Echocardiography in Aortic Diseases: EAE Recommendations for Clinical Practice

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European Journal of Echocardiography (2010) 11, 645–658 RECOMMENDATIONS doi:10.1093/ejechocard/jeq056

Echocardiography in aortic diseases: EAE recommendations for clinical practice

Arturo Evangelista 1*, Frank A. Flachskampf 2, Raimund Erbel 3, Francesco Antonini-Canterin 4, Charalambos Vlachopoulos 5, Guido Rocchi 6, Rosa Sicari 7, Petros Nihoyannopoulos 8, and Jose Zamorano 9 on behalf of the European Association of Echocardiography Downloaded from Document Reviewers: Mauro Pepi a, Ole-A. Breithardt b, and Edyta Plon´ska-Gos´ciniakc

1Servei de Cardiologia, Hospital Vall d’Hebron, P8 Vall d’Hebron 119, 08035 Barcelona, Spain; 2University of Erlangen, Erlangen, Germany; 3University of Essen, Essen, Germany; 4Hospital Pordenone, Pordenone, Italy; 5Hippokration Hospital, Athens, Greece; 6S. Orsola University Hospital, Bologna, Italy; 7Institute of Clinical Physiology, Pisa, Italy; 8Hammersmith Hospital, London, UK; and 9Hospital Clı´nico San Carlos, Madrid, Spain aInstituto di Cardiologia dell’Universita` degli Studi. Milan, Italy; bMedizinische Klinik 2, University Hospital, Erlangen, Germany; and cPomeranian Medical School, Szczecin, Poland ejechocard.oxfordjournals.org Received 28 March 2010; accepted after revision 29 March 2010

Echocardiography plays an important role in the diagnosis and follow-up of aortic diseases. Evaluation of the aorta is a routine part of the standard echocardiographic examination. Transthoracic echocardiography (TTE) permits adequate assessment of several aortic segments, particularly the aortic root and proximal ascending aorta. Transoesophageal echocardiography (TOE) overcomes the limitations of TTE in thoracic aorta assessment. TTE and TOE should be used in a complementary manner. Echocardiography is useful for assessing aortic size, biophysical properties, and atherosclerotic involvement of the thoracic aorta. Although TOE is the technique of choice in the diagnosis of aortic dissection, TTE may be used as the initial modality in the emergency setting. Intimal flap in proximal ascending aorta, pericardial by guest on January 17, 2011 effusion/tamponade, and left ventricular function can be easily visualized by TTE. However, a negative TTE does not rule out aortic dissection and other imaging techniques must be considered. TOE should define entry tear location, mechanisms and severity of aortic regurgitation, and true lumen compression. In addition, echocardiography is essential in selecting and monitoring surgical and endovascular treatment and in detecting possible complications. Although other imaging techniques such as computed tomography and magnetic resonance have a greater field of view and may yield complementary information, echocardiography is portable, rapid, accurate, and cost-effective in the diagnosis and follow-up of most aortic diseases. ------Keywords Aortic diseases † Transoesophageal echocardiography † Transthoracic echocardiography † Contrast echocardiography

Introduction role in the diagnosis and follow-up of aortic diseases. The aorta is divided into segments: the aortic root, ascending aorta, aortic arch, Aortic diseases are an important cause of cardiovascular morbidity descending aorta, and abdominal aorta. Ultrasound techniques for and mortality. Except when complications are life-threatening, such imaging of the aorta include transthoracic echocardiography (TTE), as acute aortic syndrome or aortic rupture, aortic diseases are transoesophageal echocardiography (TOE), abdominal ultrasound, asymptomatic and without abnormalities on physical examination; and intravascular ultrasound (IVUS). In the present article, we will thus, diagnosis and follow-up depend exclusively on imaging tech- focus on TTE and TOE methodologies in the assessment of aortic niques. Echocardiography has become the most used imaging test diseases, their strengths and limitations for its use in various clinical in the evaluation of cardiovascular disease and plays an important situations and recommendations for appropriate applications of

* Corresponding author. Tel: +34 932746212; fax: +34 932746244, Email: [email protected] Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2010. For permissions please email: [email protected]. 646 A. Evangelista et al. echocardiography based on available evidence. It is not the main Transthoracic echocardiography objective of this manuscript to compare the usefulness of echocardiography with other imaging techniques or to describe the stan- Echocardiographic evaluation of the aorta is a routine part of the 1 dard diagnostic management of different aortic diseases. standard echocardiographic examination. Although TTE is not the technique of choice for overall assessment of the aorta, it is useful for the diagnosis and follow-up of some segments of the aorta. TTE is one of the techniques most used to measure proximal aortic segments in clinical practice. Using different windows, the proximal ascending aorta is visualized in the left and right parasternal long-axis views (Figure 1) and, to a lesser extent, in basal short-axis views. The long-axis view affords the best opportunity for measuring aortic root diameters by taking advantage of the superior axial image resolution. In all patients with suspected aortic disease, the right parasternal view is recommended for estimating the true size of the ascending aorta. The ascending aorta is also visualized in the apical long-axis and modiﬁed apical ﬁve-

chamber views; however, in these views, the aortic walls are Downloaded from seen with suboptimal lateral resolution. Modiﬁed subcostal views may in some cases (more frequently in children) be helpful, but here the ascending aorta is far from the transducer. All these views also permit assessment of the aortic valve, which is often involved in diseases of the ascending aorta (e.g. bicuspid valve, Figure 1 Transthoracic echocardiography. (A) Parasternal aortic regurgitation due to dilatation of the ascending aorta or ejechocard.oxfordjournals.org long-axis view (transthoracic echocardiography). The following aortic dissection, and other diseases). diameters are shown: outﬂow tract diameter (1), sinuses of Val- Of paramount importance for evaluation of the thoracic aorta is salva (2), sinotubular junction (3), and tubular ascending aorta (4). the suprasternal view (Figure 2A). This view primarily depicts the (B) Right parasternal long-axis view, mid and distal parts of ascending aorta may be visualized. AAo, ascending aorta; LA, aortic arch and the three major supra-aortic vessels (innominate, left atrium; LV, left ventricle; RV, right ventricle. left carotid, and left subclavian arteries), with variable lengths of the descending and, to a lesser degree, ascending aorta. Although by guest on January 17, 2011

