*1.1.3 Special cannulation (Avalon® cannula)*

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

use the TOE for the correct positioning of the Avalon® catheter. In fact, the tip of the cannula is advanced under the TOE guide until the cannula drainage holes are positioned in the inferior and in the superior venae cave (like a normal two-stage cannula used for cardiopulmonary bypass), and the re-entry is perfectly aligned with the inflow of the tricuspid valve [27]. This alignment is investigated with the colour Doppler which will measure the linear flow in case of correct positioning or a turbulent flow, in case of malposition. It is best to advance and withdraw the cannula under the TOE guide until the flow is laminar and directed through the centre of the tricuspid valve. Particular attention should be paid to visualising the cannula tip in the hepatic vein. A malposition of the cannula will cause recirculation, because the oxygenated blood from the cannula is drained immediately from the suction areas of the cannula to the ECMO circuit before being circulated systematically [28, 30].

#### **1.2 Veno-venous ECMO**

In the treatment of severe respiratory failure (severe ARDS), VV-ECMO is a valid option [31]. It can be considered a bridge to the healing of the lung, allowing the therapies to act effectively. Moreover, unlike the VA-ECMO it does not present problems of oxygenation north-south (harlequin syndrome). All this is valid if cardiac function is maintained normal and able to effectively support the systemic circulation. Therefore, before a VV-ECMO is established, a complete evaluation of both the patient's echocardiographic and haemodynamic parameters is essential [11, 16]. Echocardiography, both TTE and TOE, must ensure a correct evaluation of the right ventricular function and evaluate the degree of tricuspid insufficiency and the estimate of pulmonary artery pressure, potentially altered parameters in the course of ARDS, and sepsis [32].

VV-ECMO could improve the performance of the right ventricle and the whole heart. There is an irrelevant modification of the right preload, an increase in the left load due to a reduction in pulmonary pressure with a further increase in SvO2, and the saturation of the coronary blood. Approximately 20–25% of patients with ARDS develop an acute cor pulmonale (ACP) with right ventricular dilatation, inter-ventricular septum shift, left ventricular hypo-diastolic status, and pulmonary hypertension [32, 33]. This clinical picture is also typical of the right ventricular failure induced by the septic state. Echocardiography helps to choose the right timing for extracorporeal support and allows to follow the evolutionary state (improvement) of the right performance following VV-ECMO support: reduction of pulmonary pressure, increase in right contractility (increased systolic excursion of the tricuspid annular plane (TAPSE)), and improvement of the cardiac output (CO) [11, 16, 34].

TTE echocardiographic evaluation in patients with ARDS may present some resolution problems; therefore, normally the TOE is used, also because of low invasiveness as the patients are already intubated and sedated.

The presence of pulmonary hypertension and sepsis can create the conditions for a rapid deterioration of cardiac function, so that can worsen from initial presence of respiratory failure to cardiorespiratory insufficiency. Through echocardiographic and haemodynamic monitoring, we can anticipate the worsening of the clinical picture and establish a cardiorespiratory support (VA-ECMO).

#### *1.2.1 Echo in VV-ECMO*

The right ventricle echocardiographic assessment in the ECMO patients with acute respiratory distress syndrome (ARDS) plays a key role to reduce complications and to improve the outcome [11, 14, 16, 31].

It is simple to understand the role of ECHO in the risk stratification of patients undergoing VV-ECMO. In fact, ARDS requires an initial aggressive ventilatory

**77**

in pre-ECMO stage.

**1.3 VA-ECMO**

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

hemodynamic improvement.

be straightforward, and TOE is preferred.

still poorly described in the literature.

treatment that brings to haemodynamic instability [33]. Patient presents high CVP associated to fluid accumulation in the pleural and abdominal spaces. ECHO shows a dilatation of the right ventricle with associated pulmonary hypertension. This clinical picture is described as ACP [8, 32, 33]. To minimise the impact of the positive end-expiratory pressure (PEEP) on right ventricular haemodynamic,

physicians have choice a right balance between the PEEP value and cardio-

The daily evaluation of echocardiography in this case is mandatory.

solution to support both the lung and the right ventricle [35, 36].

circulatory stability. The therapeutic request is the protective ventilation aimed at reducing right ventricular failure related to an increase in the afterload of the right chambers [8, 33]. The aim of the treatment is the reduction of pulmonary arterial hypertension to reduce enlargement of right ventricle and consequent shift of the inter-ventricular septum. Unfortunately, despite implementation of protective lung ventilation, ACP still remains until 25% [32, 33, 34]. VV-ECMO represents a real

