Echocardiography in the diagnosis of thoracic aortic pathology

Transthoracic two-dimensional and Doppler echocardiography has been well established as a useful technique for evaluating many pathologic processes affecting the thoracic aorta. However, the distance of the aortic arch and descending thoracic aorta from the chest wall and the interposition of highly attenuating lung and highly reflective mediastinal structures between the transducer and the aorta present unavoidable limitations. Transesophageal echocardiography is a relatively new technology that overcomes many of the inherent limitations with transthoracic imaging. Complete echocardiographic evaluation of the entire thoracic aorta can now be achieved in nearly all patients. This article will review the continually expanding role of echocardiography in the evaluation of thoracic aortic pathology, including the dramatic impact of transesophageal imaging on the diagnosis of life-threatening disorders such as aortic dissection.     

Transoesophageal echocardiography in the longitudinal axis: correlation between anatomy and images and its clinical implications

Transoesophageal echocardiographic imaging in the longitudinal axis is a recent addition to the non-invasive evaluation of congenital and acquired heart disease. The technique provides unique images of intracardiac anatomy but their interpretation remains difficult. A heart specimen was therefore cut according to the echocardiographic imaging planes to elucidate the morphological details. The results suggested that longitudinal transoesophageal imaging complements the transverse axis approach. It gave new imaging information on the right ventricular outflow tract and the pulmonary trunk, the atrioventricular valves, the interventricular septum, the cardiac apex, and the thoracic aorta. In particular, it showed the entire length of the right ventricular outflow tract. When longitudinal imaging was used in combination with transverse imaging almost all the thoracic aorta could be examined. Imaging in the longitudinal axis may also allow better assessment of the mechanisms of atrioventricular valve regurgitation.     

Transoesophageal echocardiography in the longitudinal axis: correlation between anatomy and images and its clinical implications.

Transoesophageal echocardiographic imaging in the longitudinal axis is a recent addition to the non-invasive evaluation of congenital and acquired heart disease. The technique provides unique images of intracardiac anatomy but their interpretation remains difficult. A heart specimen was therefore cut according to the echocardiographic imaging planes to elucidate the morphological details. The results suggested that longitudinal transoesophageal imaging complements the transverse axis approach. It gave new imaging information on the right ventricular outflow tract and the pulmonary trunk, the atrioventricular valves, the interventricular septum, the cardiac apex, and the thoracic aorta. In particular, it showed the entire length of the right ventricular outflow tract. When longitudinal imaging was used in combination with transverse imaging almost all the thoracic aorta could be examined. Imaging in the longitudinal axis may also allow better assessment of the mechanisms of atrioventricular valve regurgitation.     

Magnetic Resonance Imaging of the Thoracic Aorta

Magnetic resonance imaging (MRI) is well-suited for imaging the vascular system and is of particular value in assessing the anatomy and pathologies of the thoracic aorta. The intrinsic contrast between the blood pool and the vascular structures allows excellent depiction of intra- and extravascular anatomy and eliminates the need for intravenous contrast agents. A large field of view provides a complete evaluation of the mediastinum and chest. Both qualitative and quantitative techniques are available, which can yield physiological data in addition to anatomical information. The multiplanar capability offers images in any plane, allowing an accurate assessment of the longitudinal extent of disease and providing images perpendicular to vessels, even when tortuous. MRI currently represents an essential component of the imaging strategies available to assess the thoracic aorta and may come to function as a gold standard for certain conditions. As the technology continues its rapid evolution, MRI will most likely be able to serve as an effective noninvasive evaluation to provide all of the anatomical, pathological, and physiological information required of a comprehensive examination of the thoracic aorta.     

