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Echocardiography in Aortic Valve Stenosis Chapter | 13 139
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2
FIGURE 13.4 Aortic stenosis (AS) associated with systolic aortic regurgitation. (A) Color M-mode echocardiography, the arrow indicates the mosaic dispersion of the aortic diastolic flow, extended
into systole (goes beyond the QRS complex on the electrocardiogram). (B) Pulsed wave Doppler (PWD) of the aortic valve, showing that the aortic diastolic curve extended into systole (goes beyond the
QRS complex on the electrocardiogram). (C) Two-dimensional (2D) echocardiography long axis. Ao, aorta with calcified leaflets; the green line stands for the left ventricular outlet tract (LVOT). (D)
Continuous wave Doppler (CWD) of the aortic valve, the systolic and diastolic aortic flow can be observed. Aortic valve area (AVA) = 0.69 cm
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2
− 0.54 cm
2
FIGURE 13.5 Aortic stenosis associated with a noncompliant ventricle, reduced ejection fraction and left ventricular outlet tract (LVOT) presystolic flow. (A) Continuous wave Doppler (CWD) of the
aortic valve, maximum velocity 3.74 m/s. (B) Transmitral pulsed wave Doppler (PWD). A special pattern of the diastolic flow, with a very low E-wave velocity (0.2 m/s) and a prolonged deceleration time
(401 ms). (C) Transaortic PWD. During presystole, a diastolic flow induced by atrial contraction can be observed. (D) Two-dimensional (2D) echocardiography long axis, Ao, aorta with calcified leaflets
and the measurement of the LVOT diameter. Aortic valve area (AVA) = 0.43 cm
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FIGURE 13.6 Low-flow, low-gradient severe aortic stenosis. Dobutamine stress test. (A) the dilated left ventricle (LV) cavity, with hypokinesia of the apical third of the interventricular septum
(B) after dobutamine, septum thickening, LV cavity reduction, increase in ejection fraction (EF) over 20% (C) calcified aortic cusps (Ao), transvalvular aortic flow with a 37 mmHg pressure
gradient (D) after dobutamine, transvalvular aortic flow with a 50 mmHg pressure gradient demonstrates contractile reserve.
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FIGURE 13.7 Paradoxical low-flow, low-gradient aortic stenosis. (A) Two-dimensional (2D) echocardiography, long axis. The reduced left ventricle
(LV) cavity is visible, with concentric wall hypertrophy. Ao, aorta. (B) Continuous wave Doppler (CWD) echocardiography of the aortic valve, maximum
flow velocity 3.2 m/s, aortic valve area (AVA) 0.69 cm2. (C) Speckle tracking echocardiography. Although ejection fraction (EF) is normal, the longitudinal
strain is reduced. (D) Three-dimensional (3D) echocardiography for evaluating EF: 52.17%, and stroke volume: 15.3 mL.
In patients with asymptomatic AS who have no contraindications for exercise testing, the following are assessed during
physical stress:
l possible symptom onset
l systolic and diastolic function, LV contractile reserve, and pulmonary artery pressure [4,8]
The posteffort increase in s’ wave velocity by tissue Doppler imaging of the lateral mitral annulus by more than 5 cm/s
and of longitudinal strain in speckle tracking by more than 1.4% indicates the present LV contractile reserve [14,15].
An increase in pulmonary artery pressure over 50 mmHg and the identification of diastolic dysfunction, with an increment in the E/e′ ratio, are associated with a poor prognosis in asymptomatic AS patients [13,16].
CONCLUSIONS
Evaluating severity and valve replacement indication are the key elements of echocardiography in patients with AS.
Identifying new pathophysiological varieties of AS (described in Table 13.3), associated with HOCM, severe aortic
regurgitation (systolic regurgitation) or in the context of a noncompliant LV with a low EF and presystolic flow, warrants
further studies at rest, upon exercise, or pharmacologic stress, to assess for risk stratification and the indication for aortic
valve replacement.
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REFERENCES
[1] Iung B, Baron G, Butchart, et al. A prospective survey of patients with valvular heart disease in Europe: the Euro heart survey on valvular heart
disease. Eur Heart J July 2003;24(13):1231–43.
