**2. Venoarterial extracorporeal membrane oxygenation function**

VA-ECMO support is a well-established technology that allows for full cardiopulmonary support with the goal to recover organ injury. Patients who may require this therapy include: refractory cardiogenic shock (CS), cardiac arrest (CA), refractory ventricular arrhythmia, acute or decompensated biventricular failure (AHF), pulmonary hypertension associated with right ventricular failure, fulminant myocarditis, and postcardiotomy cardiogenic shock (PCCS) [3].

The primary goal of VA-ECMO is restoration of tissue perfusion and avoidance of permanent end organ dysfunction. It has a unique hemodynamic effect due to its dual circulatory support circuit. The venous drainage cannula reduces flow through the lung vasculature, decreasing stress on the right heart while the arterial outflow cannula increases flow to the systemic arterial vasculature and the afterload to the left ventricle proportionate to the pump speed/flow. With incremental changes in speed and flow, the increased afterload reduces aortic valve opening and, in cases of severe left ventricular dysfunction, severe right ventricular dysfunction or asystole, the aortic valve may not open at all. The implications of the latter include increased LV end diastolic pressure and the development of pulmonary edema.

#### **3. Venoarterial extracorporeal membrane oxygenation outcomes**

VA-ECMO has been shown to increase survival to hospital discharge in patients with advanced heart disease with some cases having favorable long-term survival [4]. However, outcomes differ depending on the underlying etiology of cardiopulmonary collapse at the time of VA-ECMO cannulation. In a large national inpatient database from Japan with 5263 patients receiving ECMO, the in-hospital mortality was 37.9%, with 64.4% weaned off the device. Cardiac arrest at the time of hospital presentation was recognized as the primary factor for poor survival compared to cardiogenic shock alone. Moreover, higher age and smaller BMI were associated with in hospital mortality. The majority of patients presenting with cardiogenic shock had underlying ischemic heart disease, followed by heart failure, valvular heart disease and myocarditis. Notably, the preponderance of patients discharged from the hospital after weaning from ECMO were those with heart failure (31.1%) and myocarditis (41.9%) compared to those with ischemic heart disease (20.3%). In-hospital mortality after weaning however remained elevated with about half of the patients who were weaned dying in the hospital. This high mortality suggests non-modifiable risk factors with persistence of critical illness even after weaning VA-ECMO, as well as differences in survival depending on the underlying etiology of shock, with those having ischemic heart disease at the time of presentation experiencing a 79.1% in-hospital mortality [5].

In patients presenting with PCCS, VA-ECMO is a viable salvage strategy associated with increased survival to hospital discharge. In a meta-analysis of 21 studies with 1866 patients, survival to hospital discharge was achieved in 20.8–65.4% of patients placed on VA-ECMO [6]. Even more, PCCS patients undergoing VA-ECMO have an acceptable 5-year survival of 55.8% compared to other types of cardiogenic shock [7].

**157**

*ECMO Weaning Strategies to Optimize Outcomes DOI: http://dx.doi.org/10.5772/intechopen.85614*

TIMI flow grade ≤2 and profound cardiogenic shock.

selection to those who can be weaned from device support.

18% showing cardiac recovery [12, 13].

These findings drastically differ to those presenting with acute myocardial infarction associated CS (AMI-CS) where their survival to hospital discharge remains low (33–59%) [8]. This could potentially be mitigated by early intervention at the time of AMI-CS presentation and VA-ECMO support, specifically in those undergoing simultaneous revascularization. In a study of 334 patients with ST elevation AMI, the group that underwent early VA-ECMO support at the time of percutaneous intervention had a lower 30-day mortality compared to those without the support (30.1 vs. 41.7%) with a strong benefit in those with profound shock—defined as systolic blood pressure <75 mmHg despite intravenous inotropic agent administration and intra-aortic balloon pump (IABP) support associated with altered mental status and respiratory failure—compared to those without (72 vs. 39.1% for 30-day death) [9]. Among notable predictors for 30 days mortality were the presence of advanced heart failure (defined as NYHA ≥ III), post intervention

