Postoperative imaging of thoracic aortic repairs

Imaging plays a crucial role in the postoperative monitoring of thoracic aortic repairs. With the development of multiple surgical techniques to repair the ascending aorta and aortic arch, it can be a daunting challenge for the radiologist to diagnose potential pathologies in this sea of various techniques, each with their own normal postoperative appearance and potential complications. In this paper, we will provide a comprehensive review of the postoperative imaging in the setting of thoracic aortic repairs, including the role of imaging, components of thoracic aortic repairs, the normal postoperative appearance, and potential complications.

Misdiagnosis of Thoracic Aortic Emergencies Occurs Frequently Among Transfers to Aortic Referral Centers: An Analysis of Over 3700 Patients

Background

Acute aortic syndromes may be prone to misdiagnosis by nonreferral aortic centers with less diagnostic experience. We evaluated regional variability in these misdiagnosis trends among patients transferred to different regional quaternary care centers with presumed acute aortic syndromes.

Methods and Results

Two institutional aortic center databases were retrospectively reviewed for emergency transfers in patients diagnosed with acute aortic dissection, intramural hematoma, penetrating aortic ulcer, thoracic aortic aneurysm, or aortic pseudoaneurysm between 2008 and 2020. Transferring diagnoses versus actual diagnoses were reviewed using physician notes and radiology reports. Misdiagnoses were confirmed by a board‐certified cardiothoracic surgeon. A total of 3772 inpatient transfers were identified, of which 1762 patients were classified as emergency transfers. The mean age was 64 years (58% male). Patients were transferred from 203 medical centers by ground (51%) or air (49%). Differences in transfer diagnosis and actual diagnosis were identified in 188 (10.7%) patients. Of those, incorrect classification of Type A versus B dissections was identified among 23%, and 30% of patients with a referring diagnosis of an acute aortic dissection did not have one. In addition, 14% transferred for contained/impending rupture did not have signs of rupture. All misdiagnoses were secondary to misinterpretation of imaging, with motion artifacts (n=32, 17%) and postsurgical changes (n=44, 23%) being common sources of diagnostic error.

Conclusions

Misdiagnosis of acute aortic syndromes commonly occurred in patients transferred to 2 separate large aortic referral centers. Although diagnostic accuracy may be improving, there are opportunities for improved physician awareness through standardized web‐based imaging education.

CT of Postoperative Repair of the Ascending Aorta and Aortic Arch

While many of the classic open surgical repairs are still used to repair the ascending aorta, management of the aortic arch has become more complex via implementation of newer open surgical and endovascular techniques. Furthermore, techniques are often combined in novel repairs or to allow extended anatomic coverage. As such, a framework that rests on understanding the expected postoperative appearance is necessary for the diagnostic radiologist to best interpret CT studies in these patients. After reviewing the imaging appearances of the common components used in proximal aortic repair, the authors present a structured approach that focuses on the key relevant questions that diagnostic radiologists should consider when interpreting CT studies in these patients. For repair of the ascending aorta, this includes determining whether the aortic valve has been repaired, whether the sinuses of Valsalva have been repaired, and how the coronary arteries were managed, when necessary. In repairs that involve the aortic arch, the relevant considerations relate to management of the arch vessels and the distal extent of the repair. In focusing on these questions, the diagnostic radiologist will be able to identify and describe the vast majority of repairs. Understanding these questions will also facilitate improved understanding of novel repairs, which often use these basic building blocks. Finally, complications-which typically involve infection, noninfectious repair breakdown, hemorrhage, problems with endografts, or disease of the remaining adjacent aorta-will be identifiable as deviations from the expected postoperative appearance. Online supplemental material is available for this article. ^©RSNA, 2021.

A biomimetic approach for designing stent-graft structures: Caterpillar cuticle as design model

Stent-graft (SG) induced biomechanical mismatch at the aortic repair site forms the major reason behind postoperative hemodynamic complications. These complications arise from mismatched radial compliance and stiffness property of repair device relative to native aortic mechanics. The inability of an exoskeleton SG design (an externally stented rigid polyester graft) to achieve optimum balance between structural robustness and flexibility constrains its biomechanical performance limits. Therefore, a new SG design capable of dynamically controlling its stiffness and flexibility has been proposed in this study. The new design is adopted from the segmented hydroskeleton structure of a caterpillar cuticle and comprises of high performance polymeric filaments constructed in a segmented knit architecture. Initially, conceptual design models of caterpillar and SG were developed and later translated into an experimental SG prototype. The in-vitro biomechanical evaluation (compliance, bending moment, migration intensity, and viscoelasticity) revealed significantly better performance of hydroskeleton structure than a commercial SG device (Zenith(™) Flex SG) and woven Dacron(®) graft-prosthesis. Structural segmentation improved the biomechanical behaviour of new SG by inducing a three dimensional volumetric expansion property when the SG was subjected to hoop stresses. Interestingly, this behaviour matches the orthotropic elastic property of native aorta and hence proposes segmented hydroskeleton structures as promising design approach for future aortic repair devices.

