Clinical and patho-anatomical factors affecting expansion of thoracic aortic aneurysms

Differential expansion and outcomes of ascending and descending degenerative thoracic aortic aneurysms

OBJECTIVE

To evaluate expansion of degenerative thoracic aortic aneurysms (TAAs) and compare results between ascending and descending TAAs.

METHODS

Among patients with diagnosis of degenerative TAA (1995-2015) in Olmsted County, we studied those having at least 2 computed tomography scans of TAA throughout the follow-up. Patients were classified as ascending or descending groups according to the segment where the maximal aortic diameter was measured. Primary end points were expansion rates and factors associated with TAA growth.

RESULTS

We investigated 137 patients, 70 (51.1%) of whom were women; 78 (56.9%) were in the ascending and 59 (43.1%) were in the descending group. Median baseline maximal aortic diameter was 48.5 mm (interquartile range, 47.0-49.9 mm) for ascending and 42.4 mm (interquartile range, 40.0-45.4 mm) for descending group (P < .001). Median expansion rate was higher in the descending than the ascending group (2.0 mm/year [interquartile range, 0.9-3.2 mm/year] vs 0.2 mm/year [IQR, 0.1-0.6 mm/year]; P < .001). Aneurysm in the descending aorta and larger baseline maximal aortic diameter were independently associated with TAA expansion. Advanced age and chronic obstructive pulmonary disease but not aneurysm size or location were independently associated with overall mortality (P < .05). Aneurysm in the descending aorta was associated with aortic-related events (P < .05).

CONCLUSIONS

Degenerative TAAs under surveillance expand slowly. Descending TAA and larger baseline maximal aortic diameter were independently associated with more rapid TAA expansion, but these factors did not influence all-cause mortality.

Thoracic Aortic Aneurysms and Arch Disease

Aortic arch and descending thoracic pathology have historically remained in the realm of open surgical repair. Technology is quickly pushing to bring these under the endovascular umbrella, with lower morbidity repairs proving safe in their early experience. Much work remains particularly for acute aortic syndromes, however, to understand who is best treated medically, surgically, endovascularly, or with hybrid approaches.

Epidemiology of thoracoabdominal aortic aneurysms

Thoracoabdominal aortic aneurysms, although rare, continue to be associated with high morbidity and mortality in the modern era of vascular surgery, and knowledge of this disease is essential for those in clinical practice. Given the clinically silent nature of the disease, it is difficult to determine disease incidence, with most epidemiologic recommendations not made based on evidence regarding those diagnosed with the disease, but extrapolated from data on surgical outcomes. It appears that although men are more likely to develop thoracoabdominal aortic aneurysms, the distribution is not as skewed as in abdominal aortic aneurysms. Current evidence suggests that Black and Hispanic patients continue to have disproportionately poor disease outcomes, mostly attributed to later presentation and undergoing interventions at lower-volume centers. Although select patients meet criteria for disease screening based on personal or family history of aneurysmal disease, general population screening has not been recommended by any professional organization to date. Vascular surgeons need to continue to be at the forefront of thoracoabdominal aortic aneurysm management, especially as care becomes centered around comprehensive "aortic care centers" and as more endovascular therapies become available.

Repair of descending thoracic aortic aneurysms with Ankura Thoracic Stent Graft

OBJECTIVE

The aim of the study was to present the results for patients with atherosclerotic aneurysm of the descending thoracic aorta (DTA) treated with a novel thoracic stent graft.

METHODS

A single-center retrospective review of prospectively collected data was performed. We extracted demographic variables as well as atherosclerotic comorbidities and operation-related and imaging-related data from patients' medical records. We estimated technical success rate, in-hospital and 30-day mortality, and mortality at the end of follow-up as well as complication and reintervention rate in our study cohort. Follow-up computed tomography angiography was performed after 1 month and 6 months and yearly thereafter.