Figure 2 (A) Suprasternal view of aortic arch and supra-aortic great arteries. (B) Mid part of the descending thoracic aorta visualized by long- axis view from apical window. (C) Abdominal aorta visualized by subcostal view. In non-obese patients, it is not difficult to visualize distal abdominal aorta. art, artery; PA, pulmonary artery; AAo, ascending aorta; DAo, descending aorta; CT, coeliac trunk. Echocardiography in aortic diseases 647 this view may be obstructed, particularly in patients with emphy- and TOE made to detect aortic plaques and thrombi revealed sema or short, wide necks, it should be systematically sought if high sensitivity for the detection of aortic arch atheromas protrud- aortic disease is evaluated. From this window, aortic coarctation ing ≥4 mm into the lumen.2 can be visualized and functionally evaluated by continuous-wave The entire thoracic descending aorta is not well visualized by Doppler; a persistent ductus arteriosus may also be identifiable TTE. A short-axis view of the descending aorta can be imaged pos- by colour Doppler. Dilatation and aneurysm, plaque, calcification, teriorly to the left atrium in the parasternal long-axis view. From thrombus, or a dissection membrane are detectable if image the apical window, a short-axis cross-section of the descending quality is sufficient. A systematic comparison of harmonic TTE aorta is seen lateral to the left atrium in the four-chamber view and a long-axis stretch in the two-chamber view. By 908 transducer, a rotation long-axis view is obtained and a mid part of the descending thoracic aorta may be visualized (Figure 2B). Although a Table 1 Echocardiographic views of the aorta partial assessment of the size of the descending aorta and detec- View Part of aorta tion of large abnormal structures such as dissection membranes ...... are possible in these views, the descending aorta lies far from Transthoracic echo the transducer and the assessment is incomplete, suboptimal and Parasternal long + short axis Ascending + descending thoracic not accurate. However, in acute aortic syndrome with left Apical four-chamber Descending thoracic pleural effusion, scanning from the back may provide good or Downloaded from Apical two-chamber and/or Descending thoracic optimal views of the descending aorta. long axis In contrast, since the abdominal descending aorta is relatively + Suprasternal Arch, descending ascending easily visualized to the left of the inferior vena cava in sagittal thoracic (superior–inferior) subcostal views, the systematic search for Subcostal Abdominal (+ascending thoracic) abdominal aortic aneurysms has been advocated as part of the

Transoesophageal echo ejechocard.oxfordjournals.org routine echocardiographic exam3,4 (Figure 2C), although transthor- Upper oesophageal Ascending thoracic long + short axis acic echo transducers are not optimal for abdominal sonography. Aortic (long + short axis) Descending thoracic + arch In summary, although TTE is not the ideal tool for visualizing all aortic segments, important information can always be gained by careful use of all echo windows (Table 1). by guest on January 17, 2011

Figure 3 Transoesophageal echocardiography. (A) Ascending aorta in long-axis view at 1208.(B) Aortic arch in transverse view. (C) Descend- ing aorta visualized by transverse view. (D) Descending aorta visualized by longitudinal view. 648 A. Evangelista et al.

Recommendation perpendicular dimension and gain settings are appropriate. Stan- TTE permits adequate assessment of several aortic segments, par- dard measurement conventions established the leading ticularly the aortic root and proximal ascending aorta. All scanning edge-to-leading edge diameter in end-diastole,9 and the normative planes should be used to obtain information on most aortic seg- data published in the literature were obtained using the leading ments. However, if inconclusive information or abnormalities are edge technique.10 – 12 Some experts13,14 favour inner edge-to-inner present, another imaging modality is required to either complete edge diameter measurements to increase reproducibility and or add diagnostic information. match those obtained by other methods of imaging the aorta. However, recent improvements in echocardiographic image Transoesophageal quality and resolution minimize the differences between these measurement methods. Two-dimensional (2D) aortic measure- echocardiography ments are preferable to M-mode, as cyclic motion of the heart Proximity of the oesophagus and the thoracic aorta permits high- and resultant changes in M-mode cursor location result in systema- resolution images from higher-frequency TOE. Furthermore, the tic underestimation by 1–2 mm of aortic diameter by M-mode in availability of multiplane imaging permits improved incremental comparison with the 2D aortic diameter. Standard diameter assessment of the aorta from its root to the descending aorta.5 measurements are at the aortic annulus, at the level of the The most important transoesophageal views of the ascending sinuses of Valsalva and at the sinotubular junction (Figure 1). aorta, aortic root and aortic valve are the high transoesophageal Aortic annular diameter is measured between the hinge points Downloaded from long-axis (at 1208–1508)(Figure 3A) and short-axis (at 308–608) of the aortic valve leaflets (inner edge–inner edge) in the left views. A short segment of the distal ascending aorta, just before parasternal long-axis view, during systole, which reveal the the innominate artery, remains unvisualized owing to interposition largest aortic annular diameter. In a normal ascending aorta, the of the right bronchus and trachea (blind spot). Images of the diameter at sinus level is the largest, followed by the sinotubular ascending aorta often contain artefacts due to reverberations junction and the aortic annulus. If aortic dilatation is detected at ejechocard.oxfordjournals.org from the posterior wall of the ascending aorta or the posterior any level, its maximum diameter should be measured and wall of the right pulmonary artery, presenting as aortic intraluminal reported. linear horizontal lines moving in parallel with the reverberating structures, as can be ascertained on M-mode tracings.6 The des- Normal values cending aorta is easily visualized in short-axis (08) and long-axis Aorta size is related most strongly to body surface area (BSA) 10,11 (908) views from the coeliac trunk to the left subclavian artery and age. Therefore, BSA may be used to predict aortic 10 (Figure 3C and D). Further withdrawal of the probe shows the root diameter in several age intervals. Roman et al. considered aortic arch, where the inner curvature and anterior arch wall are three age strata: younger than 20 years, 20–40 years, and older than 40 years by published equations. These normal values have usually well seen all the way to the ascending aorta. In the distal by guest on January 17, 2011 part of the arch (Figure 3B), the origin of the subclavian artery is been accepted to date as the reference values. Some groups have easily visualized. However, in awake patients, the origin of innomi- suggested indexing by height to avoid the influence of overweight nate and left carotid arteries is not clearly visualized, although in on BSA. Nevertheless, large series defining normal ranges of this anaesthetized patients, it is possible to identify the origin of index are lacking. Aortic root dilatation at the sinuses of Valsalva these supra-aortic arteries.7 The proximal part of the coeliac is defined as an aortic root diameter above the upper limit of the trunk is visualized in most cases and the superior mesenteric 95% confidence interval of the distribution in a large reference 2 artery in 50% of cases.8 One of the limitations of TOE is to population. In adults, a diameter of 2.1 cm/m has been con- 15 locate the exact level of a given abnormality in the descending sidered the upper normal range in ascending aorta. TTE suffices aorta. When no reference vessels, such as subclavian artery or to quantify maximum aortic root and proximal ascending aorta coeliac trunk, are visualized, this limitation can be overcome by diameters when the acoustic window is adequate. Nevertheless, rotating the transducer and identifying the level of the descending the technique is more limited for measuring the remaining aorta in comparison with the structures of the heart or great aortic segments. TOE overcomes part of these TTE limitations vessels (anterior structures). Like the ascending aorta, the des- by affording better measurement of aortic arch and descending cending aorta often produces an artefactual pseudo-aorta thoracic aorta size. TOE may make oblique measurements located posteriorly to the true aorta (‘double-barrel aorta’). when the descending aorta is elongated or tortuous. To avoid Recommendation this overestimation, aortic diameter measurement by TOE TOE is the ultrasound technique of choice in thoracic aorta assess- should be attempted only when circular sections are obtained. ment and provides high-resolution images of the entire thoracic Measurements of descending thoracic aorta in short axis and of aorta except for a small portion of the distal ascending aorta near the aortic arch in long axis are recommended. The absolute the innominate artery. TOE overcomes limitations encountered and indexed normal values of the various aortic segments are by TTE. TTE and TOE should be used in a complementary manner. shown in Figure 4. Recommendation Aorta size TTE permits precise and reproducible measurements of the diameters of the aortic root and proximal part of the ascending aorta. Measurements of aortic diameter by echocardiography are The relationship between aorta size and age and body surface accurate and reproducible when care is taken to obtain a true should be considered when defining normal ranges. Given its Echocardiography in aortic diseases 649 Downloaded from ejechocard.oxfordjournals.org

