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Role of Transoesophageal
Echocardiography in the Diagnosis
of Acute Aortic Syndrome

Arturo Evangelista, MD; Gustavo Avegliano, MD;
Cristina Elorz, MD; Teresa González-Alujas, MD;
Herminio García del Castillo, MD

Laboratorio de Ecocardiografía, Servicio de Cardiología,
Hospital Universitario Vall d´Hebron, Barcelona, Spain

   In recent years, technological advances in echocardiography have led to improvements in the diagnosis of acute aortic disease. With transesophageal echocardiography (TEE) and, particularly, bi-and multiplane probes, the physiopathologic understanding of these diseases has widened. Thus, new entities such as penetrating ulcer and intramural haematoma have been described and differentiated from classical aortic dissection.

   Owing to the high mortality rate in these diseases (1) and the need for early medical and surgical treatment, rapid and accurate diagnostic techniques, which can be applied in critically- ill patients, are essential. Echocardiography is precise, rapid and available. Compared with other , highly accurate diagnostic techniques (helical CT, magnetic resonance), echocardiography has the advantage of being applicable in any hospital department (emergency, intensive care, operating theatre), without the need to transfer the patient who is often in an unstable hemodynamic situation, monitored and with an intravenous line in place.

   The first echocardiographic signs for diagnosing aortic dissection by M-mode were described in 1973 (2). Although by bidimensional echocardiography the results were acceptable, particularly in ascending aorta (3), their use in clinical practice has been scant.

   Thanks to TEE, the usefulness of the technique has improved greatly. The proximity of the esophagus to the aorta, without interference from the chest wall or lung, permits high-quality images to be obtained. Since the first works published by Erbel et al (4), several studies have demonstrated the accuracy of TEE in the diagnosis of aortic dissection. Monoplane probes only permit us to see a transverse section of the aorta. They do not show the upper third of the ascending aorta, owing to the interposition of the trachea between the esophagus and aorta. Biplane and multiplane probes permit visualization of the major part of the ascending aorta and facilitate the interpretation of images in two planes, particularly in elongated aortas.

   The ideal diagnostic technique in acute aortic dissection should have high sensitivity and specificity and, furthermore, permit assessment of the main anatomical and functional aspects of interest for their management. These are:

- extent of the dissection.
- intimal tear location.
- diagnosis of complications: aortic insufficiency, principal aortic branch involvement (coronary arteries, supra-aortic vessels, renal arteries), signs of blood extravasation (pericardial effusion or aortic rupture). Each of these aspects, taking into account the advantages and disadvantages of echocardiography compared with other techniques, are critically analyzed below.

AORTIC DISSECTION DIAGNOSIS
a) Diagnostic accuracy
   Demonstration of the presence of an intimal flap that divides the aorta into two lumina, the true and the false, forms the basis of echocardiographic diagnosis of the dissection.

   Transthoracic echocardiography has 78%-100% sensitivity in ascending aorta dissection, but only 31-55% in descending aorta. Thus, it constitutes an acceptable technique for type A dissection, but not for type B.

   The use of all possible views is fundamental for correct assessment of the aorta by transthoracic echocardiography. Using the parasternal view, it is possible to see the aortic root, the lower third of the ascending aorta and also part of the descending thoracic aorta behind the left atrium (fig. 1). The right parasternal view permits visualization of the major part of the ascending aorta when the study is of good quality (fig. 2). The aortic arch, the origin of supra-aortic trunks and the proximal third of the descending aorta, can be assessed by the suprasternal view. Finally, the distal portion of the thoracic aorta and the start of the abdominal aorta can be viewed using the modified apical view and the subcostal approach. The use of colour Doppler may aid diagnosis of the dissection when two different flow patterns, separated by the intimal flap, along the aorta, are identified.

Figure 1.- Long-axis view of transthoracic echocardiography showing an intimal flap (arrow) in aortic root. AOA: Ascending aorta; AI: Left atrium; VI: Left ventricle.

