Diseases of the Great Arteries

Basic Principles

▪ A systematic approach is needed for echocardiographic evaluation of the great arteries.
▪ Transesophageal echocardiography (TEE) is more sensitive than transthoracic imaging for detection of aortic aneurysm and dissection.
▪ Wider field of view tomographic imaging techniques, including chest computed tomography (CT) or cardiac magnetic resonance (CMR) imaging, provide optimal evaluation of the great vessels.

Key Points

□ Many segments of the aorta and pulmonary artery can be visualized on transthoracic imaging, but:
- □ Evaluation of branch pulmonary arteries and the branching of systemic arteries from the aorta often is not possible.
- □ Ultrasound imaging artifacts must be distinguished from an intraluminal dissection flap.
□ The colloquial term aortic root includes the aortic annulus, sinuses of Valsalva, sinotubular junction, and ascending aorta.
□ When the echocardiogram is nondiagnostic or equivocal, additional imaging techniques should be recommended, based on the clinical signs and symptoms.

Step-By-Step Approach

Transthoracic Echocardiography

▪ Examination of the aorta is based on visualization of several segments from different acoustic windows.
▪ The sequence suggested here follows the sequence of a standard transthoracic study; other exam sequences may be appropriate with an acute clinical presentation.

Step 1: Record Blood Pressure

▪ Aortic disease often presents as a medical/surgical emergency; appropriately trained health care providers should be available during the study.
▪ Blood pressure is recorded at the beginning of the study, because findings may change with altered loading conditions.

Key Points

□ When time is of the essence, limited imaging and Doppler data should be focused on the specific clinical question.
□ It may be appropriate to proceed directly to TEE when aortic dissection is suspected; the echocardiographer should consult with the referring provider to ensure that the most appropriate test is performed in a timely manner.

Step 2: Aortic Sinuses and Ascending Aorta

▪ The aortic sinuses are seen in the standard and high parasternal long-axis view (Fig. 16.1 and Fig. 16.2 ).
▪ Diameter measurements are reported at end-diastole for the aortic annulus, sinuses of Valsalva, and sinotubular junction and in the mid-ascending aorta (Fig. 16.3).
▪ Color Doppler allows detection of aortic regurgitation and evaluation of the flow pattern in the ascending aorta.

Key Points

□ After recording the standard parasternal long-axis view of the aortic sinuses, the transducer is moved up one or more interspaces to visualize as much of the ascending aorta as possible.
□ The sinotubular junction is defined as the top of the sinuses of Valsalva and is recognized by the acute angle at the transition from the curved sinuses to the tubular ascending aorta.
□ Aortic dimensions are measured on two-dimensional (2D) images from the inner white–black border to the inner black–white border of the aortic lumen.
□ Comparison of measurements on serial studies or by different modalities should be made at the same time point in the cardiac cycle.
□ In comparing measurements from different modalities (CT and MRI), both imaging physics differ and measurement norms may vary, leading to apparent discrepancies.
Fig. 16.3 Example of aortic measurements.Diameter is measured at the sinuses, sinotubular junction, and mid-ascending aorta at end-diastole. Current guidelines recommend a leading-edge to leading-edge measurement, but many centers continue to measure from the inner white–black border of the anterior wall to the black–white border of the posterior aortic wall, because reproducibility is higher and for comparison with prior studies. Care is needed to ensure that the image plane is centered in the aorta and that measurements are perpendicular to the long axis of the vessel. An off-center image plane will underestimate aortic size; conversely, oblique measurements will overestimate aortic size.

Step 3: Descending Thoracic Aorta

▪ The midportion of the descending thoracic aorta can be visualized from the parasternal long-axis view, posterior to the left atrium (LA), by rotating the image plane clockwise to obtain a longitudinal view of the aorta (Fig. 16.4).
▪ The descending thoracic aorta also can be imaged from the apical 2-chamber view by lateral angulation of the image plane (Fig. 16.5).
Fig. 16.4 Parasternal views of descending aorta.In a Marfan patient, the descending aorta is seen posterior to the LA. A long-axis view of the descending thoracic aorta can be obtained by rotating the transducer clockwise into a parasternal short-axis plane. Ao, Aorta; DA, descending aorta.
▪ Color Doppler is helpful in distinguishing image artifacts from an intraluminal flap in these views.

