**3.1.3 Endothelial cells**

The vascular endothelium is actively involved during the pathologic processes of the SIRS by means of endothelial cells activation. During the SIRS the several endothelium control mechanisms of the vascular tone and permeability can modify. A large variety of agonist plays an important role in endothelial cells activation. Among them cytokines such as IL-1β, TNF-α, thrombin and complement C5 are the most important (Beghetti et al. 1998). In particular, IL-1β, TNF-α may induce the expression of P-Selectin and of E-Selectin by the endothelium. The P-Selectin is a glycoprotein that is stored in platelets and in the body of endothelial cells. P-Selectin participates in myocardial injury caused by myocardial ischemia-reperfusion mechanism (Robertson & Coopersmith 2006; Royston 1997). E-Selectin is minimally expressed on activated endothelium and for this reason this glycoprotein and its soluble form are considered a very strong marker of endothelial damage and activation (Asimakopoulous & Taylor 1998). Moreover E-Selectine is elevated in congestive heart failure (Chong et al. 2003). The activated endothelium induces also the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-2 (VCAM-2). These two molecules bind monocytes and neutrophils to the endothelium (Asimakopoulous & Taylor 1998).

#### **3.1.4 Platelets**

Platelets are directly involved during the SIRS and several potent platelet agonists activate them. Thrombin is probably the most important of platelet agonist. Other platelet agonist activators are epinephrine, vasopressin, platelet-activating factor (PAF), serotonin and thromboxane A2 (Downing & Edmunds. 1992). Activation of platelets during and after ECC leads to platelet aggregation and aggregates with monocytes and neutrophils.

#### **3.2 Other inflammation mediators**

#### **3.2.1 Cytokines**

Cytokines are small pro-inflammatory peptides produced and released by tissue and blood cells. Cytokines influence hemodynamic mechanism and regulation and negatively affect

Neutrophils are strongly activated during ECC. When activated, the neutrophils are recruited to inflammation site by inflammatory cytokines (IL-1β, TNF-α, IL-8), complement proteins and adhesion molecules (Royston 1997). The activated neutrophils can contribute to myocardial damage by infiltrating the myocardium and worsening the mechanism of ischemiareperfusion damage that initiates after aortic cross clamp removal (Paparella et al 2002). Moreover the neutrophils can infiltrate not only the myocardium but also the lungs and the brain (Lagan et al. 2008). Usually the neutrophils blood count and the total white blood cell count increase during ECC and over the first 48 hours after the operation (Fromes et al 2002)

Monocytes are activated during ECC and play a role in thrombin formation, but also they can produce a potent arsenal of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-8, MCP-1 and CD40 ligand), reactive oxygen substances and prostaglandin (Borregaard & Cowland 1997). Monocytes also release different types of enzymes (elastase, collagenases, lipooxygenase), interferons, growth factors, matrix proteins. Moreover, monocytes produce

The vascular endothelium is actively involved during the pathologic processes of the SIRS by means of endothelial cells activation. During the SIRS the several endothelium control mechanisms of the vascular tone and permeability can modify. A large variety of agonist plays an important role in endothelial cells activation. Among them cytokines such as IL-1β, TNF-α, thrombin and complement C5 are the most important (Beghetti et al. 1998). In particular, IL-1β, TNF-α may induce the expression of P-Selectin and of E-Selectin by the endothelium. The P-Selectin is a glycoprotein that is stored in platelets and in the body of endothelial cells. P-Selectin participates in myocardial injury caused by myocardial ischemia-reperfusion mechanism (Robertson & Coopersmith 2006; Royston 1997). E-Selectin is minimally expressed on activated endothelium and for this reason this glycoprotein and its soluble form are considered a very strong marker of endothelial damage and activation (Asimakopoulous & Taylor 1998). Moreover E-Selectine is elevated in congestive heart failure (Chong et al. 2003). The activated endothelium induces also the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-2 (VCAM-2). These two molecules bind

monocytes and neutrophils to the endothelium (Asimakopoulous & Taylor 1998).

leads to platelet aggregation and aggregates with monocytes and neutrophils.