Figure 2.- Right paraesternal view of transthoracic echocardiography showing the intimal flap in ascending aorta (arrows),

   Good quality images are the main limitation of transthoracic echocardiography. On the other hand, diagnostic errors are frequent when the dissection is small or another type of aortic disease is present. The low negative predictive value of transthoracic echocardiography does not permit the diagnosis of dissection to be ruled out, and further tests will be required (4).

   TEE has constituted a decisive advance in the diagnosis of aortic dissection (fig. 3). Sensitivity is 99%, specificity 98%, positive predictive value 98% and negative predictive value 99%. Only one false negative was obtained in a patient with a small dissection in the aortic root and two false positives in two patients with aortic ectasia (4). Later studies have confirmed the diagnostic accuracy of TEE in the assessment of patients with suspected aortic dissection, with sensitivity of 86-100%, specificity 90-100% and negative predictive value 86-100% (5,6,10). The low specificity of the technique described in some series, such as that of Nienaber et al (7) is explained, as will be commented on later, by the fact that the majority of intraluminal images in ascending aorta were considered diagnostic of dissected intima. Our group published (11) one of the largest series (132 patients) with biplane or multiplane technique, with sensitivity and specificity of 96.8% and, 100 %, respectively. In our experience, the use of the longitudinal plane provided greater information in some cases of retrograde dissection of the ascending aorta or when the dissection began in the middle third of the ascending aorta.

Figure 3.- Ascending aortic dissection diagnosed by transoesophageal echocardiography in longitudinal plane . The arrows identified the intimal flap.

b) Diagnostic errors
   The main diagnostic limitation of transesophageal echocardiography is the dissection that affects only the ascending aorta (type II). Analysis of 8 large studies (4, 6-10, 12) shows that 14 of 435 patients (3.5%) with clinically-suspected dissection were erroneously diagnosed of ascending aorta dissection . On the other hand, 9 false negatives were obtained from 212 patients (4.2%) with ascending aorta dissection; the dissection was small and located in the aortic root in 3, retrograde from the arch in 3 and affected only the upper third of the ascending aorta in a further 3.

   Altogether, the experience accumulated in recent years demonstrates that the presence of an intraluminal linear image in the ascending aorta alone should not be accepted as a dissection criterion. False positive diagnoses may be potentially catastrophic since the treatment of choice for ascending aorta dissection is surgery. Some authors consider that the diagnosis of type A dissection should only be accepted when other accompanying findings such as aortic insufficiency, intimal tear, intraluminal thrombosis or pericardial effusion are present. Nevertheless, although this could increase the specificity, it would be at the expense of considerably decreasing the sensitivity of the technique.

    In the ascending aorta, particularly when dilated, linear artifact images are very common, being observed in 44%-55% of studies (11,12). They may appear in the transverse or longitudinal plane. Although 80% of artifacts are easily diagnosed by biplane or multiplane probes, some may be difficult to differentiate from a intimal flap. It has been suggested that the flow pattern of colour Doppler may be highly useful, but has not been so in our experience. Thirteen percent of artifacts had a different flow pattern on both sides owing to an eccentric jet due to aortic valve disease. Furthermore, 6% of ascending aorta dissections could have had the same flow signal in the true and false lumina (11).

   Very often, artifacts situated in the aortic root are a reverberation from the anterior wall of the left atrium. The reverberation is located within the aortic lumen when the diameter of the vessel is greater than the diameter of the left atrium (12). In one series (11), half of the artifacts were produced for this reason and were located in the aortic root. Using M-mode echocardiography, it can be verified that the reverberation linear image is situated double the distance from the transducer than the left atrium, and its displacement is doubly wide (fig. 4).

Figure 4.- Ascending aortic artifact secondary to left atrial posterior wall (PAI). M-mode shows as this image (R) is located double distance to the trasnducer of PAI and with twice movement amplitude.

   Forty percent of artifacts are located in the middle third of the ascending aorta and are due to reverberations from the posterior wall of the right pulmonary artery. The posterior wall of the aorta is equidistant from the wall of the pulmonary artery and the artifact. The movement will depend, therefore, on the movement of the two structures.

