**2.2. Operation**

the other hand, PCI before redo CABG increased from 14.5% (1990 through 1994) to 26.6% (2005 through 2009). The likely explanation for this is increased use of PCI for patients with previous CABG and more effective risk factor control. Also, use of internal thoracic artery (ITA) grafts to left anterior descending (LAD) coronary artery graft decreases the risk of reoperation and this had become standard graft choice for CABG. The patients who underwent reoperative CABG had more diabetes, dyslipidemia, hypertension, peripheral vascular disease and left main disease. In another words, we are seeing less reoperative CABG in a higher risk patients. Because ITA grafts rarely develop atherosclerosis, reoperation is primarily based on the patency of the saphenous venous grafts or other arterial grafts. Atherosclerosis occurs in majority of vein grafts explanted more than 10 years after surgery and this account for almost all the late graft stenosis. The friability of vein graft atherosclerosis is a substantial risk of distal

Current recommendations for reoperation CABG include late stenotic vein grafts perfusing large area of myocardium mainly LAD or new distal CAD which is not perfused by the previous grafts. [3, 4, 5] Avoidance of graft injury during reentry is the key since perioperative myocardial infarction is the most significant predictor of mortality in patients undergoing

**Previous History** Detailed specifics of the previous surgery must be obtained. Date of the surgery, operating surgeon, technical aspects of surgery including number of the grafts performed, which target was bypassed, presence of ITA grafts and what kind of grafts were harvested. Also presence of any complication during the last surgery can be obtained from medical record or directly from the patient. Information regarding aspirin, clopidogrel, warfarin and dabigatran is important that may dispose to intraoperative and postoperative

**Physical Examination** Physical examination should include assessment of grafts such as Allen's test for radial arterial graft and previous scars to show saphenous vein harvest. Presence of peripheral artery disease should be assessed in case axillary or femoral cannulation is used for establishment of cardiopulmonary bypass. Venous Doppler study can be used for presence of greater and lesser saphenous vein and arterial Doppler studies can be used to

**Cardiac Catheterization** Cardiac Catheterization is the golden standard test to identify the new CAD. This will show native vessel anatomy, location of the lesion, patency of the previous graft including the LITA and size of the conduit. Non patency generally suggests presence of graft occlusion¸ but one must realize there is a chance that this may be incomplete study.

**CT Angiography** Another test that is being used in evaluation of the conduit is Computed tomography (CT) angiography. [8, 9] They are useful because they are able to precisely define the course of the previously placed conduits especially the LITA grafts. The condition of the Aorta, stenosis in the subclavian artery can also be assessed. Information gained from these methods will help guide the surgeons where the previous conduit will be during sternal entry.

coronary artery embolization during PCI and reoperation CABG.

assess the patency of radial and inferior epigastric arteries.

reoperation. [6, 7]

**2.1. Work up**

174 Artery Bypass

bleeding.

The reoperation CABG is more complex surgery compared to primary CABG. Technical challenges include sternal reentry, identification of old grafts, presence of graft stenosis and lack of bypass conduits.

**Cardiopulmonary bypass strategy** Typically, due to risk of graft injury, axillary or femoral artery cannulation is performed prior to sternotomy. Venous cannulation is obtained using femoral vein cannulation. For high risk cases, such as LITA lying underneath the sternum, Aorta underneath the sternum or right ventricle severly adhered to the sternum, CPB may be established prior to sternotomy. This allows lung deflation which retracts the heart away from the sternum.

**Operating Room Setup** External defibrillators must be attached to the patient prior to incision in case patient develops nonsustained ventricular arrhythmia during entry and dissection. For specific cases, thoracotomy can be performed for left sided graft to enable safe and efficient approach to the targets. [10]

**Sternal Reentry** Sternal wires are cut and midline of the sternum is marked for sternal reentry. Oscillating saw is used to divide the anterior table of the sternum. The sternal wires are left in place to protect the saw from cutting through the posterior table and possibly injuring the heart. When the anterior table has been divided, ventilation is stopped. And assistant elevate each side of sternum and posterior table is then sharply divided. Sternal wires are removed as posterior table is divided.

**Dissection** Once the sternum is divided, dissection of the mediastinum is performed. Traction superiorly not laterally is important, since lateral traction can tear the right ventricle and other important structures. Typically, dissection is performed from inferior to superior direction to minimize the chance of injuring critical structures. Identification of the diaphragm and pericardial edge is a marker for correct plane. Right pericardial edge is dissected from pericardiophrenic angle to the superior vena cava/right atrium junction and aorta is identified. Innominate vein is identified and dissected to avoid stretch injury. Anticipation of proximal anastomosis and graft is the key using the preoperative images and operative report. If there is an injury to the graft, CPB should be initiated and further dissection can be carried out. CPB can also be initiated on high risk patients to empty the heart and allow it to fall away from the sternum. Downside of this technique is the need to dissect while on heparin which results in more bleeding.