Non-Gadolinium-Enhanced 3-Dimensional Magnetic Resonance Angiography for the Evaluation of Thoracic Aortic Disease: A Preliminary Experience

We compared image quality and diagnostic accuracy of a noncontrast 3-dimensional magnetic resonance angiography (NC-MRA) technique (balanced steady-state free-precession sequence) to contrast-enhanced MRA (CE-MRA) for evaluation of thoracic aortic disease.The CE-MRA provides 3-dimensional high-resolution images of the thoracic aorta that are important in the evaluation of patients with aortic disease. However, recent concerns with the potential nephrotoxic effects of gadolinium contrast medium limit the application of CE-MRA for patients who have significant renal insufficiency.Twenty-one patients (mean age, 51 yr; 18 men) who underwent NC-MRA and CE-MRA for evaluation of thoracic aortic disease were retrospectively identified. Data sets were reviewed by 2 readers who were blinded to the patients'' information. The thoracic aorta was divided into 5 segments. Image quality and reader confidence for diagnosis of aortic pathology were rated on 5-point scales. The Wilcoxon matched-pairs signed rank test and the Student t test were used for comparisons.The NC-MRA identified all pathologic findings with 100% diagnostic accuracy and similar reader confidence, when compared with CE-MRA. Although overall image quality was not significantly different, superior image quality was observed at the aortic root (4.4 ± 0.8 vs 3.2 ± 0.9, P <0.0005) and ascending aorta (4.1 ± 1 vs 3.7 ± 0.9, P=0.05) respectively.In conclusion, NC-MRA is a useful alternative for evaluation and follow-up of thoracic aortic disease, especially for patients with poor intravenous access or contraindications to gadolinium use.Key words: Aneurysm, dissecting/diagnosis; aorta, thoracic/pathology; aortic aneurysm, thoracic/diagnosis; aortic diseases/diagnosis/radiography; artifacts; contrast media/toxici-ty; gadolinium/diagnostic use/toxicity; magnetic resonance angiography; retrospective studiesContrast-enhanced magnetic resonance angiography (CE-MRA) is often used for initial assessment and follow-up of thoracic aortic disease.^1,2 Fast, reproducible, 3-dimensional (3-D) high-resolution imaging of the thoracic aorta is essential for surgical planning and follow-up after intervention. Although computed tomographic angiography has advanced rapidly over the past few years and now can provide high-resolution images of the thoracic aorta, it has several drawbacks, including its use of ionizing radiation and nephrotoxic iodinated contrast agents and its inability to quantify blood flow. Contrast-enhanced MRA has such limitations as its need for intravenous gadolinium-chelate contrast, its frequent application without cardiac gating (which leads to motion artifacts), and its predominantly intraluminal imaging of the aorta³ (with restricted imaging of the aortic wall for the evaluation of mural and extraluminal disease such as intramural hematoma or vasculitis). Gadolinium--chelate contrast agents are far less likely to elicit allergic-type reactions than are iodinated contrast agents, and are, in general, considered safer for use in patients with impaired renal function. Recently, however, they have been associated with nephrogenic systemic fibrosis, a potentially life-threatening disease that chiefly affects patients on dialysis or with severe renal dysfunction.^4,5Electrocardiographic (ECG) gated 2-dimensional noncontrast imaging techniques, including spin-echo, gradient-echo, and time-of-flight pulse sequences, enable improved visualization of the aorta without need for contrast but are hampered by long-er imaging times and nonvolumetric data acquisition.⁶ Recently, a respiratory- and cardiac-gated, fat-suppressed, noncontrast 3-D magnetic resonance angiography (NC-MRA) technique (balanced steady-state free-precession sequence) has been developed for whole-heart imaging,^7,8 and this provides high and isotropic spatial resolution for the evaluation of coronary arteries.^9,10 It is unknown whether this technique can be applied to the imaging of various aortic diseases with reliable diagnostic accuracy, although recent preliminary results are promising.^11–13 The aim of this study was to examine our institution''s initial experience in comparing the image quality and diagnostic accuracy of NC-MRA to those of CE-MRA for the evaluation of the anatomy and pathology of the thoracic aorta and branch vessels.     