Figure 4 Normal size of thoracic aortic segments. The thoracic aorta can be divided into three segments: the ascending aorta that extends from the aortic annulus to the innominate artery and is typically measured at the level of the aortic annulus, the sinuses of Valsalva, the sinotubular junction, and the proximal (tubular) ascending aorta; the aortic arch that extends from the innominate artery to the ligamentum arteriosum; and the descending aorta that extends from the ligamentum arteriosum to the level of the diaphragm. PA, right pulmonary artery. Modiﬁed from Diseases of the aorta. In: Feigenbaum H, Armstrong WF, Ryan T, eds. Feigenbaum’s Echocardiography. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005. p673; Ascending aorta values from Erbel et al.46 by guest on January 17, 2011

better visualization, TOE is the ultrasound modality of choice for determined using TTE or TOE, but estimation of the pressure measuring the size of the aortic arch and descending aorta. changes at the same site may be unreliable because of the amplification of the pulse pressure (i.e. systolic pressure increases Aortic and arterial biophysical progressively towards the periphery) and inaccuracy of all cuff sphygmomanometer systems, particularly in young subjects. properties However, studies have shown a good correlation between aortic The aorta plays an important role in modulating left ventricular distensibility calculated using echocardiography and non-invasive performance and arterial function throughout the entire cardiovas- brachial artery pressure measurements and aortic distensibility cal- cular system.16 Arterial function is modified by several factors that culated invasively, using contrast aortography and direct aortic affect the arterial wall and is reliably assessed by non-invasive pressure recordings. Changes in arterial diameter can be measured methods.17 The velocity of the pulse wave is fast enough for it at the level of the ascending aorta, 3 cm above the aortic valve in to be able to travel to the periphery and then return within a 2D-guided M-mode of parasternal long-axis view, with the diastolic single cardiac cycle. The elastic properties of arteries vary along aortic diameter measured at the peak of the QRS complex and sys- the arterial tree, with more elastic proximal arteries and stiffer tolic aortic diameter measured at the maximal anterior motion of distal arteries. A comprehensive assessment of aortic and arterial the aorta. Other levels for measuring the arterial diameters are biophysical properties includes: (i) evaluation of the aortic limited to the mid-portion of the abdominal aorta. pressure–dimension relationship; (ii) arterial stiffness (measured There are several indices derived from aortic or arterial dimen- by wave velocities); and (iii) the reflected waves.16,17 sions and pressures and used for the estimation of the elastic properties of the aorta. The indices most frequently used are aortic/ Aortic pressure–dimension relationship arterial distensibility (the relative change in diameter or area for An increase in distending pressure during systole induces an a pressure change), compliance (the absolute change in diameter increase in aortic dimension, which is directly related to the or area for pressure), and a non-dimensional index of local arterial elastic properties of the aorta. Diameter or area changes can be stiffness named the b-index [defined as the ratio of logarithm 650 A. Evangelista et al.

