**2. Technical aspects**

#### **2.1 Anesthesia**

After standard sternotomy and appropriate graft harvesting, a pericardial well is created. A standard dose of heparin is administered by the anaesthesiologist. The anaesthesia team should be prepared to perform appropriate hemodynamic monitoring. We use transesophageal echocardiography and Swan-Gantz catheters to monitor cardiac function in all patients. Activated clotting time above 350 is sufficient to perform OPCAB; however, a full dose of heparin may be given in cases undergoing emergent conversion to CABG using CPB. The anaesthesiologist should inform the surgical team any abrupt decrease in blood pressure, ST changes on EKG and arrhythmia, because these are signs for possible emergent conversion to CPB.

#### **2.2 Retropericardial suture**

The patient is placed in the Trendelenburg position and the sternal retractor is open widely. Right side stitches holding the pericardial well are released to minimize compression of the right heart. While the apex of the heart is gently elevated using one hand, retropericardial sutures are placed to support the heart (Figure 1). To minimize hemodynamic instability, we place the first retropericardial stitch into the mid-portion of the diaphragm. The stitch is pulled out to the right side of the lower edge of the skin incision and tightly secured so that the heart is somewhat elevated. The second deep pericardial stitch is applied to the midportion between the inferior vena cava and the left lower pulmonary vein, and the stitch is passed though a rubber catheter so that the heart will not be injured by the retropericardial sutures.

Current Trend of Off-Pump Coronary Artery Bypass Grafting 49

The third stitch is applied inferior to the left upper pulmonary vein and is also passed through a rubber catheter. Usually three retropericardial sutures are sufficient to support the heart; however, an additional retropericardial suture can be added between the last two retropericardial sutures. An abrupt drop in blood pressure may occur during retropericardial suture placement. This hemodynamics instability is usually transient and injection of a small dose of vasoconstrictor or volume management will be enough to regain blood pressure. ST segment changes on EKG during the heart displacement is often observed in patients with severe left main disease. Preoperative intra-aortic balloon pump (IABP) placement would be helpful to maintain hemodynamic stability. If there is a persistent drop in blood pressure, STsegment changes, and/or ventricular arrhythmia occurs during the manipulation of the heart, it is an indication to abort the OPCAB and convert to on-pump CABG. If the patient is not tolerating the short period of heart displacement during retropericardial suture placement, the patient most likely would not tolerate a longer period of heart displacement while performing anastomoses. Some surgeons may use suction-cup device to place the heart in an appropriate position. The use of a suction cup device and the use of retropericardial sutures have been

Anastomosis to the left anterior descending artery (LAD) using the internal mammary artery (IMA) graft is key to the success of OPCAB so that the LAD can be perfused after anastomosis. Without the Trendelenburg position, minimal elevation of the left heart with one or two sponges is usually sufficient to approach to the LAD. If the right ventricle is compressed and venous return is decreased, a significant decrease in blood pressure can occur. To avoid stress on the right system, the right pleura may be opened. This allows the heart to herniate into the right pleural space during heart displacement and minimizes the hemodynamic compromise.. After exposure of the target vessel, a suction type coronary stabilizer is placed on the target vessel. Before making coronary arteriotomy, a proximal snare is placed to the coronary artery slightly proximal to the anastomosis area using a silicone suture (Figure 2 top). EKG and blood pressure are carefully monitored by anesthesiologists. An arteriotomy is made on the target. Then a intracoronary shunt is quickly inserted into the coronary artery (Figure 2 middle) and

The sizing of the shunt is important. If a larger shunt is selected relative to the coronary artery size, the surgeon may encounter difficulty in placing the shunt into the coronary artery; moreover, vigorous forceful insertion of the shunt may cause injury or local dissection of the coronary artery. On the contrary, if a smaller shunt relative to the coronary artery is selected, the surgeon may experience excessive amount of bleeding from the anastomosis site, and smaller shunt may not able to supply enough blood distally. A CO2 mister-blower helps to provide a bloodless operative field. Anastomosis is performed in the standard manner; however additional care is always taken not to place a suture into the shunt. Right before completion of the anastomosis the proximal snare is tightened, the shunt is removed, and then the sutures are tied. Removal of the proximal snare allows abrupt restoration of distal coronary flow. In some cases of a small target coronary artery, the anastomosis can be performed without a shunt using a proximal snare only. If the target vessel is totally occluded vessel, the proximal snare is not necessary because of lack of forward blood flow. The IMA flow should be checked with ultrasound doppler before

proven to have similar effects (Gunnert et al., 2008).

the proximal snare is released (Figure 3 bottom) (Emmiler et al., 2008).