Transesophageal echocardiographic assessment of a floating thrombus located in the ascending aorta

Transesophageal echocardiography (TEE) has become a unique imaging technique that provides improved visualization of aorta because of its proximity to the esophagus. It is a reliable method for the diagnosis of thoracic aorta diseases and detection of protruding atheromas or thrombi as sources of systemic emboli. We report a case in which TEE revealed a floating aortic thrombus located in the ascending aorta in a patient with chronic renal failure.     

Endovascular stent grafting for chronic proximal thoracic aortic pseudoaneurysm

Chronic descending aortic pseudoaneurysm generally result from traumatic and can spontaneously progress to rupture. We report the case of a 70-year-old patient presenting a chronic pseudoaneurysm of the thoracic aorta treated by endovascular stent-grafting. The patient underwent imaging evaluation for endoluminal repair: thoracic aorta was evaluated by contrast-enhanced CT scan and supra-aortic and iliac vessels were evaluated by MRI-imaging. Stent-graft was deployed under fluoroscopic guidance across the aneurysmal defect. The left sub-clavian artery was covered, but no ischemic symptoms appeared and transposition of the left sub-clavian artery was not necessary. Clinical and radiological follow-up at 6 and 30 months showed total exclusion and thrombosis of the pseudoaneurysm. Chronic pseudoaneurysm of the thoracic aorta do benefit from endoluminal repair, which is adapted to patients with high surgical risk.     

Transesophageal Echocardiographic Imaging for Congenital Lesions of the Left Ventricular Outflow Tract and the Aorta

A comprehensive transthoracic echocardiographic imaging is possible for most pediatric patients. However, for patients in whom accurate anatomical and physiological assessment is not possible, transesophageal echocardiography (TEE) provides a supplemental diagnostic modality. Imaging the left ventricular outflow tract and the aorta involves a complicated technique of rotation, flexion, and changes in the depth of the transesophageal probe because the areas of interrogation involve multiple planes within the thoracic cavity. Furthermore, the relationship between the esophagus and the cardiovascular structures changes at various levels of the thorax. Transesophageal probes having characteristics of frequency agility, all forms of Doppler capability, and a higher number of crystal elements are now available. Abnormalities of the subaortic area, the aortic valve, coronary arteries, and the entire thoracic aorta can be clearly demonstrated. TEE also has played a complementary role in diagnostic and interventional catheterization. It has become vital in the operating room for the preoperative definition of certain aspects of the anatomy and for immediate postoperative evaluation of the result of surgery.     

Magnetic resonance angiography: state of the art

The recently developed three-dimensional ultrafast sequences are able to acquire the entire aorta or the peripheral district in just 15 s. These sequences offer the possibility to obtain breath-hold images (that avoid breath artifacts) during the contrast medium peak. The technique is called three-dimensional angiography with contrast bolus. To perform the evaluation with this technique, high performance magnet units are needed (high magnetic fields, high gradient with fast ramping times). Clinical indications include the aortic district and especially thoracic aorta diseases and aortic dissections. This technique has great potentialities in the evaluation of the supra-aortic trunks, renal arteries and peripheral district. Shifting the table it is now possible to obtain the contemporary evaluation of both aorta and peripheral district with a single injection of contrast medium. The definition of the arterial district is comparable in many cases to that offered by digital angiography. The combination of magnetic resonance angiography and tomographic magnetic resonance technique is helpful for the endoluminal evaluation (as with digital angiography) and for the study of thrombi and wall as well.     

Cardiovascular aging: Insights from local and regional measures of aortic stiffness using magnetic resonance imaging

Aortic stiffness is now established as an independent marker of cardiovascular aging and cardiovascular risk. However, the specific role of the proximal aorta, specifically the ascending aorta, remains understudied. Magnetic resonance imaging (MRI), a non-invasive technique has recently been proposed to measure new local and regional imaging biomarkers of stiffness in the thoracic aorta. We will here review recent data on aortic stiffness assessed by MRI. We will discuss the methodological advantages and challenges of MRI, combined with applanation tonometry, to evaluate local aortic distensibility and pulse wave velocity (PWV) and summarize available results concerning the age related distribution of such parameters.Aortic distensibility has been shown to be an early subclinical marker of vascular target organ damage in the general population and expected ranges for ascending aortic distensibility and aortic arch pulse wave velocity assessed in MRI have been described. Changes in aortic distensibility and arch PWV have been related to age-related geometric changes, specifically lengthening, enlargement and unfolding of the thoracic aorta. Increased proximal aortic stiffness measured by MRI has also been related to decreased systolic and diastolic function and concentric remodeling of the left ventricule in healthy individuals.     

