Comparison of conventional and transesophageal echocardiography with magnetic resonance imaging for anatomical mapping of thoracic aortic dissection

Thirty-five consecutive patients with clinically suspected aortic dissection were subjected to a dual noninvasive imaging protocol using comprehensive echocardiography and ECG-triggered MRI with multi-slice spin echo and cine sequences in random order. The purpose of this dual imaging study was to compare the diagnostic accuracy of two-dimensional and color-coded Doppler echocardiography using the conventional transthoracic (TTE) and the transesophageal approach (TEE) with magnetic resonance imaging (MRI) for the exact morphologic evaluation and anatomical mapping of the thoracic aorta. The results of each diagnostic method were validated independently against the gold standard of intraoperative findings (n=17), necropsy (n=4) or contrast angiography (n=22).Compared to conventional transthoracic echocardiography both TEE and MRI were more reliable in detecting aortic dissections (TTE vs TEE: p<0.02; TTE vs MRI: p<0.01) and associated epiphenomena. Moreover, the reliability of TTE decreased significantly from proximal to distal segments of the aorta, e.g. from the ascending segment to the arch (p<0.05) and to the descending aorta (p<0.005), whereas the sensitivities of both TEE and MRI were excellent irrespective of the site of dissection. With regard to epiphenomena such as thrombus formation and entry location, MRI emerged as the optimal method for detailed morphologic information in all segments of the aorta. No serious side effects were encountered with either method.Thus, in patients with suspected acute or subacute aortic dissections the echocardiographic assessment should include the transesophageal approach for significant improvement of the moderate sensitivity and specificity of TTE. Both TEE and MRI are non-traumatic, safe and diagnostically accurate to identify and classify acute and subacute dissections of the thoracic aorta irrespective of their location. MRI provides superb anatomical mapping of all type A and B dissections and more detailed information on the site of entry and thrombus formation than TEE. These features of TEE and MRI may render retrograde contrast angiography obsolete in the setting of thoracic aortic dissection and may encourage surgical interventions exclusively on the basis of noninvasive imaging.     

Magnetic resonance imaging of thoracic aortic dissections

Magnetic resonance imaging is an excellent noninvasive method for evaluating thoracic aortic dissections. A variety of magnetic resonance scans of aortic dissections are shown, documenting the ability of magnetic resonance to image the true lumen, the false channel, and the intimal septum. Detail is provided on magnetic resonance imaging techniques and findings.     

食管超声引导覆膜支架介入治疗胸主动脉夹层

目的　评价应用食管超声经股动脉植入覆膜支架治疗DeBakeyⅢb型主动脉夹层动脉瘤的安全性和效果。方法　 8例男性患者均经磁共振血管造影 (MRA)证实为DeBakeyⅢb型主动脉夹层。平均年龄 55 8± 10 2 (2 8～ 71)岁。在食管超声引导和透视监测下 ,经股动脉切开植入覆膜支架封闭近端或近、远端主动脉夹层破口。并评价术后即刻和随访结果。结果　 8例患者共成功植入覆膜支架 11枚 ,支架平均直径为 2 9 4(2 2～ 3 8)mm。术后即刻 3例有极少量内漏 ,2例有微量烟雾状分流。 1例在球囊扩张后升主动脉出现局限夹层。术后平均住院时间为 9d。随访 8例 ,平均随访时间 10 5(6～ 18)个月 ,4例残余分流消失 ,无发生支架移位或新生内漏者。升主动脉局限夹层患者于术后 11个月行MRA复查示病情稳定未再发展。 1例于术后 1年复查MRA仍有极少量内漏 ,后因咯血突发死亡。结论　联合应用食管超声 ,经股动脉植入覆膜支架治疗DeBakeyⅢb型主动脉夹层是一项有前景的方法 ,而且创伤小、安全有效 ,近中期效果满意 ,远期结果需进一步观察     

Diagnosis of aortic dissection: The value and limitations of transesophageal echocardiography

