The Aortic Arch: Markers, Imaging, and Procedure Planning for Carotid Intervention
- Volume 6 - Issue 1 - Jan/Feb 2009
- Posted on: 1/14/09
- 1 Comments
- 22512 reads
Christos D. Liapis, MD, Efthimios D. Avgerinos, MD, Achilles Chatziioannou, MD
From the University Hospital Attikon, Department of Vascular Surgery, Athens, Greece.
Correspondence: Christos D. Liapis, MD, University Hospital Attikon, Department of Vascular Surgery, 1 Rimini Street, Chaidari, Athens 12462, Greece. E-mail: email@example.com.
Manuscript submitted September 15, 2008, provisional acceptance given, November 5, 2008, accepted November 13, 2008.
Disclosure: The authors report no financial relationships or conflicts of interest regarding the content herein.
Among the several anatomic risk predictors for carotid stenting (e.g., extensive plaque ulceration, aneurysmal internal carotid artery, lesion length > 3 cm) (CAS), the aortic arch emerges as a key anatomic feature. Gaining access to the carotid lesion necessitates traversing the aortic arch and the proximal carotid arteries. Most technical failures in carotid stenting are related to a complex aortic arch whose role in CAS outcome rises as a crucial element of patient selection. The arch markers for selecting patients for carotid interventions include arch elongation, arch vessel origin configuration, arch calcification, and arch vessel origin stenosis. These markers get significantly unfavorable with increasing age. Cautious pre-interventional imaging is paramount in indentifying potential arch complexity and direct the interventional strategy. CAS practitioners would be advised to start their experience in younger patients with predominantly noncalcified type 1 arches.
Despite increasing experience in carotid angioplasty and stenting (CAS), optimal patient and anatomy selection remain the most important considerations for a successful outcome. Technical limitations and complications still exist, denoting that several issues still remain to be resolved.
Contrary to carotid endarterectomy (CEA) being non-favorable for patients with severe medical comorbidities, CAS is usually not indicated on the basis of anatomical limitations, not only of the carotids, but of the entire pathway, from the puncture site to the cerebral arteries.1 Among the several anatomic risk predictors (e.g., extensive plaque ulceration, aneurysmal internal carotid artery, lesion length > 3 cm), the aortic arch emerges as a key anatomic feature for CAS success (or failure).1,2
Regardless of the complexity of the internal carotid lesion or the degree of stenosis, accessing those lesions with the appropriate filter and stent is usually technically feasible. The arch, however, is a different challenge. Initially, its role had been underestimated and was not considered a major procedural limitation. Recently, the aortic arch has become a crucial element in patient selection for CAS, with arch markers being used to guide the operator for case selection and pre-interventional planning.2,3
The arch markers for selecting patients for carotid interventions include arch elongation, arch vessel origin configuration, arch calcification, and arch vessel origin stenosis. This review focuses on aortic arch features, anatomy assessment, patient selection, and planning and execution without compromising patient safety.
Arch elongation and arch vessel configuration. It is important to recognize the type of aortic arch and the configuration of the great vessels in each patient, since these anatomic features influence procedure complexity.
The aortic arch elongation classification was conceived to picture an increasing procedural difficulty in vessel cannulation (Figure 1), which was also helpful in designing catheter configurations, allowing easier access to the great vessels off the arch. There are three types of aortic arches based on the relationship of the innominate artery to the aortic arch or on the parallel planes perpendicular to the greater (outer) curvature and lesser (inner) curvature of the arch.4–6 Some authors have also suggested a type IV arch.2
Alternatively, arch complexity can be assessed by drawing a line horizontally across the upper inner aspect of the arch. When the origin of the target artery is above the horizontal line and to the patients’ right, catheterization presents a moderate degree of challenge. The closer the arch branch origin is to the horizontal line, the more challenging it becomes.7
• Type I arch. The arch vessels arise from the outer curvature of the arch in the same horizontal plane (no angulation). The vertical distance from the origin of the innominate artery to the top of the arch is < 1 diameter of the left common carotid artery (CCA) (Figure 1a).
• Type II arch. The arch vessels arise between the parallel planes delineated by the outer and inner curves of the arch (moderate angulation). The vertical distance from the origin of the innominate artery to the top of the arch is between 1 and 2 left CCA diameters (Figure 1b).
• Type III arch. The arch vessels arise proximal or caudal to the lesser curvature of the arch or off the ascending aorta (severe angulation). The vertical distance from the origin of the innominate artery to the top of the arch is > 2 left CCA diameters (Figure 1c).
• Type IV arch. The arch vessels arise with severe angulation, accompanied by increased length and transverse diameters of the arch. This arch type is associated with redundancy of the CCA. It is more frequently noted on the right, where tortuosity and the redundant loop exist in the proximal segment of the CCA.
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