What is a false lumen, also known as a pseudo-lumen (false passage)?

From the Guidelines

A false lumen is an abnormal channel for blood flow that develops when blood forces its way between layers of an artery wall, creating a second passageway separate from the normal blood vessel channel (true lumen). This typically occurs in aortic dissection, where a tear in the inner lining of the aorta allows blood to enter and split the arterial wall layers 1. The false lumen can extend along variable lengths of the aorta and may cause complications by restricting blood flow to vital organs, weakening the arterial wall leading to rupture, or causing malperfusion syndromes.

Key Characteristics of False Lumens

• False lumens can be acute or chronic, with some eventually thrombosing (filling with clot) while others remain patent (open) 1.
• The presence and characteristics of a false lumen are important factors in determining treatment approaches for aortic dissections, which may include medical management, endovascular procedures, or open surgical repair depending on the location, extent, and complications of the dissection 1.
• Imaging criteria for distinguishing the true and false lumens have also been described for intravascular ultrasound and CT, including the wedgelike angle (the “beak sign”) where the dissection flap meets the aortic wall, the presence of strand-like structures (“cobwebs”) in the lumen, and the lack of a laminar structure in the outer wall of the lumen 1.

Clinical Implications

• The distinction between a false lumen and a true lumen is crucial in the management of aortic dissections, as it can affect the choice of treatment and the patient's outcome 1.
• Antegrade or retrograde false lumen flow, false lumen thrombosis, and the presence of communications have prognostic implications and are easily detected by transesophageal echocardiography (TOE) 1.
• The presence of a large proximal entry tear (.10 mm) defined by TOE has a high risk of mortality and indicates the need for surgical or endovascular treatment during the follow-up 1.

Diagnosis and Treatment

• Imaging studies, such as CT and TOE, play a critical role in the diagnosis and management of aortic dissections, including the identification of false lumens and the assessment of their characteristics 1.
• The treatment of aortic dissections with false lumens depends on the location, extent, and complications of the dissection, as well as the patient's overall health status 1.

From the Research

Definition of False Lumen

• A false lumen is a compartment or space that forms in the aorta as a result of an aortic dissection, which is a tear in the inner layer of the aorta 2, 3, 4, 5.
• This tear allows blood to flow between the layers of the aorta, creating a false lumen or channel that can lead to various complications, including aortic rupture, visceral or limb malperfusion, and acute expansion 2, 3.

Characteristics of False Lumen

• The false lumen can be characterized by its morphology, including minimal, extensive, proximal, or distal thrombosis 2.
• The pressure in the false lumen can also vary, with proximal thrombosis associated with reduced false lumen pressure 2.
• The false lumen can also be associated with abnormal blood flow patterns, including reverse flow and stagnant flows 4.

Clinical Significance of False Lumen

• The presence of a false lumen can be associated with worse outcomes in patients with aortic dissection, including increased risk of complications and mortality 3.
• Interventions that target the false lumen, such as endovascular therapy, can improve outcomes by promoting thrombosis and remodeling of the aorta 3, 4, 5.
• The Knickerbocker technique is an innovative approach that involves controlled rupture of the dissection membrane to occlude distal backflow into the false lumen aneurysm 5.