Aortic dissection requires prompt and reliable diagnosis. The purpose of this study was to assess the accuracy and limitations of transesophageal echocardiography (TEE) for the diagnosis of aortic dissection. Twenty seven patients with clinically suspected aortic dissection were investigated by means of TEE. TEE results were compared to intraoperative findings (n=18), necropsy (n=4), and magnetic resonance imaging (n=5). The DeBakey classification was used for differentiation of dissection type. Twenty-three patients (85%) were correctly identified as having aortic dissection. Four false-positive TEE findings (15%) were confined to the nondissecting aneurysm of the ascending aorta in elderly patients. Retrospectively we found that protruding atherosclerotic plaques were recognized as small intimal flaps. Type of dissection was correctly diagnosed in all 23 patients, the primary entry site was identified in 15 patients (65%), aortic regurgitation was found in 55.5% of patients, and pericardial effusion was detected in 33.3%. We conclude that TEE allows accurate diagnosis and classification of aortic dissection. However, some cases could be overdiagnosed in lesions of the ascending aorta, especially in nondissecting aneurysms. Another limitation of TEE is the inability to define the primary entry site in some cases. Still, overall results may favor TEE as the primary bedside diagnostic procedure to identify patients requiring urgent surgical intervention.Presented at the 35th World Congress, International College of Angiology, Copenhagen, Denmark, July 1993     

Diagnosis of aortic dissection with magnetic resonance imaging

Eight patients with suspected or known aortic dissection were imaged with magnetic resonance (MR). All of them were eventually shown to have dissection. In most instances the diagnosis was established by aortography and/or computed tomography (CT) prior to the MR study. MR demonstrated the intimal flap and determined whether the dissection was type I, type II or type III. In addition, MR differentiated between the true and false lumens. Our early experience suggests that MR can serve as the initial imaging test in clinically suspected cases of aortic dissection and that the information provided by MR obviates the use of iodinated contrast media.     

Diagnostic accuracy of transesophageal echocardiography, helical computed tomography, and magnetic resonance imaging for suspected thoracic aortic dissection: systematic review and meta-analysis

BACKGROUND: Patients with suspected thoracic aortic dissection require early and accurate diagnosis. Aortography has been replaced by less invasive imaging techniques including transesophageal echocardiography (TEE), helical computed tomography (CT), and magnetic resonance imaging (MRI); however, accuracies have varied from trial to trial, and which imaging technique should be applied to which risk population remains unclear. We systematically reviewed the diagnostic accuracy of these imaging techniques in patients with suspected thoracic aortic dissection. METHODS: Published English-language reports on the diagnosis of thoracic aortic dissection by TEE, helical CT, or MRI were identified from electronic databases. Sensitivity, specificity, and positive and negative likelihood ratios were pooled in a random-effects model. RESULTS: Sixteen studies involving a total of 1139 patients were selected. Pooled sensitivity (98%-100%) and specificity (95%-98%) were comparable between imaging techniques. The pooled positive likelihood ratio appeared to be higher for MRI (positive likelihood ratio, 25.3; 95% confidence interval, 11.1-57.1) than for TEE (14.1; 6.0-33.2) or helical CT (13.9; 4.2-46.0). If a patient had shown a 50% pretest probability of thoracic aortic dissection (high risk), he or she had a 93% to 96% posttest probability of thoracic aortic dissection following a positive result of each imaging test. If a patient had a 5% pretest probability of thoracic aortic dissection (low risk), he or she had a 0.1% to 0.3% posttest probability of thoracic aortic dissection following a negative result of each imaging test. CONCLUSION: All 3 imaging techniques, ie, TEE, helical CT, and MRI, yield clinically equally reliable diagnostic values for confirming or ruling out thoracic aortic dissection.     

Usefulness of transesophageal echocardiography in assessment of aortic dissection

BACKGROUND. The value of transesophageal echocardiography in the assessment of patients with aortic dissection was studied. METHODS AND RESULTS. Group 1 (34 patients) represented all patients studied at our institution with this technique in whom aortic dissection was proven by aortography, surgery, or autopsy. Group 2 (27 patients) represented all patients studied with this technique at our institution in whom aortic dissection was excluded by aortography. Transesophageal echocardiography made a correct diagnosis of aortic dissection in 33 of 34 patients (sensitivity, 97%; specificity, 100%). It also correctly demonstrated the type of dissection in all 29 patients with aortographic or surgical proof. On the other hand, computed tomography scanning, performed in 24 of 34 patients in group 1, made a correct diagnosis in only 67% of patients and misclassified the type of dissection in 33%. Transesophageal echocardiography correctly identified involvement of the coronary arteries by aortic dissection in six of seven patients as well as absence of both left and right coronary artery involvement in 10 patients with aortic dissection. This technique was also useful in detecting communications between the true and false lumens, presence of thrombi in the false lumen, and, in two patients, localized dissection rupture with formation of a false aneurysm. In both groups 1 and 2, transesophageal echocardiography correctly identified patients with moderate to severe aortic regurgitation. CONCLUSIONS. Transesophageal echocardiography is very useful in the assessment of aortic dissection.     