RESULTS

A total of 30 patients (80% male; mean age, 73.7 ± 6.33 years) were treated with Ankura Thoracic Stent Graft (Lifetech, Shenzhen, China) for DTA aneurysm from February 2014 until June 2017. Technical success of the thoracic endovascular aortic repair (TEVAR) was 97% (29/30 patients). A surgical conduit was required in one patient; in three patients, we intentionally covered the left subclavian artery because of insufficient proximal landing zone. No aorta-related deaths were recorded during follow-up. During the early postoperative period, two patients (7%) with long DTA coverage developed paralysis or paraparesis, which immediately resolved after lumbar drainage. No renal complications requiring dialysis were observed. One patient (3%) developed postoperative pulmonary infection, whereas access site complications were 7%. Two symptomatic patients treated outside instructions for use (7%) developed early type IA endoleak and one patient (3%) developed type IB endoleak; type II endoleak was recorded in 3% of the study cohort. During the 30-day postoperative period, two patients died of non-TEVAR-related causes, one of gastrointestinal bleeding and the other of pulmonary infection. During a median follow-up of 31.7 (range, 38.4) months, two more patients also died of non-TEVAR-related causes, one of stroke from carotid artery disease and the other of motor vehicle trauma. In the rest of the cohort, no other adverse events were noted.

CONCLUSIONS

This novel endograft showed early evidence of a safe, effective, and durable endoprosthesis for the treatment of DTA aneurysms.

Hybrid Treatment with Complete Transposition of Supra-Aortic Trunks versus Conventional Surgery for the Treatment of Aortic Arch Aneurysm

OBJECTIVE

The disease of the aortic arch is traditionally approached by open surgical repair requiring cardiopulmonary bypass and circulatory arrest. This study performed a retrospective analysis comparing outcomes through primary hybrid patients submitted to aortic arch surgery without cardiopulmonary bypass with patients submitted to conventional open surgery.

METHODS

25 patients submitted to the aortic arch surgery were selected in the period 2003-2012 at the Madre Teresa Hospital in the city of Belo Horizonte, Brazil; 13 of these underwent hybrid technique without cardiopulmonary bypass and 12 underwent conventional open surgery.

RESULTS

The mortality rate for the hybrid group was 23% and for the conventional surgery group was 17% (P=0.248). The postoperative complication rate was also similar in both groups, with no significant difference.

CONCLUSION

Both techniques proved to be similar in mortality and morbidity. However, due to the small sample, more analytical studies with larger samples and long-term follow-up are needed to clarify this issue.

The Role Matrix Metalloproteinases in the Production of Aortic Aneurysm

Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of aortic aneurysm because the histology of thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) is characterized by the loss of smooth muscle cells in the aortic media and the destruction of extracellular matrix (ECM). Furthermore, AAA have evidence of inflammation and the cellular elements involved in inflammation such as macrophages can produce and/or activate MMPs This chapter focuses on human aortic aneurysm that are not due to specific known genetic causes because this type of aneurysm is the more common type. This chapter will also focus on MMP protein expression rather than on genetic data which may not necessarily translate to increased MMP protein expression. There are supporting data that certain MMPs are increased in the aortic wall. For TAA, it is most notably MMP-1, -9, -12, and -14 and MMP-2 when a bicuspid aortic valve is present. For AAA, it is MMP-1, -2, -3, -9, -12, and -13. The data are weaker or insufficient for the other MMPs. Several studies of gene polymorphisms support MMP-9 for TAA and MMP-3 for AAA as potentially important factors. The signaling pathways in the aorta that can lead to MMP activation include JNK, JAK/stat, osteopontin, and AMP-activated protein kinase alpha2. Substrates in the human vasculature for MMP-3, MMP-9, or MMP-14 include collagen, elastin, ECM glycoprotein, and proteoglycans. Confirmed and potential substrates for MMPs, maintain aortic size and function so that a reduction in their content relative to other components of the aortic wall may produce a failure to maintain aortic size leading to dilatation and aneurysm formation.

