ECPella… what is it good for?

ECPella is the simultaneous use of VA-ECMO with Impella for the management of acute CS.

• It is mainly used in acute myocardial infarction-related CS patients at high risk of LV distension
• Generally, whilst on ECPella support, the Impella generates 1.5-2 L/min of flow to unload the LV (usually P2-P4 level).

Reasons include:

• To actively unload the LV and prevent LV distension syndrome
• It may be considered in cases of pulmonary oedema, arrhythmias and evidence of blood stagnation within the LV

Reasons include:

• Progressive CS requiring increasing cardiac support above the capability of the inserted Impella. For example, an Impella 2.5 catheter’s maximum flow rate is 2.5 L/min which may be inadequate in a patient with evolving CS after protected PCI.
• Concomitant right heart failure^1,2.
• Cardiac arrest

LV distension syndrome is a pathological increase in LV end-diastolic pressure (LVEDP) or volume (LVEDV) caused or exacerbated by VA ECMO.

• While ECMO can be life-saving in cardiogenic shock, the pathological increase in LVEDP and LVEDV that can sometimes affect patients on VA-ECMO can be disastrous and fatal if not addressed quickly³.
• The increased LVEDP can worsen subendocardial ischemia, which can jeopardise cardiac recovery.
• LV dilatation and pressure overload leads to increased left atrial pressure and pulmonary oedema⁴. Furthermore, if the LV dysfunction is severe the aortic valve (AV) may remain closed, even during systole, which can lead to stasis of blood in the LV and increasing the risk of intracardiac thrombus forming.

There are multiple contributing mechanisms:^5,6

• During VA-ECMO the arterial return cannula generates retrograde flow in the aorta towards the aortic valve, resulting in increased afterload on the left ventricle (more than seen in a normal physiological state). This marked increase in afterload leads to increased LV wall stress, LV distension and increased myocardial 0₂ demand.
• The ECMO pump and retrograde flow towards the AV can worsen any aortic regurgitation, particularly if there is little or no LV ejection.
• Native cardiac output may be so poor that it is insufficient to eject the volume of blood entering the LV from the right side via the pulmonary veins.

Impella has several important haemodynamic effects: increasing cardiac power output, improving 0₂ supply and decreasing 0₂ demand.

• The Impella outflow port sits in the aortic root and provides an active forward flow that helps to drain and unload the LV. The degree of forward flow is dependent on the pump support setting (P level) and the pressure gradient between the aorta and LV⁷.
• Coronary artery blood flow is influenced by the aortic pressure. In addition to increasing ascending aortic pressure, by draining the LV of blood the Impella reduces LVEDP and LVEDV – leading to reduced LV wall tension and less mechanical work. As a result myocardial 0₂ demand is reduced, whilst coronary perfusion and oxygen supply are increased⁸.
• As a result, the total balance of oxygen demand/delivery becomes more favourable⁹

Patients with:

• Predominantly left heart failure
• Advanced chronic cardiomyopathy
• Pre-existing aortic regurgitation
• Prolonged cardiac arrest

Measures used to prevent LV distention include:

• Medical management to reduce LV afterload
  • Vasodilator therapy to reduce MAP to 60-70mmHg
  • PEEP (>15cmH₂0)
• Medical management to support native contractility and maintain pulsatility
  • Inotropes
  • Manage circulating volume with fluid removal (diuresis, CVVH)
  • Mechanical unloading therapies⁵
  • Impella
  • Trans-aortic LV catheter¹⁰
  • Trans-apical surgical LV vent¹⁰
  • Intra-aortic balloon pump
  • Atrial septostomy (balloon or surgical)

See Everything ECMO 020 to learn more about LV distention.

Advantages include:

• Impella insertion is percutaneous and can be performed before, during, or after VA-ECMO cannulation.
• Insertion can be performed in the operating theatre, cardiac lab, or bedside in ICU – particularly attractive for a patient who is critically unstable on VA-ECMO
• The additional flow provided by the Impella may facilitate ECMO weaning. As a result, ECMO may potentially be weaned faster – shortening the time on ECMO and the development of ECMO related complications¹¹.
• There is a growing body of evidence suggesting that patients supported with this strategy have not only lower 30-day mortality and lower inotrope use, but also demonstrate a trend towards higher LV ejection fraction after weaning of support when compared with VA-ECMO alone^{12, 13}. However, there is currently no data available from randomised controlled trials to confirm these findings.

Disadvantages include:

• Cost and availability
• Increased haemolysis and bleeding when compared to VA-ECMO alone¹¹
• Increased incidence of insertion site-related complications – both minor bleeding and limb ischemia¹⁴
• Migration and malposition can frequently occur, requiring regular echocardiographic studies to reposition
• In patients with Impella on ECMO, the delivery of blood flow to the LV from the right ventricle (RV) is reduced as most of the venous return is diverted to the ECMO from the right atrium (RA). This may lead to LV suction even when the level is low at P2. Therefore, VA ECMO support may need to be reduced to allow more blood flow delivery to the LV. If feasible, VA-ECMO flow of 3-4 L/min (partial support) should be maintained to preserve native cardiac contractility and avoid suction events⁹. Adequate anticoagulation therefore needs to be ensured to prevent any thrombus formation in either the Impella catheter or the VA ECMO circuit as both devices are likely to be on partial support.