**2.3 Anterior wall revascularization** 

posterior or inferior wall revascularization.

Fig. 1. A model of retropericardial suture.

Fig. 1. A model of retropericardial suture.

The third stitch is applied inferior to the left upper pulmonary vein and is also passed through a rubber catheter. Usually three retropericardial sutures are sufficient to support the heart; however, an additional retropericardial suture can be added between the last two retropericardial sutures. An abrupt drop in blood pressure may occur during retropericardial suture placement. This hemodynamics instability is usually transient and injection of a small dose of vasoconstrictor or volume management will be enough to regain blood pressure. ST segment changes on EKG during the heart displacement is often observed in patients with severe left main disease. Preoperative intra-aortic balloon pump (IABP) placement would be helpful to maintain hemodynamic stability. If there is a persistent drop in blood pressure, STsegment changes, and/or ventricular arrhythmia occurs during the manipulation of the heart, it is an indication to abort the OPCAB and convert to on-pump CABG. If the patient is not tolerating the short period of heart displacement during retropericardial suture placement, the patient most likely would not tolerate a longer period of heart displacement while performing anastomoses. Some surgeons may use suction-cup device to place the heart in an appropriate position. The use of a suction cup device and the use of retropericardial sutures have been proven to have similar effects (Gunnert et al., 2008).

#### **2.3 Anterior wall revascularization**

Anastomosis to the left anterior descending artery (LAD) using the internal mammary artery (IMA) graft is key to the success of OPCAB so that the LAD can be perfused after anastomosis. Without the Trendelenburg position, minimal elevation of the left heart with one or two sponges is usually sufficient to approach to the LAD. If the right ventricle is compressed and venous return is decreased, a significant decrease in blood pressure can occur. To avoid stress on the right system, the right pleura may be opened. This allows the heart to herniate into the right pleural space during heart displacement and minimizes the hemodynamic compromise.. After exposure of the target vessel, a suction type coronary stabilizer is placed on the target vessel. Before making coronary arteriotomy, a proximal snare is placed to the coronary artery slightly proximal to the anastomosis area using a silicone suture (Figure 2 top). EKG and blood pressure are carefully monitored by anesthesiologists. An arteriotomy is made on the target. Then a intracoronary shunt is quickly inserted into the coronary artery (Figure 2 middle) and the proximal snare is released (Figure 3 bottom) (Emmiler et al., 2008).

The sizing of the shunt is important. If a larger shunt is selected relative to the coronary artery size, the surgeon may encounter difficulty in placing the shunt into the coronary artery; moreover, vigorous forceful insertion of the shunt may cause injury or local dissection of the coronary artery. On the contrary, if a smaller shunt relative to the coronary artery is selected, the surgeon may experience excessive amount of bleeding from the anastomosis site, and smaller shunt may not able to supply enough blood distally. A CO2 mister-blower helps to provide a bloodless operative field. Anastomosis is performed in the standard manner; however additional care is always taken not to place a suture into the shunt. Right before completion of the anastomosis the proximal snare is tightened, the shunt is removed, and then the sutures are tied. Removal of the proximal snare allows abrupt restoration of distal coronary flow. In some cases of a small target coronary artery, the anastomosis can be performed without a shunt using a proximal snare only. If the target vessel is totally occluded vessel, the proximal snare is not necessary because of lack of forward blood flow. The IMA flow should be checked with ultrasound doppler before posterior or inferior wall revascularization.

Current Trend of Off-Pump Coronary Artery Bypass Grafting 51

After IMA-LAD anastomosis, anastomoses to the obtuse marginal branch (OM) or posterior descending artery can be performed. Prior to the OM anastomosis, the patient is placed in a steep Trendelenburg and left side up position on the operating table. The heart is gently elevated using a hand and then the heart can be rested on the retropericardial sutures. If the blood pressure drops, the heart is placed back into the natural position and wait for recovery. The previous IMA-LAD graft should stay open and this IMA-LAD flow will help the hemodynamics during the OM anastomosis is completed. Phenylephrine is a first drug of choice for hypotension during the anastomosis, because phenylephrine increase blood pressure without causing tachycardia. If persistent hypotension occurs, conversion to onpump should be considered. However, we found most of patient with normal left ventricular function will tolerate displacement of the heart during the anastomoses. After adequate exposure of the target vessel, a stabilizer is placed onto the target. Confirmation of stable hemodynamics is necessary prior to making an arteriotomy. In a sequential manner, proximal snare placement, arteriotomy, shunt placement, release of the proximal snare, and then anastomosis are performed. Arterial blood drawn by the anesthetist should be avoided during the anastomosis of the posterior wall. After the OM anastomosis, the position of the operating table is returned to zero and maintain the Trendelenburg position. Anastomosis to

