The natural history of intimal flaps caused by angioscopy

Minimal Aortic Injury: Mechanisms, Imaging Manifestations, Natural History, and Management

Over the last 2 decades, increased depiction of minimal aortic injury (MAI) in the evaluation of patients who have sustained trauma has mirrored the increased utilization and improved resolution of multidetector CT. MAI represents a mild form of blunt traumatic aortic injury (BTAI) that usually resolves or stabilizes with pharmacologic management. The traditional imaging manifestation of MAI is a subcentimeter round, triangular, or linear aortic filling defect attached to an aortic wall, representing a small intimal flap or thrombus consistent with grade I injury according to the Society for Vascular Surgery (SVS). Small intramural hematoma (SVS grade II injury) without external aortic contour deformity is included in the MAI spectrum in several BTAI classifications on the basis of its favorable outcome. Although higher SVS grades of injury generally call for endovascular repair, there is growing literature supporting conservative management for small pseudoaneurysms (SVS grade III) and large intimal flaps (>1 cm, unclassified by the SVS), hinting toward possible future inclusion of these entities in the MAI spectrum. Injury progression of MAI is rare, with endovascular aortic repair reserved for these patients as well as patients for whom medical treatment cannot be implemented. No consensus on the predetermined frequency and duration of multidetector CT follow-up exists, but it is common practice to perform a repeat CT examination shortly after the initial diagnosis. The authors review the evolving definition, pathophysiology, and natural history of MAI, present the primary and secondary imaging findings and diagnostic pitfalls, and discuss the current management options for MAI. Online DICOM image stacks are available for this article. ^©RSNA, 2020.

To reduce routine computed tomographic angiography for thoracic aortic injury assessment in level II blunt trauma patients using three mediastinal signs on the initial chest radiograph: a preliminary report

PURPOSE

CTA is routinely ordered on level II blunt thoraco-abdominally injured patients for assessment of injury to the thoracic aorta. The vast majority of such assessments are negative. The question being asked is, Does the accurate interpretation of the three mediastinal signs permit reliable determination of which patients need CTA for aortic assessment? The purpose of this investigation was to evaluate the role of three specifically selected mediastinal anatomic signs on the initial supine chest radiograph (CXR) of adult level II blunt thoraco-abdominally injured patients for the presence or absence of a mediastinal hematoma. The presence of a mediastinal hematoma is typically used as an indicator for computed tomographic angiography (CTA). The three mediastinal signs are the right para-tracheal stripe (RPTS), left para-spinal line (LPSL), and the left apical extra-pleural area (LAPA).

MATERIALS AND METHODS

The patient triage designation (level II trauma) was made by the attending physician at the time of admission. The initial CXR image and the CTA report of the 197 adult blunt level II thoraco-abdominally injured patients obtained on the day of admission were compared. The CXR of each of the 197 patients was independently assessed by each of four observers specifically for the status of the three mediastinal signs. Each observer was blinded to the CTA report until after the status of the three mediastinal sign evaluation had been determined. Two or three of the mediastinal signs being positive were required to determine that the CXR was positive for a mediastinal hematoma.

RESULTS

Two or three of the selected mediastinal signs were normal in 192 (97.5%) patients. None of these patients had either a mediastinal hematoma or a major aortic injury on CTA. In each of the remaining five (2.5%) patients, two or three of the mediastinal signs were abnormal. Each of these patients had a mediastinal hematoma and a major thoracic aortic injury on CTA.

CONCLUSIONS

This preliminary study suggests that the accurate interpretation of the three specifically selected mediastinal signs on the initial supine CXR of adult level II blunt thoraco-abdominally injured patients could reduce the need for routine CTA for thoracic aortic injury assessment, and requires verification by an additional study.

Influence of Angioscopic Vein Graft Preparation on Development of Neointimal Hyperplasia in an Organ Culture Model of Human Saphenous Vein

Purpose:

Angioscopy for in situ vein graft preparation has been criticized on the basis that the trauma of instrumentation may predispose to accelerated intimal hyperplasia, jeopardizing patency rates following infrainguinal revascularization. The aim of this study was to assess the effects of angioscopic preparation on endothelial integrity and smooth muscle cell (SMC) behavior in an established organ culture model of human saphenous vein (HSV).

