**1. Introduction**

Cardiac surgeons and/or cardiac anaesthesiologists after cardiac operations prevalently use the ECMO in its VA-ECMO configuration for cardio-circulatory failure [1, 2]. Recently, ECMO in its veno-venous configuration is becoming widely used in ICU by intensivists to treat severe form of respiratory failure (ARDS) [3, 4] after the recent successes obtained with the use of ECMO in the A(H1N1) influenza epidemic [5, 6], linked to the results of CESAR Trial [7].

At the same time, the practice of echocardiographic investigation in intensive care units by the intensivists combined the echocardiographic method to haemodynamic monitoring, favouring the use of echocardiography for the assessment of haemodynamic and respiratory instability [8].

The patient who needs extracorporeal support is thus evaluated by the echocardiographer who establishes the timing of the support, the need for support, and the


#### **Table 1.**

*Main indications for the use of ECMO assistance.*

contraindications to the support and follows the phases of cannulation and functioning of the extracorporeal support [9].

ECMO is a rescue therapy used to provide cardiac and/or respiratory support for critically ill patients in whom maximal conventional medical management failed [3, 4]. VV-ECMO provides adequate oxygenation and removal of carbon dioxide in isolated refractory respiratory failure, while VA-ECMO is used when support for cardiac and /or respiratory failure is needed [1] (**Table 1**).

#### **1.1 General role of echocardiography**

Echocardiography (ECHO) plays a pivotal role in the management of critical patients, particularly those supported with ECMO [9–11]. ECHO can be used to not only evaluate function and diagnose diseases requiring ECMO but also to detect all cardiac complications or vascular diseases that may arise following ECMO [12, 13].

The central role of ECHO is important to identifying various diseases such as cardiac /undiagnosed valve lesions and left ventricular (LV) dysfunction, which could be the cause of severe haemodynamic instability, as well as to exclude them to avoid ECMO support [11].

The detection of aortic dissection represents an absolute contraindication in VA-ECMO, whereas a moderate to severe aortic valve regurgitation (AVR) is a relative contraindication in VA-ECMO, because the LV afterload increase, determining by ECMO itself, leads a worsening in AVR. ECHO provides information on aortic atherosclerosis and then guides the intensivist to decide the suitable cannulation sites (central versus peripheral) or the technique (surgical versus percutaneous) [13]. ECHO also helps to evaluate the right heart morphology for any structural abnormality, which could prevent the positioning of venous cannula for VV-ECMO or VA-ECMO [14].

In addition, as stated above, ECHO has a key role during ECMO cannulation. First, it guides the correct placement of the ECMO cannulae [15]. TTE may not be able to guide ECMO cannulation because of limited spatial resolution, and therefore transoesophageal echocardiography (TOE) represents the examination of choice to guiding the insertion. Echocardiographer and intensivist have to work together in order to correct the final position of the cannulae [15]. In VV-ECMO the position of the tips of the venous cannulae is essential for the correct functioning of the ECMO. Indeed, the drainage cannula must be positioned just before the entrance of the inferior vena cava (IVC) in the right atrium (RA), while the tip of the return cannula must be positioned in the central part of the RA just before the tricuspid valve but far away from the inter-atrial septum [16].

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*Echocardiography Evaluation in ECMO Patients DOI: http://dx.doi.org/10.5772/intechopen.85047*

*1.1.1 Ultrasonography for ECMO cannulation*

especially the need for surgical placement [20, 21].

as having to provide with dedicated shunts.

*1.1.2 Cannula position/complications*

However, the echocardiographic evaluation is also essential for the identification and management of specific complications that may arise during ECMO support and may determine its malfunction. For the problems related to TTE resolution, also involving to the patient's respiratory pathology, the TOE is preferred to make it clear any possible complication [17]. ECHO allows a rapid evaluation not only of the positioning of the cannula but mainly of the cardiac filling, of the cardiac function, and of the cardiac tamponade [16, 17]. Detection of cardiac tamponade and evaluation of the significance of pericardial effusion or collection may be difficult in patients supported with ECMO because the heart is in a partially bypassed state. In conclusion, ECHO is mandatory during the start of ECMO, cannulae insertion, haemodynamic monitoring, and detection of complications during weaning [16–18].