(systolic/diastolic pressures) to relative change in diameter]17 –19 source of embolism.28 Aortic atheromas are characterized by irre- which is less affected by arterial pressure changes and is easily gular intimal thickening of at least 2 mm, with increased echogeni- measured using echo-tracking devices.17 In Marfan patients, city. They often have superimposed mobile components, mainly aortic stiffness proved to have an important value in predicting thrombi. The morphology of atheromatous plaques is dynamic, progressive aortic dilatation.20,21 Also, indices of aortic stiffness with frequent formation and resolution of mobile components.29 are used in clinical studies for the assessment of the efﬁcacy of TOE is the imaging modality of choice for diagnosing aortic ather- different therapeutic regimens in these patients.22 Abnormal omas. It provides higher-resolution images than TTE and has good aortic elastic properties were demonstrated also in patients with interobserver reproducibility.30 However, suprasternal harmonic bicuspid aortic valve with no or mild aortic valve impairment.23 imaging by TTE also permits the visualization of protruding arch atheromas in many cases2 and may be helpful in the routine assess- Pulsed-wave velocity ment of the source of embolism. The prevalence of aortic athero- Pulsed-wave velocity (PWV) is deﬁned as the travel speed through- mas on TOE varies depending on the population studied. In a out the aorta of the pulse wave. With increased aortic stiffness, community-based TOE study, aortic atheromas were present in PWV increases. PWV is expressed as the ratio of the distance 51% of the population over 45 years, being complex in 7.6%.31 between the two sites at which the onset of the wave is being Atheroma prevalence increased with age, smoking, and pulse recorded to the time of travel of the wave from the proximal to pressure. TOE characterizes the plaque by assessing plaque thick-

the distal sites. Accordingly, carotid–femoral PWV is considered ness, ulceration, calcification and superimposed mobile thrombi, Downloaded from the gold standard measurement of arterial stiffness and is the thereby determining the embolic potential of each plaque. The most widely used index.16 PWV can be assessed by echocardiogra- advantages of TOE over other non-invasive modalities include its phy, measuring the time from the QRS to the onset of the pulsed- ability to assess the mobility of plaque in real time. Another echo- wave Doppler envelope in proximal (carotid artery, ascending cardiographic modality is intraoperative epiaortic ultrasound which aorta) and distal (femoral artery, descending aorta) sites (the facilitates the selection of a suitable aortic clamping site by avoiding ejechocard.oxfordjournals.org difference between them is the transit time), and the pulsed wave- calcifications with an increased risk of embolization. length between the two points where the Doppler tracings were The French Aortic Plaque in Stroke group showed that increas- recorded.17,19 Normal PWV values increase from 4–5 m/s in the ing plaque thickness of ≥4 mm is associated with a significantly ascending aorta to 5–6 m/s in the abdominal aorta.24 The indepen- increased embolic risk.32 The presence of mobile lesions dent prognostic value of PWV, as an index of aortic stiffness, for (thrombi) superimposed on aortic atheromas has been recognized all-cause and cardiovascular mortality has been demonstrated in to imply a high embolic risk. Other characteristics of the lesions different populations including hypertensive, diabetic, or renal seen on TOE, such as ulceration ≥2 mm in aortic plaques and non- patients, the elderly, and the general population.16,25 – 27 calcified plaques, were also associated with a higher risk of stroke.33 Thus, atherosclerotic plaques are defined as complex in by guest on January 17, 2011 Reflected waves the presence of protruding atheromas of .4 mm in thickness, When the stiffness of the aorta and the large arteries is increased, mobile debris, or the presence of plaque ulceration, and defined PWV is increased and the backward waves from the periphery as simple if the plaques lack these morphological features. Two return early to the ascending aorta, thereby increasing central systo- recent community-based studies found no association between lic and decreasing central diastolic blood pressure.17 The point aortic atheromas and future stroke.31,34 An alternative explanation where the incident wave merges with the reflected one can be is that atheromatous plaque is merely a marker for diffuse athero- identified in the central waveform and thus the augmented pressure, sclerosis that predisposes patients to systemic embolism by other the difference between the merging point (shoulder of the wave- cardiovascular mechanisms. form) and the peak systolic pressure, is computed.17 Augmentation The embolic potential of atherosclerotic aortic lesions during index, calculated as the ratio between the augmentation pressure invasive procedures or during open-heart surgery is well estab- and the pulse pressure and expressed as a percentage, is an index lished.35,36 Some studies have shown the risk of stroke or periph- used for the evaluation of the reflected wave function. Echo-tracking eral embolism after cardiac catheterization or intra-aortic balloon systems implemented in echocardiographic machines are able to pump placement in patients with severe aortic atherosclerosis measure this index at carotid level.17 As with PWV, wave reflection diagnosed by TOE.35 A strong association between aortic stenosis indices have been demonstrated to be independent predictors of and aortic atherosclerosis has recently been established.37 The cardiovascular events in several diseases. presence of plaques in the aorta of patients with aortic stenosis Recommendation has important implications since these patients often undergo inva- Aortic and arterial biophysical properties can be easily and reliably sive diagnostic and therapeutic procedures that can dislodge par- assessed by echocardiography and provide important pathophysio- ticularly thick plaques and the attached thrombotic material. logical and prognostic information that may have clinical impli- Large mobile aortic thrombi are possible causes of systemic cations both in disease states and in the general population. emboli and appear to be a complication of atherosclerosis. TOE is the best technique for diagnosing and monitoring the evolution of these large thrombi.38 The optimal management of these com- Aortic atherosclerosis plications remains to be defined. Anticoagulation therapy appears The presence of detectable atherosclerotic plaques in the aorta to be a logical approach, although surgical removal has been indi- indicates the presence of atherosclerotic disease and is a possible cated in cases with recurrent embolic events.39 Echocardiography in aortic diseases 651