Key Points

□ Dilation of the descending aorta and dissection flaps can be identified in these views when image quality is adequate.
□ Only some segments of the descending thoracic aorta are visualized, so significant pathology may be missed.
□ The aorta is in the far field of the image in these views, limiting evaluation for aortic atheroma.
□ In patients with a large left pleural effusion, the descending aorta can be imaged from the posterior chest wall, using the pleural effusion as an acoustic window.

Step 4: Proximal Abdominal Aorta

▪ The proximal abdominal aorta is seen in the subcostal view by medial angulation from the inferior vena cava (IVC) image plane (Fig. 16.6).
▪ Holodiastolic flow reversal is seen in the proximal abdominal aorta in patients with severe aortic valve regurgitation (see Fig. 12.5).

Key Points

□ Diameter of the proximal abdominal aorta is routinely measured in patients with aortic disease, such as Marfan syndrome.
Fig. 16.5 Apical views of descending aorta.The descending thoracic aorta can be imaged from the apical 2-chamber view with lateral angulation of the image plane. DA, Descending aorta.
□ With a normal pattern of flow, antegrade systolic flow is followed by early diastolic flow reversal due to coronary blood flow, mid-diastolic low-velocity antegrade flow, and a very brief late diastolic flow signal due to elastic recoil of the aorta (Fig. 16.7).
Fig. 16.6 Proximal abdominal aorta.From the subcostal window, the image plane is turned medially from the inferior vena cava (IVC) to visualize the aorta in a long-axis view. Color Doppler (right) shows normal laminar antegrade flow in systole. DA, Descending aorta.
Fig. 16.7 Normal flow in the proximal abdominal aorta.There is antegrade flow in systole, brief early diastolic reversal (arrow), low-velocity forward flow in mid-diastole, and then a slight flow reversal at end-diastole.
Fig. 16.8 Aortic arch.From the suprasternal notch position (left), a long-axis view of the aortic arch shows segments of the ascending and descending thoracic aorta, the arch, and the origins of the head and neck vessels. The right pulmonary artery is seen under the curve of the arch. In the short-axis view of the arch (right), the LA and pulmonary veins are seen inferior to the right pulmonary artery. Ao, Aorta; PA, pulmonary artery; RPA, right pulmonary artery.
□ In order to detect the holodiastolic flow reversal seen with severe aortic regurgitation, the filters are adjusted to show low-velocity flow.
□ Holodiastolic flow reversal also is seen with other aortic diastolic flow abnormalities (such as a patent ductus arteriosus, surgical systemic-to-pulmonary shunt [e.g., Blalock-Taussig shunt], or aorto-pulmonary window) or other large arteriovenous communication (such as an upper extremity dialysis fistula in patients with end-stage renal disease).

Step 5: Aortic Arch

▪ The aortic arch is visualized in long- and short-axis views from the suprasternal notch window (Fig. 16.8)
▪ Pulsed Doppler recordings of flow in the proximal descending aorta show holodiastolic flow reversal when moderate to severe aortic regurgitation is present (Fig. 16.9). The normal flow pattern is shown in Fig. 16.10.

Key Points

□ The aortic arch is measured in its midsection, where the ultrasound beam is perpendicular to the aortic walls.
□ The descending aorta appears to “taper,” even when normal, due to the oblique plane of the ultrasound image compared with the curvature of the aorta.
□ The distance from the aortic valve that holodiastolic flow reversal persists correlates with regurgitant severity. Thus, reversal in the proximal descending aorta is seen with moderate regurgitation, but reversal in the abdominal aorta indicates severe regurgitation.
□ The right pulmonary artery is seen in cross-section, under the arch, in the long-axis view of the aortic arch.
□ A longitudinal view of the left pulmonary artery can be obtained by leftward rotation and angulation of the image plane.

Step 6: Decide if TEE or Other Imaging Procedures Are Needed

▪ Echocardiographic interpretation should first describe the imaging and Doppler findings, along with a differential diagnosis for these findings. The level of confidence in any diagnosis should be indicated.
▪ Second, the interpretation should indicate any areas of uncertainly and suggest additional diagnostic procedures in consultation with the referring physician.

