Recommendations
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RECOMMENDATIONS Echocardiography in aortic diseases: EAE recommendations for clinical practice Arturo Evangelista 1 *
2 , Raimund Erbel 3 ,
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 Document Reviewers: Mauro Pepi a , Ole-A. Breithardt b , and Edyta Plon´ska-Gos´ciniak c 1
2 University of Erlangen, Erlangen, Germany; 3 University of Essen, Essen, Germany; 4 Hospital Pordenone, Pordenone, Italy; 5 Hippokration Hospital, Athens, Greece; 6 S. Orsola University Hospital, Bologna, Italy; 7 Institute of Clinical Physiology, Pisa, Italy; 8 Hammersmith Hospital, London, UK; and 9 Hospital Clı´nico San Carlos, Madrid, Spain a Instituto di Cardiologia dell’Universita` degli Studi. Milan, Italy; b Medizinische Klinik 2, University Hospital, Erlangen, Germany; and c Pomeranian Medical School, Szczecin, Poland 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 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 diag- nosis and follow-up of most aortic diseases. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Keywords Aortic diseases † Transoesophageal echocardiography † Transthoracic echocardiography † Contrast echocardiography Introduction Aortic diseases are an important cause of cardiovascular morbidity and mortality. Except when complications are life-threatening, such as acute aortic syndrome or aortic rupture, aortic diseases are asymptomatic and without abnormalities on physical examination; thus, diagnosis and follow-up depend exclusively on imaging tech- niques. Echocardiography has become the most used imaging test in the evaluation of cardiovascular disease and plays an important role in the diagnosis and follow-up of aortic diseases. The aorta is divided into segments: the aortic root, ascending aorta, aortic arch, descending aorta, and abdominal aorta. Ultrasound techniques for imaging of the aorta include transthoracic echocardiography (TTE), transoesophageal echocardiography (TOE), abdominal ultrasound, and intravascular ultrasound (IVUS). In the present article, we will focus on TTE and TOE methodologies in the assessment of aortic diseases, their strengths and limitations for its use in various clinical situations and recommendations for appropriate applications of * Corresponding author. Tel: +34 932746212; fax: +34 932746244, Email: aevangel@vhebron.net Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2010. For permissions please email: journals.permissions@oxfordjournals.org. European Journal of Echocardiography (2010) 11, 645–658 doi:10.1093/ejechocard/jeq056 by guest on January 17, 2011 ejechocard.oxfordjournals.org Downloaded from
echocardiography based on available evidence. It is not the main objective of this manuscript to compare the usefulness of echocar- diography with other imaging techniques or to describe the stan- dard diagnostic management of different aortic diseases. Transthoracic echocardiography Echocardiographic evaluation of the aorta is a routine part of the standard echocardiographic examination. 1 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 proxi- mal aortic segments in clinical practice. Using different windows, the proximal ascending aorta is visualized in the left and right para- sternal 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 esti- mating 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 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, aortic regurgitation due to dilatation of the ascending aorta or aortic dissection, and other diseases). Of paramount importance for evaluation of the thoracic aorta is the suprasternal view (Figure 2 A). This view primarily depicts the aortic arch and the three major supra-aortic vessels (innominate, left carotid, and left subclavian arteries), with variable lengths of the descending and, to a lesser degree, ascending aorta. Although Figure 1
Transthoracic echocardiography. (A) Parasternal long-axis view (transthoracic echocardiography). The following diameters are shown: outflow tract diameter (1), sinuses of Val- salva (2), sinotubular junction (3), and tubular ascending aorta (4). (B) Right parasternal long-axis view, mid and distal parts of ascending aorta may be visualized. AAo, ascending aorta; LA, left atrium; LV, left ventricle; RV, right ventricle. 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. A. Evangelista et al. 646 by guest on January 17, 2011 ejechocard.oxfordjournals.org Downloaded from this view may be obstructed, particularly in patients with emphy- sema or short, wide necks, it should be systematically sought if aortic disease is evaluated. From this window, aortic coarctation can be visualized and functionally evaluated by continuous-wave Doppler; a persistent ductus arteriosus may also be identifiable by colour Doppler. Dilatation and aneurysm, plaque, calcification, thrombus, or a dissection membrane are detectable if image quality is sufficient. A systematic comparison of harmonic TTE and TOE made to detect aortic plaques and thrombi revealed high sensitivity for the detection of aortic arch atheromas protrud- ing ≥4 mm into the lumen. 2 The entire thoracic descending aorta is not well visualized by TTE. A short-axis view of the descending aorta can be imaged pos- teriorly to the left atrium in the parasternal long-axis view. From the apical window, a short-axis cross-section of the descending 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 transdu- cer, a rotation long-axis view is obtained and a mid part of the des- cending thoracic aorta may be visualized (Figure 2 B). Although a partial assessment of the size of the descending aorta and detec- tion of large abnormal structures such as dissection membranes are possible in these views, the descending aorta lies far from the transducer and the assessment is incomplete, suboptimal and not accurate. However, in acute aortic syndrome with left pleural effusion, scanning from the back may provide good or optimal views of the descending aorta. In contrast, since the abdominal descending aorta is relatively easily visualized to the left of the inferior vena cava in sagittal (superior – inferior) subcostal views, the systematic search for abdominal aortic aneurysms has been advocated as part of the routine echocardiographic exam 3 ,
(Figure 2 C), although transthor- acic echo transducers are not optimal for abdominal sonography. 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 ).
