What are the differences between Veno-Arterial (VA) and Veno-Venous (VV) Extracorporeal Membrane Oxygenation (ECMO) in terms of patient selection and management?

From the Guidelines

VA ECMO is recommended for patients with both cardiac and respiratory failure, while VV ECMO is preferred for isolated respiratory failure with adequate cardiac function. The primary difference between VA and VV ECMO lies in their indications, circulatory support capabilities, and management approaches 1. VA ECMO provides both hemodynamic support and oxygenation by draining blood from a vein and returning it to an artery, making it suitable for cardiogenic shock, post-cardiotomy failure, and as a bridge to cardiac transplantation. In contrast, VV ECMO supports only gas exchange, relying on the patient's own cardiac function, and is typically chosen for severe ARDS, pneumonia, or status asthmaticus.

Key Differences in Management

• Anticoagulation: typically heparin with target PTT of 45-60 seconds for both, though VA may require tighter control 1
• Hemodynamic monitoring: VA requires careful attention to arterial pressure, left ventricular distention, and distal limb perfusion
• Weaning protocols: individualized based on the patient's specific cardiopulmonary failure pattern

Complications and Risks

• VA ECMO carries higher risks of arterial injury, limb ischemia, and systemic thromboembolism
• Both types share risks of bleeding, infection, and hemolysis
• Neurological monitoring is crucial, especially in VA ECMO patients, due to the increased risk of acute brain injury (ABI) 1

Patient Selection

• VA ECMO is selected when cardiac support is needed
• VV ECMO is preferred when only respiratory support is required
• The choice between VA and VV ECMO must be individualized based on the patient's specific cardiopulmonary failure pattern 1

From the Research

Patient Selection for VA and VV ECMO

• VA ECMO is indicated for patients with primary RV injury or RV failure with concomitant left ventricle (LV) failure, as well as those with cardiogenic shock 2, 3.
• VV ECMO is an appropriate initial configuration for patients with isolated RV failure from acute hypoxemic respiratory failure, even if the patient is in shock 2.
• For adult patients with acute respiratory distress syndrome (ARDS) requiring precannulation hemodynamic support, VV ECMO may be a reasonable initial choice, reserving VA ECMO for conversion for refractory hypotension 4.

Management of VA and VV ECMO

• Both VA and VV ECMO provide indirect support to the RV by reducing preload, reducing RV wall tension, and delivering oxygenated blood to the coronary circulation 2.
• Peripheral cannulation is required in VV-ECMO and is most commonly used in VA-ECMO, allowing for rapid cannulation even in emergencies 2.
• Changes in pulsatility on an arterial catheter waveform can indicate changes in clinical status, including changes in myocardial function, inadequate preload, worsening RV failure, and excessive VA-ECMO support leading to an elevated LV afterload 2.

Comparison of VA and VV ECMO Outcomes

• Survival to discharge was higher in VV ECMO patients compared to VA ECMO patients in some studies 4, 5.
• VV ECMO was associated with less gastrointestinal bleeding and hemolysis compared to VA ECMO in one study 4.
• No significant difference was noted in functional outcomes or comorbidities at discharge between VV and VA ECMO patients in another study 5.
• VA ECMO is unique in that it provides immediate and complete hemodynamic support as well as concomitant gas exchange, making it a valuable option for patients with cardiogenic shock 3.