The effect of proximal anastomosis on the expansion rate of a dilated ascending aorta in coronary artery bypass surgery: a prospective study

Background:

This study was designed to determine the short- and long-term effects of proximal aortic anastomosis, performed during isolated coronary artery bypass grafting (CABG) in patients with dilatation of the ascending aorta who did not require surgical intervention.

Methods:

The study was performed on 192 (38 female and 160 male patients; mean age, 62.1 ± 9.2 years; range, 42–80 years) patients with dilatation of the ascending aorta who underwent CABG surgery between 1 June 2006 and 31 May 2014. In group 1 (n = 114), the saphenous vein and left internal mammarian artery grafts were used, and proximal anastomosis was performed on the ascending aorta. In group 2 (n = 78), left and right internal mammarian artery grafts were used, and proximal aortic anastomosis was not performed. Pre-operatively and in the first and third years postoperatively, the ascending aortic diameter was measured and recorded using transthoracic echocardiography at four different regions (annulus, sinus of Valsalva, sinotubular junction and tubular aorta).

Results:

A statistically significant difference was found between the groups for the number of grafts used and the duration of aortic cross-clamping and cardiopulmonary bypass. No significant intergroup difference was seen for the mean diameter of the ascending aorta (p > 0.05). Annual changes in the aortic diameter were found to be extremely significantly different in both groups (p = 0.0001). Mean values of the aortic diameter at the level of the sinotubular junction and tubular ascending aorta, mean aortic diameters (p = 0.002 and p = 0.0001, respectively), annual increase in diameter (p = 0.0001 and p = 0.0001, respectively), and mean annual difference in diameter (p = 0.0001 and p = 0.0001, respectively) at one and three years postoperatively were statistically significantly different between the groups.

Conclusion:

In patients with ascending aortic dilatation who did not require surgical intervention and who had proximal anastomosis of the ascending aorta and underwent only CABG, we detected statistically significant increases in the diameter of the sinotubular junction and tubular aorta up to three years postoperatively.

Pathobiology of Idiopathic Ascending Aortic Aneurysms

The majority of ascending aortic aneurysms cannot be related to any specific etiology and should be qualified as idiopathic. The pathobiology of ascending aortic aneurysms remains incompletely understood. Data from direct study are still scarce and often limited because of patient heterogenicity. Currently available information suggests that destructive remodeling of the aortic wall, inflammation and angiogenesis, biomechanical wall stress, and molecular genetics are relevant mechanisms of idiopathic ascending aortic aneurysm formation and progression. Further understanding of these mechanisms will likely provide novel diagnostic, prognostic, and therapeutical tools for the clinician.

Medical treatment of aortic aneurysms in Marfan syndrome and other heritable conditions

Thoracic aortic aneurysms can be triggered by genetic disorders such as Marfan syndrome (MFS) and related aortic diseases as well as by inflammatory disorders such as giant cell arteritis or atherosclerosis. In all these conditions, cardiovascular risk factors, such as systemic arterial hypertension, may contribute to faster rate of aneurysm progression. Optimal medical management to prevent progressive aortic dilatation and aortic dissection is unknown. β-blockers have been the mainstay of medical treatment for many years despite limited evidence of beneficial effects. Recently, losartan, an angiotensin II type I receptor antagonist (ARB), has shown promising results in a mouse model of MFS and subsequently in humans with MFS and hence is increasingly used. Several ongoing trials comparing losartan to β-blockers and/or placebo will better define the role of ARBs in the near future. In addition, other medications, such as statins and tetracyclines have demonstrated potential benefit in experimental aortic aneurysm studies. Given the advances in our understanding of molecular mechanisms triggering aortic dilatation and dissection, individualized management tailored to the underlying genetic defect may be on the horizon of individualized medicine. We anticipate that ongoing research will address the question whether such genotype/pathogenesis-driven treatments can replace current phenotype/syndrome-driven strategies and whether other forms of aortopathies should be treated similarly. In this work, we review currently used and promising medical treatment options for patients with heritable aortic aneurysmal disorders.

