What is a tortuous aorta?

What is a Tortuous Aorta?

A tortuous aorta is an abnormal elongation, twisting, and increased curvature of the aorta that deviates from the normal relatively straight vascular anatomy, often developing with aging or associated with specific genetic connective tissue disorders. 1

Definition and Anatomical Characteristics

A tortuous aorta represents excessive curvature and elongation of the aortic vessel, quantifiable through tortuosity indices that measure the deviation of the vessel's centerline from a straight path. 2

• Normal anatomy: In healthy individuals under 40 years, the aorta maintains relatively straight geometry with tortuosity coefficients typically less than 0.20 2
• Pathological tortuosity: Coefficients several times greater than 0.20 indicate significant vessel twisting, loops, and acute curves 3, 2
• Age-related changes: Beyond age 40, there is rising incidence of aortic tortuosity due to loss of longitudinal vessel wall stiffness 2

Clinical Associations and Causes

Genetic Connective Tissue Disorders (most clinically significant):

• Loeys-Dietz Syndrome: Arterial tortuosity is a distinguishing feature, particularly affecting head and neck vessels, with tortuosity of the aorta and its branches being a diagnostic criterion 1
• Arterial Tortuosity Syndrome: Rare autosomal recessive disorder characterized by elongation, tortuosity, and aneurysmal formation of large and middle-sized arteries, sometimes with pulmonary artery or aortic stenosis 3
• Larsen Syndrome: Can present with hugely dilated tortuous aortic arch with multiple acute curves 4

Acquired Conditions:

• Aging: Progressive development of tortuosity in previously straight vessels like the abdominal aorta 2
• Kyphoscoliosis: Skeletal deformity can be associated with aortic tortuosity 5

Clinical Significance and Complications

Hemodynamic Consequences:

• Creates flow profile asymmetries leading to abnormal wall shear stress 2
• Predisposes vessels to atherosclerosis development 2
• Should be considered a geometric risk factor for vascular disease 2

Procedural Implications:

• Increased risk of endoleak after TEVAR: Tortuosity at the proximal landing zone significantly predicts type III endoleak, stroke, and all-cause mortality 1, 6
• Bird-beak configuration: Highly angulated or curved arch prevents proper stent graft apposition, creating gaps associated with type Ia endoleak 1
• Technical challenges: Extremely tortuous anatomy requires adjunct techniques like brachio-femoral wire approaches for endovascular device delivery 7

Diagnostic Evaluation

When tortuosity is suspected in genetic syndromes:

• Magnetic resonance angiography of head, neck, thorax, abdomen, and pelvis is required for complete vascular evaluation 1
• Tortuosity can be isolated (e.g., only in head and neck), necessitating comprehensive imaging 1
• Echocardiography must be augmented by CT or MRA when Loeys-Dietz syndrome is suspected 1

Imaging Pitfalls:

• With tortuous or ectatic aorta, "longitudinal" and "transverse" views must be obtained with respect to the vessel axis to avoid artifactual exaggeration of aortic diameter 1
• Oblique or angled cuts exaggerate true aortic diameter 1
• Scanning planes should be exactly aligned with or at exact right angles to the vessel's main axis 1

Management Considerations

In genetic syndromes with tortuosity:

• Annual MRA surveillance of affected vessels is recommended for Loeys-Dietz syndrome patients 1, 8
• Lower thresholds for surgical intervention apply due to increased dissection risk at smaller diameters 1
• Beta-blockade is recommended for aortic root dilation 1, 8

For procedural planning:

• Quantitative analysis of aortic curvature on CTA identifies high-risk patients requiring closer post-TEVAR surveillance 1
• Assessment of tortuosity index at landing zones is essential for predicting complications 1, 6