**3. Advantages of OPCAB**

52 Front Lines of Thoracic Surgery

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

revascularization.

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


Table 1. The patients that benefit most from CABG

### **3.1 Mortalities**

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

#### **3.2 Stroke**

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.

#### **3.3 Neurocongnitive dysfunction**

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

Current Trend of Off-Pump Coronary Artery Bypass Grafting 55

Atrial fibrillation is the most common arrhythmia after cardiac surgery and occurs in 25-40 % of patients. The incidence of atrial fibrillation after OPCAB is known to be less than that for on-pump CABG (Ascione et al., 2000, Raga et al., 2004). Avoiding atrial cannulation and preserving the anterior epiaortic fat pad may contribute to lowering the incidence of

Due to the benefits listed above, OPCAB provides overall decreased postoperative complications and mortality (Puskas et al., 2008, Reston et al., 2003, Legare et al., 2004). Postoperative hospitalization is shorter in OPCAB patients than that in on-pump CABG (Puskas et al., 2003, Cleveland et al., 2001, Van Dijk et al., 2001). Earlier patient recovery in OPCAB could be related to reduced inflammatory reaction compared to that after on-pump CABG. The benefits of early recovery following OPCAB are more strongly apparent in high-

The cost effectiveness of OPCAB can be explained by the reduced utilization of the blood products, shorter intubation time, shorter ICU stay, shorter hospitalization, and reduced postoperative complications, as described above (Scott et al., 2009, Puskas et al., 2004).

In general, the disadvantage of OPCAB is associated with surgical technique. Despite advances in surgical instruments, exposure of the posterior wall could be potentially difficult, especially in a patient with poor ventricular function or when the surgeon has not had adequate training in OPCAB. Inadequate exposure of the target results in fewer number of distal anastomoses and incomplete revascularization. Table 2 summaries poor candidates

Postoperative cardiac enzyme release is lower after OPCAB than after on-pump CABG. (Van Dijk et al., 2001) However, in a patient in cardiogenic shock with a failing heart, placement on the CPB is unavoidable to prevent further end organ damage, and the role of OPCAB is limited because of hemodynamic instability. If the patient is experiencing global ischemia, pump failure and unstable hemodynamics, OPCAB should not be performed.

**3.8 Atrial fibrillation** 

**3.9 Patient recovery** 

**3.10 Cost** 

for OPCAB.

Cardiogenic shock

Poor coronary target

Young healthy patient

**4.1 Myocardial protection** 

Redo surgery

postoperative atrial fibrillation (Cummings et al., 2004).

risk patients (Stamou et al., 2005, Puskas et al., 2009).

**4. Potential problems and disadvantages of OPCAB** 

Unable to maintain hemodynamics during anastomosis ST changes or ventricular tachycardia during anastomosis

Poor ventricular function, ischemic mitral regurgitation

Table 2. The patients that the benefit least from OPCAB

Small, intramyocardial, and/or calcified coronary artery

state, and most importantly micro-emboli from CPB. Studies of s100 protein, a marker of neurological damage, have shown lowers s100 protein after OPCAB compared to those after on-pump CABG; however, the incidence of clinical neurocongnitive manifestation was similar between OPCAB and on-pump CABG (Lloyd et al., 2000). The benefit of OPCAB in relation to neurocongnitive disorder remains controversial (Van Dijk et al., 2002, Browne et al., 1999, Marasco et al., 2008).

#### **3.4 Inflammatory reaction**

Contact between the blood and the CPB circuit triggers an inflammatory cascade. Cytokines, complements and coagulation-fibrinolytic system are activated by CPB, which inducing CPB-related inflammatory responses (Ngaage, 2003). This inflammatory response contributes to the increase in capillary permeability, fluid shift, and decrease in tissue perfusion. Systemic inflammatory response syndrome may cause multi-organ failure, including lung, brain, kidney and heart, which may promote patient mortality. Significant decrease in inflammatory markers has been observed in OPCAB compared to that in onpump CABG (Ascione et al., 2000). Avoidance of CBP reduces the inflammatory state and contributes to early patient recovery (Raga, 2004). CPB-related inflammatory response could cause pulmonary edema resulting in hypoxia, brain edema resulting in neurocognitive disorder, renal hypoperfusion resulting in acute renal failure, and edema of the heart resulting in low cardiac output syndrome.

## **3.5 Blood transfusion**

Perioperative anaemia among the patient undergoing CABG is common. Hemodilution may occur from the circuit and tubing of the CPB. The use of CPB activate fibrinolytic activity and reduce the actual number of platelet and function of the platelet, which aggregates perioperative blood loss anaemia (Khuri et al., 1992). Studies have shown that OPCAB has clear benefits in blood preservation. Postoperative blood loss and transfusion requirements are smaller in OPCAB than in on-pump CABG in almost all studies (Muneretto et al., 2003). Avoiding the need for transfusion is critical in caring for Jehovah's Witness patients.

#### **3.6 Renal function**

Hypoperfusion of the kidney during CABG may cause postoperative renal dysfunction. Risk factors for renal dysfunction are often observed in patients who undergo CABG, such as patients with diabetes, hypertension and peripheral vascular disease. Non-pulsatile flow and low perfusion pressure due to CPB contribute to hypoperfusion of the kidney, causing postoperative kidney injury (Laffey et al., 2002). The duration of CPB has been known to be directly related to the incidence of postoperative renal failure. The postoperative rise in creatinine after OPCAB is less frequently observed than that after on-pump CABG (Celik et al., 2005). A lower incidence of postoperative renal failure is observed after OPCAB (Calafiore et al., 2003). This renal protection with OPCAB would be most beneficial for patients showing moderate or severe preoperative renal dysfunction (Hirose et al., 2001).

#### **3.7 Respiratory function**

A randomized trial showed that OPCAB provides lower pulmonary compliance, better gas exchange after surgery than on-pump CABG (Staton et al., 2005). Clinically, intubation time after surgery as shorter after OPCAB than after on-pump CABG (Puskas et al., 2008).