Recommendation TOE is the imaging modality of choice for diagnosing aortic atheromas. Table 2 Determinants of functional aortic Advantages of TOE over other non-invasive modalities [computed regurgitation with anatomically normal aortic valve and tomography (CT) and magnetic resonance imaging (MRI)] include ascending aorta aneurysm by transoesophageal the accurate measurement of size and mobility of the plaque in real echocardiography time. When atherosclerosis is present, the severity and location of Annulus, Valsalva sinuses, sinotubular junction, and tubular tract the most severe atheromas should be reported. The suprasternal dimensions window may be useful for the diagnosis of plaques in the aortic arch Coaptation leaflet height: maximum distance between protodiastolic by TTE when the acoustic window is optimal. coaptation of the leaflet tips and the annulus plane. Diastolic tenting of the leaflets .8–10 mm Sinotubular junction/annulus ratio .1.6 Aortic aneurysm TTE is an excellent modality for imaging aortic root dilata- 10,13,14 tion, which is important for patients with annuloaortic segments. Thus, the modalities of choice are MRI and CT. Although ectasia, Marfan syndrome, or bicuspid aortic valve. Since the pre- TTE transducers are not optimal for assessing the abdominal aorta, dominant sites of dilatation are in the proximal aorta, TTE often the segment of the aorta between the coeliac trunk and renal suffices for screening (Figure 5). In ascending aorta dilatation, arteries is frequently well visualized. The presence of abdominal Downloaded from some echocardiographic features play an important role in the aorta aneurysms in patients with atherosclerosis or aortic diseases assessment of the mechanisms of functional aortic regurgitation. is not uncommon and assessment of the abdominal aorta may be Functional classification of aortic root abnormalities responsible useful. 40 – 42 for aortic insufficiency has been suggested. This classification Recommendation is based on assessment of leaflet function and aortic root size and In aortic root aneurysms, the accurate measurement of diameters ejechocard.oxfordjournals.org provides important information for surgical management strategies. by TTE or TOE is crucial for surgical indication and surgical man- Tethering of the leaflets is the feature most closely associated with agement strategies. In the arch and descending aorta, other imaging functional aortic regurgitation. This tethering depends on the sino- modalities with better reproducibility and larger field of view, such tubular junction/annulus mismatch. This information is useful for as CT or MRI, may be more suitable. targeting the optimal time and strategy for aortic valve-sparing surgery in the setting of ascending aorta aneurysms (Table 2). Acute aortic syndrome diagnosis Thus, tethering of aortic leaflets might be useful to monitor the progressive impact of sinotubular junction dilatation on valve func- Acute aortic syndrome has a high mortality rate and early medical and surgical treatment is crucial. Therefore, rapid and accurate tion in patients with ascending thoracic aorta aneurysm for valve- by guest on January 17, 2011 sparing surgery to be indicated before leaflet damage occurs. diagnostic techniques, which can be applied in critically ill patients, TTE suffices in the assessment of proximal ascending aorta are essential. The diagnosis of acute aortic syndrome can be made when the acoustic window is adequate. However, TOE is clearly with similar accuracy using different imaging techniques such as 43 superior to TTE for assessing aneurysms located in the aortic TOE, CT, or MRI; however, the decision to use a specific tech- arch and descending thoracic aorta. However, TOE is limited in nique depends on two major factors: availability of the techniques tortuous aortas, since in these cases, the aorta may be separated and experience of the imaging staff. Compared with other highly from the oesophagus, resulting in inability to image these aorta accurate diagnostic techniques (CT and MR), echocardiography has the advantage of being applicable in any hospital setting (emergency, intensive care, and operating theatre), without the need to transfer the patient who is often in an unstable haemodynamic situ- ation, monitored, and with intravenous drugs. However, in two large registries, the international registry of acute aortic dissec- tion44 and the Spanish registry of acute aortic syndrome,45 CT was the first most used imaging technique in the diagnosis of dissection, (61 and 77%, respectively). A possible explanation for this fact is that patients with acute aortic syndrome are usually admitted to the emergency departments of community hospitals where TOE may not be available. Nevertheless, it should be emphasized that even in experienced centres, most patients with acute aortic syndrome undergo more than one imaging modality; this syndrome is much too critical to leave room for diagnostic doubts. Figure 5 Parasternal long-axis view by transthoracic echocardiography. (A) Annuloaortic ectasia with pyriform morphology. Echocardiographic diagnosis (B) Ascending aorta aneurysm located in the upper part of the sinotubular junction. Aortic dissection and its variants, included in the ESC classification of aortic dissection,46 can be correctly diagnosed by 652 A. Evangelista et al. echocardiography. The diagnosis of classical aortic dissection is cardiac status, TTE may be used as the initial imaging modality based on the demonstration of the presence of an intimal flap when aortic dissection is clinically suspected in the emergency that divides the aorta into two, true and false, lumina. In most room.49 The low negative predictive value of TTE does not cases, false lumen flow is detectable by colour Doppler but may permit dissection to be ruled out, and further tests will be required be absent in totally thrombosed and retrograde dissections. Intra- if the TTE exam is negative. The value of TTE is also limited in mural haematoma is characterized by circular or crescentic patients with abnormal chest wall configuration, obesity, pulmon- thickening of the aortic wall .5 mm and penetrating aortic ulcer ary emphysema, and in those on mechanical ventilation. These (PAU) presents as an image of crater-like outpouching with limitations may prevent adequate decision-making in some cases, jagged edges in the aortic wall, generally associated with extensive but have been overcome by TOE. In patients with acute chest aortic atheromas. pain, special attention should be paid during the TTE exam to aortic root dilatation, aortic regurgitation, and/or pericardial effu- Transthoracic echocardiography sion, since these findings should raise the suspicion of acute Classically, TTE has been considered limited in the diagnosis of aortic syndrome. If a dissection cannot be directly visualized, aortic dissection. In older series, sensitivity in the diagnosis of other imaging techniques are mandatory (Figure 7). ascending aorta dissection was 78–90% but only 31–55% in descending aortic dissection. Specificity for type A aortic dissection Transoesophageal echocardiography was reported to range from 87 to 96% and for type B dissection TOE has constituted a decisive advance in the diagnosis of aortic Downloaded from 60–83%.47 However, these data are derived from old studies dissection. It can image the entire thoracic aorta except for a when the current imaging technology, such as harmonic imaging, small portion of the distal ascending aorta near the proximal was not available. Recently, harmonic imaging (Figure 6) and the arch. The proximity of the oesophagus to the aorta, without inter- use of contrast enhancement have been shown to improve the ference from the chest wall or lung, permits high-quality images to

sensitivity and specificity of TTE in the diagnosis of aortic dissec- be obtained (Figure 8). ejechocard.oxfordjournals.org tion.48 Contrast-TTE has similar accuracy to TOE in the diagnosis Since the first multicentre European Cooperation study by Erbel of type A aortic dissection (sensitivity 93% and specificity 97%), et al.,47 several studies have demonstrated the accuracy of TOE in although it is more limited in type B involvement (sensitivity 84% the diagnosis of aortic dissection with sensitivity of 86–100%, and specificity 94%), mainly in the presence of non-extended dis- specificity 90–100%, and a negative predictive value of 86– section, intramural haematoma, and aortic ulcers.48 However, 100%.47 – 50 The low specificity of the technique described in given its availability, rapidity, and additional information on some series51 is explained by the fact that the majority of by guest on January 17, 2011