Proximal anastomoses are performed after all distal anastomoses. The patient is placed in a slight reverse Trendelenburg position, systolic blood pressure is controlled by anesthesia with a target of 110 mm Hg, so that the proximal clamp is not dislodged during the proximal anastomosis. Displacement of the proximal clamp during the proximal anastomosis is dangerous and may cause massive exsanguination, and may also cause aortic dissection. After achieving an adequate blood pressure, a side-biting clamp is gently applied to the ascending aorta. An aortotomy is made and proximal anastomosis is completed in the standard manner. The side-biting clamp is removed and the grafts are de-aired. Proximal anastomosis of the graft may be performed before the distal anastomosis, especially if a proximal automatic anastomosis device is used. The automatic proximal anastomosis device

After completion of all anastomoses, the blood flow of the grafts should be accessed using an ultrasound flow probe. A poor graft flow mandates additional attention to the anastomosis and consider revision of the graft anastomosis (Kim et al., 2005). Protamine is administered after confirmation of the graft flow and then the chest is closed in the standard

Without using CPB, the fibrinolytic activity of the patient who undergo OPCAB is lower than those who undergo conventional CABG using CPB. After OPCAB surgery, patient may develop a hypercoagulable state. To avoid platelet aggregation at the anastomosis site, clopidogrel is started as early as postoperative day 0 (Quigley et al, 2003). Other

postoperative managements are similar to those after on-pump CABG.

**2.4 Posterior and inferior wall revascularization** 

the inferior wall is performed in a similar manner.

is useful for the patient with severe calcification of the aorta.

**2.6 Doppler assessment to the grafts** 

**2.7 Postoperative management** 

manner.

**2.5 Proximal anastomosis** 

Fig. 2. Suction stabilizer and proximal snare is placed on to the target vessel (top). A shunt tube is placed thought the arteriotomy (middle). Proximal snare is open after shunt tube placement and the coronary vessel is ready to anastomose (bottom)

#### **2.4 Posterior and inferior wall revascularization**

50 Front Lines of Thoracic Surgery

Fig. 2. Suction stabilizer and proximal snare is placed on to the target vessel (top). A shunt tube is placed thought the arteriotomy (middle). Proximal snare is open after shunt tube

placement and the coronary vessel is ready to anastomose (bottom)

After IMA-LAD anastomosis, anastomoses to the obtuse marginal branch (OM) or posterior descending artery can be performed. Prior to the OM anastomosis, the patient is placed in a steep Trendelenburg and left side up position on the operating table. The heart is gently elevated using a hand and then the heart can be rested on the retropericardial sutures. If the blood pressure drops, the heart is placed back into the natural position and wait for recovery. The previous IMA-LAD graft should stay open and this IMA-LAD flow will help the hemodynamics during the OM anastomosis is completed. Phenylephrine is a first drug of choice for hypotension during the anastomosis, because phenylephrine increase blood pressure without causing tachycardia. If persistent hypotension occurs, conversion to onpump should be considered. However, we found most of patient with normal left ventricular function will tolerate displacement of the heart during the anastomoses. After adequate exposure of the target vessel, a stabilizer is placed onto the target. Confirmation of stable hemodynamics is necessary prior to making an arteriotomy. In a sequential manner, proximal snare placement, arteriotomy, shunt placement, release of the proximal snare, and then anastomosis are performed. Arterial blood drawn by the anesthetist should be avoided during the anastomosis of the posterior wall. After the OM anastomosis, the position of the operating table is returned to zero and maintain the Trendelenburg position. Anastomosis to the inferior wall is performed in a similar manner.