The improvement of gas exchange and the reduction of airway pressures both contribute at the reduction of pulmonary vascular resistance with consequent

Because the high acoustic impedance is caused by high PEEP values, TTE cannot

A recently published summary paper on the management of ECMO recommends that physician training in echocardiography be part in the ECMO patient care team [37]. However, the role of echocardiography in ECMO is not widely accepted and is

The echocardiographic examination of the right ventricle requires a long axis and a short axis view to evaluate the size of the cavity with the relationship of the left ventricle and the kinetics of the septum. The examination can be completed by the Doppler of the right ventricular outflow and tricuspid regurgitation when present, to measure the systolic pressure of the pulmonary artery. The measurement of the TAPSE, simple and useful from prognostic point of view, avoids measuring the fractional area change (FAC) of the right ventricle more complicated. Right ventricle TDI (tissue Doppler imaging) is useful to evaluate diastolic and systolic functions [38]. Moderate to severe right ventricular dilatations, defined as a ratio greater than 0.6 and as a ratio greater than or equal to 1, are associated with paradoxical septum motion at the end systole complicating the left ventricular function [8, 39, 40]. Pulmonary hypertension is usually associated with tricuspid regurgitation, but it also depends on right ventricular systolic function, and its value can be very low when associated with low CO [38, 39]. The right ventricular remodelling in ARDS patients is represented by the thickness of free wall, related to the increase in afterload [40]. Most important is also the detection of a PFO that can complicate the oxygenation of ARDS patients [39] (**Figures 5** and **6**). The displacement of septum due to right ventricular dilatation causes the left ventricular hypo-diastolic status, with a consequent low CO syndrome related to the difficult preload of the left ventricle. This is considered an ECHO evaluation of right ventricular function

The purpose of the VA-ECMO is to support cardio-circulatory function in patients with heart failure refractory to medical therapy [1, 36]. Based on the INTERMACS class it belongs to, VA-ECMO can be used in major risk classes, not only as bridge to recovery or bridge to destination therapy (left ventricular assist device (LVAD) or heart transplantation (HTx)) but also as bridge to decision [41] (**Table 2**). In addition, the VA-ECMO can be used in haemodynamic support to

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

*Advances in Extracorporeal Membrane Oxygenation - Volume 3*

**1.2 Veno-venous ECMO**

use the TOE for the correct positioning of the Avalon® catheter. In fact, the tip of the cannula is advanced under the TOE guide until the cannula drainage holes are positioned in the inferior and in the superior venae cave (like a normal two-stage cannula used for cardiopulmonary bypass), and the re-entry is perfectly aligned with the inflow of the tricuspid valve [27]. This alignment is investigated with the colour Doppler which will measure the linear flow in case of correct positioning or a turbulent flow, in case of malposition. It is best to advance and withdraw the cannula under the TOE guide until the flow is laminar and directed through the centre of the tricuspid valve. Particular attention should be paid to visualising the cannula tip in the hepatic vein. A malposition of the cannula will cause recirculation, because the oxygenated blood from the cannula is drained immediately from the suction areas of the cannula to the ECMO circuit before being circulated systematically [28, 30].

In the treatment of severe respiratory failure (severe ARDS), VV-ECMO is a valid option [31]. It can be considered a bridge to the healing of the lung, allowing the therapies to act effectively. Moreover, unlike the VA-ECMO it does not present problems of oxygenation north-south (harlequin syndrome). All this is valid if cardiac function is maintained normal and able to effectively support the systemic circulation. Therefore, before a VV-ECMO is established, a complete evaluation of both the patient's echocardiographic and haemodynamic parameters is essential [11, 16]. Echocardiography, both TTE and TOE, must ensure a correct evaluation of the right ventricular function and evaluate the degree of tricuspid insufficiency and the estimate of pulmonary artery pressure, potentially altered parameters in the course of ARDS, and sepsis [32]. VV-ECMO could improve the performance of the right ventricle and the whole heart. There is an irrelevant modification of the right preload, an increase in the left load due to a reduction in pulmonary pressure with a further increase in SvO2, and the saturation of the coronary blood. Approximately 20–25% of patients with ARDS develop an acute cor pulmonale (ACP) with right ventricular dilatation, inter-ventricular septum shift, left ventricular hypo-diastolic status, and pulmonary hypertension [32, 33]. This clinical picture is also typical of the right ventricular failure induced by the septic state. Echocardiography helps to choose the right timing for extracorporeal support and allows to follow the evolutionary state (improvement) of the right performance following VV-ECMO support: reduction of pulmonary pressure, increase in right contractility (increased systolic excursion of the tricuspid annular plane (TAPSE)), and improvement of the cardiac output (CO) [11, 16, 34]. TTE echocardiographic evaluation in patients with ARDS may present some resolution problems; therefore, normally the TOE is used, also because of low

invasiveness as the patients are already intubated and sedated.

tions and to improve the outcome [11, 14, 16, 31].

clinical picture and establish a cardiorespiratory support (VA-ECMO).

