What is the recommended evaluation, medical management, and indications for repair of a thoracic aortic arch aneurysm in an adult?

Thoracic Aortic Arch Aneurysm: Evaluation, Medical Management, and Repair Indications

Recommended Evaluation

For initial diagnosis of aortic arch aneurysm, obtain CT angiography (CTA) or cardiac MRI to establish baseline diameter, assess extent of involvement, and evaluate branch vessel anatomy. 1

Initial Imaging Strategy

• Transthoracic echocardiography (TTE) is inadequate for arch aneurysm assessment and should not be used for surveillance of distal ascending, arch, or descending aortic aneurysms 1
• CTA or cardiac MRI are the required modalities for accurate measurement of arch diameter, detection of asymmetry, and determination of baseline dimensions 1
• Evaluate the entire aorta from root to iliacs at baseline, as arch aneurysms commonly occur with adjacent ascending or descending thoracic disease 1
• Assess for high-risk features including rapid expansion, symptoms, chronic dissection, and patient age 1

Clinical Assessment

Look specifically for symptoms indicating operative urgency 1:

• Hoarseness (left recurrent laryngeal nerve compression)
• Dysphagia (esophageal compression)
• Dyspnea (tracheal compression)
• Chest or back pain (aneurysm expansion)

Any of these symptoms mandate prompt surgical evaluation regardless of aneurysm size unless life expectancy is severely limited 1

---

Medical Management

All patients with thoracic arch aneurysm require aggressive blood pressure control as the cornerstone of medical therapy to reduce wall stress and slow expansion. 1

Pharmacologic Therapy

• Beta-blockers are first-line agents to reduce aortic wall stress by decreasing heart rate (target <60 bpm) and blood pressure 2
• Strict blood pressure control with target systolic BP <120-130 mmHg using additional agents (ACE inhibitors, ARBs, calcium channel blockers) as needed 2
• Statin therapy for cardiovascular risk reduction in all patients 2
• Avoid fluoroquinolone antibiotics due to increased risk of aortic dissection and rupture 2

Cardiovascular Risk Factor Management

• Smoking cessation (mandatory)
• Lipid management with statins
• Treatment of hyperlipidemia (associated with faster expansion rate >5.5 mm/year) 3

---

Surveillance Intervals

For isolated aortic arch aneurysms <4.0 cm in diameter, reimage with CTA or cardiac MRI at 12-month intervals. 1

For isolated aortic arch aneurysms ≥4.0 cm in diameter, reimage with CTA or cardiac MRI at 6-month intervals. 1

Modified Surveillance Based on Growth

• If rapid expansion ≥3 mm per year or approaching surgical threshold, increase surveillance to every 6 months 1
• If stable over years with diameter <45 mm, may extend intervals beyond 12 months in non-genetic aneurysms 1
• For arch diameter 50-55 mm, reimage every 6 months until intervention threshold reached 1

---

Indications for Surgical Repair

For asymptomatic patients with low operative risk and isolated degenerative or atherosclerotic aortic arch aneurysm, operative treatment is reasonable when diameter exceeds 5.5 cm. 1, 4

Size-Based Thresholds

• ≥5.5 cm diameter for isolated arch aneurysm in degenerative disease 1, 4
• ≥6.0 cm diameter represents significantly increased rupture risk (60 mm threshold shows significant rise in adverse event risk) 1
• Consider indexing to body surface area for patients significantly smaller or taller than average (intervention at aortic cross-sectional area to height ratio ≥10 cm²/m) 4

Growth Rate Criteria

Growth rate >0.5 cm/year is an indication for operation even if diameter <5.5 cm. 1, 4

• Expansion rate >5.5 mm/year carries 67% likelihood of rupture compared to 8.3% for slower growth 3
• Expansion rate is the sole independent risk factor for rupture on multivariate analysis (odds ratio 1.43) 3

Symptom-Based Indications

Any symptoms attributable to the arch aneurysm (hoarseness, dysphagia, dyspnea, chest pain, back pain) are absolute indications for operative intervention regardless of size unless life expectancy is quite limited 1, 4

Extent-Based Indications

Replacement of the entire aortic arch is reasonable for:

• Aneurysms of the entire arch 1
• Chronic dissection when the arch is enlarged 1
• Distal arch aneurysms that also involve the proximal descending thoracic aorta (usually with elephant trunk procedure) 1

Partial arch replacement is reasonable for:

• Thoracic aortic aneurysms involving the proximal aortic arch (together with ascending aorta repair using right subclavian/axillary artery inflow and hypothermic circulatory arrest) 1

---

Surgical Approach Considerations

Open surgical arch replacement with hypothermic circulatory arrest remains the gold standard for low-risk patients with isolated arch aneurysms ≥5.5 cm. 1, 5

Technical Requirements

• Cardiopulmonary bypass with hypothermic circulatory arrest is required 1
• Brain protection via antegrade cerebral perfusion, retrograde perfusion, or profound hypothermia alone 1
• The innominate, left carotid, and left subclavian arteries require separate grafting or patch reconstruction 1
• Right subclavian/axillary artery inflow reduces stroke risk 1

Hybrid Approaches for High-Risk Patients

For high-risk surgical candidates who cannot tolerate conventional open repair, hybrid arch repair combining supra-aortic debranching with thoracic endovascular aortic repair (TEVAR) may be considered. 5

• Hybrid techniques offer reduced perioperative morbidity compared to total arch replacement requiring deep hypothermic circulatory arrest 5
• Two-stage approach is standard for extensive disease involving arch and descending aorta 5
• Endovascular stent grafts are NOT FDA-approved for isolated aortic arch treatment 1, 2

---

Critical Pitfalls to Avoid

• Do not rely on TTE for arch aneurysm surveillance – it is inadequate for distal ascending, arch, or descending aortic measurements 1
• Do not delay referral of symptomatic patients – symptoms indicate impending rupture or dissection with >50% mortality if untreated 4, 2
• Do not ignore expansion rate – it is the strongest independent predictor of rupture, more important than absolute diameter 3
• Do not use the same imaging modality inconsistently – follow-up should use the same technique and ideally the same center 1
• Do not overlook hyperlipidemia – it is a determining factor for rapid expansion (>5.5 mm/year) and should be aggressively treated 3
• Refer to high-volume multidisciplinary aortic centers – arch surgery requires specialized expertise with hypothermic circulatory arrest and cerebral perfusion strategies, with significantly better outcomes at experienced centers 4, 2
• Screen first-degree relatives with aortic imaging, as familial clustering is common even in non-syndromic cases 4, 2