Infograph: VV vs. VA ECMO

ECMO (Extracorporeal Membrane Oxygenation) comes in two main configurations, each serving distinct clinical purposes.

Core Function

VV ECMO provides isolated pulmonary support, handling only gas exchange (oxygenation and CO₂ removal) without any circulatory assistance. VA ECMO provides dual heart and lung support, acting as an extracorporeal right-to-left shunt that unloads a failing heart while maintaining organ perfusion.

Native Cardiac Requirement

This is a critical distinction — VV ECMO requires a functioning heart to pump oxygengenated blood through the body, whereas VA ECMO can drive circulation independently of heart function, making it suitable for patients in cardiac failure.

Cannulation Pathway

VV ECMO uses a venous-to-venous path, returning blood to the venous system. It can use two sites or a single specialized double-lumen cannula (often in the neck), making it surgically simpler. VA ECMO uses a venous-to-arterial path, returning blood to a large artery (femoral or aorta), bypassing both heart and lungs.

Clinical Indications

VV ECMO is used for severe ARDS, pneumonia, and trauma when mechanical ventilation has failed. VA ECMO is indicated for cardiac arrest (E-CPR), refractory cardiogenic shock, and as a bridge to heart transplantation.

Unique Risks

VV ECMO carries the risk of recirculation, where oxygenated blood is pulled back into the circuit before completing systemic circulation, typically from cannula malposition. VA ECMO carries a significant risk of limb ischemia (10–70%) due to arterial cannulation, plus a “watershed phenomenon” that can impair brain oxygenation.