In many cases, cannulation can be performed without ultrasound guidance. However, the use of ultrasound can help to reduce the rate of complications associated with cannulation such as haematoma, retroperitoneal haematoma, vascular damage, cardiac tamponade, and ischemia of the lower leg [19]. In the paediatric patient, the eco-guided cannulation has been shown to reduce complications,

The ultrasound evaluation of the diameter of the vessels to be cannulated, especially the femoral artery, allows to choose the right size of the cannula, avoiding vascular occlusions distal to the cannulation point, with consequent ischemia, for example, of the lower limb [15, 19]. Cannulation can be carried out echo-guided or echo-assisted, i.e. only by identifying the insertion point. Today the ultrasound shows a greater sensitivity and specificity compared to radiography in identifying the exact point of arrival of the cannulae. The exact position of the femoral arterial cannula allows to optimise the flow, as well as the exact position of the venous cannula in IVC, above the hepatic vein, and contributes to an excellent drainage, clearly optimising hepatic drainage [22] (**Figure 1**). The echocardiography, after the positioning of the cannulae, must be performed to highlight early cardiac tamponade and problems of acute dilatation of the ventricles [14, 16, 23]. The use of colour Doppler also highlights problems of distal perfusion in the lower limb, such

Before dilating vein for venous cannulation, it is necessary to make sure that guide wires, percutaneously inserted, are positioned inside the heart or large vessels. Only after ultrasound confirmation, physicians can proceed to advance the cannulae on these wires. However, it is necessary to discriminate the real images from the echocardiographic artefacts generated by these wires and cannulae, before proceeding to the final position of the cannulae. In the peripheral configurations of ECMO, especially in the VA-ECMO, we must assist with ultrasound the placement of the venous cannula in the middle of the right atrium in order to obtain an optimal drainage [13, 14] (**Figure 2**). With TOE, the bi-caval projection is able to orient perfectly on the optimal position of the venous cannula (**Figure 3**). Although the ultrasounds cannot indicate the level of the arterial cannula tip, which reaches the iliac artery from the femoral artery, they can confirm that the guide wire used in percutaneous arterial cannulation is located in the lumen of the aorta, before the femoral artery

dilatation, reducing the risk of extra-arterial placement of the cannula.

Therefore, summing up, it is essential to visualise in real time the positioning of the guide wires in the caval districts (IVC and SVC) with the middle oesophageal

#### *Echocardiography Evaluation in ECMO Patients DOI: http://dx.doi.org/10.5772/intechopen.85047*

*Advances in Extracorporeal Membrane Oxygenation - Volume 3*

tioning of the extracorporeal support [9].

*Main indications for the use of ECMO assistance.*

**Table 1.**

**1.1 General role of echocardiography**

avoid ECMO support [11].

cardiac and /or respiratory failure is needed [1] (**Table 1**).

valve but far away from the inter-atrial septum [16].

contraindications to the support and follows the phases of cannulation and func-

ECMO is a rescue therapy used to provide cardiac and/or respiratory support for critically ill patients in whom maximal conventional medical management failed [3, 4]. VV-ECMO provides adequate oxygenation and removal of carbon dioxide in isolated refractory respiratory failure, while VA-ECMO is used when support for

Echocardiography (ECHO) plays a pivotal role in the management of critical patients, particularly those supported with ECMO [9–11]. ECHO can be used to not only evaluate function and diagnose diseases requiring ECMO but also to detect all cardiac complications or vascular diseases that may arise following ECMO [12, 13]. The central role of ECHO is important to identifying various diseases such as cardiac /undiagnosed valve lesions and left ventricular (LV) dysfunction, which could be the cause of severe haemodynamic instability, as well as to exclude them to