Interleukin-6 Receptor Inhibition Prevents Descending Thoracic Aortic Aneurysm Formation

BACKGROUND

Thoracic aortic aneurysms (TAA) and abdominal aortic aneurysms (AAA) represent related but distinct disease processes. Interleukin-6 (IL-6) is known to be significantly upregulated in human TAA and AAA. We hypothesize that loss of IL-6 is protective in experimental TAA and AAA.

METHODS

Murine TAAs or AAAs were created using a novel model in C57/B6 mice by treating the intact aorta with elastase. Cytokine profiles were analyzed with antibody arrays (n = 5 per group). Separately, to determine the role of IL-6, thoracic (n = 7) or abdominal (n = 7) aortas of wild type mice and IL-6 knockout (KO) mice were treated with elastase. Additionally, thoracic animals treated with either the IL-6 receptor antagonist tocilizumab (n = 8) or vehicle (n = 5). Finally, human TAA and AAA were analyzed with human cytokine array.

RESULTS

Elastase treatment of thoracic aortas yielded dilation of 86.8% ± 9.6%, and abdominal aortas produced dilation of 85.6% ± 16.2%. Murine IL-6, CXCL13, and matrix metalloproteinase-9 were significantly elevated in TAA compared with AAA (p = 0.004, 0.028, and 0.001, respectively). The IL-6KO mice demonstrated significantly smaller TAA size relative to wild type mice (wild type 100.1% versus IL-6KO 76.5%, p = 0.04). The IL-6KO mice did not show protection from AAA (p = 0.732). Pharmacologic inhibition of IL-6 resulted in significant reduction in TAA size (tocilizumab 71.5% ± 13.2% versus vehicle 103.6% ± 20.7%, p = 0.005). Human TAA showed significantly greater IL-6 (p < 0.0001) compared with AAA and normal thoracic and abdominal aorta.

CONCLUSIONS

Interleukin-6 is significantly greater in both murine and human TAA compared with AAA, suggesting fundamental differences in these disease processes. Interleukin-6 receptor antagonism attenuates experimental TAA formation, indicating that IL-6 may be a potential target for human thoracic aneurysmal disease.

Three-dimensional sensitivity assessment of thoracic aortic aneurysm wall stress: a probabilistic finite-element study

OBJECTIVES

In clinical practice, maximum diameter is used as a criterion to estimate aneurysm-rupture risk; however, it is only a general indicator and its value becomes difficult to estimate in the thoracic segment. Improved understanding of aortic aneurysm complexity and biomechanics is needed to achieve advancements in surgical repair techniques. The objective of this study was to determine the maximum wall stress by using imaging-derived data and a specific probabilistic design integrated into finite element (FE) analysis.

METHODS

Computed tomography images of thoracic aortic aneurysms from our database were analysed and the main morphological features were identified by means of a specific automatic routine. Morphological data were used to develop an idealized finite element library of thoracic aortic arch models. Sensitivity analyses were performed by using the geometrical parameters as input variables for a statistical wall stress assessment. Numerical results were compared with those obtained from deterministic analysis on patient-specific three-dimensional reconstructions.

RESULTS

The results showed that in small aneurysms, wall stress values similar to those of large aneurysms can be obtained if a significant eccentricity is achieved. In small aneurysms, the peak stress is primarily affected by the eccentricity of the bulge [correlation coefficient (CC) = 0.86], while for diameters in the range of 50-60 mm, the CC is 0.43 for the eccentricity and 0.72 for the maximum diameter.

CONCLUSIONS

The stress distribution in small aneurysms may contribute to the pathogenesis of aortic rupture and dissections. Our method can provide a novel and efficient procedure for generating computational models to estimate the wall stress in a comparative multivariate manner.

A Perspective on Natural History and Survival in Nonoperated Thoracic Aortic Aneurysm Patients

There are many questions that remain unanswered in the understanding of the natural history of thoracic aortic aneurysm (TAA). This review will critically appraise the current published evidence on the natural history of TAA in nonoperated patients and their present rates of survival.