   In the majority of ascending aorta dissections, in contrast, the movement of the intima was free (83%) and did not meet reverberation criteria. Cases of dissection in which the intima has movement parallel to the aorta are retrograde dissections and are differentiated from artifacts by their location within the aortic lumen and their greater longitudinal extension. In the series by Rondaut et al (13), with 13 acute and 8 chronic dissections, 76% of studies had a dissected intima with movement parallel to that of the aortic wall without the typical systolic oscillation, and complete thrombosis of the false lumen was present in five. In our opinion, assessment of the location and mobility of intraluminal images by M-mode and their longitudinal extension permits correct identification of artifacts in the ascending aorta (11).

   The differential diagnosis between total false thrombosis and aneurysm is not always easy by TEE. The high echogenicity on the internal surface, semilunar form and smooth surface increase the probability of it being a thrombosed false lumen (fig. 5) (13). However, the intima must not necessarily be fibrosed or calcified, and occasionally neo-intima calcification of an intraluminal thrombus, when old, may exist. The presence of thrombi in ascending aorta aneurysm is rare; a thrombosed retrograde dissection should therefore be considered.

Figure 5.- False lumen thrombosis and intraluminal thrombosis. The arrow shows the intimal flap calcification.

   Other structures which may give rise to poor image interpretation and to false positive diagnoses of dissection include innominate vein, periaortic lung atelectasia, pleural effusion, left pulmonary vein and hemiazygous vein (14).

DISSECTION EXTENSION
   Ascending aorta involvement has high mortality and urgent surgery is indicated; it is of importance to determine the proximal extension of the dissection. Treatment of type A is surgical and that of non-complicated type B medical. TEE permits correct assessment of the proximal extension of the dissection, except when it is located in the upper third of the ascending aorta and the proximal half of the aortic arch. The majority of the diagnostic errors published occurred because the involvement of this segment in type III dissections with retrograde extension to the distal part of the ascending aorta was not diagnosed. To avoid this, the TEE study should always be complemented by a transthoracic study using the high right parasternal and suprasternal views. When the echocardiographer is familiar with these projections, acceptable information can be obtained in the majority of cases. In over 10% of cases, the ascending aorta dissection extends along the descending aorta (15-16). TEE only permits assessment of the abdominal aorta in its highest part, as far as the origin of the celiac trunk. Study of the abdominal aorta, if required, necessitates the use of another imaging technique.

INTIMAL TEAR LOCATION
   The surgical approach may differ depending on the location of the entry tear, particularly in retrograde dissections of the ascending aorta (20% of cases) (16). Erbel et al (17) demonstrated a different evolutive pattern depending on the presence and location of the tear. TEE permits identification of the tear in 78%-100% of cases (fig. 6) (5-6), a much higher rate than that obtained by transthoracic echocardiography (42%). With the use of colour Doppler, TEE permits small communications between true and false lumina, mainly in descending aorta, to be visualized. It is important to differentiate these secondary communications from the main intimal tear. The latter is usually identified by two-dimensional echocardiography, tends to measure more than 5 mm and be located in the proximal part of the ascending aorta in type A dissections and immediately after the origin of the left subclavian artery in type B dissections. On occasions, two-dimensional echocardiography does not permit visualization of the intimal tear in the proximal part of the arch. In these cases, colour Doppler may be helpful by showing a turbulent jet directed towards the false lumen. Using pulsed Doppler, it can be verified that the flow velocity at the tear is usually below 1.5 m/s and the flow goes from the true to the false lumen in systole. In diastole, the velocity is lower and the flow usually goes from the false to the true lumen.

Figure 6.- Large entry tear at the upper part of descending aorta (arrows).

FALSE LUMEN IDENTIFICATION
   In certain circumstances, identification of the false lumen is of special clinical interest. When the aortic arch is involved, the surgeon needs to know whether the supra-aortic vessels originate from the false lumen. Similarly, when the descending aorta dissection affects visceral arteries and ischaemic complications arise, it may be important to identify the false lumen prior to surgery or endovascular treatment, such as intima fenestration (18) or endoprosthesis implantation (19). Percutaneous fenestration of intima may be a therapeutic alternative when main artery branches originate from the false lumen.

