Radiological evaluation of composite aortic grafts.

Aneurysm of the ascending aorta with aortic regurgitation is most commonly caused by cystic medial necrosis. Replacement of the aortic valve and diseased aorta with a composite graft and re-implantation of coronary arteries is the surgical treatment of choice at the authors' institution. The most important late complication of this procedure is hemorrhage at the anastomotic sites. Radiology plays an important role in the management of these patients. The angiographic appearance of cystic medial necrosis and the radiological features and postoperative complications of composite grafts in 15 patients are described.     

Composite graft replacement of the ascending aorta: leakage detection with gadolinium-enhanced MR imaging.

PURPOSE: To assess the value of magnetic resonance (MR) imaging in the detection of postoperative complications after composite valve graft replacement. MATERIALS AND METHODS: Spin-echo and gradient-echo MR imaging was performed in 52 patients 1/2 to 200 months after composite graft replacement of the ascending aorta (22 for dissection, 30 for aneurysm). The prosthetic aortic segment, distal and proximal anastomoses, general morphologic characteristics, and diameter of the reimplanted coronary arteries were evaluated. In patients with abnormal perigraft thickening, additional spin-echo imaging was performed after injection of gadopentetate dimeglumine. RESULTS: Normal postoperative perigraft thickening (< or = 10 mm) was observed in 42 patients. Ten patients had abnormal periprosthetic thickening of 15-52 mm. Gadolinium-enhanced MR imaging demonstrated leakage in five of those 10 patients. The lack of enhancement excluded the presence of bleeding in the remaining five patients (three with chronic hematomas, one with infection, and one with granulation tissue). These findings were confirmed at surgery or with subsequent follow-up MR examinations. CONCLUSION: MR imaging was an optimal imaging modality for evaluating the morphologic characteristics of composite grafts and reimplanted coronary arteries. Gadolinium-enhanced MR imaging is a simple, accurate, and noninvasive method for detecting a leak, which necessitates urgent repeat surgery.     

人工心脏瓣膜血液动力学的MRI初步研究

目的应用MRI测量人工心脏瓣膜远端血流野及三维图像的描绘,来评价人工心脏瓣膜功能,并为长期随访瓣膜血栓等并发症的出现和发展提供原始资料.方法27例人工主动脉瓣膜置换患者进行MR血流速度测量检查,置换双叶机械瓣20例,单叶机械瓣7例.于升主动脉内距主动脉瓣环0.5、1.0及2.0个人工瓣环直径处进行血流速度测量.应用血流分析及Matlab 6.5软件进行二维及三维血流图形重组.结果16例置换Sorin双叶机械主动脉瓣患者,三维血流图人工心脏瓣膜的形状特点为近似对应于2个瓣孔及2个瓣叶之间缝隙的3个喷射峰;4例置换Sorin双叶机械主动脉瓣患者,出现对应于2个瓣孔的双喷射峰.20例置换双叶机械主动脉瓣患者,血流速度在加速射血相及最大射血相血流速度图变成倾斜.7例置换单叶机械主动脉瓣患者在收缩加速相见对应单叶瓣口的1个主喷射峰.26例反向血流出现在人工瓣膜侧孔的位置.MR血流速度三维图反映了人工心脏机械瓣膜的设计形状.距主动脉瓣环1.0人工瓣环直径处的轴向血流速度图较远端（2.0人工瓣环直径处）及近端（0.5人工瓣环直径处）的轴向血流速度图能更详细反映人工瓣膜的设计形状.结论MR可以无创、直观、在体地了解瓣膜功能,为发现术后并发症奠定基础.     

Aortic annulus and ascending aorta: Comparison of preoperative and periooperative measurement in patients with aortic stenosis

Background

Precise determination of the aortic annulus size constitutes an integral part of the preoperative evaluation prior to aortic valve replacement. It enables the estimation of the size of prosthesis to be implanted. Knowledge of the size of the ascending aorta is required in the preoperative analysis and monitoring of its dilation enables the precise timing of the operation. Our goal was to compare the precision of measurement of the aortic annulus and ascending aorta using magnetic resonance (MR), multidetector-row computed tomography (MDCT), transthoracic echocardiography (TTE), and transoesophageal echocardiography (TEE) in patients with degenerative aortic stenosis.

Methods and results

A total of 15 patients scheduled to have aortic valve replacement were enrolled into this prospective study. TTE was performed in all patients and was supplemented with TEE, CT and MR in the majority of patients. The values obtained were compared with perioperative measurements. For the measurement of aortic annulus, MR was found to be the most precise technique, followed by MDCT, TTE, and TEE. For the measurement of ascending aorta, MR again was found to be the most precise technique, followed by MDCT, TEE, and TTE.

