**2. Reoperative CABG**

Data suggests that fewer patients are undergoing reoperative CABG. [2] From 1990 through 1994, 7.2% of CABG was reoperations which decreased to 2.2% from 2005 through 2009. On

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 coronary artery embolization during PCI and reoperation CABG.

**Other images** Chest X-ray will provide the information regarding the sternal wires and aortic calcification and lateral view will provide proximity of the heart to the sternum. If the patient does not have a sternal wire after previous CABG, it may indicate patient had sternal wound dehiscence with flap closure. Echocardiogram will provide any wall motion abnormality as well as any valve abnormality which may change operative strategy. Nuclear stress tests such as thallium scanning and positron emission tomography and/or stress (exercise or dobuta‐ mine) echocardiogram can be used to assess the viability of the myocardium. If there is no

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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

**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

**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

**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

**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

viability, surgical revascularization may not be indicated.

**2.2. Operation**

the sternum.

lack of bypass conduits.

approach to the targets. [10]

posterior table is divided.

more bleeding.

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 reoperation. [6, 7]

## **2.1. Work up**

**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 bleeding.

**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 assess the patency of radial and inferior epigastric arteries.

**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. **Other images** Chest X-ray will provide the information regarding the sternal wires and aortic calcification and lateral view will provide proximity of the heart to the sternum. If the patient does not have a sternal wire after previous CABG, it may indicate patient had sternal wound dehiscence with flap closure. Echocardiogram will provide any wall motion abnormality as well as any valve abnormality which may change operative strategy. Nuclear stress tests such as thallium scanning and positron emission tomography and/or stress (exercise or dobuta‐ mine) echocardiogram can be used to assess the viability of the myocardium. If there is no viability, surgical revascularization may not be indicated.