Figure 6 Aortic dissection diagnosis by transthoracic echocardiography. Intimal ﬂap (arrows) and two lumina are visualized in: (A) aortic root, (B) aortic arch and distal ascending aorta, (C) proximal descending aorta (arrowhead shows the entry tear), and (D) dissection of abdominal aorta. Colour Doppler helps to identify the true lumen (TL). Arrowheads signal secondary communications. Echocardiography in aortic diseases 653

Figure 7 Algorithm of diagnostic strategy of acute aortic dissection depending on whether the ﬁrst test was transthoracic echocardiography or computed tomography. *Depending on availability, complications, and examiner experience. **Deﬁnitive diagnosis of type A dissection by transthoracic echocardiography permits the patient to be sent directly to surgery provided intraoperative transoesophageal echocardiography is Downloaded from performed before surgery.

located at twice the distance from the right pulmonary artery posterior wall as from the posterior aortic wall.6 TOE is clearly superior to TTE in the diagnosis of intramural ejechocard.oxfordjournals.org haematoma and aortic ulcers. Echocardiographic findings of intramural haematoma are circular or crescentic thickening (.5 mm) of the aortic wall (Figure 9A and B) and there should be no flow within.52 –54 Diagnosis is straightforward in typical cases, but the haematoma may sometimes be mistaken for an intraluminal thrombus or a dissection with thrombosed false lumen. Displace- ment of intimal calcification caused by accumulation of blood within the aortic media is useful for the differential diagnosis. Figure 8 Transoesophageal echocardiography. (A) ascending by guest on January 17, 2011 Usually, the inner margin of intramural haematoma is smooth, aorta dissection by long-axis view. Arrows show the intimal and aortic thickening occurs beneath the bright echo-dense flap. (B) descending thoracic aorta dissection by transverse view. Two jets from true lumen to false lumen identified the pres- intima, whereas an irregular margin with dilated aorta is commonly ence at secondary communications. observed in patients with aneurysmal dilatation and mural thrombi. In some cases, echolucent areas are present but no flow into these areas is detected. Intramural haematoma is quite easily differen- intraluminal images in the ascending aorta were considered diag- tiated from classical aortic dissection with flow in two lumina. nostic of dissected intima. The analysis of larger studies6,47,50,51 However, the diagnosis can be difficult when the false lumen of dis- showed that 3.5% of cases with clinically suspected dissection section is totally thrombosed.55,56 were erroneously diagnosed as having ascending aorta dissection. Diagnosis of penetrating ulcers by echocardiography is based on Altogether, the experience accumulated in recent years demon- the image of crater-like outpouching of the aortic wall, generally strates that the presence of an intraluminal linear image in the associated with extensive aortic atheroma57 (Figure 9C). Although ascending aorta alone should not be accepted as a dissection cri- both CT and MRI permit an easy diagnosis of these images terion. In the ascending aorta, particularly when dilated, linear because of their larger field of view, TOE may provide better infor- reverberation images are very common, being observed in 44– mation on the differential diagnosis of ulcerated plaques, penetrat- 55% of studies.6 Artefacts in the aortic root are a reverberation ing atherosclerotic ulcers or ulcer-like images secondary to focal from the anterior wall of the left atrium. In the middle third of intimal rupture in the evolution of intramural haematomas. the ascending aorta, they are due to reverberations from the pos- Aortic wall thickening with inward displacement of intimal calcifica- terior wall of the right pulmonary artery. The assessment of tion was an indication of associated intramural haematoma. location and movement of these intraluminal images by M-mode TOE is semi-invasive and requires sedation and may cause a rise echocardiography is the best way to differentiate between in systemic pressure from retching and gagging. Although isolated intimal flap and imaging reverberations. Typically, intraluminal cases of aortic rupture during the procedure have been reported, reverberations in the aortic root are located twice as far from the incidence in prospective series is very low, being more related the transducer as the posterior aortic wall, and their movement to the intrinsic risk of the disease than the procedure itself, as is parallel to the posterior aortic wall but with double displacement these events also occur during CT or MRI. However, adequate amplitude. Intraluminal reverberations in ascending aorta are sedation with strict blood pressure control is mandatory. When 654 A. Evangelista et al.

Figure 9 Transoesophageal echocardiography. (A) Crescentic intramural haematoma in ascending aorta (large arrow) adjacent to the left main coronary ostium (small arrow). (B) Intramural haematoma in descending aorta. Arrow shows intima calcification. (C) Penetrating aortic ulcer deforming the adventitia (arrow). Downloaded from therapeutic decision-making is definitive by other techniques, TOE should be performed in the operating theatre before surgery or Table 3 Differentiation between true and false lumina when the patient is haemodynamically stable with no chest pain. True lumen False lumen Given its accuracy in the diagnosis of aortic dissection, intramural ...... haematoma and aortic ulcers, TOE is a technique of choice in Size True , false Most often: false . true ejechocard.oxfordjournals.org acute aortic syndrome diagnosis when an expert echocardiogra- lumen pher is available. Pulsation Systolic expansion Systolic compression Recommendation Flow direction Systolic antegrade Systolic antegrade flow flow reduced or absent, or Although TOE is the technique of choice in aortic dissection diag- retrograde flow nosis, TTE may be used as the initial imaging modality in the emer- Communication From true to false gency setting. Contrast may improve its accuracy. If the diagnosis of flow lumen in systole type A dissection by TTE or contrast-TTE is definitive, surgical Contrast echo Early and fast Delayed and slow treatment could be directly indicated, provided intraoperative flow