Imaging Modalities in the Diagnosis of Acute Aortic Dissection

The management of patients with acute aortic dissection requires a rapid diagnosis and precise information about the localization and extent of the dissection. Four imaging techniques are currently available to diagnose aortic dissection: aortography; contrast-enhanced computerized tomography (CECT); magnetic resonance imaging (MRI); and transesophageal echocardiography (TEE). All of these techniques have their specific advantages and inherent limitations. Recent studies have demonstrated that MRI may best provide a comprehensive and detailed evaluation of the thoracic aorta, therefore proposing this technique as a "new gold standard" in the diagnosis of acute aortic dissection. TEE, however, may be the best alternative technique, as it combines high sensitivity and specificity with high practicality. The practicality is particularly important in hemodynamically unstable patients in whom a rapid bedside imaging modality is required. CECT might be necessary in selected cases in whom TEE fails to provide a definite diagnosis. Aortography may be necessary in patients in whom clinical signs are suggestive of organ ischemia and in whom coronary anatomy needs to be delineated before operation.     

正常胸主动脉内径磁共振成像测量

本文磁共振成像（ＭＲＩ）测量５０例正常胸主动脉不同部位的内径，并进行性别、年龄分组比较，得出一组胸主动脉内径ＭＲＩ正常值。结果显示：①降主动脉总是比升主动脉细；②男性胸主动脉各部内径比女性大；③除主动脉瓣环直径、主动脉窦内径和升主动脉近侧内径外．胸主动脉其余各部内径随年龄增长而增大。了解这些正常值和正常关系有助于评价胸主动脉病变。     

Cone-beam CT angiography of the thorax: an experimental study.

The authors recently developed a cone-beam computed tomography (CT) scanner and this report presents their evaluation of its potential for thoracic vascular imaging. An X-ray tube and a video-fluoroscopic system were rotated around the objects and 360 projected images were collected in a 12-s scan. Each image was digitized and a 3 dimensional (D) image (256x256x256 voxel volume with a voxel dimension of 0.9x0.9x0.9 mm) was reconstructed. Two different 3D-CT angiographies were investigated in 2 pigs: right atriography and thoracic aortography. Each pig was anesthetized, mechanically ventilated and positioned within the scanner. Contrast agent was infused through the right atrium or the aortic root at a rate of 3 ml/s during the scan. The right atriography scan clearly delineated the anatomy of the pulmonary artery, heart chambers and thoracic aorta. The thoracic aortography scan also clearly delineated the aortic anatomy including the internal thoracic and intercostal arteries. In conclusion, cone-beam CT angiography is potentially useful for thoracic vascular imaging.     

血小板源生长因子对离体大鼠胸主动脉血管张力的影响

目的 :观察血小板源生长因子对主动脉血管环舒缩作用的影响。方法 :采用离体灌流SD大鼠胸主动脉血管环标本 ,观察不同浓度的血小板源生长因子 BB（PDGF BB）对大鼠胸主动脉血管环的舒缩作用的影响 ,并与去甲肾上腺素 （NE）作对比。结果 :PDGF BB对大鼠胸主动脉有明显的收缩作用 ,阈浓度为 2× 10 -10 mol/L ,且呈现出一种浓度依赖关系 ;与NE相比 ,PDGF BB对血管的收缩幅度低于NE ,但其收缩血管的活性高于NE。PDGF BB对去内皮的血管同样产生收缩作用 ,鱼精蛋白可抑制PDGF BB收缩大鼠的胸主动脉的作用。结论 :PDGF BB对大鼠胸主动脉有明显的收缩作用 ,且呈现出一种浓度依赖关系 ,其血管收缩作用为非内皮依赖性收缩作用 ,鱼精蛋白可抑制PDGF BB收缩血管的作用。     