Medical therapy of thoracic aortic aneurysms

Thoracic aortic aneurysm is a major health problem with multiple etiologies and potentially devastating consequences. Currently, no large randomized trial has shown that medical therapy can significantly slow or halt the progressive dilatation that eventually leads to dissection and rupture. A recent study that suggested that angiotensin receptor blocking agents slow the development of aneurysm dilatation in Marfan syndrome has revived interest in medical interventions to improve outcomes for patients with aortic aneurysm. In this article, we review the available data on established medical therapies and investigational medical therapies for thoracic aortic aneurysms.

Endovascular stenting of thoracic aortic aneurysm

In 2005, the findings of the multicenter Gore Tag study led to United States Food and Drug Administration approval for endovascular repair of thoracic aortic aneurysms (TEVAR). TEVAR provides a therapeutic option for patients who have thoracic aortic aneurysm and for the treatment of type B aortic dissection with malperfusion. Spinal cord ischemia and stroke are recognized neurologic complications of TEVAR. Identification of high-risk patients combined with targeted anesthetic and perioperative management may decrease the risk of neurologic complications after TEVAR.

[Pathobiology of idiopathic ascending aortic aneurysms]

BACKGROUND

The majority of ascending aortic aneurysms cannot be related to any specific etiology and should be qualified as idiopathic. The incidence of this disease is increasing in the population of the developed countries but its pathobiology is poorly understood.

AIM

This article is reviewing the publications concerning the pathobiology of idiopathic ascending aortic aneurysms.

SOURCES

A PubMed search on articles published in English or French, between January 1965 and December 2007, on key-words << aortic root >>, << ascending aorta >>, << aortic arch >>, << thoracic aorta >>, << aneurysm >>, << dilatation >> and << dissection >> was undertaken. Articles on aneurysms related to inflammatory and infectious diseases, congenital or genetic syndromes were excluded.

RESULTS

The presented data suggests that destructive remodeling of the aortic wall, inflammation and angiogenesis, biomechanical wall stress, and molecular genetics are relevant mechanisms of idiopathic ascending aortic aneurysm formation and progression.

LIMITS

Sparse data available from few direct studies offer limited knowledge on pathobiology of idiopathic ascending aortic aneurysms.

CONCLUSION

A more intimate knowledge of the triggers and perpetrating factors of this disease might offer new diagnostic and treatment options.

A rapidly expanding descending thoracic aortic aneurysm: an unusual complication

The rate of enlargement of a descending thoracic aortic aneurysm is usually low, related to initial size and anatomical position. We report a case of an old, diabetic woman, with previous history of ischemic heart disease, admitted for a broncopneumia, in which a small descending thoracic aortic aneurysm was detected by a routine computed tomography (CT) scan. Because of the presence of comorbid condition, especially in the woman with an infectious respiratory disease, a closer follow-up by a 3-month CT scan was programmed. An impressive enlargement of the aneurysm, occurred in the next 2 months, caused patient's asphyxia and subsequent death. In patients with thoracic aortic aneurysm, mostly in females with comorbid condition, a closer CT scan control should be carried out, irrespective of the previous aneurysm size.

Regulation of Nogo-B expression in the lesion of aortic aneurysms

1. Our previous study showed that Nogo-B was highly expressed in endothelial cells and downregulated in endothelial cells following induction by lysophosphatidylcholine, which contributed to atherosclerotic lesions. However, the role of Nogo-B in the development of aortic aneurysms remains unclear. 2. In the present study, segments of thoracic aortic aneurysms (TAA) and adjacent normal thoracic aortic tissues (NTA) without aneurysmal changes were obtained from 31 patients undergoing graft surgery. The mRNA and protein expression levels of Nogo-B were measured with semiquantitative reverse transcription-polymerase chain reaction, western blotting and immunohistochemistry. 3. The results demonstrate that Nogo-B mRNA expression levels in TAA lesions decreased to 45% compared with levels in NTA lesions and that protein levels in TAA decreased to 35%. Tissue Nogo immunohistochemical staining in aortic specimens suggested the involvement of Nogo in neovascularization and smooth muscle cell proliferation. The weaker brown staining of endothelial cells in TAA lesions suggested the lower expression of Nogo-B in TAA lesions. 4. These results demonstrate that Nogo-B mRNA and protein expression are downregulated in TAA lesions. It is concluded that the reduction of Nogo-B protein expression in TAA lesions is closely correlated to the formation of aneurysm and that Nogo-B may play a protective role in the pathological process of aneurysms.