The presence of pulmonary hypertension and sepsis can create the conditions for a rapid deterioration of cardiac function, so that can worsen from initial presence of respiratory failure to cardiorespiratory insufficiency. Through echocardiographic and haemodynamic monitoring, we can anticipate the worsening of the

The right ventricle echocardiographic assessment in the ECMO patients with acute respiratory distress syndrome (ARDS) plays a key role to reduce complica-

It is simple to understand the role of ECHO in the risk stratification of patients undergoing VV-ECMO. In fact, ARDS requires an initial aggressive ventilatory

**76**

*1.2.1 Echo in VV-ECMO*

treatment that brings to haemodynamic instability [33]. Patient presents high CVP associated to fluid accumulation in the pleural and abdominal spaces. ECHO shows a dilatation of the right ventricle with associated pulmonary hypertension. This clinical picture is described as ACP [8, 32, 33]. To minimise the impact of the positive end-expiratory pressure (PEEP) on right ventricular haemodynamic, physicians have choice a right balance between the PEEP value and cardiocirculatory stability. The therapeutic request is the protective ventilation aimed at reducing right ventricular failure related to an increase in the afterload of the right chambers [8, 33]. The aim of the treatment is the reduction of pulmonary arterial hypertension to reduce enlargement of right ventricle and consequent shift of the inter-ventricular septum. Unfortunately, despite implementation of protective lung ventilation, ACP still remains until 25% [32, 33, 34]. VV-ECMO represents a real solution to support both the lung and the right ventricle [35, 36].

The improvement of gas exchange and the reduction of airway pressures both contribute at the reduction of pulmonary vascular resistance with consequent hemodynamic improvement.

The daily evaluation of echocardiography in this case is mandatory.

Because the high acoustic impedance is caused by high PEEP values, TTE cannot be straightforward, and TOE is preferred.

A recently published summary paper on the management of ECMO recommends that physician training in echocardiography be part in the ECMO patient care team [37].

However, the role of echocardiography in ECMO is not widely accepted and is still poorly described in the literature.

The echocardiographic examination of the right ventricle requires a long axis and a short axis view to evaluate the size of the cavity with the relationship of the left ventricle and the kinetics of the septum. The examination can be completed by the Doppler of the right ventricular outflow and tricuspid regurgitation when present, to measure the systolic pressure of the pulmonary artery. The measurement of the TAPSE, simple and useful from prognostic point of view, avoids measuring the fractional area change (FAC) of the right ventricle more complicated. Right ventricle TDI (tissue Doppler imaging) is useful to evaluate diastolic and systolic functions [38].

Moderate to severe right ventricular dilatations, defined as a ratio greater than 0.6 and as a ratio greater than or equal to 1, are associated with paradoxical septum motion at the end systole complicating the left ventricular function [8, 39, 40].

Pulmonary hypertension is usually associated with tricuspid regurgitation, but it also depends on right ventricular systolic function, and its value can be very low when associated with low CO [38, 39]. The right ventricular remodelling in ARDS patients is represented by the thickness of free wall, related to the increase in afterload [40]. Most important is also the detection of a PFO that can complicate the oxygenation of ARDS patients [39] (**Figures 5** and **6**). The displacement of septum due to right ventricular dilatation causes the left ventricular hypo-diastolic status, with a consequent low CO syndrome related to the difficult preload of the left ventricle. This is considered an ECHO evaluation of right ventricular function in pre-ECMO stage.

#### **1.3 VA-ECMO**

The purpose of the VA-ECMO is to support cardio-circulatory function in patients with heart failure refractory to medical therapy [1, 36]. Based on the INTERMACS class it belongs to, VA-ECMO can be used in major risk classes, not only as bridge to recovery or bridge to destination therapy (left ventricular assist device (LVAD) or heart transplantation (HTx)) but also as bridge to decision [41] (**Table 2**). In addition, the VA-ECMO can be used in haemodynamic support to

**Figure 6.** *Colour Doppler bi-caval view in which you see the shunt through the PFO.*

refractory cardiac arrest that can result in patient recovery or be used as a procedure for donation of splanchnic organs in non-beating heart [42, 43].