TOE is performed just prior to surgery to confirm the diagnosis. by guest on January 17, 2011 In suspected type B dissections, TOE or CT should be performed according to clinical presentation, complications, and examiner experience. When contrast-TTE fails to show abnormalities, tear which usually has a diameter over 5 mm and is frequently another imaging technique must be applied for acute aortic syn- located in the proximal part of the ascending aorta in type A dis- drome to be definitively ruled out. sections and immediately below the origin of the left subclavian artery in type B dissections. On occasions, 2D echocardiography does not permit visualization of the intimal tear in the proximal Diagnosis of morphological and part of the arch. In these cases, contrast echocardiography may haemodynamic findings in aortic help by showing how contrast flows in the false lumen from the dissection more proximal part of the aortic arch dissection.48 TOE permits assessment of the main anatomical and functional aspects of interest for the management of aortic dissection. True lumen identification Identification of the true lumen is of special clinical interest. When Intimal tear location the aortic arch is involved, the surgeon needs to know whether the The intimal tear appears as a discontinuity of the intimal flap. TOE supra-aortic vessels originate from the false lumen. Similarly, when provides a direct image of the tear and permits its measurement. the descending aorta dissection affects visceral arteries and ischae- 55 Erbel et al. demonstrated a different evolutive pattern according mic complications arise, it may be important to identify the false to the presence and location of the tear. TOE permits identifi- lumen prior to surgery or endovascular treatment such as intima 55 cation of the tear in 78–100% of cases. Colour Doppler can fenestration or stent-graft implantation. Echocardiographic signs reveal the presence of multiple small communications between for differentiating the true lumen from the false lumen are summar- the two lumina, especially in descending aorta. Anatomical controls ized in Table 3. showed that most of these communications might correspond to the origin of intercostal or visceral arteries. By pulsed Doppler imaging, flow velocities through the intimal tear reflect the Diagnosis of complications pressure gradient between the two lumina. It is important to differ- Appropriate diagnosis of dissection complications during the initial entiate these secondary communications from the main intimal study may affect therapeutic decisions in the acute phase. Echocardiography in aortic diseases 655

Pericardial effusion and periaortic bleeding these cases, the TTE suprasternal view appears very useful. TOE Pericardial effusion is not always due to extravasation of blood permitted the diagnosis of coeliac trunk involvement, dissection, from the aorta and may be secondary to irritation of the adventitia or compression in most cases. Visceral or peripheral malperfusion produced by the aortic haematoma or small effusion from the wall. syndrome is a complication with high morbidity and mortality. In any event, the presence of pericardial effusion in an ascending However, CT provides far more precise information and is irre- aorta dissection is an indicator of poor prognosis and suggests placeable for diagnosing renal and iliac artery disease. TOE, like rupture of the false lumen in the pericardium. Echocardiography CT, can diagnose two types of circulation disorders of arterial is the best diagnostic technique for estimating the presence and branches: dissection or dynamic obstruction of the intimal severity of tamponade. Periaortic haematoma and pleural effusion dissection at the ostium of the arterial branches leaving the are best diagnosed by CT. The presence of periaortic haematoma aorta. Differentiating the two mechanisms has important thera- has been related to an increase in mortality.47,55 peutic implications.8 Recommendation Aortic regurgitation TOE should define the entry tear location, mechanisms and sever- Aortic regurgitation is a frequent complication, occurring in 40– ity of aortic regurgitation, and true lumen compression. Pericardial 76% of patients. The diagnosis and quantification of aortic regurgi- effusion/tamponade and left ventricular function (global and seg- tation severity can be correctly made with Doppler echocardiogra- mental) may be assessed by TTE. In some specific complications,

phy, both TTE and TOE. Furthermore, TOE provides information such as periaortic haematoma or involvement of the abdominal Downloaded from on possible mechanisms that inﬂuence aortic regurgitation, which arterial trunks, additional information by CT or MRI is advisable. may greatly aid the surgeon in deciding whether to replace the aortic valve58 (Table 4). Diagnosis of traumatic and iatrogenic aortic lesions Arterial vessel involvement

Blunt chest trauma may cause aortic rupture, dissection, or intra- ejechocard.oxfordjournals.org Diagnosis of involvement of the main arterial vessels of the aorta is mural haematoma. Rupture is due to a complete transection of important as it may explain some of the symptoms or visceral com- the aorta where all three vascular layers are disrupted circumfer- plications that accompany the dissection and permit selection of an entially. However, the adventitia may remain intact, or adjacent appropriate therapeutic strategy. Involvement of coronary arteries structures may contain the haemorrhage. A pseudoaneurysm in dissection has been considered to be 10–15%, with the right then results, defined as disruption of at least one layer of the coronary artery being most frequently affected. Detection of seg- vessel wall and containment of rupture by the remaining layers mental wall motion abnormalities of the left ventricle by TTE may and/or surrounding tissues. TOE has several advantages over help to identify this complication. In any event, left ventricular func- other imaging methods in the evaluation of critically ill patients tion assessment should be included in the TTE exam when acute 59 with trauma. It can be performed quickly, at the bedside, by guest on January 17, 2011 aortic syndrome is suspected since some patients have previous without interrupting therapeutic measures. Nevertheless, it left ventricular dysfunction secondary to hypertensive heart cannot be performed in patients with cervical spine fractures, disease or other conditions. On the other hand, TOE shows the which represent 5–25% of trauma victims. most proximal segment of the coronary arteries; thus, it can be Iatrogenic dissection of the aorta rarely occurs during heart verified whether the coronary ostium originates in the false catheterization. It is not infrequently seen following angioplasty lumen or whether coronary dissection is present. TOE is not a of an aortic coarctation but can also be observed after cross- good technique for assessing supra-aortic branch involvement. clamping of the aorta and after intra-aortic balloon pumping. However, in a recent work, sensitivity, specificity, and accuracy Most catheter-induced dissections are retrograde dissections. Pro- in the diagnosis of supra-aortic trunks were 60, 85, and 78%, gression of the coronary dissection into the aortic root may be respectively.7 The origin of the left subclavian artery is easily observed. Iatrogenic aortic trauma from vascular manipulation observed. However, the origin of innominate or brachiocephalic may cause dislodgement of debris from protruding or mobile trunk and left carotid arteries remains inconsistently detected. In atheromas. TOE may be the technique of choice for visualizing such lesions and assessing their embolic potential. Table 4 Mechanisms of significant aortic Recommendation regurgitation in aortic dissection TOE should be considered a technique of choice when aortic complications are suspected after thoracic trauma since it is accurate, Dilatation of the aortic annulus secondary to dilatation of the rapid, and can be performed at the bedside. Similarly, TOE is ascending aorta highly useful to rule out iatrogenic complications due to intravas- Rupture of the annular support and tear in the implantation of one of cular procedures. the valvular leaflets Asymmetrical dissections, the haematoma itself may displace a sigmoid below coaptation level Acute aortic syndrome prognosis Prolapse of the intima in the outward tract of the left ventricle through the valvular orifice and follow-up Previous aortic valve disease Age, signs and/or symptoms of organ malperfusion and clinical instability, fluid extravasation into the pericardium, and periaortic 656 A. Evangelista et al. haematoma have poor prognosis in the acute phase.55 Imaging highly accurate anatomical assessment of all types of aortic regur- techniques play an important role in identifying predictors of com- gitation lesions. In addition, the functional anatomy of aortic regur- plications during follow-up.60 The maximum aortic diameter in the gitation defined by TOE is strongly and independently predictive of subacute phase was a significant predictor of progressive dilatation. valve reparability and post-operative outcome.41 The combination Other variables have been considered to have poor prognosis, of functional evaluation by TOE and anatomical inspection at such as compression of the true lumen61 or partial false lumen surgery is therefore paramount when assessing the suitability of thrombosis.62 In contrast, a completely thrombosed false lumen the conditions for repair. By echocardiography, the tethering showed a protective role.55,62 Prognostic and therapeutic impli- indices might have the potential to guide the planning of aortic cations of TOE in aortic dissection are well established. Antegrade valve-sparing surgery (see aortic aneurysm section). Accurate or retrograde false lumen flow, false lumen thrombosis, and the echocardiographic measurements of aortic root diameters are presence of communications have prognostic implications and also essential in other types of surgery such as the Ross procedure, are easily detected by TOE.55 TOE has an important role in the homograft aortic valves64 or in percutaneous aortic valve follow-up of patients with aortic dissection as it shows the struc- implantation.65,66 ture of the dissection, surgical repair, healing of the dissection Pre-operative or intraoperative TOE is essential for planning the and obliteration of the false lumen, or blood flow dynamics in surgical treatment of acute aortic syndrome and in deciding true and false lumina. However, TOE is less useful than CT or whether to replace the aortic valve58 (see section on TOE) and

