What is the role of pulmonary artery (PA) venting in a patient with right ventricular (RV) failure on veno-arterial (VA) extracorporeal membrane oxygenation (ECMO)?

PA Venting in RV Failure on VA ECMO

In patients with RV failure on VA ECMO, pulmonary artery venting is a critical intervention to prevent catastrophic pulmonary hemorrhage and progressive RV distension by decompressing the pulmonary circulation when the native RV cannot adequately eject against elevated pulmonary pressures.

The Core Problem: VA ECMO Creates a Dangerous Hemodynamic Trap

When VA ECMO is initiated for RV failure, the circuit bypasses the pulmonary circulation by returning oxygenated blood directly to the arterial system. However, this creates a critical problem:

• The failing RV still attempts to eject blood into the pulmonary circulation, but with severely impaired contractility 1
• VA ECMO increases RV afterload by raising systemic arterial pressure, which increases RV wall stress and oxygen demand 2
• Pulmonary artery pressures rise dramatically because blood is being pumped into the pulmonary circulation by any residual RV function, but the left heart is already filled by ECMO flow, creating a "dead-end" for pulmonary venous return 2
• This leads to progressive RV distension, worsening tricuspid regurgitation, and critically, pulmonary hemorrhage from vascular rupture due to excessive pulmonary artery and capillary pressures 2, 1

Why PA Venting is Essential

PA venting directly addresses this pathophysiology by:

• Decompressing the pulmonary circulation to prevent pulmonary capillary pressures from reaching hemorrhagic levels 2
• Unloading the RV by providing an outlet for any blood the failing RV manages to eject, preventing progressive distension 1
• Preventing leftward septal shift that would otherwise compromise LV filling despite adequate ECMO flow 2
• Avoiding pulmonary vascular damage from sustained high pressures, which is particularly critical in patients with underlying pulmonary hypertension 2

Clinical Implementation

Indications for PA Venting on VA ECMO:

• Severe RV failure with minimal native cardiac output where the RV cannot effectively eject against pulmonary vascular resistance 1
• Evidence of pulmonary hypertension (sPAP >40 mmHg) or acute cor pulmonale on echocardiography 2
• Rising pulmonary artery pressures despite VA ECMO support, indicating inadequate RV ejection 2
• Pulmonary hemorrhage or risk thereof in patients with fixed elevated pulmonary vascular resistance 2

Technical Approach:

The PA vent can be achieved through several methods:

• Direct PA cannulation with drainage to the venous side of the ECMO circuit, creating a hybrid configuration 1
• Atrial septostomy to decompress the right heart by allowing right-to-left shunting, though this causes systemic desaturation 2
• Conversion to alternative support such as lung assist devices (Novalung) that connect PA to LA in parallel, bypassing the pulmonary bed entirely 2

Critical Monitoring Requirements:

• Serial echocardiography to assess RV size, function, septal position, and tricuspid regurgitation 2
• Continuous arterial blood pressure monitoring and ECMO flow rates 2
• Avoid thermodilution cardiac output monitoring as it gives erroneous results with ECMO circuits 2
• Strict fluid balance monitoring as positive fluid balance independently predicts poor outcomes in ECMO patients 2

Key Pitfalls to Avoid

Volume overload is particularly dangerous: The traditional teaching that "the RV is preload dependent" leads to harmful volume loading in RV failure. The RV actually prefers euvolemia (CVP 8-12 mmHg), and excessive volume worsens RV distension and tricuspid regurgitation 2. Diuresis improves biventricular coupling even on ECMO support 2.

Inotropes may worsen outcomes: Calcitropic agents can cause progressive RV dysfunction, particularly when systemic vasodilation reduces RV perfusion pressure in the setting of elevated RV pressures 2. If inotropes are necessary, combine with vasopressors (vasopressin or norepinephrine) to maintain RV perfusion pressure 2.

Forced pulmonary perfusion without venting causes hemorrhage: Right ventricular assist devices (RVADs) that pump blood into the PA without adequate LV preload or with elevated pulmonary vascular resistance can cause pulmonary vascular damage and hemorrhage 2. This is why PA venting or alternative configurations are preferred in fixed pulmonary hypertension 2.

Comparison with Alternative Strategies

VV ECMO is insufficient for RV failure with cardiogenic shock: While VV ECMO can reduce pulmonary artery hypertension by improving oxygenation and reducing hypoxic vasoconstriction 2, it provides no hemodynamic support and cannot address cardiogenic shock from RV failure 2, 3.

VA ECMO without PA venting risks catastrophic complications: The evidence shows that VA ECMO alone in severe RV failure with pulmonary hypertension leads to progressive pulmonary pressure elevation and hemorrhage 1. PA venting or conversion to PA-LA bypass configurations are necessary to prevent these complications 2.

Temporary support with PA venting allows RV recovery: Studies demonstrate that ECMO-facilitated RV support with appropriate hemodynamic management achieves RV recovery rates of 90% over 3-11 days, with acceptable long-term survival 4, 5.