Invisible Active Bleeding Due to the Watershed Phenomenon.

Area of Science:

• Radiology
• Cardiovascular Medicine
• Critical Care Medicine

Background:

• Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is a life-support intervention for severe cardiac or respiratory failure.
• Computed tomography (CT) angiography is frequently used to evaluate patients on VA-ECMO for complications, including bleeding.
• Altered hemodynamics in VA-ECMO can present diagnostic challenges.

Observation:

• An 83-year-old female patient on VA-ECMO with suspected active bleeding showed no contrast blush on initial CT angiography.
• The vascular watershed phenomenon, a flow-related artifact, can obscure active bleeding during CT angiography in VA-ECMO patients.

Findings:

• The absence of a contrast blush on CT angiography does not exclude active bleeding in patients undergoing VA-ECMO.
• Flow-related artifacts, specifically the vascular watershed phenomenon, can mimic the absence of bleeding.

Implications:

• Radiologists and clinicians must be aware of VA-ECMO-specific hemodynamic alterations and potential imaging artifacts.
• Careful interpretation of CT angiography is essential in VA-ECMO patients to avoid misdiagnosis of active bleeding.
• Further investigation or alternative diagnostic methods may be warranted when active bleeding is strongly suspected but not visualized on CT angiography.