MRI in the follow-up of aortic diameter dilatation, which is one can further be used to evaluate the placement of cannulae, Downloaded from of the predictors of worse prognosis. assess perfusion in the different compartments of the aorta, and The intramural haematoma can heal or evolve to aneurysm for- whether or not the true lumen has been perfused.67 TOE may mation or even dissection.63 In addition to maximal aortic diam- help to avoid early reoperations by showing the correct connec- eter, some TOE information such as echolucent areas has been tion of the distal part of the graft tube to the true lumen, arch related to dissection and enlargement evolution.61 The natural and supra-aortic vessel involvement, and the severity of residual ejechocard.oxfordjournals.org history of PAU is unknown. Like intramural haematomas, several aortic regurgitation. Finally, intraoperative TOE may detect compli- evolutive possibilities have been proposed. As in other acute cations such as pseudoaneurysm formation, most of which are sec- aortic syndromes, ascending aorta involvement carries a higher ondary to a leak in coronary artery reimplantation to the graft risk of severe complications than type B involvement. Both in intra- tube, communication of the distal part of the tube to the false mural haematoma and aortic ulcer, CT and MRI with a larger field lumen, significant aortic regurgitation, periaortic haemorrhage, or of view have some advantages in the follow-up of complications of segmental abnormalities in left ventricular contraction. these diseases. In cases where TOE cannot be performed intraoperatively, it Recommendation should be attempted prior to extubation of the patient in the post- Although TOE provides prognostic information on acute aortic operative period for the early detection of complications. by guest on January 17, 2011 syndrome evolution, particularly in aortic dissection, CT or MRI Recommendation is more useful in the follow-up of arch and descending aorta Echocardiography is crucial in selecting and monitoring surgical diameters. treatment and detecting complications. Thus, intraoperative TOE should be considered mandatory. When intraoperative TOE has Intraoperative and post-operative echo not been performed, the study should be made immediately Echocardiography plays a crucial role in the pre-operative, intrao- after surgical treatment. perative, and post-operative assessment of aortic diseases. Repla- cement by a composite graft (synthetic graft, valve mechanical prosthesis, and reimplantation of coronary arteries) has been con- Endovascular therapy monitoring sidered the conventional treatment for patients with significant aortic incompetence caused by aortic root dilatation. Wall wrap- by intraoperative transoesophageal ping with stent-graft implantation has also been used as a treat- echocardiography ment option. However, when the root is dilated but the leaflets Intraoperative TOE is highly useful during endovascular therapy of are normal, valve-sparing root resection yields excellent results the descending thoracic aorta, especially in type B aortic dissection, without the need to implant a prosthetic aortic valve. Knowledge since it provides additional information to angiography/fluoroscopy of aortic root dimensions, aortic regurgitation severity and its for guiding correct stent-graft placement. For example, TOE is able mechanisms would enable pre-operative selection of the best sur- to detect peri-stent leaks and/or small re-entry tears with much gical strategy and preparation of an adequately sized graft tube, higher sensitivity than angiography.68 –72 In several publications, repair or replacement of aortic valve, and shorten surgical ischae- TOE provided decisive additional information to angiography/ mia time. Previous studies have demonstrated that pre-operative fluoroscopy, leading to successful procedural changes in up to measurement of aortic annular diameter by TTE and multiplane 40–50% of patients.70 –72 TOE is useful in the operating theatre TOE is accurate and clinically feasible. both before and after stent-graft deployment. The important role of echocardiography in aortic valve repair lies in the recognition of the exact lesions that may be responsible (1) Prior to stent-graft deployment in patients with type B aortic for the insufficiency, and the selection of adequate operative dissection, TOE is useful for guidewire repositioning (not poss- manoeuvres to correct these abnormalities. TOE provides a ible with fluoroscopy) from the false to the true lumen and for Echocardiography in aortic diseases 657

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