   On most occasions, the distinction between true and false lumina is easy. The false lumen is usually larger and has less flow than the true lumen. M-mode shows how the intima moves towards the false lumen at the start of systole by expansion of the true lumen (fig. 7). Partial thrombosis of the false lumen is frequently present and total thrombosis occasionally. Indications of reduced or absent flow are: near absence of signal by colour or pulsed Doppler, presence of spontaneous contrast and thrombus formation.

Figure 7.- M-mode of TEE showing the systolic expansion (arrow) of the true lumen (VL).

DIAGNOSIS OF COMPLICATIONS
   Appropriate diagnosis of dissection complications during the initial study may affect therapeutic decisions in the acute phase;

   a) Pericardial and pleural effusions. Pericardial or pleural effusion is not always due to extravasation of blood from the aorta and may be secondary to irritation of the adventitia produced by the aortic haematoma or small effusion from the wall. In any event, the presence of pericardial effusion in an ascending aorta dissection is a sign of poor prognosis which should suggest rupture of the false lumen in the pericardium. Echocardiography is the best diagnostic technique for estimating the presence and severity of pericardial effusion, which occurs in 20-30% of ascending aorta (4,7) and 6% of descending aorta (10) dissections.

   The presence of left pleural effusion located next to the descending aorta can also be identified by TEE, although plain X-ray may suffice for this diagnosis.

   b) Aortic rupture. The diagnosis of aortic rupture may be difficult to establish by TEE. As stated previously, pericardial or pleural effusion, particularly when significant, must raise the suspicion of aortic rupture. Emergency surgery must be indicated when echocardiography data of cardiac tamponade are present. An echo-free space around the aorta is suspicious of periaortic haematoma (fig. 8) (16). Some studies have suggested that the increase in the distance between the esophagus and left atrium or descending aorta are echocardiographic signs of hemo-mediastinum; nevertheless, other techniques are more specific in the diagnosis of this complication. Colour Doppler may be very useful in the diagnosis of aortic rupture to cardiac cavities such as the left atrium or right ventricle; a signal of continuous flow is defined by pulsed Doppler.

Figure 8.- TEE shows the presence of periaortic haematoma secondary to aortic rupture. The arrow shows the increased distance between the oesophafus and the descending aorta.

   c) Aortic insufficiency. The diagnosis and quantification of aortic insufficiency severity can be correctly performed with Doppler echocardiography, both TTE and TEE. Significant aortic insufficiency has been detected in 52% of type I, 64% of type II and 8% of type III dissections (17). Furthermore, TEE provides information on possible mechanisms that influence aortic insufficiency, which may greatly aid the surgeon in deciding to replace the aortic valve (20). Several mechanisms may determine the onset of significant aortic insufficiency: 1) dilation of the aortic annulus secondary to dilation of the ascending aorta; 2) rupture of the annular support and tear in the implantation of one of the valvular leaflets; 3) in asymmetric dissections, the haematoma itself may displace a sigmoidea below the coaptation level; 4) prolapse of the intima in the outward tract of the left ventricle through the valvular orifice (fig. 9) (15,20,21); and 5) previous aortic valvular disease. In a study conducted by Armstrong et al (15), aortic insufficiency was severe in 45% of ascending aorta dissections. Its mechanism was dilation of the annulus in 50% of cases, valvular integrity and structure alteration in 33% and prolapse of the intima through the valve in 17%.

Figure 9.- TEE identifies the mechanism of aortic regurgitation. The arrow shows the intimal flap prolapse in the leftt ventricular outflow tract.

   d) Arterial branch involvement. Diagnosis of involvement of the main arterial vessels of the aorta is important as it may explain some of the symptoms or visceral complications that accompany the dissection and aid election of appropriate therapeutic strategy. The right brachiocephalic trunk is one of the arterial branches most frequently affected. TEE is not a good technique for assessing supra-aortic branch involvement. In a recent work using multiplanar probes, sensitivity, specificity and accuracy in the diagnosis of supra-aortic trunks were 60%, 85% and 78%, respectively (9). TTE visualized the carotid artery and left subclavian artery in 92% of cases and the right brachiocephalic trunk in 62% (fig. 10).