[2] Michelena HI, Khanna AD, Mahoney D, et al. Incidence of aortic complications in patients with bicuspid aortic valves. JAMA September 14,
2011;306(10):1104–12.
[3] Courtesy of Dinu Dusceac, MD, NAL, Sweden; 2016.
[4] Vahanian A, Alfieri O, Andreotti F, et al. Guidelines on the management of valvular heart disease (version 2012). Eur Heart J October
2012;33(19):2451–96.
[5] Baumgartner H, Hung J, Bermejo J, et al. Echocardiographic assessment of valve stenosis: EAE/ASE recommendations for clinical practice.
Eur J Echocardiogr January 2009;10(1):1–25.
[6] Lang MR, Goldstein AS, Kronzon I, et al. ASE’s comprehensive echocardiography. Elsevier Saunders; 2016. ExpertConsult.com.
[7] Cormier B, Iung B, Porte JM, et al. Value of multiplane transesophageal echocardiography in determining aortic valve area in aortic stenosis.
Am J Cardiol April 15, 1996;77(10):882–5.
[8] Nishimura RA, Otto CM, Bonow RO, et al. 2014 AHA/ACC guideline for the management of patients with valvular heart disease: executive sum-
mary: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines. J Am Coll Cardiol June 10,
2014;63(22):2438–88.
[9] Awtry E, Davidoff R. Low-flow/low-gradient aortic stenosis. Circulation December 6, 2011;124(23):e739–741.
[10] Clavel MA, Burwash IG, Mundigler G, et al. Validation of conventional and simplified methods to calculate projected valve area at normal flow rate
in patients with low flow, low gradient aortic stenosis: the multicenter TOPAS (True or Pseudo Severe Aortic Stenosis) study. J Am Soc Echocardiogr
April 2010;23(4):380–6.
[11] Pibarot P, Dumesnil JG. Low-flow, low-gradient aortic stenosis with normal and depressed left ventricular ejection fraction. J Am Coll Cardiol
November 6, 2012;60(19):1845–53.
[12] Lancellotti P, Magne J, Donal E, et al. Clinical outcome in asymptomatic severe aortic stenosis: insights from the new proposed aortic stenosis grad-
ing classification. J Am Coll Cardiol January 17, 2012;59(3):235–43.
[13] Lancellotti P, Karsera D, Tumminello G, et al. Determinants of an abnormal response to exercise in patients with asymptomatic valvular aortic
stenosis. Eur J Echocardiogr May 2008;9(3):338–43.
[14] Donal E, Thebault C, O’Connor K, et al. Impact of aortic stenosis on longitudinal myocardial deformation during exercise. Eur J Echocardiogr
March 2011;12(3):235–41.
[15] Van Pelt NC, Stewart RA, Legget ME, et al. Longitudinal left ventricular contractile dysfunction after exercise in aortic stenosis. Heart June
2007;93(6):732–8.
[16] Malouf JF, Enriquez-Sarano M, Pellikka PA, et al. Severe pulmonary hypertension in patients with severe aortic valve stenosis: clinical profile and
prognostic implications. J Am Coll Cardiol August 21, 2002;40(4):789–95.
