What is the clinical significance of tortuosity and atherosclerotic changes of the thoracic aorta?

Clinical Significance of Thoracic Aortic Tortuosity and Atherosclerotic Changes

Tortuosity and atherosclerotic changes of the thoracic aorta are clinically significant markers of increased cardiovascular risk, predisposing to aneurysm formation, dissection, embolic events, and procedural complications, particularly in patients undergoing thoracic endovascular aortic repair (TEVAR).

Atherosclerotic Changes: Direct Clinical Impact

Aneurysm Formation and Rupture Risk

• Atherosclerosis is the primary cause of thoracic aortic aneurysms, with severe atherosclerosis involving more than 70% of the aortic surface in over 90% of patients with aneurysms 1
• The pathophysiology involves intimal thickening with massive fibrosis and calcification, which compromises nutrient supply to the media, resulting in medial thinning and increased vessel stiffness 1
• Fusiform thoracic aortic aneurysms have a 61% rupture risk, significantly higher than abdominal aortic aneurysms 1
• Hypertension is present in 85% of patients with ruptured aneurysms, making it the dominant modifiable risk factor 1

Embolic Complications

• Atherosclerotic lesions of the thoracic aorta cause stroke and peripheral embolization in approximately 27% of patients with previous embolic events 2
• Plaque thickness ≥4 mm correlates strongly with embolic risk, with 12% of patients experiencing recurrent stroke within one year and up to 33% having stroke or peripheral embolus 2
• During cardiac surgery requiring cardiopulmonary bypass, aortic arch atheromas detected by transesophageal echocardiography result in stroke in approximately 12% of operations—six times the general intraoperative stroke rate 2

Penetrating Aortic Ulcer Development

• Atherosclerotic plaques can ulcerate and penetrate the internal elastic lamina, creating penetrating aortic ulcers (PAU) with rupture risk as high as 33-75% when complicated by intramural hematoma 3
• PAU typically affects older males (>65 years) with multiple comorbidities including hypertension, coronary artery disease, COPD, and renal insufficiency 3
• High-risk imaging features requiring intervention include maximum PAU width ≥13-20 mm, depth ≥10 mm, or growth >5 mm/year 3

Tortuosity: Procedural and Prognostic Implications

TEVAR Complications

• Increased aortic tortuosity in the proximal landing zone is independently associated with higher risk of endoleak, stroke, and all-cause mortality after TEVAR 1
• Patients with high tortuosity index have significantly elevated rates of type III endoleaks, particularly when tortuosity affects both the proximal fixation zone and diseased segment 1
• In the aortic arch, highly angulated or curved anatomy prevents proper stent graft apposition, creating a "bird-beak configuration" associated with type Ia endoleak 1

Disease-Specific Tortuosity Patterns

• Tortuosity is significantly more pronounced in diseased aortas compared to controls, with the highest degree in aneurysmal disease (tortuosity index 1.31 vs 1.20 in dissection vs 1.11 in controls) 4
• In patients with descending thoracic aortic aneurysm, maximum tortuosity averages 43.83 degrees compared to 28.17 degrees in controls 4
• Aortic arch tortuosity is independently increased in bicuspid aortic valve patients (median 1.76 vs 1.63 in tricuspid valve controls), potentially identifying those at higher risk for thoracic aortic disease 5

Anatomic and Metabolic Associations

• Visceral fat obesity independently contributes to thoracic aortic tortuosity, likely through diaphragm elevation from excessive intraabdominal fat and obesity-related metabolic disorders causing aortic elongation 6
• Tortuosity increases with age and is associated with larger ascending aortic dimensions, particularly when measured from the aortic arch to the celiac artery 7

Clinical Management Implications

Pre-Procedural Planning

• Quantitative assessment of aortic tortuosity using CT angiography should be performed before TEVAR to identify high-risk patients requiring enhanced procedural planning and postoperative surveillance 1
• Assessment must include iliofemoral artery diameters, calcification extent, and tortuosity for complete TEVAR planning 1
• ECG-gated CT is particularly important for ascending aorta measurements, as 5-10% diameter variation occurs between systole and diastole 1

Medical Management of Atherosclerotic Disease

• For patients with aortic atherosclerosis, LDL-C reduction by ≥50% from baseline with goal <55 mg/dL is recommended 3
• Low-dose aspirin (75-162 mg/day) should be used to reduce cardiovascular event risk 3
• Strict blood pressure control (systolic <120 mmHg) and heart rate control (≤60 bpm) are essential, particularly in penetrating aortic ulcer 3

Surveillance Strategy

• Patients with identified tortuosity and atherosclerotic changes require closer imaging follow-up to screen for late-developing complications, particularly endoleak after TEVAR 1
• The combination of tortuosity and atherosclerotic plaque thickness ≥4 mm warrants aggressive risk factor modification and consideration of anticoagulation strategies, though prospective randomized data are still needed 2

Critical Pitfalls to Avoid

• Do not dismiss incidental findings of aortic tortuosity or atherosclerotic plaques on imaging—these are independent predictors of adverse cardiovascular outcomes requiring risk stratification 1, 2
• Avoid proceeding with TEVAR without quantitative tortuosity assessment, as visual estimation alone is inadequate for predicting complications 1
• Do not assume that normal aortic diameter excludes significant risk—tortuosity and atherosclerotic burden are independent risk factors beyond diameter alone 4, 5
• In patients with thoracic aortic atherosclerosis undergoing cardiac surgery, failure to use intraoperative epiaortic ultrasound or transesophageal echocardiography to assess atheromas significantly increases perioperative stroke risk 2