Lastly in those with AHF, outcomes on VA-ECMO are less promising depending on the original insult. For those with acute presentations, outcomes on VA-ECMO are more favorable compared to those with a chronic cardiomyopathy [10–12]. Specifically, those with fulminant myocarditis and CS or CA survival to discharge ranged from 60 to 88% [10], compared to only 56% in those with chronic cardiomyopathy [11, 12]. In those with long standing heart failure though the decision to bridge to another salvage strategy is of paramount importance as their cardiac reserve is limited (characterized by low cardiac index and cardiac power) with 77–79% requiring more advanced MCS support including durable VAD to allow for both short-term and long-term survival [11, 12]. Nevertheless, the high mortality rates in patients who receive VA-ECMO heighten the importance of limiting patient

When patients present with CS, inserting a VA-ECMO as a bridge to decision device allows for assessment of neurological and end-organ recovery, making short-term prognostication possible. In many instances, commencing support prior to hemodynamic deterioration and multiorgan failure or cardiac arrest can allow for transition to viable long-term therapies including VAD or heart transplantation. Studies have shown that in patients presenting with refractory cardiogenic shock requiring mechanical circulatory support, 56% survive with 26% of patients transitioning to an implantable VAD, 11% undergoing heart transplantation and

**4. Venoarterial extracorporeal membrane oxygenation complications**

Although ECMO can improve survival to hospital discharge, several studies show significant morbidity with rates increasing with prolonged duration on support. A meta-analysis of 20 studies including 1866 patients demonstrated bleeding as one of the most common complications (40.8%), followed by requirement of dialysis (46%), significant infection (30.4%), limb ischemia (16.9%), and stroke (5.9%). Vascular complications, bleeding and blood transfusions were associated with significant in-hospital mortality [6]. Many of the complications relate to the vascular access site, with femoral cannulation requiring surgical intervention in 20% of the cases [14]. A negative downstream effect of cannulation is distal ischemia which can lead to arterial thrombosis and gangrene. This complication can be mitigated by preemptively placing a small antegrade perfusion cannula to bypass the area of obstruction from the ECMO arterial cannula [15]. Moreover, vascular complications can lead to unsuccessful weaning trials as serious bleeding events increase the need for blood product transfusions and the incidence of thrombotic

#### *ECMO Weaning Strategies to Optimize Outcomes DOI: http://dx.doi.org/10.5772/intechopen.85614*

*Advances in Extracorporeal Membrane Oxygenation - Volume 3*

weaning strategies.

pulmonary edema.

In this chapter we will review the basic principles of VA-ECMO function, predictors of survival, conditions conducive towards successful weaning and lastly,

VA-ECMO support is a well-established technology that allows for full cardiopulmonary support with the goal to recover organ injury. Patients who may require this therapy include: refractory cardiogenic shock (CS), cardiac arrest (CA), refractory ventricular arrhythmia, acute or decompensated biventricular failure (AHF), pulmonary hypertension associated with right ventricular failure, fulminant

The primary goal of VA-ECMO is restoration of tissue perfusion and avoidance of permanent end organ dysfunction. It has a unique hemodynamic effect due to its dual circulatory support circuit. The venous drainage cannula reduces flow through the lung vasculature, decreasing stress on the right heart while the arterial outflow cannula increases flow to the systemic arterial vasculature and the afterload to the left ventricle proportionate to the pump speed/flow. With incremental changes in speed and flow, the increased afterload reduces aortic valve opening and, in cases of severe left ventricular dysfunction, severe right ventricular dysfunction or asystole, the aortic valve may not open at all. The implications of the latter include increased LV end diastolic pressure and the development of

**2. Venoarterial extracorporeal membrane oxygenation function**

**3. Venoarterial extracorporeal membrane oxygenation outcomes**

experiencing a 79.1% in-hospital mortality [5].

