assessing graft patency intraoperatively is transit-time flowmetry, but this is of limited value since coronary flow is affected in many ways by coronary resistance and morphology of the anastomosis.
This method is less accurate than angiography and may fail to detect non-occlusive, but haemodynamically significant stenosis [ 14 ]. Despite those limitations, the Doppler analysis of arterial and venous grafts is the simplest and the most widely available method to assess graft patency in the operating room.
Patients with a SVG culprit also suffered higher rates of mortality at 30 days Risk factors for mortality were prior heart failure and age. Redo CABG does not seem to further improve clinical outcomes. 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.
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.
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. When a mammary artery was used in the first surgery, there are generally four types of mammary artery to sternal relationships that can be encountered.
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. 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 significantly due to the large number of options for proximal as well as distal anastomosis sites.
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. 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. 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 cardioplegia solution is considered safer through retrograde coronary sinus perfusion than anterograde 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.
In such a way, the entire myocardium is provided with continuous, cold cardioplegic solution through coronary sinus perfusion. 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, atheromatous 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. 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. 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. 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. A total of patients with refractory post-CABG ischemia and at least one of five high-risk features i. In the much larger retrospective observational study from the Cleveland Clinic of patients with prior CABG who underwent multivessel revascularization between and were evaluated. After adjustment, PCI was associated with a nonsignificant increase in mortality risk hazard ratio 1.
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.
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, consecutive patients with graft failure were assigned by the heart-team to PCI or redo CABG. At 5 year, the rate of composite all-cause death, MI or target vessel revascularization was comparable, Target lesion revascularization was Independent predictors for the composite outcome were creatinine and peak creatine kinase MB.
These results have to be confirmed in larger studies before definite conclusion can be drawn. 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 symptoms and risk factor reduction.
The choice of treatment modality is influenced by clinical and angiographic characteristics. 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 ultimately result in practical patient-tailored therapeutic strategies to enhance graft function and control intimal hyperplasia and accelerated atherosclerosis.
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Table 1. Conclusion Patients with prior CABG remain at risk for future cardiac events, including graft failure. More Print chapter. How to cite and reference Link to this chapter Copy to clipboard.
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