Chapter 14
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Echocardiographic Assessment of the
Aorta
Maria Florescu
1
University and Emergency Hospital of Bucharest, Bucharest, Romania; 2University of Medicine and Pharmacy Carol Davila, Bucharest, Romania
1,2
, Roxana O. Darabont
1,2
, Dragos Vinereanu
1,2
Chapter Outline
Introduction 145
Echography for the Assessment of Normal Thoracic
Aorta 145
Normal Anatomy and Dimensions of the Thoracic Aorta 145
Echocardiography for the Assessment of Thoracic
Aorta 146
Echography for the Assessment of Pathology of Thoracic
Aorta 148
Acute Aortic Syndrome 148
Chronic Aortic Conditions 150
Intraoperative and Postsurgical Echocardiographic
Assessment 151
Duplex Ultrasound and Other Echographic Techniques for the
Assessment of Abdominal Aorta 151
Sonographic Anatomy 151
Scanning Technique by Duplex Ultrasound and Normal
Appearance of Abdominal Aorta 151
Echographical Assessment of Abdominal Aorta Diseases 152
Abdominal Aortic Aneurysm 152
Abdominal Aortic Dissection 154
Abdominal Aortic Stenosis 154
Choice of the Imaging Modality 154
Conclusion 155
References 155
INTRODUCTION
Aortic diseases represent a significant cause of mortality and morbidity; therefore, an integrated assessment of both thoracic
and abdominal aorta is essential [1]. Chronic aortic conditions are most often asymptomatic. Thus, the diagnosis of their
progression, the detection of acute, potentially life-threatening complications, and the indication of optimal timing for interventions are mandatory and usually based on noninvasive serial imaging techniques [2]. An ideal imaging test for assessing
aorta should be able to evaluate rapidly and safely the acute or chronic aortic conditions, giving precise information on
the extent of the disease, identifying high risk patients, contributing to the management plan and to the postinterventional
evaluation [3]. Although in the last years, there were remarkable advances in computed tomography (CT) and magnetic
resonance imaging (MRI), echography remains an important tool for detection and monitoring of the aortic pathology [4].
Transthoracic echocardiography (TTE) allows only a limited evaluation of the ascending aorta and of a small part of the
descending aorta. Transesophageal echocardiography (TEE) overcomes some of these limitations, being widely used for
the assessment of thoracic aorta, while duplex ultrasound is used for assessing abdominal aorta. Recently, new echocardiographic techniques, such as three-dimensional echo or contrast-enhanced ultrasound, have evolved with both research and
clinical implications. This chapter will review the role of echography for the assessment of thoracic and abdominal aorta in
normal and pathological settings.
ECHOGRAPHY FOR THE ASSESSMENT OF NORMAL THORACIC AORTA
Normal Anatomy and Dimensions of the Thoracic Aorta
Aorta is an elastic artery, representing the largest vessel in the body. Fig. 14.1 shows the two distinct parts of the aorta:
thoracic and abdominal [5–8]. Thoracic aorta extends from aortic annulus to the diaphragm and has four segments: segment
I—aortic root, comprising aortic annulus, interleaflets triangles, semilunar leaflets, three Valsalva sinuses, and sino-tubular
New Approaches to Aortic Diseases from Valve to Abdominal Bifurcation. http://dx.doi.org/10.1016/B978-0-12-809979-7.00014-6
Copyright © 2018 Elsevier Inc. All rights reserved.
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FIGURE 14.1 Normal aortic anatomy: thoracic aorta, consisting of ascending aorta, aortic arch, and thoracic portion of the descending aorta, and the
abdominal aorta [1,4,6].
junction; segment II—tubular segments of the aorta subdivided in IIa, from the sino-tubular junction to the level of the
right pulmonary artery, and IIb, from the right pulmonary artery to the brachiocephalic artery; segment III—aortic arch,
from the brachiocephalic artery to the ligamentum arteriosum, including the origin of the major neck vessels; and segment
IV—descending thoracic aorta, subdivided in IVa, from the ligamentum arteriosum to the pulmonary artery, and IVb, from
the pulmonary artery to the diaphragm [5,6]. Noninvasive imaging techniques, such as echography, CT, and MRI, have
emerged as methods for the measurements of aortic dimensions, with better accuracy than invasive angiography; however,
each of them has limitations and advantages (Table 14.1) [2,4].
Use of different techniques for the assessment of aortic dimensions has led to different values [4]. Most of the studies
report aortic dimensions at the level of the aortic root, assessed by TTE from the parasternal long-axis view [9,10], perpendicular on the axis at end-diastole, using the leading-edge-to-leading-edge method [6]. It is also recommended to report the
level of the aortic measurements in relation to a specific landmark, according to the guidelines [1,4]. Aortic dimensions are
correlated with age, gender, and body surface area [6,10,11] and are shown in Fig. 14.1 for different aortic segments [1,4,6].