VA-ECMO has been shown to increase survival to hospital discharge in patients with advanced heart disease with some cases having favorable long-term survival [4]. However, outcomes differ depending on the underlying etiology of cardiopulmonary collapse at the time of VA-ECMO cannulation. In a large national inpatient database from Japan with 5263 patients receiving ECMO, the in-hospital mortality was 37.9%, with 64.4% weaned off the device. Cardiac arrest at the time of hospital presentation was recognized as the primary factor for poor survival compared to cardiogenic shock alone. Moreover, higher age and smaller BMI were associated with in hospital mortality. The majority of patients presenting with cardiogenic shock had underlying ischemic heart disease, followed by heart failure, valvular heart disease and myocarditis. Notably, the preponderance of patients discharged from the hospital after weaning from ECMO were those with heart failure (31.1%) and myocarditis (41.9%) compared to those with ischemic heart disease (20.3%). In-hospital mortality after weaning however remained elevated with about half of the patients who were weaned dying in the hospital. This high mortality suggests non-modifiable risk factors with persistence of critical illness even after weaning VA-ECMO, as well as differences in survival depending on the underlying etiology of shock, with those having ischemic heart disease at the time of presentation

In patients presenting with PCCS, VA-ECMO is a viable salvage strategy associated with increased survival to hospital discharge. In a meta-analysis of 21 studies with 1866 patients, survival to hospital discharge was achieved in 20.8–65.4% of patients placed on VA-ECMO [6]. Even more, PCCS patients undergoing VA-ECMO have an acceptable 5-year survival of 55.8% compared to other types of cardiogenic

myocarditis, and postcardiotomy cardiogenic shock (PCCS) [3].

**156**

shock [7].

These findings drastically differ to those presenting with acute myocardial infarction associated CS (AMI-CS) where their survival to hospital discharge remains low (33–59%) [8]. This could potentially be mitigated by early intervention at the time of AMI-CS presentation and VA-ECMO support, specifically in those undergoing simultaneous revascularization. In a study of 334 patients with ST elevation AMI, the group that underwent early VA-ECMO support at the time of percutaneous intervention had a lower 30-day mortality compared to those without the support (30.1 vs. 41.7%) with a strong benefit in those with profound shock—defined as systolic blood pressure <75 mmHg despite intravenous inotropic agent administration and intra-aortic balloon pump (IABP) support associated with altered mental status and respiratory failure—compared to those without (72 vs. 39.1% for 30-day death) [9]. Among notable predictors for 30 days mortality were the presence of advanced heart failure (defined as NYHA ≥ III), post intervention TIMI flow grade ≤2 and profound cardiogenic shock.

Lastly in those with AHF, outcomes on VA-ECMO are less promising depending on the original insult. For those with acute presentations, outcomes on VA-ECMO are more favorable compared to those with a chronic cardiomyopathy [10–12]. Specifically, those with fulminant myocarditis and CS or CA survival to discharge ranged from 60 to 88% [10], compared to only 56% in those with chronic cardiomyopathy [11, 12]. In those with long standing heart failure though the decision to bridge to another salvage strategy is of paramount importance as their cardiac reserve is limited (characterized by low cardiac index and cardiac power) with 77–79% requiring more advanced MCS support including durable VAD to allow for both short-term and long-term survival [11, 12]. Nevertheless, the high mortality rates in patients who receive VA-ECMO heighten the importance of limiting patient selection to those who can be weaned from device support.

When patients present with CS, inserting a VA-ECMO as a bridge to decision device allows for assessment of neurological and end-organ recovery, making short-term prognostication possible. In many instances, commencing support prior to hemodynamic deterioration and multiorgan failure or cardiac arrest can allow for transition to viable long-term therapies including VAD or heart transplantation. Studies have shown that in patients presenting with refractory cardiogenic shock requiring mechanical circulatory support, 56% survive with 26% of patients transitioning to an implantable VAD, 11% undergoing heart transplantation and 18% showing cardiac recovery [12, 13].