Figure 10.- By transthoracic echocardiography in supraesternal view we can identifiy the dissection (arrow) of braquiocephalic trunk (TB) . CI: Left carotid artery; SI: Left subclavian artery.

   Involvement of coronary arteries in dissection has been considered to be 10-15%, with the right coronary artery being most frequently affected (17). TEE permits assessment of the most proximal segment of the coronary arteries; thus, it can be verified whether the coronary ostium originates in the false lumen (fig. 11) or whether coronary dissection is present (6). Ballal et al (8), in a series of 34 patients, visualized the origin of the left coronary artery in 30 and of the right coronary artery in 17. TEE diagnosed 6 of 7 cases with coronary artery involvement confirmed by surgery.

Figure 11.- TEE shows that the main coronary artery (large arrow) is conneted to the true lumen and the ostium to the right coronary artery (small arrow) is in the false lumen.

SECONDARY FINDINGS
    a) Secondary tears. The dissected intima usually presents diverse fenestrations through which flow passes between the true and false lumina, as can be seen by colour Doppler. Multiple communication tears in ascending aorta have been detected in 35% of cases (15); however, these tears are far more frequent in descending aorta dissections (fig. 12). In our experience and that of other authors, at least one communication tear is detected in 70% of cases and several communicating tears in 20% (5,6). These communications are small-sized, under 2-3 mm and, when located in descending aorta, might correspond to ostia of intercostal or lumbar arteries (21) sectioned by the dissecting haematoma.

Figure 12.- By colour Doppler TEE identify one secondary communication between true and false lumen.

   b) False lumen thrombi. Transesophageal study is one of the most sensitive methods for detecting false lumen thrombi (fig. 5). In the series of Chirillo et al (6), TEE showed 90% accuracy in the diagnosis of surgically-proven thrombi but aortography only 65%. Thrombus formation in false lumen depends on the type of dissection, flow and location of the tear. Thrombosis of the false lumen is more frequent in descending than in ascending aorta, and has been described in only 7% of ascending aorta dissections (8,15). In dissections where the tear is not detected or when the dissection is retrograde and confined to the descending aorta, the frequency of thrombi is high. Thrombus formation in false lumen has been considered a sign of good prognosis (16).

   c) Intima movement. The dissected intima has a movement during the cardiac cycle that corresponds to the difference in flow between the true and false lumina (fig. 7). When the false lumen has little flow, the intima has low amplitude of movement. In chronic dissections, the intima tends to decrease its mobility. In the series of Roudat et al (13) with 13 acute and 8 chronic dissections, the intima remained immobile in 16 cases.

   d) Predisposing factors. Echocardiography can also provide information on factors predisposing to dissection. The diagnosis of annuloaortic ectasia, presence of a bicuspid aorta, finding of an intramural haematoma or a penetrating ulcer, size of the non-dissected aorta and left ventricle hypertrophy may help to identify predisposing factors to dissection which, in some cases, may imply a greater tendency towards new dissections in other segments of the aorta. Maximum aorta diameter in the acute phase is, in our experience, one of the data of greatest value for predicting progressive dilation of the aorta during follow-up (22).

AORTIC INTRAMURAL HAEMATOMA
   Aortic intramural haematoma forms part of the acute aortic syndrome. Diagnosis by transoesophageal echocardiography is made when a circular or semilunar image (fig. 13), which may contain echolucent zones and occasionally be distributed in layers, is observed on the aorta wall. Wall thickness should be more than 7 mm and there should be no flow within (fig. 14) (23,24). Diagnosis is straightforward in typical cases, but the haematoma may sometimes be mistaken for the presence of an intraluminal thrombus or a dissection with thrombosed false lumen. Other imaging techniques such as computerized tomography that shows an attenuated signal zone, or magnetic resonance with a hyperintense signal, confirm the diagnosis. These techniques contribute better information to the chronological assessment of haematoma and the presence of periaortic haematoma (23).