Key Points

□ Complete evaluation of the aorta may require additional imaging procedures, including:
- □ TEE
- □ Chest CT
- Fig. 16.11 TEE long-axis view of the ascending aorta.This view is obtained from a high TEE probe position at about 120° to 140° rotation. The aortic valve, sinuses, sinotubular junction, and ascending aorta are visualized. Only trace aortic regurgitation (arrow) is present on color Doppler flow imaging. Ao, Aorta.
- □ CMR imaging
- □ Cardiac catheterization with aortography
□ Selection of the most appropriate diagnostic modality depends on several clinical factors, including the differential diagnosis, acuity of symptoms, concurrent diseases, and local expertise in imaging.

Transesophageal Echocardiography

Step 1: Aortic Sinuses and Ascending Aorta

▪ Long-axis views of the ascending aorta provide excellent image quality for detection of aortic dilation or dissection.
▪ Short-axis images provide confirmation of findings and are helpful in distinguishing artifact from intraluminal abnormalities.
▪ Color Doppler evaluation of the flow pattern in the aorta helps identify dissection flaps.

Key Points

□ The long-axis view typically is obtained at 120° rotation, but there is individual variability, so the image plane should be adjusted to show the ascending aorta in a long-axis orientation (Fig. 16.11).
□ From the long-axis view, the transducer is moved up in the esophagus to image as much of the ascending aorta as possible.
□ Slow medial and lateral turning of the image plane from the long-axis view may identify abnormalities not seen in the centered long-axis view.
□ The short-axis view is used to provide an orthogonal image plane. The short-axis view should be recorded from the aortic valve level to as high as possible in the ascending aorta (Fig. 16.12).
□ Color Doppler in long- and short-axis views may show flow in two lumens when a dissection is present.
□ The mid- and distal ascending aorta may be better seen by decreasing the rotation to about 100° and slightly withdrawing the probe.
Fig. 16.12 Aortic dissection.In a long-axis TEE view (left), the ascending aorta is dilated with a linear echo in the lumen with undulating motion in real time consistent with a dissection flap. Color Doppler (right) shows an eccentric jet of aortic regurgitation with a vent contracta width of 4 mm. The cause of valve regurgitation most likely is dilation of the sinotubular junction, distorting the normal aortic commissural relationships. Ao, Aorta.
□ The distal ascending aorta just proximal to the arch is often not well seen due to the interposed air column (trachea) between the esophagus and aorta.
□ Imaging artifacts commonly seen in the ascending aorta often include linear reverberations from the aorta itself or adjacent structures. Artifacts are distinguished from anatomic abnormalities by examination in at least two imaging planes; their location, appearance, and pattern of motion relative to the aortic wall; and correlation with color Doppler flow patterns.

Step 2: Aortic Valve Anatomy and Function

▪ The presence of aortic valve disease prompts careful evaluation for associated disease of the aortic sinuses and ascending aorta (Tables 16.1 and 16.2).
▪ Conversely, aortic disease may result in secondary aortic valve regurgitation.

Key Points

□ The risk of aortic dilation and dissection is higher in patients with a congenitally bicuspid or unicuspid valve, compared with those with a trileaflet valve (Fig. 16.13).
□ Aortic disease may result in aortic regurgitation either due to dilation of the aortic sinuses and central non-coaptation of the leaflets or due to extension of a dissection flap into the valve, resulting in a flail leaflet.
□ Aortic valve anatomy and function is evaluated with 2D imaging and color Doppler in a long-axis view at about 120° rotation and in the short-axis view at about 30° rotation.
□ Additional scanning medially and laterally from the long-axis view and superiorly and inferiorly from the short-axis view also is helpful.

Step 3: Descending Thoracic Aorta

▪ The descending thoracic aorta is well visualized on TEE by turning the image plane posteriorly.
▪ The short-axis view is recorded with the transducer slowly withdrawn from the transgastric level to the high esophagus (Fig. 16.14).
▪ The aortic arch is visualized from the high TEE position by turning the image plane medially with inferior angulation.

Key Points

□ Long-axis views of the descending aorta supplement short-axis views and are helpful for evaluation of any abnormal findings. However, the long-axis view alone may miss abnormalities that are located medial and lateral to the image plane.
□ Color flow provides visualization of flow in the true and false lumens when dissection is present.
□ Color flow also is helpful in distinguishing image artifacts from dissection flaps and atheroma.
□ When the aorta is tortuous, care is needed to distinguish intraluminal abnormalities from an oblique image plane.

