Thoracic Aortic Aneurysm

Aging impact on thoracic aorta 3D morphometry in intermediate-risk subjects: looking beyond coronary arteries with non-contrast cardiac CT

An increasing number of intermediate risk asymptomatic subjects benefit from measures of atherosclerosis burden like coronary artery calcification studies with non-contrast heart computed tomography (CT). However, additional information can be derived from these studies, looking beyond the coronary arteries and without exposing the patients to further radiation. We report a semi-automatic method that objectively assesses ascending, arch and descending aorta dimension and shape from non-contrast CT datasets to investigate the effect of aging on thoracic aorta geometry. First, the segmentation process identifies the vessel centerline coordinates following a toroidal path for the curvilinear portion and axial planes for descending aorta. Then, reconstructing oblique planes orthogonal to the centerline direction, it iteratively fits circles inside the vessel cross-section. Finally, regional thoracic aorta dimensions (diameter, volume and length) and shape (vessel curvature and tortuosity) are calculated. A population of 200 normotensive men was recruited. Length, mean diameter and volume differed by 1.2 cm, 0.13 cm and 21 cm(3) per decade of life, respectively. Aortic shape uncoiled with aging, reducing its tortuosity and increasing its radius of curvature. The arch was the most affected segment. In conclusion, non-contrast cardiac CT imaging can be successfully employed to assess thoracic aorta 3D morphometry.

Characteristics of TAV- and BAV-associated thoracic aortic aneurysms--smooth muscle cell biology, expression profiling, and histological analyses

OBJECTIVE

Past studies on the pathogenesis of thoracic aortic aneurysms have, by concentrating on histological and total tissue analyses, revealed several disease-relevant processes. Despite these studies, there is still a significant lack in the understanding of aneurysmal cell biology today. Hence, it was the goal of this study to assess differences between aneurysmal and healthy aortic smooth muscle cells (SMCs) on a broad - screening-like - basis, allowing us to formulate new hypotheses on the role of SMCs in thoracic aneurysm formation.

METHODS AND RESULTS

After histological characterization of a total of 16 samples from healthy aortas and thoracic aortic aneurysms (TAA) of patients with bicuspid (BAV) and tricuspid (TAV) aortic valves, we isolated aortic SMCs and subjected them to cell biological and gene expression analyses. The data obtained indicate that aneurysmal SMCs exert reduced proliferation and migration rates compared to controls. BAV TAA SMCs have significantly shorter telomeres, whereas TAV TAA SMCs showed a reduced metabolic activity. In BAV TAA SMCs osteopontin (OPN) expression was significantly elevated, and TAV TAA SMCs showed decreased expression of tissue inhibitor of metalloproteinase 3 (TIMP3).

CONCLUSION

Our study provides evidence that TAA-associated aortic wall disintegration in BAV and TAV TAAs shows similarities, but also significant differences. BAV and TAV TAAs differ with regard to medial elastic fiber mass and the occurrence of fibroblasts, SMC telomere length, metabolism, and gene expression. This study may form the basis for future in-depth analyses on the relevance of these findings in the pathophysiology of BAV and TAV TAAs.

Aorta Measurements are Heritable and Influenced by Bicuspid Aortic Valve

Objectives: To determine whether the contributions of genetics and bicuspid aortic valve (BAV) independently influence aortic (Ao) dimensions. Background: Ao dilation is a risk factor for aneurysm, dissection, and sudden cardiac death. Frequent association of BAV with Ao dilation implicates a common underlying defect possibly due to genetic factors. Methods: Families enriched for BAV underwent standardized transthoracic echocardiography. In addition to BAV status, echocardiographic measures of Ao (annulus to descending Ao), pulmonary artery, and mitral valve annulus (MVA) diameters were obtained. Using variance components analysis, heritability was estimated with and without BAV status. Additionally, bivariate genetic analyses between Ao dimensions and BAV were performed. Results: Our cohort was obtained from 209 families enriched for BAV. After adjusting for age, body surface area, and sex, individuals with BAV had a statistically significant increase in all echocardiographic measurements (p < 0.006) except descending Ao and MVA. Individuals with BAV were at greater odds of having Ao dilation (OR = 4.44, 95% CI 2.93–6.72) than family members without BAV. All echocardiographic measurements exhibited moderate to strong heritability (0.25–0.53), and these estimates were not influenced by inclusion of BAV as a covariate. Bivariate genetic analyses supported that the genetic correlation between BAV and echo measures were not significantly different from zero. Conclusion: We show for the first time that echocardiographic measurements of Ao, pulmonary artery and MVA diameters are quantitative traits that exhibit significant heritability. In addition, our results suggest the presence of BAV independently influences the proximal Ao and pulmonary artery measures but not those in the descending Ao or MVA.