The detection of aortic dissection represents an absolute contraindication in VA-ECMO, whereas a moderate to severe aortic valve regurgitation (AVR) is a relative contraindication in VA-ECMO, because the LV afterload increase, determining by ECMO itself, leads a worsening in AVR. ECHO provides information on aortic atherosclerosis and then guides the intensivist to decide the suitable cannulation sites (central versus peripheral) or the technique (surgical versus percutaneous) [13]. ECHO also helps to evaluate the right heart morphology for any structural abnormality, which could prevent the positioning of venous cannula for VV-ECMO or VA-ECMO [14]. In addition, as stated above, ECHO has a key role during ECMO cannulation. First, it guides the correct placement of the ECMO cannulae [15]. TTE may not be able to guide ECMO cannulation because of limited spatial resolution, and therefore transoesophageal echocardiography (TOE) represents the examination of choice to guiding the insertion. Echocardiographer and intensivist have to work together in order to correct the final position of the cannulae [15]. In VV-ECMO the position of the tips of the venous cannulae is essential for the correct functioning of the ECMO. Indeed, the drainage cannula must be positioned just before the entrance of the inferior vena cava (IVC) in the right atrium (RA), while the tip of the return cannula must be positioned in the central part of the RA just before the tricuspid

**72**

However, the echocardiographic evaluation is also essential for the identification and management of specific complications that may arise during ECMO support and may determine its malfunction. For the problems related to TTE resolution, also involving to the patient's respiratory pathology, the TOE is preferred to make it clear any possible complication [17]. ECHO allows a rapid evaluation not only of the positioning of the cannula but mainly of the cardiac filling, of the cardiac function, and of the cardiac tamponade [16, 17]. Detection of cardiac tamponade and evaluation of the significance of pericardial effusion or collection may be difficult in patients supported with ECMO because the heart is in a partially bypassed state.

In conclusion, ECHO is mandatory during the start of ECMO, cannulae insertion, haemodynamic monitoring, and detection of complications during weaning [16–18].

#### *1.1.1 Ultrasonography for ECMO cannulation*

In many cases, cannulation can be performed without ultrasound guidance. However, the use of ultrasound can help to reduce the rate of complications associated with cannulation such as haematoma, retroperitoneal haematoma, vascular damage, cardiac tamponade, and ischemia of the lower leg [19]. In the paediatric patient, the eco-guided cannulation has been shown to reduce complications, especially the need for surgical placement [20, 21].

The ultrasound evaluation of the diameter of the vessels to be cannulated, especially the femoral artery, allows to choose the right size of the cannula, avoiding vascular occlusions distal to the cannulation point, with consequent ischemia, for example, of the lower limb [15, 19]. Cannulation can be carried out echo-guided or echo-assisted, i.e. only by identifying the insertion point. Today the ultrasound shows a greater sensitivity and specificity compared to radiography in identifying the exact point of arrival of the cannulae. The exact position of the femoral arterial cannula allows to optimise the flow, as well as the exact position of the venous cannula in IVC, above the hepatic vein, and contributes to an excellent drainage, clearly optimising hepatic drainage [22] (**Figure 1**). The echocardiography, after the positioning of the cannulae, must be performed to highlight early cardiac tamponade and problems of acute dilatation of the ventricles [14, 16, 23]. The use of colour Doppler also highlights problems of distal perfusion in the lower limb, such as having to provide with dedicated shunts.

Before dilating vein for venous cannulation, it is necessary to make sure that guide wires, percutaneously inserted, are positioned inside the heart or large vessels. Only after ultrasound confirmation, physicians can proceed to advance the cannulae on these wires. However, it is necessary to discriminate the real images from the echocardiographic artefacts generated by these wires and cannulae, before proceeding to the final position of the cannulae. In the peripheral configurations of ECMO, especially in the VA-ECMO, we must assist with ultrasound the placement of the venous cannula in the middle of the right atrium in order to obtain an optimal drainage [13, 14] (**Figure 2**). With TOE, the bi-caval projection is able to orient perfectly on the optimal position of the venous cannula (**Figure 3**). Although the ultrasounds cannot indicate the level of the arterial cannula tip, which reaches the iliac artery from the femoral artery, they can confirm that the guide wire used in percutaneous arterial cannulation is located in the lumen of the aorta, before the femoral artery dilatation, reducing the risk of extra-arterial placement of the cannula.