Table 1 Echocardiographic views of the aorta View Part of aorta Transthoracic echo Parasternal long + short axis Ascending + descending thoracic Apical four-chamber Descending thoracic Apical two-chamber and/or long axis Descending thoracic Suprasternal Arch, descending + ascending thoracic
Subcostal Abdominal ( +ascending thoracic) Transoesophageal echo Upper oesophageal long
+ short axis Ascending thoracic Aortic (long + short axis) Descending thoracic + arch
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. Echocardiography in aortic diseases 647 by guest on January 17, 2011 ejechocard.oxfordjournals.org Downloaded from Recommendation TTE permits adequate assessment of several aortic segments, par- ticularly the aortic root and proximal ascending aorta. All scanning planes should be used to obtain information on most aortic seg- ments. However, if inconclusive information or abnormalities are present, another imaging modality is required to either complete or add diagnostic information. Transoesophageal echocardiography Proximity of the oesophagus and the thoracic aorta permits high- resolution images from higher-frequency TOE. Furthermore, the availability of multiplane imaging permits improved incremental assessment of the aorta from its root to the descending aorta. 5 The most important transoesophageal views of the ascending aorta, aortic root and aortic valve are the high transoesophageal long-axis (at 1208 – 1508) (Figure 3 A) and short-axis (at 308 – 608) views. A short segment of the distal ascending aorta, just before the innominate artery, remains unvisualized owing to interposition of the right bronchus and trachea (blind spot). Images of the ascending aorta often contain artefacts due to reverberations from the posterior wall of the ascending aorta or the posterior wall of the right pulmonary artery, presenting as aortic intraluminal linear horizontal lines moving in parallel with the reverberating structures, as can be ascertained on M-mode tracings. 6 The des-
cending aorta is easily visualized in short-axis (08) and long-axis (908) views from the coeliac trunk to the left subclavian artery (Figure 3
aortic arch, where the inner curvature and anterior arch wall are usually well seen all the way to the ascending aorta. In the distal part of the arch (Figure 3 B), the origin of the subclavian artery is easily visualized. However, in awake patients, the origin of innomi- nate and left carotid arteries is not clearly visualized, although in anaesthetized patients, it is possible to identify the origin of these supra-aortic arteries. 7 The proximal part of the coeliac trunk is visualized in most cases and the superior mesenteric artery in 50% of cases. 8 One of the limitations of TOE is to locate the exact level of a given abnormality in the descending aorta. When no reference vessels, such as subclavian artery or coeliac trunk, are visualized, this limitation can be overcome by rotating the transducer and identifying the level of the descending aorta in comparison with the structures of the heart or great vessels (anterior structures). Like the ascending aorta, the des- cending aorta often produces an artefactual pseudo-aorta located posteriorly to the true aorta (‘double-barrel aorta’). Recommendation TOE is the ultrasound technique of choice in thoracic aorta assess- ment and provides high-resolution images of the entire thoracic aorta except for a small portion of the distal ascending aorta near the innominate artery. TOE overcomes limitations encountered by TTE. TTE and TOE should be used in a complementary manner. Aorta size Measurements of aortic diameter by echocardiography are accurate and reproducible when care is taken to obtain a true perpendicular dimension and gain settings are appropriate. Stan- dard measurement conventions established the leading
edge-to-leading edge diameter in end-diastole, 9 and the normative data published in the literature were obtained using the leading edge technique. 10 –
Some experts 13 , 14 favour inner edge-to-inner edge diameter measurements to increase reproducibility and match those obtained by other methods of imaging the aorta. However, recent improvements in echocardiographic image quality and resolution minimize the differences between these measurement methods. Two-dimensional (2D) aortic measure- ments are preferable to M-mode, as cyclic motion of the heart and resultant changes in M-mode cursor location result in systema- tic underestimation by 1 – 2 mm of aortic diameter by M-mode in comparison with the 2D aortic diameter. Standard diameter measurements are at the aortic annulus, at the level of the sinuses of Valsalva and at the sinotubular junction (Figure 1 ). Aortic annular diameter is measured between the hinge points of the aortic valve leaflets (inner edge – inner edge) in the left parasternal long-axis view, during systole, which reveal the largest aortic annular diameter. In a normal ascending aorta, the diameter at sinus level is the largest, followed by the sinotubular junction and