Methods:

HSV was harvested from 12 patients during bypass surgery before and after angioscopic preparation. Endothelial integrity was evaluated by immunohistochemical staining with JC-70 and scanning electron microscopy (SEM); remaining segments of pre-and postangioscopy vein were maintained in culture for 14 days in medium supplemented with 30% fetal calf serum. Viability was confirmed by measurement of tissue adenosine triphosphate on day 14 and thickness of the neointima was measured by computerized image analysis of histologic sections. Monoclonal antibodies to proliferating cell nuclear antigen (PCNA) were used as an immunohistochemical marker for proliferating SMCs.

Results:

There was a significant reduction in the percentage staining by JC-70 (71.3% versus 20.4%) in pre- versus postangioscopy vein (p = 0.002 by Wilcoxon's rank test; n = 12). This was supported by SEM images. Despite this, there were no significant differences between the pre- and postangioscopy HSVs after 14 days of culture with respect to neointimal thickness (61 versus 56 μm) and staining with PCNA (4.80 versus 4.08 nuclei per 10 (μm), all according to Wilcoxon's rank test.

Conclusions:

Angioscopic vein graft preparation is associated with endothelial cell loss but does not induce additional neointimal hyperplasia in HSV in vitro. These results suggest that angioscopic manipulation does not alter SMC behavior.

Natural history of minimal aortic injury following blunt thoracic aortic trauma

BACKGROUND

Endovascular repair of blunt traumatic thoracic aortic injuries (BTAI) is common at most trauma centres, with excellent results. However, little is known regarding which injuries do not require intervention. We reviewed the natural history of untreated patients with minimal aortic injury (MAI) at our centre.

METHODS

We conducted a retrospective database review to identify all patients with a BTAI between October 2008 and March 2010. The cohort comprised patients initially untreated because of the lesser degree of injury of an MAI. We reviewed initial and follow-up computed tomography (CT) scans and clinical information.

RESULTS

We identified 69 patients with a BTAI during the study period; 10 were initially untreated and were included in this study. Degree of injury included intimal flaps (n = 7, 70%), pseudoaneurysms with minimal hematoma (n = 2, 20%) and circumferential intimal tear (n = 1, 10%). Six (60%) patients were male, and the median age was 40 years. Duration of clinical follow-up ranged from 1 month to 6 years (median 2 mo) after discharge, whereas CT radiologic follow-up ranged from 1 week to 6 years (median 6 wk). Seven (70%) patients had complete resolution or stabilization of their MAI, 1 (10%) with circumferential intimal tear showed extension of the injury at 8 weeks postinjury and underwent successful repair, and 2 (20%) were lost to follow-up.

CONCLUSION

There appears to be a subset of patients with BTAI who require no surgical intervention. This includes those with limited intimal flaps, which often resolve. Radiologic surveillance is mandatory to ensure MAI resolution and identify any progression that might prompt repair.

Potential long-term complications of endovascular stent grafting for blunt thoracic aortic injury

Blunt thoracic aortic injury (BTAI) is a rare, but lethal, consequence of rapid deceleration events. Most victims of BTAI die at the scene of the accident. Of those who arrive to the hospital alive, expedient aortic intervention significantly improves survival. Thoracic endovascular aortic repair (TEVAR) has been accepted as the standard of care for BTAI at many centers, primarily due to the convincing evidence of lower mortality and morbidity in comparison to open surgery. However, less attention has been given to potential long-term complications of TEVAR for BTAI. This paper focuses on these complications, which include progressive aortic expansion with aging, inadequate stent graft characteristics, device durability concerns, long-term radiation exposure concerns from follow-up computed tomography scans, and the potential for (Victims of Modern Imaging Technology) VOMIT.