#### *1.1.2 Cannula position/complications*

Therefore, summing up, it is essential to visualise in real time the positioning of the guide wires in the caval districts (IVC and SVC) with the middle oesophageal

#### **Figure 1.**

*Cannulation scheme in VV-ECMO. The red arrows indicate the reinfusion of oxygenated blood, the purple arrow indicates the recirculating blood, and the light blue arrows indicate the drainage of the venous blood. SVC, superior vena cava; IVC, inferior vena cava; TV, tricuspid valve; RA, right atrium.*

*Bi-caval view of the TOE: the drainage cannula from the IVC is visible in the middle atrium (arrow light blue).*

bi-caval projection to the TOE [11] (**Figures 2–4**). This is to avoid incorrect positioning of the cannula in the right ventricle, in the coronary sinus, or, worse, in the left atrium through a patent foramen ovale (PFO) [11, 13, 16]. During the entire positioning manoeuvres of the venous cannulae, particular attention must be paid to the presence of pericardial effusion, from atrial/right ventricular trauma, and to

**75**

**Figure 3.**

**Figure 4.**

*Echocardiography Evaluation in ECMO Patients DOI: http://dx.doi.org/10.5772/intechopen.85047*

the possible suction of the inter-atrial septum, with the obstruction of the drainage flow, linked to the venous aspiration from an adherent cannula to the septum itself [24, 25]. In the case of loss of oxygen performance of the ECMO, when a recirculation phenomenon is suspected due to a close position of the tips of the drainage and reinfusion cannulae, TOE can guide the correct repositioning of the cannulae [26].

*(A) Drainage cannula in IVC (light blue arrow) and (B) colour Doppler showing the flow in the cannula.*

*Bi-caval view to the 3D TOE: the drainage cannula from the IVC can be seen in the middle atrium (arrow light blue).*

Compared to the classic configuration of the VV-ECMO which provides a double cannulation, the development of newer devices, such as the Dual Lumen Bi-Caval catheter (Avalon®, *Maquet Cardiopulmonary GmbH Kehler Str. 31, 76,437 Rastatt, Germany*), allowed VV-ECMO with a single cannula inserted in the right internal jugular vein [27]. This allows greater patient mobility, also reducing the femoral cannula decubitus and the infectious risk that this entails. However, being a stiffer and larger diameter cannula, the placement of the bi-luminal cannula involves greater risks of vessel injury and cardiac tamponade, in addition to the possible malfunction due to migration of the cannula from its original position [28, 29]. It is essential to

*1.1.3 Special cannulation (Avalon® cannula)*

*Echocardiography Evaluation in ECMO Patients DOI: http://dx.doi.org/10.5772/intechopen.85047*

#### **Figure 3.**

*Advances in Extracorporeal Membrane Oxygenation - Volume 3*

bi-caval projection to the TOE [11] (**Figures 2–4**). This is to avoid incorrect positioning of the cannula in the right ventricle, in the coronary sinus, or, worse, in the left atrium through a patent foramen ovale (PFO) [11, 13, 16]. During the entire positioning manoeuvres of the venous cannulae, particular attention must be paid to the presence of pericardial effusion, from atrial/right ventricular trauma, and to

*Bi-caval view of the TOE: the drainage cannula from the IVC is visible in the middle atrium (arrow light blue).*

*Cannulation scheme in VV-ECMO. The red arrows indicate the reinfusion of oxygenated blood, the purple arrow indicates the recirculating blood, and the light blue arrows indicate the drainage of the venous blood. SVC, superior* 

*vena cava; IVC, inferior vena cava; TV, tricuspid valve; RA, right atrium.*

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**Figure 2.**

**Figure 1.**

*Bi-caval view to the 3D TOE: the drainage cannula from the IVC can be seen in the middle atrium (arrow light blue).*

#### **Figure 4.**

*(A) Drainage cannula in IVC (light blue arrow) and (B) colour Doppler showing the flow in the cannula.*

the possible suction of the inter-atrial septum, with the obstruction of the drainage flow, linked to the venous aspiration from an adherent cannula to the septum itself [24, 25]. In the case of loss of oxygen performance of the ECMO, when a recirculation phenomenon is suspected due to a close position of the tips of the drainage and reinfusion cannulae, TOE can guide the correct repositioning of the cannulae [26].