Etiology, pathogenesis and management of thoracic aortic aneurysm

Given the growing proportion of elderly people in Western societies and the increasing prevalence of chronic hypertension, the management of aneurysmal aortic disease is an ever growing challenge. Although degenerative changes in the aortic wall are common to thoracic aortic aneurysm (TAA) and to various types of dissection in general, TAA can result from specific heritable disorders of connective tissues. Today, increased awareness of vascular diseases and access to tomographic imaging equipment facilitate the diagnosis of TAA, even when asymptomatic. While most TAA cases with ascending aortic involvement are treated with surgical repair (primarily valve-preserving techniques), aneurysms of the distal arch and descending thoracic aorta are amenable to alternatives to classic open repair such as the emerging endovascular treatment techniques. In this Review, we provide a comprehensive overview of the etiology, pathophysiology and clinical management of patients with TAA, and discuss the most recent literature on the condition.

Aortic Enlargement and Late Reoperation After Repair of Acute Type A Aortic Dissection

BACKGROUND

The natural history of the residual aorta after repair of acute type A aortic dissection is incompletely understood.

METHODS

During a 22-year period, 201 patients underwent repair of acute type A dissection by 25 surgeons. For 168 operative survivors, mean late follow-up for reoperation or death was 6.5 +/- 5.5 years and was 100% complete. Late blood pressure and medication history were available for 136 patients. Overall, 412 computed tomography scans were analyzed for segmental diameter and false lumen patency from 69 patients who underwent multiple follow-up imaging studies at our institution.

RESULTS

Freedom from reoperation at 10 years (range, 1 to 170 months) was 74% +/- 5% (28 reoperations in 26 patients). A nonresected primary tear (p = 0.05), Marfan syndrome (p < 0. 001), elevated systolic blood pressure at follow-up (p = 0.008), and absence of beta-blocker therapy (p = 0.02) were independent predictors of late reoperation. Aortic growth between consecutive imaging studies was detected in 18% of intervals (62/343) affecting 49% patients (34/69), with mean yearly growth rate of 5.3 +/- 4.5 mm. Onset of enlargement was unpredictable and occurred 59 +/- 45 months postoperatively (range, 1 to 167 months). Risk factors for growth included aortic diameter (p < 0. 001), elevated systolic blood pressure (p = 0.04), and presence of a patent false lumen (p = 0.05). Maximum aortic diameter of less than 35 mm predicted growth in 11% of intervals, 35 to 49 mm in 22%, and more than 49 mm in 37% (p < 0.001). Different proximal or distal surgical strategies did not affect aortic growth or need for reoperation (p > 0.17).

CONCLUSIONS

Optimal long-term outcome of patients with acute type A dissection demands rigorous antihypertensive therapy and lifelong radiographic follow-up because aortic enlargement can begin more than a decade postoperatively.

MR Imaging of the Aorta

Recent advances in noninvasive imaging methods, such as CT and MR imaging, have replaced most of invasive angiographic procedures in the diagnosis of acquired aortic disease, decreasing the cost and morbidity of diagnosis. This article reviews and illustrates present MR imaging methods for evaluation of the aorta. Common diseases of the aorta also are discussed with a focus on their unique morphologic and functional features and characteristic MR imaging findings. Knowledge of pathologic conditions of common aortic diseases and proper MR imaging techniques enables accurate and time-efficient aortic evaluation.