Minimal aortic injury: a lesion associated with advancing diagnostic techniques

BACKGROUND

With the increasing use of high-resolution diagnostic techniques, minimal aortic injuries (MAI) are being recognized more frequently. Recently, we have used nonoperative therapy as definitive treatment for patients with MAI. The current study examines our institutional experience with these patients from July 1994 to June 2000.

METHODS

All patients suspected of blunt aortic injury (BAI) by screening helical CT (HCT) underwent confirmatory aortography with or without intravascular ultrasound (IVUS). MAI was defined as a small (<1 cm) intimal flap with minimal to no periaortic hematoma.

RESULTS

Of the 15,000 patients evaluated by screening HCT, 198 (1.3%) were suspected of having BAI. BAI was confirmed in 87 (44%), and 9 (10%) of these had MAI. The initial aortogram was considered normal in five of the MAI patients. The correct diagnosis was made by IVUS (four patients), and video angiography (one patient). One MAI patient had surgery, and two (22%) died of causes not related to the aortic injury. Follow-up studies were done on the six MAI patients that were discharged. In two, the flap had completely resolved, and in one it remained stable. The remaining three patients formed small pseudoaneurysms.

CONCLUSION

Ten percent of BAI diagnosed with high resolution techniques have MAI. These intimal injuries heal spontaneously and hence may be managed nonoperatively. However, the long-term natural history of these injuries is not known, and hence caution should be exercised in using this form of treatment.

Influence of angioscopic vein graft preparation on development of neointimal hyperplasia in an organ culture model of human saphenous vein

PURPOSE

Angioscopy for in situ vein graft preparation has been criticized on the basis that the trauma of instrumentation may predispose to accelerated intimal hyperplasia, jeopardizing patency rates following infrainguinal revascularization. The aim of this study was to assess the effects of angioscopic preparation on endothelial integrity and smooth muscle cell (SMC) behavior in an established organ culture model of human saphenous vein (HSV).

METHODS

HSV was harvested from 12 patients during bypass surgery before and after angioscopic preparation. Endothelial integrity was evaluated by immunohistochemical staining with JC-70 and scanning electron microscopy (SEM); remaining segments of pre- and postangioscopy vein were maintained in culture for 14 days in medium supplemented with 30% fetal calf serum. Viability was confirmed by measurement of tissue adenosine triphosphate on day 14 and thickness of the neointima was measured by computerized image analysis of histologic sections. Monoclonal antibodies to proliferating cell nuclear antigen (PCNA) were used as an immunohistochemical marker for proliferating SMCs.

RESULTS

There was a significant reduction in the percentage staining by JC-70 (71.3% versus 20.4%) in pre- versus postangioscopy vein (p = 0.002 by Wilcoxon's rank test; n = 12). This was supported by SEM images. Despite this, there were no significant differences between the pre- and postangioscopy HSVs after 14 days of culture with respect to neointimal thickness (61 versus 56 microns) and staining with PCNA (4.80 versus 4.08 nuclei per 10 microns), all according to Wilcoxon's rank test.

CONCLUSIONS

Angioscopic vein graft preparation is associated with endothelial cell loss but does not induce additional neointimal hyperplasia in HSV in vitro. These results suggest that angioscopic manipulation does not alter SMC behavior.

Angioscopy in vascular surgery: the state of the art

Although angioscopy is considered by many vascular surgeons to be a valuable clinical tool, others view it as expensive and unnecessary. To better define the appropriate role for angioscopy in vascular surgery, a critical review of the recent literature was undertaken. Angioscopy allows more complete valvulotomies with fewer endothelial injuries when preparing autogenous veins to be used as arterial conduits, and results in more complete thromboembolectomy of native arteries and grafts. Angioscopy can replace completion arteriography in infrainguinal arterial reconstructions with an equivalent clinical outcome. Angioscopy may be useful in the assessment of carotid endarterectomy, femoral vein valve repair, and pulmonary embolectomy. It has been useful in various research applications. The rate of complications is less than 1%. Angioscopy is of benefit in preparing veins to be used as arterial conduits and in performing thromboembolectomy. In some circumstances it can replace intraoperative arteriography. Other applications await further validation. The risks of angioscopy are acceptably low.