the aortic annulus. If aortic dilatation is detected at any level, its maximum diameter should be measured and reported. Normal values Aorta size is related most strongly to body surface area (BSA) and age. 10 , 11 Therefore, BSA may be used to predict aortic root diameter in several age intervals. Roman et al. 10 considered three age strata: younger than 20 years, 20 – 40 years, and older than 40 years by published equations. These normal values have been accepted to date as the reference values. Some groups have suggested indexing by height to avoid the influence of overweight on BSA. Nevertheless, large series defining normal ranges of this index are lacking. Aortic root dilatation at the sinuses of Valsalva is defined as an aortic root diameter above the upper limit of the 95% confidence interval of the distribution in a large reference population. In adults, a diameter of 2.1 cm/m 2 has been con- sidered the upper normal range in ascending aorta. 15 TTE suffices to quantify maximum aortic root and proximal ascending aorta diameters when the acoustic window is adequate. Nevertheless, the technique is more limited for measuring the remaining aortic segments. TOE overcomes part of these TTE limitations by affording better measurement of aortic arch and descending thoracic aorta size. TOE may make oblique measurements when the descending aorta is elongated or tortuous. To avoid this overestimation, aortic diameter measurement by TOE should be attempted only when circular sections are obtained. Measurements of descending thoracic aorta in short axis and of the aortic arch in long axis are recommended. The absolute and indexed normal values of the various aortic segments are shown in Figure 4 . Recommendation TTE permits precise and reproducible measurements of the diam- eters of the aortic root and proximal part of the ascending aorta. The relationship between aorta size and age and body surface should be considered when defining normal ranges. Given its A. Evangelista et al. 648 by guest on January 17, 2011 ejechocard.oxfordjournals.org Downloaded from better visualization, TOE is the ultrasound modality of choice for measuring the size of the aortic arch and descending aorta. Aortic and arterial biophysical properties The aorta plays an important role in modulating left ventricular performance and arterial function throughout the entire cardiovas- cular system. 16 Arterial function is modified by several factors that affect the arterial wall and is reliably assessed by non-invasive methods.
17 The velocity of the pulse wave is fast enough for it to be able to travel to the periphery and then return within a single cardiac cycle. The elastic properties of arteries vary along the arterial tree, with more elastic proximal arteries and stiffer distal arteries. A comprehensive assessment of aortic and arterial biophysical properties includes: (i) evaluation of the aortic pressure– dimension relationship; (ii) arterial stiffness (measured by wave velocities); and (iii) the reflected waves. 16 , 17 Aortic pressure – dimension relationship An increase in distending pressure during systole induces an increase in aortic dimension, which is directly related to the elastic properties of the aorta. Diameter or area changes can be determined using TTE or TOE, but estimation of the pressure changes at the same site may be unreliable because of the amplification of the pulse pressure (i.e. systolic pressure increases progressively towards the periphery) and inaccuracy of all cuff sphygmomanometer systems, particularly in young subjects. However, studies have shown a good correlation between aortic distensibility calculated using echocardiography and non-invasive brachial artery pressure measurements and aortic distensibility cal- culated invasively, using contrast aortography and direct aortic pressure recordings. Changes in arterial diameter can be measured at the level of the ascending aorta, 3 cm above the aortic valve in 2D-guided M-mode of parasternal long-axis view, with the diastolic aortic diameter measured at the peak of the QRS complex and sys- tolic aortic diameter measured at the maximal anterior motion of the aorta. Other levels for measuring the arterial diameters are limited to the mid-portion of the abdominal aorta. There are several indices derived from aortic or arterial dimen- sions and pressures and used for the estimation of the elastic prop- erties of the aorta. The indices most frequently used are aortic/ arterial distensibility (the relative change in diameter or area for a pressure change), compliance (the absolute change in diameter or area for pressure), and a non-dimensional index of local arterial stiffness named the b-index [defined as the ratio of logarithm 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 sino- tubular junction, and the proximal (tubular) ascending aorta; the aortic arch that extends from the innominate artery to the ligamentum arter- Yüklə 455,25 Kb. Dostları ilə paylaş:
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