Evaluation of acute chest pain in the emergency department: "triple rule-out" computed tomography angiography

Triage of patients with acute, potentially life-threatening chest pain is one of the most important issues currently facing physicians in the emergency department. Appropriate evaluation of these patients begins with a skilled assessment of the individual patient's presenting symptoms and a careful review of his or her history and physical examination, often followed by serial recording of electrocardiograms and measurement of serum biochemical markers such as troponin and d-dimer. Stress testing, often accompanied by rest and stress myocardial perfusion imaging or echocardiography, and other diagnostic testing such as radionuclide lung scanning and invasive angiography may be required. A rapid, accurate, and cost-effective approach for the evaluation of emergency department patients with chest pain is needed. Development of newer generations of multidetector computed tomographic (MDCT) scanners, which are capable not only of performing high-quality noninvasive coronary angiography, but also concurrent aortic and pulmonary angiography, has led to increased use of MDCT for the so-called "triple rule out." MDCT is used for the detection of 3 of the most common life-threatening causes of chest pain-coronary artery disease, acute aortic syndrome, and pulmonary emboli. While triple rule-out protocol can be very useful and potentially cost effective when used appropriately, concern has risen regarding the overuse of this technology, which could expose patients to unnecessary radiation and iodinated contrast. The triple rule-out protocol is most appropriate for patients who present with acute chest pain, but are judged to have low to intermediate increased risk for acute coronary syndrome, and whose chest pain symptoms might also be attributed to acute pathologic conditions of the aorta or pulmonary arteries. MDCT should not be used as a routine screening procedure. Continued technical improvements in acquisition speed and spatial resolution of computed tomography images, and development of more efficient image reconstruction algorithms which reduce patient exposure to radiation and contrast, may result in increased popularity of MDCT for "triple rule-out."

Cardiovascular surgery in Marfan syndrome: implications of new molecular concepts in thoracic aortic disease

Acute dissection and rupture of aortic aneurysms comprise for 1–2% of all deaths in industrialized countries. Dilation of the aorta is caused by a multitude of mechanisms including inherited connective tissue disorders such as Marfan syndrome (MFS). MFS is one of the most common inherited connective tissue disorders affecting 1 in 5000 individuals. Although the phenotype of MFS can be quite variable, aneurysmal dilation of the aortic root and consecutive acute aortic dissection is the leading cause of death in this patient population. Over the past years it has been shown that a comprehensive understanding of this disorder provides greater understanding of vascular wall biology and identifies pathways relevant to aortic aneurysms and dissection in general. The current review discusses the surgical management of patients with MFS with a special emphasis on indications for surgery in this complex group of patients.

Presence of circulating endothelial progenitor cells and levels of stromal-derived factor-1α are associated with ascending aorta aneurysm size

OBJECTIVE

Circulating endothelial progenitor cells (EPCs) are a specialized subset of stem/progenitor cells found in bone marrow. They participate in neo-vascularization of injured vessels and predict cardiovascular outcome in patient at risk. Several factors influence their migration and proliferation, among which is the widely studied stromal-derived factor-1α (SDF-1α). In cardiovascular disease, regarding thoracic aortic aneurysms (TAAs), few studies have investigated the levels of EPC and SDF-1α. As rupture, acute dissection and hematoma are acute complications of idiopathic ascending thoracic aortic aneurysm (iATAA) that increase with the size of aneurysm, we aimed to evaluate a potential relationship between circulating EPC and SDF-1α and iATAA size.

METHODS

The aneurysm size of 27 consecutive patients suffering from iATAA and scheduled for surgery was assessed by computed tomography scan. In all patients, we measured levels of circulating EPCs by flow cytometer, and plasma levels of SDF-1α the day before surgery.

RESULTS

The median aneurysm size was 54 mm (interquartile range (IQR): 50.0-58.8]. The EPC levels of CD34+/CD144+/CD14- and CD34+/VEGF-R2+/CD14- were inversely correlated to aneurysm diameter (p = 0.038, r = -0.424 and p = 0.0046, r = -0.65, respectively) before surgery. Conversely, plasma levels of SDF-1α were positively correlated to aneurysm size (p = 0.042; r = 0.47).