Furthermore, aortic dimensions increase with hemodynamic requirements, as in endurance and strength exercise training
in competitive athletes [12] and with hypertension [13]. An increase of the aortic diameter with more than two standard
deviations above the predicted diameter defines an aortic dilatation, with important clinical implications [4].
Echocardiography for the Assessment of Thoracic Aorta
In the past, aortic angiography was the gold standard for the assessment of aorta, but recent advances and availability of the
noninvasive imaging techniques allow a better evaluation of the aorta [14]. Thus, the International Registry of Acute Aortic
Dissection showed that aortic dissection was diagnosed by CT in 63% of the cases, by TEE in 32%, by angiography in 4%,
and by MRI in 1% [15]. In the last years, advances in echocardiography have emerged this technique as one of the most
widely used for diagnosing and managing the aortic diseases [4–6].
Transthoracic echocardiography has a limited role for the complete evaluation of aorta (Table 14.1), allowing only the
assessment of aortic root and ascending aorta, aortic arch, and partially of descending aorta and proximal abdominal aorta.
However, TTE represents the most widely used imaging technique for the examination of aorta [1,5,6,16,17]. Moreover,
TTE allows also to assess cardiac complications of the acute aortic syndrome, such as myocardial infarction, aortic valve
regurgitation, or hemorrhagic pericarditis [18–20]. The most used transthoracic views are left parasternal long-axis view
for aortic valve and annulus, aortic root, and proximal ascending aorta; suprasternal view for aortic arch and its branches
(left carotid and subclavian arteries and brachiocephalic trunk, which can be visualized in up to 90%–95% of the cases);
apical three-chamber and five-chamber long-axis views for ascending aorta; apical four-chamber view for transverse view
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TABLE 14.1 Limitations, Advantages, and Recommendations of Different Imaging Modalities for the Assessment of
Aorta [1,2,4]
Imaging Methods Limitations Advantages Recommendations
Transthoracic
echocardiography
Transesophageal
echocardiography
Computed
tomography
Magnetic resonance
imaging
Aortography Invasive;
Poor visualization of distal ascending
and abdominal aorta;
Needs adding another imaging technique for complete assessment.
Poor visualization of abdominal aorta
and its branches;
Blind spot on the aortic arch and the
distal part of ascending aorta;
Semiinvasive method, needing
esophageal intubation and moderate
sedation;
Artifacts due to posterior aortic wall
calcifications or pulmonary artery;
Needs adding another imaging
technique for complete assessment.
Ionizing irradiation;
Needs contrast substance with potential
of renal damage;
Breathing artifacts;
Lack of evaluation of cardiac function.
Low risk of nephrogenic systemic
fibrosis induced by gadolinium;
Long time for acquisition and
reconstruction;
Unsuitable for unstable patients.
Ionizing irradiation and needs contrast
substance;
Carries the risk of peri-procedural
complications;
Allows evaluation only of the aortic
lumen.
Evaluation of cardiac structure and
function, aortic valve, and pericardium;
Rapid and useful at bedside in unstable
patients;
Lack of irradiation, safe and widely
available.
Optimal visualization of both ascending
and descending aorta and part of the
aortic arch;
Useful at bedside in unstable patients;
Lack of irradiation, safe, and relatively
widely available;
Intraoperative and postinterventional
aortic assessment.
Rapid acquisition;
Possibility of three-dimensional
reconstruction;
Evaluation of the entire aorta and its
branches;
Assessment of surgical or interventional
management plan.
No ionizing irradiation and no needs of
contrast substance;
Evaluation of the entire aorta and
cardiac function;
Best details of intramural haematoma,
atheroma and aortic intimal flap;
Assessment of surgical or interventional
management plan.
Evaluation of the entire aorta;
Possibility of endovascular interventions;
Concomitant assessment and possible
intervention on coronary arteries.
First and second
line in acute aortic
syndrome.
First and second
line in acute aortic
syndrome.
First-line for acute
aortic syndrome.
Third line.