TABLE 16.1

Normal Echocardiographic Valve Annulus and Great Vessel Dimensions in Adults
Range	Range	Indexed to Body Surface Area	Upper Limit of Normal Aorta (End-Diastole)∗
Annulus diameter (cm)	1.4–2.6	1.3±0.1 cm/m²	<1.6 cm/m²
Diameter at leaflet tips (cm)	2.2–3.6	1.7±0.2 cm/m²	<2.1 cm/m²
Ascending aorta diameter	2.1–3.4	1.5±0.2 cm/m²
Arch diameter (cm)	2.0–3.6
Mitral Annulus
End-diastole (cm)	2.7±0.4
End-systole (cm)	2.9±0.3
Pulmonary Artery
Annulus diameter (cm)	1.5–2.1
Main PA (cm)	0.9–2.9
Inferior Vena Cava Diameters
(1-2 cm from RA junction) (cm)	Normal <1.7 cm

Data from: Roman MJ, Devereux RB, Kramer-Fox R, O’Loughlin J: Two-dimensional echocardiographic aortic root dimensions in normal children and adults, Am J Cardiol 64(8):507-512, 1989; Pini R, Roman MJ, Kramer-Fox R, Devereux RB: Mitral valve dimensions and motion in Marfan patients with and without mitral valve prolapse. Comparison to primary mitral valve prolapse and normal subjects, Circulation 80(4):915-924, 1989; Schnittger I, Gordon EP, Fitzgerald PJ, Popp RL: Standardized intracardiac measurements of two-dimensional echocardiography, J Am Coll Cardiol 2(5):934-938, 1983; Kircher BJ, Himelman RB, Schiller NB: Noninvasive estimation of right atrial pressure from the inspiratory collapse of the inferior vena cava, Am J Cardiol 66:493-496, 1990.

TABLE 16.2

Normal Aortic Root Diameters by Age
Normal aortic root diameter by age for men with BSA of 2.0 m²
	Age (y)
	15–29	30–39	40–49	50–59	60–69	≥70
Mean normal (cm)	3.3	3.4	3.5	3.6	3.7	3.8
Upper limit of normal (cm) (95% CI)	3.7	3.8	3.9	4.0	4.1	4.2
Add 0.5 mm per 0.1 m² BSA above 2.0 m² or subtract 0.5 mm per 0.1 m² BSA below 2.0 m². BSA, Body surface area; CI, confidence interval.

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Apr 23, 2020 | Posted by admin in CARDIOLOGY | Comments Off

Key Points

Step 1: Record Blood Pressure

Key Points

Step 2: Aortic Sinuses and Ascending Aorta

Key Points

Step 3: Descending Thoracic Aorta

Key Points

Step 4: Proximal Abdominal Aorta

Key Points

Step 5: Aortic Arch

Key Points

Step 6: Decide if TEE or Other Imaging Procedures Are Needed

Key Points

Key Points

Key Points

Key Points

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Thoracic Key

Fastest Thoracic Insight Engine

Diseases of the Great Arteries

Diseases of the Great Arteries

Basic Principles

Step-By-Step Approach

Transthoracic Echocardiography

Transesophageal Echocardiography

Step 1: Aortic Sinuses and Ascending Aorta

Step 2: Aortic Valve Anatomy and Function

Step 3: Descending Thoracic Aorta

Full access? Get Clinical Tree

Thoracic Key

Fastest Thoracic Insight Engine

Diseases of the Great Arteries

Basic Principles

Key Points

Step-By-Step Approach

Transthoracic Echocardiography

Step 1: Record Blood Pressure

Key Points

Step 2: Aortic Sinuses and Ascending Aorta

Key Points

Step 3: Descending Thoracic Aorta

Key Points

Step 4: Proximal Abdominal Aorta

Key Points

Step 5: Aortic Arch

Key Points

Step 6: Decide if TEE or Other Imaging Procedures Are Needed

Key Points

Transesophageal Echocardiography

Step 1: Aortic Sinuses and Ascending Aorta

Key Points

Step 2: Aortic Valve Anatomy and Function

Key Points

Step 3: Descending Thoracic Aorta

Key Points

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