Platelets are directly involved during the SIRS and several potent platelet agonists activate them. Thrombin is probably the most important of platelet agonist. Other platelet agonist activators are epinephrine, vasopressin, platelet-activating factor (PAF), serotonin and thromboxane A2 (Downing & Edmunds. 1992). Activation of platelets during and after ECC

Cytokines are small pro-inflammatory peptides produced and released by tissue and blood cells. Cytokines influence hemodynamic mechanism and regulation and negatively affect

**3.1 Activated blood cells** 

**3.1.1 Neutrophils** 

**3.1.2 Monocytes** 

nitric oxide (Paparella et al. 2002)

**3.1.3 Endothelial cells** 

**3.1.4 Platelets** 

**3.2.1 Cytokines** 

**3.2 Other inflammation mediators** 

renal function and lung function (Royston 1997). Cytokines are strongly involved in myocardial stunning process and in multiorgan failure syndrome (Larmann & Theilmeier 2004) Important cytokines involved in the SIRS are the interleukin 1β (IL-1β), the interleukin 6 (IL-6), the tumor necrosis factor α (TNF-α), soluble CD 40 ligand (sCD40L).

IL-1β is produced mainly by monocytes. This cytokine derives from IL-1 by the action of the IL-1β converting enzyme. An increase of IL-1β was found after ECC with a peak concentration after 24 hours (Fromes et al 2002).

IL-6 is produced and released by the monocytes and endothelial cells following a stimulus by the IL-1 and TNF-α The IL-6 has the peak concentration few hours after the end of ECC and gradual decrease within the following 24 hours (Beghi et al 2006; Whipperman et al 2005; Fromes et al 2002). The IL-6 concentration increase also after major noncardiac operation and the peak concentration occur after 6-24 hours the end of operation.

TNF-α is a cytokine produced by neutrophils and monocytes. This cytokine stimulates the surrounding stromal and parenchymal cells to produce more cytokines and chemokines. A significant increase of TNF-α was shown after removal of the cross-clamp and a peak concentration is reached after 24 hours the end of ECC. The TNF-α has an inotropic negative effect and the myocardium is a major source after ischemia reperfusion injury.

sCD40L is produced by activated platelets and upregulates the expression of inflammatory adhesion receptors including E-selectin, VCAM-1, tissue factor and matrix mettalloproteinases (Nannizzi-Alaimo et al 2002). Furthermore, sCD40L was described has a major mediator of vascular inflammation (Antoniades et al 2009a). Plasma levels of CD40L increase within 1 hour on ECC and increased further to almost 4 fold hours after 2 hours. (Nannizzi-Alaimo et al 2002). High preoperative level of CD40L were associated with an high risk of postoperative atrial fibrillation in patients underwent off-pump myocardial revascularization (Antoniades et al 2009b)

#### **3.2.2 Chemotactic proteins**

Chemotactic proteins play an important role in inflammatory response to ECC. Monocyte chemotactic protein 1 (MCP-1) is implicated in transendothelian monocyte recruitment to inflammatory site (Luster 1998). Various stimuli in the heart cause the production and releasing of MCP-1, leading to recruitment of monocytes that causes a stress response in the heart. There is strong evidence that MCP-1 plays a role in atherosclerosis, myocarditis, ischemia/reperfusion injury and transplant rejection.

