What is a chimney graft into the innominate artery?

Chimney Graft into the Innominate Artery: Definition and Applications

A chimney graft into the innominate artery is an endovascular technique that involves placing a stent graft parallel to the main thoracic aortic stent graft to maintain blood flow to the innominate artery when the proximal landing zone of the main aortic stent graft extends across the origin of this vessel.

Definition and Technical Aspects

• A chimney graft is used during thoracic endovascular aortic repair (TEVAR) when the aortic pathology requires coverage of the origin of supra-aortic branches, including the innominate artery 1, 2
• The technique involves deploying a covered or uncovered stent from the innominate artery into the aortic arch, with the proximal portion extending parallel to the main aortic stent graft (creating a "chimney" appearance) 2, 3
• The chimney stent maintains blood flow to the innominate artery while allowing the main aortic stent graft to achieve adequate proximal sealing in the aortic arch 2, 4

Indications

• Used in high-risk patients with aortic arch disease who are not suitable candidates for open surgical repair 2
• Common indications include:
  • Aortic arch aneurysms with inadequate proximal landing zones 2, 3
  • Complicated type B aortic dissections extending into the arch 2, 5
  • Type I endoleaks after previous TEVAR requiring extension into the arch 5, 4
  • Emergency situations where rapid preservation of branch vessel flow is needed 3

Anatomical Considerations

• The innominate artery is the first and largest branch of the aortic arch, giving rise to the right subclavian and right common carotid arteries 1
• When planning a chimney graft procedure, careful assessment of the aortic arch morphology (Type I, II, or III) is essential as it affects technical feasibility 1
• Precise pre-procedural planning with contrast-enhanced CT is required to evaluate the diameter and length of landing zones and relationship to side branches 1

Technical Procedure

• The procedure is performed via retrograde transarterial approach, typically with femoral access for the main aortic stent graft and upper extremity or direct cervical access for the chimney stent 1
• The chimney stent is deployed first, followed by the main aortic stent graft, or they may be deployed simultaneously 2, 4
• Careful attention is paid to maintain proper alignment and prevent compression or migration of the chimney stent 4
• Completion angiography is performed to detect any endoleaks, particularly type I endoleaks at the interface between the chimney graft and main stent graft 1

Outcomes and Complications

• Technical success rates are reported to be approximately 89% in high-risk patients 2
• Potential complications include:
  • Type I endoleaks (reported in up to 13% of cases) 2, 4
  • Stroke (higher risk with unplanned chimney placement) 6, 2
  • Chimney stent compression or migration 7, 4
  • Thrombosis of the chimney stent 7
• The 1-year and 3-year survival rates after chimney graft procedures have been reported as 88% and 69%, respectively 2

Double Chimney Technique

• When multiple supra-aortic vessels need to be preserved, a double chimney technique may be employed 4
• This typically involves chimney grafts to both the innominate artery and the left common carotid artery 5, 4
• This approach allows for more extensive coverage of the aortic arch while maintaining cerebral perfusion 4

Comparison with Alternative Approaches

• Traditional open surgical repair of aortic arch disease carries significant morbidity (30-40%) and mortality (2-20%) 2
• Hybrid procedures combining surgical debranching with endovascular repair are another option for patients with aortic arch disease 1
• Fenestrated or branched endografts represent evolving technologies that may provide more durable solutions but are less widely available and require custom manufacturing 1

Pitfalls and Considerations

• Careful patient selection is crucial as not all anatomies are suitable for chimney techniques 2, 3
• Excessive length of chimney grafts should be avoided as this may lead to retrograde migration 7
• Unplanned chimney placement during TEVAR is associated with higher stroke risk 2
• Long-term durability remains a concern, with reintervention rates of approximately 33% reported in some series 2
• Diligent follow-up with regular imaging is essential to monitor for complications 2, 4