Fourth line.
of the descending aorta; right parasternal long-axis view for better evaluation of ascending aorta; and subcostal view for
the assessment of abdominal aorta [1,4,6]. In patients with pleural effusion, the descending thoracic aorta can be visualized from the back. As shown in Fig. 14.1, the normal descending aorta is smaller than the ascending aorta, narrowing to
approx. 2.0 cm [6,21]. Current guidelines recommend TTE to be used for serial measurements of aortic root and evaluation
of the thoracic aortic aneurysm. However, TTE should be combined with other imaging modalities to assess the entire aorta
[1,5,6]. Meanwhile, suprasternal aortic view is mandatory, having an essential role for the assessment of aortic arch aneu-
rysm, dissection, atherosclerosis, and coarctation [1,4,6].
Transesophageal echocardiography is one of the most important imaging technique for the assessment of aorta, overcoming the TTE limitations (Table 14.1), with a higher spatial resolution and a better quality imaging [1,4–6]. Multiplane
TEE allows the examination of almost all segments of the thoracic aorta (aortic root, ascending aorta, descending aorta,
and parts of the aortic arch) and the aortic valve [22,23]. The most used TEE views are high esophageal long-axis view
at 120–150 degrees and short-axis view at 30–50 degrees, deep transgastric view at 0 degrees for the ascending aorta and
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aortic valve, and short-axis (0 degree) and long-axis (90 degrees) views from the celiac trunk to the left subclavian artery
for the descending aorta [6]. However, a “blind spot” remains at the level of the aortic arch due to interposition of trachea
[6,24]. Current guidelines recommend that TTE and TEE should be used complementarily [1,4,5].
3D echocardiography allows better description of the anatomy of the aorta [25,26]. However, this method still has sev-
eral limitations, such as poor visualization of the distal ascending aorta and aortic arch and lower spatial resolution, and is
not included yet in routine clinical practice [27].
Choice of the imaging modality should be adapted to clinical situation, local expertise, and availability of the techniques [1,2,4,5,28]. Table 14.1 summarizes the advantages and limitations of echography by comparison with other imag-
ing techniques and highlights the guideline recommendations for choice of imaging methods for different pathologies
[1,2,4,5,29,30]. Thus, TTE and TEE are the first recommended methods to be used in case of suspicion of acute aortic
syndrome, followed by CT scan for supplementary anatomical description [1,2,4,5]. TEE used for diagnosing the acute
aortic syndrome has a sensitivity from 86% to 100%, a specificity from 90% to 100%, and a negative predictive value from
86% to 100% [31–33], similar to CT and MRI, but better than aortography [30]. Therefore, current guideline recommends
all three techniques as the first line diagnostic imaging tool for acute aortic disease [4]. Meanwhile, it is recommended that
aortic root pathology, such as presence of the aortic aneurysm, should be first evaluated by echography, whereas aneurysm
of the distal ascending or descending aorta should be assessed by either CT or MRI, because echography does not assess
well these segments [1,4,34,35].
ECHOGRAPHY FOR THE ASSESSMENT OF PATHOLOGY OF THORACIC AORTA
Acute Aortic Syndrome
Acute aortic syndrome is defined by the risk of aortic rupture due to the weakening of the aortic wall and consists of acute
aortic dissection, intramural hematoma (IMH), and penetrating aortic ulcer [6]. It represents an emergency condition and,
therefore, diagnosis and immediate intervention are crucial. Echocardiography plays an essential role for diagnosis, as well
as for choosing the optimal management [1,4–6,36,37].
Acute aortic dissection is classified according to DeBakey in type I, involving ascending and descending aorta (60%);
type II, involving the ascending aorta (10%); and type III, involving the descending aorta (30%). According to Standford,
it is classified in type A, involving ascending aorta, and type B, involving descending aorta [38,39]. According to the time
of development, aortic dissection can be acute, within 14 days; subacute, between 15 and 90 days; and chronic, more than
90 days [6].