#### **2.5 Proximal anastomosis**

Proximal anastomoses are performed after all distal anastomoses. The patient is placed in a slight reverse Trendelenburg position, systolic blood pressure is controlled by anesthesia with a target of 110 mm Hg, so that the proximal clamp is not dislodged during the proximal anastomosis. Displacement of the proximal clamp during the proximal anastomosis is dangerous and may cause massive exsanguination, and may also cause aortic dissection. After achieving an adequate blood pressure, a side-biting clamp is gently applied to the ascending aorta. An aortotomy is made and proximal anastomosis is completed in the standard manner. The side-biting clamp is removed and the grafts are de-aired. Proximal anastomosis of the graft may be performed before the distal anastomosis, especially if a proximal automatic anastomosis device is used. The automatic proximal anastomosis device is useful for the patient with severe calcification of the aorta.

#### **2.6 Doppler assessment to the grafts**

After completion of all anastomoses, the blood flow of the grafts should be accessed using an ultrasound flow probe. A poor graft flow mandates additional attention to the anastomosis and consider revision of the graft anastomosis (Kim et al., 2005). Protamine is administered after confirmation of the graft flow and then the chest is closed in the standard manner.

#### **2.7 Postoperative management**

Without using CPB, the fibrinolytic activity of the patient who undergo OPCAB is lower than those who undergo conventional CABG using CPB. After OPCAB surgery, patient may develop a hypercoagulable state. To avoid platelet aggregation at the anastomosis site, clopidogrel is started as early as postoperative day 0 (Quigley et al, 2003). Other postoperative managements are similar to those after on-pump CABG.

Current Trend of Off-Pump Coronary Artery Bypass Grafting 53

In general, those who are considered to be contraindicated for on-pump CABG, such as patients with calcified aorta, advanced age, and significant comorbidities, can be a candidate for OPCAB. OPCAB does not require CPB and theoretically eliminates all CBP-related complications. OPCAB can reduce blood loss and the need of transfusion. OPCAB has known to provide less myocardial enzyme release, fewer incidence of neurocognitive dysfunction and postoperative renal injury than conventional CABG. Studies found OPCAB can make patient

Studies have shown that postoperative mortality is favorable to OPCAB (Puskas et al., 2003, Cleveland et al., 2001, Puskas et al., 2008). Mortality benefit from OPCAB is more obvious in high risk patients. (Hirose et al., 2010). The reasons are multifactorial as discussed below;

Postoperative strokes are the most disabling complication after CABG. Avoidance of aortic cannulation and aortic cross clamping decreases the risk of stroke and distal emboli. The incidence of postoperative stroke is favorable to OPCAB compared to on-pump CABG; however stroke has not been completely eliminated by OPCAB (Puskas et al., 2003, Cleveland et al., 2001, Sabik at al., 2002). The use of side-biting clamp for proximal anastomosis is potentially the cause of postoperative stroke. Calafiore reported that the stoke rate without using side-biting clamp was 0.2%, which was significantly lower than the stroke rate with side-biting clamp (1.2%) (Calafiore et al., 2002). All in-situ grafting using bilateral mammary arteries, gastroepiploic arteries and Y-composite grafting eliminates proximal aortic anastomoses. Using this aorta-non-touch surgery, theoretically no intraoperative stroke would occur and the postoperative risk of stroke should be minimal (Hirose et al., 2004). An investigation demonstrated that OPCAB significantly reduced the incidence of intraoperative stroke; however, the incidence of delayed strokes occurring more than 48 hours after OPCAB was similar to that after on-pump CABG (Nishiyama et al., 2009). These delayed strokes are not to be related to aortic manipulation during surgery, but

could be related to a hypercoagulable state and/or postoperative atrial fibrillation.

Neurocongnitive disorder after CPB is a well known phenomenon, so called "pump head." Prolonged CPB time is a risk factor for postoperative neurocongnitive disorder, most likely related to non-pulsatile flow, hypothermia, low perfusion pressure, systemic inflammatory

recovery time shorter as well. Table 1 summarizes the best candidates for OPCAB.

**3. Advantages of OPCAB** 

Calcified aorta Advanced age

Jehovah's Witness

**3.1 Mortalities** 

**3.2 Stroke** 

Significant comorbidities Recent stroke

> Severe carotid disease Renal dysfunction

**3.3 Neurocongnitive dysfunction** 

Severer chronic lung disease

Table 1. The patients that benefit most from CABG

however, the benefit most likely related to the avoidance of CPB.

Fig. 3. Examples of anterior (top), posterolateral (middle), and inferior (bottom) revascularization.
