What is the etiology of watershed areas in the face of patients with aortic graft surgery?

Etiology of Watershed Areas in the Face of Patients with Aortic Graft Surgery

Watershed areas in the face of patients with aortic graft surgery primarily result from atheroemboli originating from the descending thoracic aorta during endovascular procedures, causing compromised perfusion in terminal vascular territories. 1

Mechanisms of Watershed Infarcts in the Face

Embolic Phenomena

• Stroke and facial watershed infarcts occur in 2.5-8% of patients undergoing thoracic endovascular procedures, with most resulting from atheroemboli dislodged from the descending thoracic aorta during device manipulation 1
• Major adverse events related to endovascular devices occur in 10-12% of patients in the initial 30-day perioperative period 1
• Thromboemboli can affect not only cerebral vessels but also facial arterial branches, creating watershed areas of compromised perfusion 1

Hemodynamic Factors

• Hypoperfusion during periods of hemodynamic instability during aortic procedures can lead to watershed infarcts in terminal vascular territories of the face 1
• Watershed areas represent junctions between different arterial territories, making them vulnerable to ischemia during periods of reduced perfusion pressure 1
• The junction between the hard and soft palate has been identified as a specific watershed area in facial artery-based allografts, suggesting similar vulnerability in native facial tissues 2

Specific Risk Factors for Facial Watershed Infarcts

Procedural Factors

• Large diameter endografts (34-36mm) are associated with higher thrombotic complications compared to smaller endografts (24-26mm) (45.5% vs 7.1%) 3
• Manipulation of the aortic arch during endovascular procedures increases the risk of embolization to the cerebral and facial circulation 1
• Increased aortic tortuosity in the proximal landing zone is associated with higher risk of endoleak and subsequent embolic complications 1

Patient-Related Factors

• Pre-existing atherosclerotic disease increases the risk of atheroemboli during endovascular manipulation 1
• Malperfusion syndromes, rather than merely timing of repair, determine early and late outcomes in aortic dissection patients 4
• Changes in aortic hemodynamics after endovascular repair, including reduced time-averaged wall shear stress and increased residence time, correlate with thrombotic complications 3

Anatomical Considerations

Facial Arterial Supply

• The maxillary artery is traditionally considered the main blood supply of the facial skeleton, but its deep location makes it vulnerable to compromise during aortic procedures 2
• The facial artery provides an alternative supply but may be insufficient in watershed areas when perfusion pressure is compromised 2
• Junctions between different arterial territories in the face create natural watershed zones vulnerable to ischemia during embolic events or hypoperfusion 2

Prevention and Management

Procedural Modifications

• Careful selection of endograft size may reduce hemodynamic alterations that lead to thrombotic complications 3
• Identification of high-risk anatomical features (such as aortic tortuosity) before intervention allows for more careful procedural planning 1
• Preservation of critical branch vessels during endovascular procedures is essential to maintain adequate facial perfusion 1

Monitoring and Follow-up

• Close monitoring for signs of facial ischemia in the perioperative period is essential, especially in high-risk patients 1
• Patient-specific computational fluid dynamic simulation can help identify patients at higher risk for thrombotic complications that may affect facial perfusion 3
• Regular follow-up imaging can detect early signs of endoleak or graft complications that may lead to embolic events 1

Complications and Long-term Outcomes

• Endoleaks occur in 10-20% of patients after thoracic endografting, with the highest frequency in the first month following implantation 1
• Late complications of thoracic aortic endografting include continued aneurysm growth, stent fracture, migration, perforation, and infection, all of which can lead to embolic phenomena 1
• The overall need for repeat interventions to maintain endograft integrity is 6-7%, with each intervention carrying additional risk of embolic complications 1

Understanding the etiology of facial watershed areas in patients with aortic graft surgery is crucial for early identification and management of this potentially serious complication.