Value of angioscopy for intraoperative assessment of carotid endarterectomy

From March 1992 to November 1993 we used angioscopy and arteriography for intraoperative assessment of 103 carotid endarterectomies in 96 patients. The indication for surgery was asymptomatic stenosis in 55 cases and neurologic and/or ocular symptoms in 48. Intraoperative angioscopy and arteriography were performed to allow comparison of findings. Intraoperative angioscopic images were normal in 67 cases and abnormal in 36. The defect was an intimal flap in 26 cases, detachment of the distal plaque in seven cases, and an intimal wedge in five cases. In two cases both detachment and a wedge were observed. The defect was not considered severe enough to warrant revision in 31 cases and was corrected in five cases by either vein bypass (n = 1) or revision of the endarterectomy (n = 4). In the latter four cases repeat angioscopy showed normal findings. Arteriographic and angioscopic findings were compared in 102 cases. In the 71 cases in which angioscopic findings were normal, arteriography revealed a major abnormality in three cases: kinking in one and stenosis > 40% in two. Kinking was treated by attachment of the common carotid artery and stenosis by venous bypass. In the 31 cases in which angioscopy revealed defects not considered to warrant revision, arteriography revealed stenosis > 40% in three cases treated by either prosthetic bypass (n = 2) or revision of the endarterectomy (n = 1). The false negative rate for angioscopy was 5.9% and concordance between the two methods was 94.1%. The combined mortality-morbidity rate was 1.9% (one stroke and one death). Postoperative evaluation of anatomic findings by arteriography or Doppler ultrasonography revealed asymptomatic internal carotid occlusion in one and internal carotid stenosis < 30% in four cases. Angioscopy is a simple, low-cost method in intraoperative control that can be used either as an adjunct to arteriography or as an alternative if arteriography cannot be performed.

Intraluminal endothelium-covered bridges in chronic fat-fed balloon-injured Yucatan miniswine

The Yucatan miniswine has been recommended as an animal model of advanced atherosclerosis. Atherosclerotic plaques developed in this model demonstrate foam cells, widespread fibrosis, and calcification, features suggestive of human atherosclerosis. We have observed the occurrence of intraluminal projections that appear peculiar to this animal model. Forty-three miniswine, weighing between 20 and 30 kg, were rendered atherosclerotic with a combination of balloon endothelial injury of the aortoiliac segments and dietary supplementation with 2% cholesterol and 15% lard. Endothelial injury was created by retrograde balloon catheter injury of the aorta and both external iliac arteries via cutdowns on the femoral arteries. Serum cholesterol prior to starting the diet and at 1, 2, and 6 weeks following initiation of the diet was 2.0 +/- 0.4, 11.6 +/- 4.0, 15.9 +/- 5.0, and 16.4 +/- 4.2 mM, respectively (p < .0001, ANOVA). Angiographically significant lesions were apparent in 33 of 37 (89%) animals (occlusion 20/37, stenosis 17/37) at 6 weeks postinjury. In three of six (50%) animals followed up to 16 weeks postinjury, trabecular areas were seen in the external iliac arteries on angiography. Light and electron microscopy demonstrated that these areas were covered with normal endothelium and projected into the lumen or bridged with the adjacent arterial wall. Foam cells and calcification were not seen in these lesions. This finding is not typical of human atherosclerosis and appears peculiar to this type of animal model.

Role of completion angioscopy in detecting technical error after carotid endarterectomy

Completion fibreoptic angioscopy was performed in 30 consecutive patients after carotid endarterectomy. The aim was to evaluate the potential role of angioscopy as a quality-control technique. Major abnormalities (two initial flaps, two large thrombi) were identified in four patients and minor adherent thrombus was encountered in five. All abnormalities were corrected before restoration of flow. This preliminary experience suggests that completion angioscopy merits further study as a method for the intraoperative detection of potentially harmful lesions after carotid endarterectomy.