Conclusion

In our study, magnetic resonance was found to be the most precise technique for the measurement of aortic annulus and ascending aorta in patients with severe degenerative aortic stenosis.     

Magnetic resonance imaging evaluation of the ascending aorta after graft-inclusion surgery: Comparison between an ultrafast contrast-enhanced MR sequence and conventional cine-MRI

The aim of this study was to compare the value of two magnitude-based MR sequences, a contrast-enhanced ultrafast MR sequence and a cine MR sequence, for the detection of flow around the graft in the postoperative ascending thoracic aorta. Thirteen patients who underwent ascending aortic surgery for dissection (n = 11) and aneurysm (n = 2) were enrolled. They were referred to MRI for mediastinum enlargement on the chest x-ray or mediastinal symptoms. All patients had replacement of the diseased ascending aorta using a graft-inclusion technique (with wrapping of the native aorta over the graft). Delays between surgery and MRI ranged from 15 days to 8 years (mean: 10 months). All patients were examined using a T1-weighted spin-echo sequence, a magnitude-based cine gradient-echo sequence, and an ultrafast contrast-enhanced MR sequence. MR images of the cine and the contrast-enhanced sequences were retrospectively and independently analyzed by two qualified radiologists for evidence of flow or thrombus around the graft, including perigraft structure and aneurysmal formations. Evidence of flow was detected by both methods in all aneurysmal formations of the ascending aorta located at suture level (n = 6). Evidence of flow in the perigraft structure was found in seven cases by contrast-enhanced MR sequence and in only four cases by cine MR sequence. Contrast-enhanced ultrafast MR sequence could be proposed as a minimally invasive and fast modality for assessing the perigraft structure, in graft-in-clusion surgical procedures of the ascending aorta, when noncontrast enhanced MR sequences do not exclude the possibility of flowing blood in this structure.     

主动脉夹层及主动脉瘤的外科治疗26例

 目的 结合主动脉夹层细化分型的临床应用,探讨主动脉夹层及主动脉瘤外科手术治疗的临床经验.方法 26例主动脉夹层及主动脉瘤患者,在深低温停循环选择性脑灌注下,行升主动脉加全弓替换4例,全弓替换1例;分段停循环下,行全胸腹主动脉替换术1例;常温阻断加血泵法血液回收股动脉输入法,行降主动脉替换2例,股动脉、股静脉转流降主动脉人工血管替换1例;常规低温体外循环下,行Bentall术6例,Wheat术3例,Bentall加二尖瓣替换1例,Bentall加冠状动脉旁路移植术2例,升主动脉替换1例,升主动脉加部分弓替换1例,主动脉瓣成形加升主动脉替换1例;全麻下带膜支架主动脉腔内修复术2例.结果 本组26例,手术早期死亡1例,病死率3.8%;术后并发严重脑功能障碍2例,昏迷时间分别为15 d,30d,占7.6%.共随访24例,随访率92%,死亡1例.结论 Stanford分型的细化对明确手术指征和确立手术预案具有指导意义.四分支人工血管的应用缩短了主动脉阻断时间,结合选择性脑灌注及分段停循环技术,降低了术后并发症.     

Complete detachment of an aortic valve prosthesis 10 years after implantation

A 47-year-old male patient died unexpectedly 10 years after replacement of the aortic valve with a Carbomedics heart valve prosthesis required for post-endocarditic valve stenosis. The man was in regular medical attendance by his general practitioner and in hospital. Clinical data and examinations did not suggest the reoccurrence of endocarditis. Three months before his death a haemolytic anaemia of unknown genesis was diagnosed. One afternoon, while lifting a heavy object, the man suffered acute chest pain and collapsed. Resuscitation failed and the patient died in hospital. Autopsy revealed the completely detached valve prosthesis within the ascending aorta. Histological examination confirmed a chronic endocarditis at the site of the valve implantation.     