CONCLUSIONS

Our findings indicate that EPC levels may be useful for monitoring ascending aorta aneurysms and that SDF-1α could be a biomarker of iATAA expansion.

Comparison of the structure of the aortic valve and ascending aorta in adults having aortic valve replacement for aortic stenosis versus for pure aortic regurgitation and resection of the ascending aorta for aneurysm

BACKGROUND

There is debate concerning whether an aneurysmal ascending aorta should be replaced when associated with a dysfunctioning aortic valve that is to be replaced. To examine this issue, we divided the patients by type of aortic valve dysfunction-either aortic stenosis (AS) or pure aortic regurgitation (AR)-something not previously undertaken.

METHODS AND RESULTS

Of 122 patients with ascending aortic aneurysm (unassociated with aortitis or acute dissection), the aortic valve was congenitally malformed (unicuspid or bicuspid) in 58 (98%) of the 59 AS patients, and in 38 (60%) of the 63 pure AR patients. Ascending aortic medial elastic fiber loss (EFL) (graded 0 to 4+) was zero or 1+ in 53 (90%) of the AS patients, in 20 (53%) of the 38 AR patients with bicuspid valves, and in all 12 AR patients with tricuspid valves unassociated with the Marfan syndrome. An unadjusted analysis showed that, among the 96 patients with congenitally malformed valves, the 38 AR patients had a significantly higher likelihood of 2+ to 4+ EFL than the 58 AS patients (crude odds ratio: 8.78; 95% confidence interval: 2.95, 28.13).

CONCLUSIONS

These data strongly suggest that the type of aortic valve dysfunction-AS versus pure AR-is very helpful in predicting loss of aortic medial elastic fibers in patients with ascending aortic aneurysms and aortic valve disease.

Endothelial cell-specific deficiency of Ang II type 1a receptors attenuates Ang II-induced ascending aortic aneurysms in LDL receptor-/- mice

RATIONALE

Human studies and mouse models have provided evidence for angiotensin II (Ang II)-based mechanisms as an underlying cause of aneurysms localized to the ascending aorta. In agreement with this associative evidence, we have published recently that Ang II infusion induces aneurysmal pathology in the ascending aorta.

OBJECTIVE

The aim of this study was to define the role of angiotensin II type 1a (AT(1a)) receptors and their cellular location in Ang II-induced ascending aortic aneurysms (AAs).

METHODS AND RESULTS

Male LDL receptor(-/-) mice were fed a saturated fat-enriched diet for 1 week before osmotic mini-pump implantation and infused with either saline or Ang II (1000 ng/kg per minute) for 28 days. Intimal surface areas of ascending aortas were measured to quantify ascending AAs. Whole body AT(1a) receptor deficiency ablated Ang II-induced ascending AAs (P<0.001). To determine the role of AT(1a) receptors on leukocytes, LDL receptor(-/-)×AT(1a) receptor(+/+) or AT(1a) receptor(-/-) mice were irradiated and repopulated with bone marrow-derived cells isolated from either AT(1a) receptor(+/+) or AT(1a) receptor(-/-) mice. Deficiency of AT(1a) receptors in bone marrow-derived cells had no effect on Ang II-induced ascending AAs. To determine the role of AT(1a) receptors on vascular wall cells, we developed AT(1a) receptor floxed mice with depletion on either smooth muscle or endothelial cells using Cre driven by either SM22 or Tek, respectively. AT(1a) receptor deletion in smooth muscle cells had no effect on ascending AAs. In contrast, endothelial-specific depletion attenuated this pathology.

CONCLUSIONS

Ang II infusion promotes aneurysms in the ascending aorta via stimulation of AT(1a) receptors that are expressed on endothelial cells.

Impact of Mendelian inheritance in cardiovascular disease

Cardiovascular disease is a leading cause of mortality worldwide. While the etiology for the majority of cardiovascular disease is presumed to be a combination of genetic and environmental factors, developments in understanding the basic biology of cardiac disorders have been greatly advanced through discoveries made studying heart diseases that exhibit Mendelian forms of inheritance. Most of these diseases primarily affect children and young adults and include cardiomyopathies, arrhythmias, aortic aneurysms, and congenital heart defects. The discovery of the genetic etiologies for these diseases have had significant impact on our understanding of more complex forms of cardiovascular disease and in some cases have led to novel diagnostic and treatment modalities. In this review, we will summarize these seminal genetic discoveries, highlighting a few that have resulted in significant impact on human disease, and discuss the potential utility of studying Mendelian-inherited heart disease with the development of new genetic technologies and our increased understanding of the human genome.