What is aortic tortuosity of the descending aorta?

Aortic Tortuosity of the Descending Aorta

Aortic tortuosity of the descending aorta refers to excessive twisting, bending, or elongation of the descending thoracic aorta beyond its normal gentle curve, creating an abnormally winding or serpentine path through the chest. 1

Anatomical Definition

• Tortuosity represents an abnormal geometric configuration where the aorta follows a more circuitous route than normal, often appearing as loops, bends, or curves on imaging studies 2
• This can be quantified using several measurements:
  • Tortuosity index: ratio of the actual aortic centerline length to the straight-line distance between endpoints (normal approximately 1.11, increasing with disease) 2
  • Maximum tortuosity angle: measured in degrees, with classifications of low (<30°), moderate (30°-60°), and high (>60°) 2, 3
  • Curvature ratio: geometric measure of vessel bending 2

Clinical Significance and Associated Conditions

• Tortuosity is commonly seen on chest radiographs as aortic widening or distortion of para-aortic structures, which may prompt further evaluation for thoracic aortic aneurysm 1
• Tortuosity increases significantly with aortic disease: patients with descending thoracic aortic aneurysms show markedly higher tortuosity (mean maximum angle 43.83°) compared to those with type B dissection (33.29°) or normal aortas (28.17°) 2
• In genetic connective tissue disorders, arterial tortuosity is a defining feature, particularly in Loeys-Dietz syndrome, where tortuosity is most commonly observed in head and neck vessels but can occur throughout the arterial tree 1

Hemodynamic Implications

• High tortuosity creates increased displacement forces on the aortic wall, particularly in the distal descending aorta (zone 4C), where forces can be more than three times higher than in patients with low tortuosity 3
• These increased sideways forces (more than double in high tortuosity cases) have important implications for endovascular repair planning, as they increase risk of stent graft migration and endoleak after TEVAR 2, 3

Relationship to Aortic Ectasia and Aneurysm

• Tortuosity often accompanies aortic ectasia (dilatation <50% over normal) and may be visible before frank aneurysmal disease develops 4
• As elastin fibers deteriorate with aging, the descending thoracic aorta becomes longer and more tortuous, creating a hostile hemodynamic environment that may accelerate aneurysm progression 3
• The maximum point of tortuosity tends to occur more distally in diseased aortas (zone 4B) compared to normal aortas (zone 4A) 2

Management Implications

• When tortuosity is noted on imaging, comprehensive evaluation with CT or MRI is warranted to assess for underlying aortic disease, measure aortic diameters, and establish baseline for surveillance 4
• In patients with genetic syndromes showing arterial tortuosity (particularly Loeys-Dietz), yearly MR imaging from cerebrovascular circulation to pelvis is recommended due to risk of aneurysms throughout the arterial tree 1
• Surgical planning for tortuous descending aortic aneurysms requires special consideration, as extreme tortuosity may necessitate alternative approaches including surgical exclusion or specialized endovascular techniques 5, 6