马凡综合征主动脉病变MRI诊断的研究

目的：评价ＭＲＩ对马凡综合征主动脉病变诊断的价值。材料与方法：分析了２０例马凡综合征主动脉病变的ＭＲＩ所见，并与１１例非马凡综合征所致的升主动脉扩张或动脉瘤进行对照研究。结果：主动脉窦和近段升主动脉瘤样扩张是马凡综合征最重要而常见的心血管病变，“瘤体”与正常段或轻度扩张的主动脉分界清楚是颇具特征性的马凡综合征心血管病变，继发于主动脉瓣狭窄和（或）关闭不全的升主动脉扩张大多呈普遍轻度扩张，而主动脉窦大多无明确扩张，其ＭＲＩ所见与马凡综合征升主动脉病变明显不同。结论：ＭＲＩ在马凡综合征主动脉病变的诊断中有优良的价值。     

MR evaluation of chronic aortic dissection

Thirty patients with suspected or known chronic aortic dissection were imaged with magnetic resonance (MR), CT, and angiography. Five of these patients had previously undergone surgical repair of the ascending aorta for a type A dissection. Magnetic resonance demonstrated an intimal flap and a double lumen in 25 cases. In four cases with a thrombosed false lumen, proved angiographically, an intimal flap and double channel were not seen. In two of four aortic dissections with a thrombosed false lumen, CT made the diagnosis by showing displaced intimal calcifications not visualized on MR. In one case the aortic dissection was made on CT and angiography but was not supported by MR which showed an aortic aneurysm, subsequently confirmed at surgery. Magnetic resonance, CT, and aortography differentiated between type A (nine patients) or B (20 patients) dissection in all cases and demonstrated extension into the abdominal aorta. Extension into the iliac arteries was seen on MR in three patients but missed in nine patients. Magnetic resonance differentiated the true and false lumen in all but one case. Thrombosis of the false channel was identified in four cases by a decrease in signal intensity on the second echo image. Cardiac gating and longitudinal contiguous sections seemed to be more suitable for appreciation of the relationships with arch vessels. Transverse contiguous slices allowed determination of the origin of celiac, mesenteric, and renal arteries from either the true or the false lumen. This study confirms that MR is an accurate and noninvasive method for the evaluation and follow-up of chronic aortic dissection, obviating the need for iodinated contrast media.     

Visualization of flow patterns distal to aortic valve prostheses in humans using a fast approach for cine 3D velocity mapping

The fluid dynamic performance of mechanical heart valves differs from normal valves and thus is considered related to late clinical complications in patients. Since flow patterns evolving around heart valves are complex in space and time, flow visualization based on time-resolved 3D velocity data might add important information regarding the performance of specific valve designs in vivo. However, previous cine 3D techniques for three-directional phase-contrast velocity mapping suffer from long scan duration and therefore might hamper assessment in patients. A hybrid 3D phase-contrast sequence combining segmented k-space acquisition with short EPI readout trains is presented with its validation in vitro. The technique was applied to study flow patterns downstream from a bileaflet aortic prosthesis in six patients. Navigator echoes were incorporated for respiratory motion compensation. Before flow visualization, spurious phase errors due to concomitant gradient fields and eddy currents were corrected. Flow visualization was based on particle paths and animated velocity vector plots. Dedicated algorithms for particle path integration were implemented to account for the considerable motion of the ascending aorta during the cardiac cycle. A distinct flow pattern reflecting the valve design was observed closest to the valve during early flow acceleration. Reverse flow occurred adjacent to high velocity jets and above the hinge housings. Later in systole, flow became confined to the central vessel area and reverse flow along the inner aortic curvature developed. Further downstream from the valve, flow patterns varied considerably among patients, indicating the impact of varying aortic anatomy in vivo. It is concluded that MR velocity mapping is a potential tool for studying 3D flow patterns evolving around heart valve prostheses in humans. J. Magn. Reson. Imaging 2001;13:690-698.     

The ascending aorta in aortic stenosis

Dilatation of the ascending aorta, a frequently reported sign of aortic stenosis, was assessed in 47 patients for whom aortic angiograms had been recorded. Twenty-eight of the patients had rheumatic valvar disease and 19 had congenital aortic stenosis. A simple ratio between the maximal width of the mid-ascending aorta and the width of the aortic root was calculated. Patients with congenital aortic stenosis had significantly greater supravalvar aortic dilatation than did those with rheumatic aortic valve involvement. There was no correlation between the pressure difference across the aortic valve and degree of dilatation of the ascending aorta.     