多平面经食管超声心动图技术对主动脉夹层的诊断价值

目的 探讨多平面经食管超声心动图(TEE)技术对主动脉夹层(AD)的诊断价值。方法 对19例疑诊AD患者进行了多平面TEE检查。结果 19例患者均由多平面TEE明确诊断，其中14例经CT或MRI证实，5例由手术证实，准确性和特异性均为100％。DeBakey分型Ⅰ型夹层患者4例，Ⅱ型3例，破口均位于升主动脉；Ⅲ型12例中，9例破口位于降主动脉近心端，3例未探及内膜破口。结论 多平面TEE技术为AD无创性诊断开辟了新途径。     

Diagnosis of acute aortic dissection by echocardiography

Until recently, the diagnosis of aortic dissection rested on aortography. The purpose of this study was to evaluate the diagnostic value of echocardiography in that disease and its ability to inform on the extent of the dissection and on the presence of associated lesions. Twenty-six patients (mean age 64 +/- 10 years) admitted for suspected aortic dissection were explored by echocardiography and the results were compared with those of angiography and/or anatomical findings. Echocardiography provided the diagnosis in 14 of the 16 patients with aortic dissection and excluded it in the remaining 10 patients. The sensitivity and specificity of the method were 87.5 p. 100 and 100 p. 100 respectively. The type of dissection was correctly determined in 90 p. 100 of the patients whose aorta had been totally explored by echocardiography. Aortic regurgitation and pericardial effusion were detected in 81 p. 100 and 50 p. 100 respectively of patients with aortic dissection. These results confirm the diagnostic value of echocardiography in dissection of the aorta. The extent of the lesion can only be evaluated when the whole of the aorta is visualized. The echocardiographic diagnosis is easier when the ascending aorta is involved (type I), while in type III aortic dissection there is a risk of missing a retrograde lesion of the aorta and confusing this type with type I. In this study two kinds of intimal flap motion were observed: in the first one the motion was independent of that of the aorta, while the second one resembled a division of the aortic, wall the motion of which is parallel to that of the aorta.     

Anomalous inferior vena cava mimicking aortic dissection on transesophageal echocardiography

Transesophageal echocardiography (TEE) is considered an excellent method for the diagnosis of aortic dissection, especially that involving the descending aorta. It has also proved useful in the evaluation of conditions mimicking aortic dissection, usually disclosing in these situations other types of severe aortic disease. We are not aware of any report dealing with venous abnormalities which presented diagnostic problems in a patient evaluated with TEE because of a suspected aortic dissection. Left ventricular (LV) free wall rupture complicated with acute myocardial infarction (AMI) usually occurs in the early phase of AMI. True aneurysm of the LV is sometimes a complication of AMI but rarely ruptures. In our patient, a 72-year-old woman, the LV free wall ruptured on Day 49 after the onset of AMI and the ruptured site was the thinnest wall of large true aneurysm of the LV. The large aneurysmal formation probably was due to corticosteroids used for pericarditis. More attention should be paid to late cardiac rupture and the use of corticosteroids.     

Emergency surgical management of acute aortic dissection: role of transesophageal echocardiography.