99m Tc-Annexin-V Functional Imaging of Luminal Thrombus Activity in Abdominal Aortic Aneurysms

Background— The mural thrombus of abdominal aortic aneurysms (AAA) is involved in aneurysm progression via several interdependent biological processes including platelet activation. 99m Tc-annexin V (ANX) is a scintigraphic tracer that binds to phosphatidylserine exposed on activated platelets and apoptotic cells. Here, we evaluated the potential of ANX imaging to assess mural thrombus biological activity in an experimental AAA model. The clinical applicability was further tested ex vivo on human samples of excised AAA thrombi.

Methods and Results— Experimental AAA was created by infusing elastase into infrarenal abdominal aorta in 17 rats, and 6 sham-operated rats were used as controls. Abdominal ANX scintigraphy was performed 2 weeks later followed by quantitative autoradiography and histological studies. Among the 13 rats which developed AAA, 11 displayed intense ANX uptake within AAA by scintigraphy. ANX uptake in the aneurysms on planar and single-photon emission computed tomography (SPECT) imaging was higher than that observed in infrarenal aorta of sham-operated controls (target/background ratio: 5.7±0.9 versus 1.33±0.21; P <0.005 for SPECT). Aneurysm-to-background activity ratios obtained by scintigraphy correlated with ANX activity in corresponding autoradiograms ( R =0.69; P <0.02). This activity was located in the thrombus area where activated platelets and polymorphonuclear leukocytes accumulated. Similar patterns were also found in all of the 7 human AAA thrombi harvested during surgery.

Conclusions— ANX imaging may assess mural thrombus renewal activity linked to permanent flowing blood interface.

Renewal of mural thrombus releases plasma markers and is involved in aortic abdominal aneurysm evolution

Human abdominal aortic aneurysm (AAA) expansion has been linked to the presence of a mural thrombus. Here we explored the mechanism of the continual luminal renewal of this thrombus and its ability to release biological markers potentially detectable in plasma. We also explored the ability of platelet inhibition to pacify the thrombus and to limit aneurysm progression in an experimental model. Blood samples and mural thrombi were collected in 20 AAA patients. In parallel, segments of sodium dodecyl sulfate-decellularized guinea pig aorta were xenografted onto the abdominal aorta of 30 rats to induce aneurysms. Fifteen rats received abciximab treatment and fifteen received irrelevant immunoglobulins. Procoagulant activity and platelet activation markers (microparticles, sP-selectin, sGPV, sCD40L) were increased threefold to fivefold in eluates from the luminal thrombus layer compared to other layers. All these markers were increased twofold to fivefold in patients' plasma compared to matched controls (P < 0.005). In the rat model, abciximab reduced both thrombus area and aneurysmal enlargement (P < 0.05). Platelet aggregation is probably responsible for the renewal of the thrombus in AAA. The luminal thrombus released markers of platelet activation that could easily be detected in plasma. Platelet inhibition limited aortic aneurysm expansion in a rat model, providing new therapeutic perspectives in the prevention of AAA enlargement.

Acquired diseases of the thoracic aorta: role of MRI and MRA

Diseases of the thoracic aorta can present with a broad clinical spectrum of symptoms and signs. Their prevalence appears to be increasing in western populations, most likely corresponding to aging and heightened clinical awareness but also influenced by the progress of high-resolution, noninvasive imaging modalities. Among them, MRI provides an excellent visualization of vascular structures and is well suited for evaluation of thoracic aorta disease. Currently, in many centers, noninvasive imaging modalities are the first choice in the cardiovascular system evaluation and diagnosis, reserving conventional angiography for use only before therapeutic intervention. Understanding the principle MRA techniques is essential for acquiring consistent diagnostic images. Basic technical considerations, which include fast spin-echo, fast gradient-echo, and MRA techniques with phase contrast and contrast-enhanced methods, are discussed and applied in the evaluation of acquired thoracic aorta diseases.