Steady-state free-precession (SSFP) cine MRI in distinguishing normal and bicuspid aortic valves

PURPOSE: To assess the diagnostic sensitivity and specificity of double-oblique true fast imaging with steady-state precession (SSFP) cine MRI in distinguishing normal and bicuspid aortic valves. MATERIALS AND METHODS: Echocardiograms on patients referred for MRI of the heart and thoracic aorta over a four-year period were reviewed retrospectively. A total of 17 patients with bicuspid aortic valve were identified and compared to 21 randomly chosen control patients. All patients had double-oblique SSFP (True FISP) cine MRI of the aortic valve independently assessed by two radiologists in a blinded fashion, and graded as bicuspid or normal. Image quality was graded as 1, 2, or 3. Discordance was resolved by consensus. RESULTS: A total of 38 cases were reviewed (27 men, 11 women; age range = 15-67 years, mean = 25.33 years). Interobserver agreement was 0.97 (36/38 cases). One case of normal tricuspid valve was reported as bicuspid by both readers (false-positive). All cases in which disparity arose were rated suboptimal by both readers (grade 2 or 3). Consensus review yielded sensitivity = 100%, specificity = 95.2%, positive predictive value = 94.4%, and negative predictive value = 100%; overall diagnostic accuracy was 97.36%. Interobserver agreement was 0.97. CONCLUSION: Double-oblique True FISP cine MR imaging of the aortic valve is 100% sensitive and 95% specific in distinguishing normal and bicuspid aortic valves.     

Progressive thoracic aortic dilatation after aortic valve replacement

Aneurysms of the ascending aorta developed after aortic valve replacement for chronic aortic insufficiency in four cases. Two of the aneurysms were complicated by dissection; one patient died. Rheumatic disease has become a less common cause of pure aortic regurgitation, and a number of etiologies primarily involving the wall of the aorta are now recognized. Although appropriately timed aortic valve replacement can prevent the irreversible left ventricular depression associated with chronic aortic insufficiency, careful evaluation of the thoracic aorta on serial postoperative chest radiographs is warranted, because the underlying pathologic process may proceed in the aortic wall with eventual aneurysm formation.     

超声、MR、CT、X线诊断主动脉夹层的比较

目的：比较超声、MR、CT及X线对主动脉夹层的诊断价值。方法：2005—01～2008—09经手术病理证实的26例主动脉夹层患者,26例均经超声、X线检查,17例经MR及CT检查,重点观察超声主动脉声像,内膜有无撕裂及撕裂部位,真假腔血流情况,主动脉瓣有无受累及瓣膜反流情况、心包积液、左室收缩功能等。结果．26例超声诊断25例,其中12例为DeB—bakeyI型,占46．2％,5例为Ⅱ型,占19．2％,9例为Ⅲ型,占34．6％,I型最常见。19例中量以上主动脉瓣反流,7例少量主动脉瓣反流,9例少一中量心包积液。16例LVEF％及LVFS％降低。17例经MR及CT检查诊断15例,26例胸片提示主动脉增宽,心影增大。结论：超声可作为诊断主动脉夹层的首选检查项目。     

Postoperative evaluation of composite aortic grafts: comparison of angiography and CT

Postoperative angiography and computerised tomography were performed in 10 patients 8 to 57 months after surgical repair (nine composite, one distal graft) of aneurysms of the thoracic aorta (six dissecting, four true aneurysms). Angiography and angio-CT showed chronic dissection of the distal aorta in five of six patients with dissecting aneurysms and detected a pseudoaneurysm originating from the distal suture line in another patient. CT may serve as an initial procedure for postoperative examinations after surgery of aortic aneurysms to demonstrate the state of the false lumen and the formation of pseudoaneurysms. The coronary arteries and aortic valve function have to be evaluated by angiography.     

Synthetic interposition grafts of the thoracic aorta: postoperative appearance on serial CT studies

PURPOSE: To determine the normal postoperative appearance of thoracic aortic interposition grafts on serial CT studies and to document CT detectable complications. MATERIALS AND METHODS: The 235 CT studies in 114 patients with one or more thoracic aortic interposition grafts were analyzed for the presence or absence of felt rings, felt pledgets, low-attenuation material surrounding the graft, pseudoaneurysm, and dissection flap. A graft was present in the ascending aorta in 93 patients, in the descending aorta in 25, and in the arch in 11. RESULTS: Low-attenuation material was seen adjacent to the ascending graft in 55%-82% of patients and adjacent to the descending graft in 60%-79% of patients, showing diminishing frequency and thickness over time. CT scans in 30 of 53 patients showed residual low-attenuation material adjacent to the graft more than 1 year after surgery. CT scans in four of 93 patients with ascending grafts and one of 25 patients with descending grafts showed a pseudoaneurysm. CONCLUSION: CT studies obtained after aortic interposition grafting show characteristic findings. Knowledge of the type of operative procedure and typical location and CT appearance of surgical materials used is important to correctly diagnose or exclude postoperative complications following thoracic aortic interposition grafting.     