Figure 13.- Intramural haematoma in ascending aorta (large arrows) . The small arrow shows a reverberation of the aortic wall. AP: pulmonary artery.

Figure 14.- Intramural haematoma in descending aorta (arrows) with a typical semilunar morphology. AOD: Descending aorta.

   On occasions, localized zones of the haematoma can be identified, which break the intima, giving rise to saccular images that may be confused with penetrating ulcers. In more than 10% of cases, aorta zones with haematoma co-existing with others with classic intima dissection are detected; in these cases, the diagnosis is aortic dissection. In over 60% of haematomas, the location is in descending aorta and is frequently accompanied by other signs of aortic arteriosclerosis. Evolution of the haematoma is highly dynamic, with complete reabsorption in more than half the cases or dissection in 40% being observed in the first six months. For this reason, closer follow-up than that undertaken in patients with classical aortic dissection is advisable (24,25).

PENETRATING ULCER
   The diagnosis of penetrating ulcer is controversial. The presence of saccular protrusion outside the aorta profile is readily identifiable by angiography and tomography with contrast. TEE is less useful in the diagnosis of these protruding images in the aorta profile, although recent studies have suggested its usefulness (26) ; nevertheless, it is highly useful for differentiating penetrating arteriosclerotic ulcers from ulcer-like projections secondary to thrombi with crater-like cavities in their surface and haematomas that evolve with disruption located in the intima (fig. 15). Absence of arteriosclerotic plaque in the intima of the aorta wall should lead us to suspect an ulcer-like projection and not a true penetrating ulcer. Aortic ulcers are also located more frequently in descending aorta. Both colour Doppler and contrast echocardiography may be helpful to confirm the presence of flow within the external saccular image to the aortic intima. While TEE is highly accurate for the diagnosis of aortic dissection, its sensitivity and specificity in the diagnosis of intramural haematoma and penetrating ulcer have not been reported; thus, it is advisable to perform another imaging technique, particularly magnetic resonance, to confirm the diagnosis and provide information on bleeding persistence and the presence of periaortic haematoma.

Figure 15.- Penetrating aortic ulcer below of an artherioesclerotic plaque. The aortic ulcer, located in descending aorta, penetrates through the intima and deformes the adventitia.

LIMITATIONS
   TEE is a semi-invasive diagnostic technique. Associated complications are rare. However, when the probe is inserted, increases are produced in cardiac frequency and arterial pressure and, on occasions, a decrease in arterial oxygen saturation. These hemodynamic changes may be dangerous in patients with aortic dissections and at least 4 cases of aortic rupture coinciding with the study have been published (7,27). For this reason, it is important to administer adequate sedation and monitor arterial pressure, with an endovenous line in place for anti-hypertensive drug administration. When diagnostic suspicion is great and the patient is hemodynamically unstable, study with anesthesia prior to surgery should be considered.

   The diagnosis of arterial vessel involvement is the main limitation of TEE. It is widely accepted that it is not necessary to perform coronariography prior to surgical treatment of an aortic dissection (28). However, complications exist which render it advisable to study arterial vessel involvement. The presence of neurologic manifestations, acute kidney failure, mesenteric or lower limb ischaemia suggests vascular involvement. In these cases, angiography is the most accurate diagnostic technique. It has recently been demonstrated that helical CT may be highly useful in the diagnosis of some of these vascular complications (9). The diagnosis of periaortic haematoma or haemomediastinum secondary to aortic rupture is not easy by echocardiography. Conventional CT offers a much more precise diagnosis.

   Although TEE permits diagnosis of aortic intramural haematoma in the initial phase of an atypical dissection, magnetic resonance is more specific and provides information on the evolution time of the haematoma (23). Finally, when tortuous arteries are present or when it is necessary to assess the dissection at abdominal level, MRI and CT provide more complete information thanks to their wider field of study.