Transesophageal Echocardiography in Thoracic Aortic Atherosclerosis

Transesophageal echocardiography opened a new window to the thoracic aorta and for the first time permitted in vivo imaging of aortic atherosclerotic disease. The technique is useful in assessing the extent of the disorder, its complications, and possible treatment modalities. It will also be useful in the assessment of the progression as well as the possible regression of the disorder with appropriate (dietary or chemical) therapy.     

Hypoplasia of the descending thoracic and abdominal aorta: a case report and review of literature

Coarctation of the aorta has been found at necropsy in approximately 1 of every 1550 individuals. The most common location for segmental coarctation (juxtaductal) is the attachment of the ductus arteriosus to the thoracic aorta, which accounts for 98% of focal lesions. Less commonly, a relatively long segment of constriction extends beyond the left subclavian artery. When longer segments of the aorta are narrowed, the term "hypoplasia" is often used. Aortic hypoplasia, an exceedingly rare cardiovascular anomaly, has been described in all portions of the thoracic and abdominal aorta. In the current case report, we described a 21-year-old man presenting with severe hypertension in whom the diagnosis of hypoplasia of the descending thoracic and abdominal aorta was made using with magnetic resonance imaging.     

Left main bronchus compression by massive thoracic aorta aneurysm as a cause of dyspnea

In the past, thoracic aorta aneurysms were common findings, especially in the older population. With the development of imaging methods and surgical treatment, the diagnosis can now be made earlier, revealing the condition at an earlier stage. However, even today we see patients, mainly the elderly, with huge thoracic aorta aneurysms. Because of ambiguous radiological findings, this condition can be initially misdiagnosed as mediastinal tumors. In this case report is presented a case of such thoracic aorta aneurysm, which caused dyspnea by left main bronchus compression. The purpose of this report is to highlight thoracic aortic aneurysms as a potential rare case dyspnea and cough.     

Duplex scanning in the diagnosis of diseases of the thoracic aorta

In the Department of Vascular Surgery, A. V. Vishnevsky Institute of Surgery, USSR Academy of Medical Sciences, Duplex scanning was used to examine 40 patients. It was demonstrated that 20 patients had aneurysms of the arch and descending thoracic aorta; 4, dissecting aneurysms of Types I and III; 5, aortic coarctation; 11 patients had thoracic aorta aneurysms resected. The optimal point for scanning in the diagnosis of aneurysms and coarctation of the thoracic aorta is the jugular fossa. The diagnostic value of the duplex scanning in the detection of aneurysms of the arch and descending thoracic aorta amounted to 90%, that of aortic coarctation, 100%. The technique is noninvasive and highly informative, assessing the results of surgical therapy of thoracic aorta abnormalities in late periods following operation.     

An unusual type of combined aortic coarctation due to fibromuscular dysplasia.

A 3-year-old patient is described with an unusual form of co-arctation due to hypoplasia of the transverse arch and fibromuscular dysplasia involving a long segment of the thoracic aorta. Surgical repair required resection of the aorta from the distal transverse arch to the mid-descending thoracic aorta, and replacement with a 16-mm Dacron interposition graft. This case demonstrates the importance of preoperative evaluation of the entire aorta in the presence of co-arctation due to fibromuscular dysplasia.     

Ultrasonic visualization of the posterior thoracic aorta in long axis: diagnosis of a saccular mycotic aneurysm

A saccular aneurysm arising from the descending thoracic aorta was identified ultrasonically in a 60-year-old man with a subsequent pathologic diagnosis of a Listeria monocytogenes mycotic aneurysm. A cross-sectional scanning technique, which permitted visualization of the descending thoracic aorta in long axis, demonstrated a 3 X 5 cm relatively echo-free mass between the heart and the aorta. A communication between the mass and the aorta established the diagnosis of an aneurysm.