Superior pericardial recess simulating aortic dissection on computed tomography

Computed tomography is frequently used in the initial workup of patients with suspected aortic dissection to distinguish dissection involving the ascending aorta from dissection limited to the descending aorta. We reviewed CT of 19 patients who were proven by aortography to have normal ascending aortas. In eight patients the superior extension of the pericardium was visualized and thought to be a potential source of a false-positive diagnosis of type A aortic dissection.     

Breathhold time‐resolved three‐directional MR velocity mapping of aortic flow in patients after aortic valve‐sparing surgery

Purpose

To evaluate the utility of breathhold time‐resolved three‐directional MR velocity mapping for quantifying the restoration of normal flow patterns in patients after aortic valve‐sparing surgery.

Materials and Methods

Breathhold time‐resolved three‐directional MR velocity mapping was performed on 13 patients with aortic valve‐sparing surgery. Ten healthy volunteers and 12 patients with ascending aortic aneurysm underwent the same MR examination for comparison. Aortic laminar flow, turbulent flow, and the presence of vortical flow in the sinuses of Valsalva were semiquantitatively assessed and statistically compared between the three groups of subjects.

Results

The average score of laminar flow in the ascending aorta for patients with surgery was not significantly different from that of volunteers (P = 0.210), but was significantly greater than that of patients with aneurysm (P < 0.01). The average score of turbulent flow in patients with surgery was significantly smaller than that of patients with aneurysm (P < 0.01). The presence of systolic vortical flow in the sinuses of Valsalva for patients with surgery was not significantly different from that of healthy volunteers (P = 0.405) and patients with aneurysm (P = 0.238).

Conclusion

Breathhold time‐resolved three‐directional MR velocity mapping allows for quantifying flow patterns in the aortic root and ascending aorta. Normal laminar flow in the ascending aorta and vortical flow in the sinuses of Valsalva can be restored in patients after aortic valve‐sparing surgery. J. Magn. Reson. Imaging 2009;29:569–575. © 2009 Wiley‐Liss, Inc.     

Visualization of aortic valve leaflets using black blood MRI.

Although magnetic resonance imaging (MRI) is capable of imaging various physiological parameters associated with the heart valves, it has generally been difficult to visualize the valve leaflets directly. The aortic valve was imaged in 120 patients referred for cardiac MRI to assess myocardial volumes or mass. The average patient age was 37 and ranged from 9 to 75 years. Heart rate ranged from 43 to 100 bpm. Imaging was performed on a 1.5 T scanner equipped with enhanced gradients and a cardiac phased-array coil. A double inversion recovery fast spin-echo sequence was used to acquire short-axis images of the aortic valve in a breath-hold (15 +/- 3 seconds). All three leaflets of the aortic valve were seen in 102 of 120 studies (85%). Two leaflets were detected in another 15 subjects. No leaflets were seen in three individuals. Seven cases of a bicuspid or thickened aortic valves were clearly distinguished from normal valves. The signal-to-noise ratio of aortic leaflets (14 +/- 5) was significantly higher than that of the residual blood signal in the aortic root (7 +/- 4, P < 0.001). MR images showed the aortic valve leaflets in a high fraction of people with suspected normal aortic valves and detected seven cases of abnormal aortic valves. The potential of MRI to study both the anatomic and functional consequences of valvular heart disease warrants further study. J. Magn. Reson. Imaging 1999;10:771-777.     

Aortic compliance in patients with aortic regurgitation: evaluation with magnetic resonance imaging

PURPOSE: To assess by means of cine magnetic resonance imaging (MRI) aortic compliance before and after aortic valve replacement (AVR with SJM valve) in patients with aortic regurgitation (AR). MATERIALS AND METHODS: Two groups (healthy controls and patients with severe isolated AR) of 10 subjects each were included in this study. Cine MRI was performed at three locations of the aorta, and aortic compliance was calculated by dividing the maximum change in the aortic area by pulse pressure. RESULTS: Cine MRI is useful to assess abnormalities of aortic compliance in patients with AR. Compared with the control group, aortic compliance in the AR group was significantly less in the ascending aorta (p<0.05), decreasing in order of aortic location. After AVR, aortic compliance improved for all locations. CONCLUSION: Cine MRI enables assessment of aortic biophysical properties such as a compliance for evaluating the progression of AR and the efficacy of treatment.