Computed tomography angiography of hybrid thoracic endovascular aortic repair of the aortic arch

Endovascular repair of the aorta has traditionally been limited to the abdominal aorta and, more recently, the descending thoracic aorta. However, recently hybrid repairs (a combination of open surgical and endovascular repair) have made endovascular repair of the aortic arch possible. Hybrid repair of the aortic arch typically involves an open surgical debranching procedure that allows for revascularization of the aortic arch vessels and subsequent endovascular stent placement. These approaches avoid the deep hypothermic circulatory arrest required for full, open surgical repair of the aortic arch. In hybrid repairs, the stent landing zone determines which branch vessels will be covered and therefore need revascularization. This article will review the preprocedure assessment with computed tomography angiography, techniques for revascularization and postprocedure complications.

Evaluation of the aortic root with MRI and MDCT angiography: spectrum of disease findings

OBJECTIVE

This article reviews the spectrum of disease processes that may involve the aortic root with particular emphasis on the role of cardiovascular MRI and MDCT angiography in their assessment. Key MRI and MDCT imaging findings are discussed and illustrated.

CONCLUSION

Radiologists should be aware of the spectrum of disease processes that may involve the aortic root and their appearances at MRI and MDCT angiography.

Unusual complications of endovascular repair of the thoracic aorta: MDCT findings

With the development of minimally invasive surgical techniques, endovascular stent-graft placement has become an accepted and widely used alternative to the traditional surgical repair of aortic disease and is gaining acceptance as the treatment of choice. Many studies show that endovascular stent-graft therapy is safe and effective, although complications related to this treatment are also recognised. Although the incidence of major complication is low, neurological sequelae remain the major concern of endovascular repair. With growing experience, however, the spectrum of mid- and long-term complications has broadened to include potentially disastrous events, other than paraplegia or stroke, that require diligent surveillance. Three-dimensional data sets acquired quickly by multidetector computed tomography (MDCT) allow multiplanar reformations and 3D viewing, as well as quantitative assessment of vessel lumens, walls and surroundings. Although a large portion of radiologists will not be involved in the actual endograft deployment, many will be involved in the interpretation of postprocedural surveillance studies. Accordingly, the goal of this report is to summarise our experience with the presentation, diagnostic approach, management and outcomes of these unusual, but potentially catastrophic, postendovascular aortic repair complications to highlight their significance and increase familiarity with them among the imaging community. Increasing awareness of these complications may facilitate rapid diagnosis and/or triage and treatment.

Endovascular management of thoracic aortic aneurysms

The overall survival of patients with thoracic aortic aneurysm (TAA) has improved significantly in the past few years. Endovascular treatment, proposed as an alternative to surgery, has been considered a therapeutic innovation because of its low degree of invasiveness, which allows the treatment of even high-surgical risk patients with limited complications and mortality. A major limitation is the lack of adequate evidence regarding long-term benefit and durability because follow-up has been limited to just a few years even in the largest series. The combination of endovascular exclusion with visceral branch revascularization for the treatment of thoraco-abdominal aortic aneurysms involving the visceral aorta has also been attempted. As an alternative, endografts with branches represent a technological evolution that allows treatment of complex anatomy. Even if only small numbers of patients and short follow-up are available, this technical approach, which has with limited mortality (<10%) and paraplegia rates, to expand endovascular treatment to TAA seems feasible. With improved capability to recognize proper anatomy and select clinical candidates, the choice of endovascular stent-graft placement may offer a strategy to optimize management and improve prognosis.

Endovascular therapy for thoracic aneurysm diseases: PRO

Although the long-term durability of stent grafts is still a concern, stent-graft treatment is already the best option in a large number of patients with descending thoracic aortic diseases who are poor candidates for surgical repair, or in an acute setting. With improved capability to recognize proper anatomy and select clinical candidates, the choice of endovascular stent-graft placement may offer a strategy to optimize management and improve prognosis.