DIAGNOSTIC STRATEGY IN ACUTE AORTIC SYNDROME
   In clinical practice, computerized tomography is the most used diagnostic technique for acute aortic syndrome. In the multicentre study of the International Registry of Aortic Dissection (29), 60% of patients were initially diagnosed with this technique. The role of TEE, once the syndrome has been diagnosed by tomography, depends on the quality of the tomography study, and whether it is a disease of the ascending or descending aorta. In cases of ascending aorta involvement, it is fundamental to locate the entry tear before considering surgical treatment. In our opinion, if the diagnosis appears to be definitive, a transthoracic study should always be performed to assess the presence and aetiology of the aortic insufficiency, pericardial effusion and ventricular function. Similarly, it is easy to obtain information on the dissection of supra-aortic vessels using the supraesternal approach. TEE should be performed prior to the operation with the patient anaesthetized, and the results assessed intraoperatively (30). If doubts exist as to involvement of the ascending aorta before surgical treatment is considered, transoesophageal study is mandatory. When the disease affects only the descending aorta, the study is recommended when the patient is hemodynamically stable and pain-free. Haemokinetic information, location of entry and re-entry sites, partial thrombosis, proximal or distal of the false lumen, may be of great prognostic value and aid the decision to implant an endoprosthesis with the aim of closing the intimal tear.

   In hospitals with cardiac surgery and sufficient experience in TEE, the latter should be performed as a first-choice diagnostic technique, since its information suffices in the majority of cases to indicate the most appropriate medical or surgical treatment. Computerized tomography should only complement TEE study in cases of suspected involvement of the main arterial vessels, particularly the abdominal vessels, which leave the aorta. As we mentioned previously, if the diagnosis is intramural haematoma or penetrating ulcer, the combination of both imaging techniques may prevent false positives and provide complementary information.

   Angiography has ceased to be the reference technique, as it is mainly limited in cases of false lumen thrombosis or atypical dissections. Although MR is the technique which best characterizes aortic anatomy, it is not appropriate in situations of emergency since it requires the patient to be transferred from the intensive care unit and involves relatively prolonged study (20-30 mins). In any event, the risk of performing several test should be weighed against their possible benefits. Nevertheless, the use of these diagnostic tests should be tailor-made according to the patient' s hemodynamic status, definitive data available and the experience of each centre in the assessment of these diseases (31).

CONCLUSIONS
   TEE offers considerable advantages in the diagnosis of acute aortic syndrome. The technique has very high sensitivity and specificity, is rapid (5-10 mins), readily available and does not require the patient to be moved. Echocardiographic study should include transthoracic assessment of the upper third of the ascending aorta, aortic insufficiency quantification, pericardial effusion diagnosis and assessment of segmental alterations of ventricular contractility. Only in the few cases in which TEE does not permit a definitive diagnosis or intramural haematoma is suspected would it be advisable to perform MR or CT. In patients with ascending aorta dissection, TEE offers sufficient information for surgery to be directly indicated. To delay surgery while conducting other tests increases the risk of death and provides few benefits.

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29. Hagan PG, Nienaber C, Isselbacher EM , et al, The International Registry of Acute Aortic Dissection (IRAD). New Insights Into and Old Disease. JAMA 2000;283:897-903.

30. Yamada E, Matsumara M, Kimura S, et al. Usefulness of Transesophageal echocardiography in detecting changes in flow dynamics reponsible for malperfusion phenomena observed during surgery of aortic dissection. Am J Cardiol 1997;79:1149-52.

31. Evangelista A, García del Castillo H, González-Alujas MT et al. Técnicas de imagen en el diagnóstico de la patología aórtica. Rev Esp Cardiol 1994;47:71-80.

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2nd Virtual Congress of Cardiology

Dr. Florencio Garófalo
Steering Committee
President
Dr. Raúl Bretal
Scientific Committee
President
Dr. Armando Pacher
Technical Committee - CETIFAC
President
fgaro@fac.org.ar
fgaro@satlink.com
rbretal@fac.org.ar
rbretal@netverk.com.ar
apacher@fac.org.ar
apacher@satlink.com

Copyright© 1999-2001 Argentine Federation of Cardiology
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