The accuracy of transesophageal echocardiography in the diagnosis and surgical management of acute aortic dissection was determined in 54 patients who underwent surgery for acute aortic dissection. Results of the investigations were compared to the surgical assessment. From April 1993 to November 1997, we operated 54 patients (44 male and 10 female) for acute aortic dissection. Mean age was 60 +/- 9 years. At surgery, a De Bakey type I aortic dissection was diagnosed in 30 patients, type II in 23 and type III retrograde in 1. Operating procedures were: replacement of ascending aorta (24 cases), replacement of ascending aorta and aortic arch (17 cases), replacement of ascending aorta and aortic valve replacement (2 cases), Bentall procedure (6 cases) and end-to-end anastomosis of the ascending aorta (4 cases). Initial diagnosis, performed in emergency wards, was done on a clinical basis in 6 patients, on CT scan in 19, on transthoracic echocardiography in 14, and on TEE basis in 12. Three patients underwent angiography before our evaluation. As per our protocol, all patients underwent confirmation of the diagnosis by TEE. Seven patients needed additional instrumental investigations, 2 with CT scan and 5 with angiography. TEE confirmed the diagnosis of aortic dissection in all cases but one. Moreover, it described the site of the intimal tear, the extension of the dissecting process and accessory findings, such as pericardial effusion, aortic incompetence and left ventricular function. The interval between patient presentation and skin incision was a maximum of 70 minutes. At surgery, diagnosis of De Bakey classification was confirmed in 98% of cases; in 90.7% of cases exact location of the entry site was confirmed. In one case, an entry site in the arch diagnosed by TEE but not recognized at surgery, was observed at necropsy. Intraoperatively, we routinely used TEE to monitor retrograde systemic perfusion and correct implant of the vascular prosthesis. One case of malperfusion of the thoracic aorta through the false lumen was observed and managed. In one case we diagnosed acute obstruction of the prosthesis by bleeding in the wrapped aorta, which required reoperation. Assessment of ventricular function was obtained in all patients: in two cases, observation of low right ventricular function led us to perform aortocoronary by-pass to the right coronary artery. In conclusion, the high level of correspondence between TEE diagnosis and surgical anatomy prompted us to perform transesophageal echocardiography as the primary and often sole diagnostic procedure in acute aortic dissection. TEE, in experienced hands, has proven to be a highly reliable, safe and low-cost diagnostic tool. It can be performed at the patient's bedside within just a few minutes of the suspected diagnosis, thereby lowering the mortality rate of the natural history. Again, it can also be used in the operating theatre as an "on-line examination" as well as for assessment of correct surgical repair. Other diagnostic procedures do not yield more information and can cause dangerous delays in intervention.     

Diagnostic goals in aortic dissection. Value of transthoracic and transesophageal echocardiography]

The combination of different ultrasound techniques like transthoracic, suprasternal, subcostal and transesophageal echocardiography have a high sensitivity and specificity in the diagnosis of aortic dissection. The limitation of this combined ultrasound technique is related to the visualization of the ascending part of the aortic arch which, cause of the interposition of the trachea, can not be visualized completely. The beginning or the end of a dissection in this part of the aorta may be misinterpreted. False negative results are rare. False positive results due to artefacts resulting from reverberations in an ectatic ascending aorta have to be taken into account. The most important diagnostic aims in acute or chronic aortic dissection can be described: 1. confirmation of the diagnosis by visualization of the intima membrane, 2. the differentiation of the true and false lumen depending on visualization of spontaneous echocardiographic contrast thrombus formation, slow or reduced reversed flow, systolic diameter reduction and signs of entry jet into the false lumen, 3. detection of intimal tear, demonstrating communication by two-dimensional or color Doppler echocardiography, 4. determination of the extent of the dissection with classification according to DeBakey type I, II and III or Stanford A and B with differentiation to communicating or non-communicating dissection, antegrade or retrograde dissection limited to the descending aorta or expanding to the ascending aorta, 5. detection of wall motion abnormalities as a sign of preexisting coronary artery disease or myocardial ischemia due to ostium occlusion by an intimal flap, coronary artery rupture or collapse of the true lumen during diastole, 6. detection and grading of aortic insufficiency, 7. detection of side branch involvement by suprasternal, subcostal and abdominal sonography, which will gain the information which side can be chosen for cannulation or catheterization at the femoral artery, 8. detection of pericardial pleural effusion and mediastinal hematoma as a sign of emergency as rupture can occur within minutes. Without surgical intervention have be performed. Based on these informations, surgery can be performed in all acute situations in type A dissection without further investigations. This decision is particularly important in patients with signs of emergency like pericardial or pleural effusion or mediastinal hematoma.