What are the potential sources of rupture in a patient with chronic type B aortic dissection that has progressed to an aneurysm and who has just undergone thoracic endovascular aortic repair (TEVAR)?

Sources of Rupture in Chronic Type B Dissection with Aneurysm Immediately Post-TEVAR

The most critical sources of rupture immediately post-TEVAR in chronic type B dissection with aneurysm are endoleaks (occurring in up to 20% of patients and representing the most important risk factor for aortic rupture), stent graft-induced new entry tears, retrograde type A dissection, and persistent false lumen perfusion through distal fenestrations. 1

Primary Rupture Sources

Endoleaks

• Endoleaks represent the single most important risk factor for aortic rupture post-TEVAR, occurring in up to 20% of patients treated for aneurysm 1
• Endoleaks are defined as continued blood flow into the aneurysm sac and are categorized into 5 types, each requiring evaluation for potential reintervention 1
• These can manifest early in the post-procedural period and necessitate immediate identification through surveillance imaging 1

Stent Graft-Induced Complications

• Stent graft-induced new entry tears are common complications post-TEVAR for type B dissection and represent a direct source of potential rupture 1
• Graft collapse, while rare, is devastating when it occurs and can lead to acute rupture 1
• Stent-graft migration (occurring in 0.7%-4% of cases) can create gaps allowing pressurization of the aneurysm sac 1
• Stent fracture represents another mechanical failure mode that can lead to loss of seal and subsequent rupture 1

Retrograde Type A Dissection

• Retrograde type A dissection is a catastrophic early complication that occurs when the stent graft causes retrograde extension of dissection into the ascending aorta 1
• This complication is particularly relevant in patients with pre-existing ascending aortic dilation 2
• Monitoring for this complication is critical in early post-TEVAR follow-up 1

False Lumen Perfusion Issues

Persistent Retrograde Perfusion

• Continued retrograde false lumen perfusion via distal fenestrations represents a major concern in chronic dissection with aneurysm, as it maintains pressurization of the aneurysm sac 2, 3
• In chronic dissection, multiple distal re-entry tears can allow persistent false lumen flow despite proximal entry tear coverage 2, 3
• This persistent perfusion prevents false lumen thrombosis and maintains wall stress, increasing rupture risk 2

Unfavorable Aortic Remodeling

• Incomplete thrombosis or failure of the false lumen diameter to shrink are negative prognostic factors indicating ongoing rupture risk 1
• The number, location, and size of intimal tears are associated with unfavorable aortic remodeling and increased rupture potential 1
• Persistent aneurysmal sac enlargement (occurring in 7-15% of cases) is suggestive of disease progression or device failure 1

Early Post-Procedural Complications

Acute Complications Requiring Surveillance

• 35% of patients undergoing TEVAR have at least one postoperative aorta-specific complication, with roughly half requiring reintervention 1
• In patients initially presenting as uncomplicated, 37.5% develop complications within a mean of 7.1 days following presentation, emphasizing the need for close early follow-up 1
• Early imaging follow-up at 1 month post-procedure is paramount for identifying these complications before rupture occurs 1

Critical Pitfalls to Avoid

Inadequate Seal Zones

• In chronic dissection, the dissection flap itself can prevent adequate stent graft apposition to the outer aortic wall, creating persistent type I endoleaks at proximal or distal landing zones 4
• Branch vessels originating from the chronic false lumen can maintain false lumen perfusion even after primary entry tear coverage 2

Hemodynamic Stress

• Uncontrolled hypertension in the immediate post-TEVAR period dramatically increases wall stress and rupture risk, particularly given that hypertension is present in 85% of patients with ruptured aneurysms 5
• Wall stress is directly proportional to pressure and radius according to the law of Laplace, making blood pressure control critical 5

Surveillance Strategy

Immediate post-TEVAR imaging should specifically assess for:

• Graft stability and position 1
• True and false lumen diameters 1
• Presence and type of endoleak 1
• Stent-graft migration or fracture 1
• Signs of retrograde dissection extension 1

CT chest, abdomen, and pelvis with IV contrast (multiphase protocol) is the standard imaging modality for comprehensive evaluation of these potential rupture sources, allowing detection of endoleaks, stent complications, and assessment of aneurysm sac size 1