TTE has a limited value for detection of the acute aortic dissection, with 78%–90% sensitivity and 87%–96% specificity for the type A dissection, but only 31%–55% sensitivity and 60%–83% specificity for the type B dissection [4,31]. This
accuracy can be increased using contrast agents [31]. Current guideline recommends TTE as the initial imaging method,
mostly in the emergency room, in order to rule out the differential diagnosis of chest pain, providing also valuable information about left and right ventricular function, pericardial effusion, aortic valve function, and pulmonary artery pressure [4].
However, it is essential to complete aortic examination for aortic dissection with other imaging tests, even in the presence
of a negative TTE [4,5].
By comparison, TEE has a high accuracy for the diagnosis of both type A and B dissections, with a sensitivity
approaching 100% [40]. However, there are still some limitations related to the “blind spot” or to the presence of artifacts due to severe aortic calcifications that can mimic the dissection [41]. 3D TEE overcomes the limitations of bidimensional TEE, describing better the entry tear or surrounding cardiac and extra-cardiac structures, as well as the aortic
arch [27].
The American Heart Association (AHA) and European Society of Cardiology (ESC) guidelines enumerate the details
required from echocardiography in order to define aortic dissection as the following: intimal flap, presence of true and false
lumina, intimal tear, entry and reentry sites and secondary communications, extent of dissection, presence of anterograde or
retrograde dissection, involvement of aortic branches with signs of malperfusion, and presence of cardiac and/or periaortic
complications [4–6,42]. The intimal flap results from cleavage of the medial layer, dividing aorta into two lumina, the true
and the false one, and represents the specific sign of aortic dissection [43]. It appears as a thin, very mobile echo inside the
aortic lumen, usually identified by TEE (Fig. 14.2A and B). Usually, the true lumen is smaller than the false lumen and
has a systolic expansion, a diastolic collapse, absence of thrombus, and forward systolic flow [4,5]. In the false lumen, the
flow velocity is generally low, resulting in a smoke-like effect or even a thrombus formation [44]. The intimal tear appears
at the beginning of dissection, as the disruption of the flap, frequently with anterograde progression. Color Doppler echocardiography enhances the tear detection, showing a communication between the true and the false lumina. The extension
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$ %
FIGURE 14.2 Ascending aortic dissection diagnosed by transesophageal echocardiography in the longitudinal (A) and transversal (B) views, with
identification of the intimal flap (arrows).
FIGURE 14.3 Intramural hematoma diagnosed by transesophageal echocardiography in the long-axis view; it is visualized as a thickening of the anterior wall of the aorta.
of dissection refers to progression in the aortic arch and involvement of the arterial branches [4,5]. Echography has also
an important role in assessing cardiac complications, such as aortic regurgitation, myocardial wall abnormalities due to
coronary arteries involvement, pericardial effusion or tamponade from ascending aorta dissection, and pleural effusion or
mediastinal hematoma from descending aorta leakage [1,4–6,45].
Echography is also essential for the management plan. Thus, current guidelines recommend that TEE should be used
to select patients suitable for surgery or endovascular treatment. Intraoperative TEE is mandatory to offer important details
during the surgery [4,5]. Moreover, TEE and intravascular ultrasound offer advantages over angiography in guiding endovascular therapy in order to choose the optimal stent graft diameter and to verify the correct placement of guidewire in the
true lumen [4–6,46,47]. Patients who have suffered from an acute event should be monitored at 1, 3, 6, and 12 months, and
annually thereafter [4,5]. Meanwhile, echography provides data associated with poor long-term prognosis after a repaired
type A dissection, such as descending aortic diameter (more than 45 mm), a persistent patent false lumen of descending
aorta, a large entry tear ≥10 mm, and a compression of the true lumen [4,5,48,49].
Intramural hematoma represents approximately 10%–25% of cases of acute aortic syndrome, being a type of noncommunicating aortic dissection due to a rupture of vasa vasorum, with bleeding between the elastic fibers [4–6,50].
Echography plays an important role in the diagnosis of IMH. It appears like a crescent, eccentric, or circular thickening of
the aortic wall, in the absence of intimal flap or entry tear, as seen in Fig. 14.3. Because the progression of IMH, such as
aneurysm formation or conversion to dissection, does not have a clinical impact, follow-up by imaging is essential, CT or
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