Compared to other mechanical cardiac assistance devices, ECMO has the advantage. of reduced costs and the possibility of being set up easily and quickly on the outside.

of the operating room (intensive care unit, cardiac catheterization theatre, or emergency departments) and also during cardiopulmonary resuscitation manoeuvres [43]. However, it is an invasive assistance technique with major problems such as the short duration of assistance, the possible increase of infections, bleeding and thrombosis, and the increase of the afterload of the left ventricle.

The ultrasound evaluation is important before the implantation of the VA-ECMO. However, the conditions of the left ventricle, the degree of aortic

**79**

p < 0.001) [44, 45].

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

insufficiency, and the presence of mitral and tricuspid valve insufficiencies must be carefully evaluated. The configuration of the VA-ECMO involves peripheral cannulations, already partially described, and central cannulations (right atrium and aorta) that can be performed in the cardiac surgery patient

In patients with cardiogenic shock, echocardiographic examination is necessary to determine cause and indication for extracorporeal support [41] (**Table 1**). Even more, the echo exam can identify situations that may contraindicate the placement

The echo examination must be as complete as possible and must highlight the morphology and the systolic and diastolic functions of the ventricles, evaluate the valve continence and the presence of pericardial effusion, and seek, in greater detail, the cause of cardiogenic shock (i.e. regional or global dysfunction of the left ventricle) [39]. In the study of cardiac valvular function, the study of the aortic valve is fundamental since its regurgitation can create unfavourable conditions for the positioning of VA-ECMO, given the increase in the afterload that the VA-ECMO generates. Clearly aortic dissection is an absolute contraindication for VA-ECMO placement. In addition, the morphology and the structure of the right atrium and of the right heart in general must be carefully evaluated. In fact, the presence of leads (pacemaker or ICD), a prominent Chiari network, a PFO, a tricuspid valve prosthesis, they are all elements

The echocardiographic examination must fundamentally focus on the systolic function of the left ventricle. The systolic function is evaluated with conventional parameters such as the size of the left ventricle (LV), ejection fraction (EF), mitral regurgitation dP/dt, and aortic velocity time integral (VTI) [39]. The blood flow of ECMO can be adjusted based on the overall assessment of ventricular systolic function and cardiac preload. Some authors have systematically studied the effect of the flow rate of oxygenation of the extracorporeal membrane on changes in cardiac parameters [44]. A decrease of flow from 4 to 0.7 L/min leads to a 22% increase in the E/E′ ratio (from 5.9 to 7.2; p < 0.001), an increase of 17% in EF (from 15 to 17.5%; 0.001), increase of 12 and 45% of VTI (from 8 to 11.6 cm; p < 0.001), and increase of 12% of the left ventricular tele-diastolic volume (from 95 to 108 ml,

who has problems in weaning from the cardiopulmonary bypass.

*1.3.1 Indications to VA-ECMO support: cardiogenic shock*

that can compromise or make atrial cannulation impossible [11].

*1.3.2 Monitoring during ECMO performance*

of circulatory assistance.

**Table 2.**

*Possible uses of VA-ECMO.*

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


#### **Table 2.** *Possible uses of VA-ECMO.*

*Advances in Extracorporeal Membrane Oxygenation - Volume 3*

*Bi-caval view in which an aneurysm of the inter-atrial septum is seen.*

**78**

**Figure 6.**

**Figure 5.**

*Colour Doppler bi-caval view in which you see the shunt through the PFO.*

for donation of splanchnic organs in non-beating heart [42, 43].

thrombosis, and the increase of the afterload of the left ventricle.

refractory cardiac arrest that can result in patient recovery or be used as a procedure

The ultrasound evaluation is important before the implantation of the VA-ECMO. However, the conditions of the left ventricle, the degree of aortic

Compared to other mechanical cardiac assistance devices, ECMO has the advantage. of reduced costs and the possibility of being set up easily and quickly on the outside. of the operating room (intensive care unit, cardiac catheterization theatre, or emergency departments) and also during cardiopulmonary resuscitation manoeuvres [43]. However, it is an invasive assistance technique with major problems such as the short duration of assistance, the possible increase of infections, bleeding and insufficiency, and the presence of mitral and tricuspid valve insufficiencies must be carefully evaluated. The configuration of the VA-ECMO involves peripheral cannulations, already partially described, and central cannulations (right atrium and aorta) that can be performed in the cardiac surgery patient who has problems in weaning from the cardiopulmonary bypass.