#### **3.2.3 Mettalloproteinases**

Metalloproteinases are proteolityc enzymes that have a role in degradation of proteins and collagens of extracellular matrix and vascular basement membrane. MMP-8 and MMP-13 increase at the end of ECC and 30 minutes later (Joffs et al. 2001). MMP-9 increases after the removal of aortic cross-clamp and the reaches the peak concentration after 24 hours

#### **3.2.4 Oxidative stress**

Oxidative stress describes an increased bioactivity of reactive oxidant substances (ROS) that can participate to endothelial and myocardial damage. The ROS are produced and released by neutrophils, monocytes and macrophages when they are activated. The ROS are a potent arsenal of cytotoxic mediators of acute inflammation response (Babior 2000). There are four enzymes that generate a various amount of ROS. They are represented by nicotamide

Miniaturized Extracorporeal Circulation 141

reduced postoperative release of IL-6 and also a low incidence of postoperative atrial fibrillation and an early extubation time. Similar results were already reported by others (Wiesenack 2004). In some prospective randomized trials comparing MECC and OPCAB, some Authors did not find dramatic difference between the two techniques. In particular Mazzei et al. (Mazzei et al. 2007) comparing 150 MECC patients with 150 OPCAB patients, found that the mortality and morbidity had not significant difference and the release of IL-6 and S-100 protein were similar in both groups as wel as the length of stay and the use of blood product. In a recent prospective randomized study (Formica et al.2009) we wanted to study the inflammatory response and the myocardial damage in two groups of patients operated either with MECC or with OPCAB technique. We can demonstrate that the releases of cardiac TNF-α and IL-6 from coronary sinus were similar in both groups during the operative period and that the hemoglobin levels were higher in MECC GROUP than in OPCAB after 24 hours. Moreover the production of blood lactate from coronary sinus did not reach statistical difference in both groups. Other Authors (Reber et al. 2010) have observed in a retrospective study that MECC system can guarantee a more complete revascularization compared to OPCAB. In a recent publication (Puelher et al 2011), the outcome of 2243 patients underwent CABG operation with MECC were reported. They found a 30-mortality of 2.3%, and a very low incidence of blood transfusion, need for inotropic support, renal substitute therapy, release of myocardial necrosis enzymes and neurological dysfunction. The rate of conversion from the MECC was extremely low

Other Autrhors (Anastasiadis et al 2011a) have reported better neurocognitive outcome in MECC system compared to conventional ECC on the day of discharge and at 3 months.

The first application of MECC for aortic valve replacement (AVR) was reported by Remady et al (Remady et al. 2004). They applied the MECC system in 45 patients requiring isolated AVR or associated with CABG. The Authors reported a very low 30-day mortality and morbidity incidence rate and considered the MECC system a new cardiopulmonary concept safe and reliable in aortic valve surgery too. Since than few Authors reported the use of MECC for AVR. In a prospective randomized study Remady et al (Remady 2004) reported better clinical results with reduced myocardial damage, good preservation of renal function and better platelets count in MECC group compared than standard ECC group. In another prospective randomized study conducted on a total of 40 patients, Castiglioni et al (Castiglioni et al. 2007) reported better clinical data with lower hemodilution, lower intraoperative blood transfusion and lower postoperative bleeding in the MECC group compared to standard ECC. Furthermore they reported a lower release of troponine in

**4.2 Miniaturized extracorporeal circulation and aortic valve replacement** 

**4.3 Miniaturized extracorporeal circulation and other surgical applications** 

At the best of our knowledge no other surgical application of MECC are schematically reported in the literature. Some reports (Anastasiadis et al 2011b; Palombo et al. 2004) described the use of MECC in elective thoracoabdominal aortic surgery. They described only 7 cases without any complications. We used the MECC system in few case of CABG associated with mitral valve annuloplasty and in 5 cases of kidney cancer and inferior vena

MECC patients than standard ECC groups.

(0.4%).

adenine dinucleotide phosphate (NADPH), oxidase, superoxide dismutase and nitric oxide dismutase. When the aortic cross clamp is removed, myocardial ischemia is followed by reperfusion, which generates oxidative stress with production of reactive oxidants (O2 -, H2O2, NO and HOCl) by the action of the four enzymes.