**Cardiopulmonary Bypass** Once Aorta and right atrium is dissected, the heart can be arrested. Effective myocardial protection is essential in previously revascularized heart. Both antegrade and retrograde coronary perfusion are critical. Antegrade cardioplegia may not be effective for areas supplied by ITA, and may dislodge emboli from the atherosclerotic debris from the disease vein grafts. On the other hand, retrograde cardioplegia protects from embolization and removes debris from the retrograde flow. 11 Epiaortic ultrasound is performed to prior to aortic crossclamp to identify any aortic plaques. [12] Mild hypothermia is induced after patient is placed on CPB. When there is patent LITA, it is standard practice to dissect and clamp. However, if the dissection is difficult, moderate hypothermia with either fibrillatory arrest or systemic hyperkalemia can be used to arrest the heart. Manipulation of the graft should be avoided until the heart is arrested since this can dislodge the debris.

quate myocardial protection and postoperative graft failure. Other significant predictors of mortality after reoperative coronary revascularization include age, female gender and emergency operations. [16] Long-term outcome is successful after a high risk surgery. 10-year survival is reported to be 55-69% and negative predictors of long term survival is preoperative

Complex Coronary Artery Disease http://dx.doi.org/10.5772/55251 177

Coronary endarterectomy is performed when the target has severe atherosclerosis and is not a suitable target. This procedure removes the atherosclerotic plaques with the intima and allows the conduit be anastomosed to the target. Often, decision of coronary endarterectomy is made intraoperatively and conduit is anastomosed to the endarterectomized vessel. This requires precise technique and experience since inadequate procedure leads to occlusion of the native artery and the bypass conduit. Main perioperative challenge is maintainance of patency because removal of the endothelial surface of the coronary artery disposed to platelet aggregation and subsequent thrombus formation. Therefore, anticoagulation method includ‐

Right coronary artery (RCA) is the most common vessel which coronary endarterectomy is performed. LAD endarterectomy is a technically complex procedure when compared to RCA endarterectomy due to the location and configuration of the septal and diagonal branches. LAD atherosclerotic core is narrow and delicate which increases the risk of disruption under tension. Unidirectional traction on the plaque can cause shearing off the branches. It is quite common that an extended arteriotomy or multiple arteriotomies are performed to achieve adequate plaque extraction. In cases where an extended arteriotomy is performed, the proximal third is used as the site of LITA anastomosis while the distal aspect of the vessel is reconstructed with a vein patch. In cases where 2 or more distinct arteriotomies are created, the LITA may be used for both sites as a separate graft; however, it is common practice that

the LITA be used for 1 arteriotomy site and vein graft(s) used for the remainder. [18]

**Endarterectomy** Endarterectomy for a diffusely diseased coronary artery is used when 1-mm probe is not passed. It is often necessary to create long arteriotomy. After the coronary arteriotomy, an endarterectomy spatula was used to identify the plane of dissection and then to mobilize the plaque proximally and distally. A 1-mm probe was advanced gently through the plane of dissection to break away resistant adhesions. A combination of gentle traction on the plaque and countertraction on the adventitia is useful to extract the plaque. When proper distal tapering of the specimen was not achieved, the arteriotomy was extended distally for complete extraction of the plaque. The proximal end of the endarterectomy should be distal to the most proximal lesion, to avoid competitive flow through the native coronary artery, to the level of the first diagonal branch at most. The atherosclerotic plaque varies from soft to extremely calcified and adherent. This characteristic dictates the length of the arteriotomy

left ventricular dysfunction, increasing age and diabetes mellitus. [17]

ing usage of postoperative heparin and clopidogrel is encouraged.

**3. Coronary endarterectomy**

**3.1. Operation**

**Revascularization** If LITA or RITA was not used, this will be the first choice for conduit. When ITA is used to replace a vein graft, the old vein graft should be left in place and arterial vessel should be anastomosed to the same coronary vessel. [13] If the vein graft is ligated this may induce ischemia to the target vessel. If saphenous vein is used for conduit, distal anastomosis can be performed directedly to the native coronary artery or to the cuff of 0.5mm of old vein graft if no distal stenosis is present. Proximal anastomosis is performed in similar fashion; however, if there are minimal aorta that can be used for anastomosis, graft can be connected to the previous proximal graft.

If there is associated procedure such as aortic procedure or valve procedure, distal anastomosis is performed prior to valve procedure to avoid manipulation of the heart after the prosthesis is in place. When adding ITA graft to stenotic LAD vein graft, it is advised to leave the stenotic vein graft to avoid hypoperfusion, although there is a risk of distal embolization from the old vein and competitive flow to the new graft.

#### **2.3. Outcomes**

From Society of Thoracic Surgeon database, surgical coronary revascularization has evolved over the last decade, with reoperative CABG now uncommonly performed in contemporary practice. reoperative CABG dropped from 6.0% in 2000 to 3.4% in 2009. [14] Reoperative mortality is high in reoperative group, operative mortality declined from 6.1% in 2000 to 4.6% in 2009 despite the fact that patients now more frequently present with left main disease, myocardial infarction, and heart failure. In centers with large operative experience, reports have demonstrated consistently lower mortality. There is increasing evidence that the preemptive strategies discussed here may minimize technical and postoperative complication. [15] Patients also now present more frequently for urgent or emergent surgery and following previous PCI. They also now have a higher incidence of other comorbidities such as increased weight, diabetes, hypertension, hypercholesterolemia, renal failure, and cerebrovascular disease.

Despite operating in patients with more complex coronary artery disease and greater medical comorbidities, there have been significant improvements in operative morbidity and mortality in this challenging population. The primary reason for increased mortality appears to be related to perioperative myocardial infarction (MI), due to graft injury, graft failure, inade‐ quate myocardial protection and postoperative graft failure. Other significant predictors of mortality after reoperative coronary revascularization include age, female gender and emergency operations. [16] Long-term outcome is successful after a high risk surgery. 10-year survival is reported to be 55-69% and negative predictors of long term survival is preoperative left ventricular dysfunction, increasing age and diabetes mellitus. [17]