Approach to the dilated aortic root

PURPOSE OF REVIEW

The dilated aortic root is often completely asymptomatic and found incidentally on routine imaging studies such as chest radiograph, echocardiography, chest computed tomography, or magnetic resonance imaging. The dilated aortic root may be associated with underlying aortic valve abnormalities as seen with bicuspid aortic valve. It may also lead to the awareness of important underlying connective tissue disorders like the Marfan syndrome. It is imperative that the dilated aortic root be observed carefully over time with serial imaging studies and that timely resection of the aneurysm be carried out before catastrophic complications such as aortic dissection, aortic rupture, or congestive heart failure from aortic insufficiency occur.

RECENT FINDINGS

In recent years, the advent of molecular genetics has heightened awareness of familial aortic disease such as the Marfan syndrome, bicuspid aortic valve disease, and hereditary aortic aneurysm and dissection. In addition to hypertension and inflammatory aortic disease, these hereditary aortopathies are important to consider in the evaluation of patients with a dilated aorta and have implications for screening of the relatives of the patient with aortic aneurysm.

SUMMARY

Because there is often uncertainty regarding the dilated aortic root, this review will summarize the approach to diagnosis, evaluation, and management of aortic root aneurysms. Clinical features, diagnostic approaches, screening of relatives, and long term follow-up will be highlighted.

Evolution of healthy thoracic aortic segment diameter during follow-up of patients with aortic aneurysm or dissection: a magnetic resonance imaging study

We studied the normal evolution over time of the diameter of the healthy descending aorta in patients suffering from aneurysm or dissection of the ascending aorta, in order to anticipate potential complications of endoprosthetic treatment in this aortic segment. During their follow-up (average 35.9 months), 52 patients suffering from aneurysm or dissection of the ascending aorta had 168 aortic MRI examinations (2-7; average 3). Measurements were taken according to conventional reference landmarks making it possible to study the evolution of the diameter of the supposed healthy descending thoracic aorta. The variations in diameter with time were on average 5 mm, and there was no significant variation in this diameter, either for early controls or for the controls carried out after more than 1 year or 3 years, whatever the age group. Thus according to our series it seems that patients with a descending aorta endoprosthesis are not exposed to graft endoleak due to inadequate contact of the prosthesis and aorta within the 5 years following its implantation.

MRA of the thoracic vessels

Magnetic resonance imaging (MRI) is well suited for the noninvasive evaluation of the thoracic vasculature, and with improvements in scanner technology, the ability of MR to illustrate the thoracic vessels has significantly improved. Dedicated vascular software and pulse sequences have become commercially available, and fast imaging, in particular, has facilitated the time-efficient and comprehensive MR evaluation of most thoracic vascular lesions. Over the years, a host of black and bright blood MRI methods have evolved into practical tools for illustration of the thoracic vessels. As with other MR applications, successful vascular depiction relies significantly on the proper selection and prescription of imaging pulse sequences. In this article, these methods with their specific technical and practical pitfalls for thoracic magnetic resonance angiography (MRA) will be discussed. Current clinical indications for thoracic MRA will also be illustrated.

Surgical repair of ruptured thoracic and thoracoabdominal aortic aneurysms

BACKGROUND

Rupture is the single most common cause of death in patients with thoracic aortic and thoracoabdominal aneurysm (TAA/TAAA) and is almost uniformly fatal.

METHODS

This was a retrospective review of patients admitted to a single practice with rupture of a TAA/TAAA between 1993 and 2000.

RESULTS

Twenty-two consecutive patients with a leaking TAA/TAAA were identified. The aetiology of rupture was either secondary to a degenerative TAAA or a type B dissection. Seventeen patients underwent surgery; one had a Crawford extent I, seven an extent II, one an extent III and two an extent IV TAAA. Six patients had an acute type B dissection with rupture in the upper descending thoracic aorta. The 30-day survival rate was 88 per cent (15 of 17 patients). Actuarial survival at 1 year in patients who had surgery was 65 per cent. Survival at 1 year for all presenting patients who consented to surgery was 40 per cent. Median survival was greater than 36 months.

CONCLUSION

As a result of improving medical care, more patients with a contained rupture of a TAA/TAAA may present for treatment. Surgery is complex and requires specialist teams for optimal care.