Aorta

Echo Rounds | Atul Jaidka

Outline

• Anatomy/Measurements
• Aortic Aneurysm
• Acute Aortic Syndromes
• Other Aortic Diseases
• Novel Echo Methods

Why Echo?

ESC Aorta Guidelines

Anatomy/

Measurements

Cardiovascular System

Echo Views

EchoSAP

Echo Views

Echocardiography in aortic diseases: EAE recommendations for clinical practice

Aortic Root + Ascending Aorta

Nagpal, P., Agrawal, M.D., Saboo, S.S. et al. Imaging of the aortic root on high-pitch non-gated and ECG-gated CT: awareness is the key!. Insights Imaging 11, 51 (2020).

ASE Quantification Guideline

Aortic Root + Ascending Aorta

ASE Aorta Guideline

1 = Aortic valve annulus (hinge point of aortic leaflets)

2 = Sinuses of Valsalva

3 = Sinotubular Junction

4 = Proximal tubular portion of the ascending aorta

Aortic Annulus Measurement

ASE Quantification Guideline

• View: PLAX AV Zoom
• Location: Hinge point of AV
• Location: Inner edge - inner edge
• Timing: Mid-systole

Aortic Annulus Measurement Notes

• Annulus is a virtual ring defined by the hinge points of the leaflets
• Much of the ring may not have visible structures
• Location can be approximated by measuring perpendicular to the long axis of the aorta
• Measurement is from the RCC hinge-point to the fibrous trigone between the left and noncoronary cusps, not between two hinge-points

ASE Quantification Guideline

Aortic Annulus Measurement Notes

• Annulus is elliptical but 2D TTE from PLAX measures only anteroposterior diameter
• Major and minor dimensions can be 6mm difference
• Multiple guidelines recommend measurement in a cross sectional view
• This can be done by 3D TEE or CT (TTE spatial resolution not high enough)
• CCS TAVI guidelines recommend CT

ASE Quantification Guideline

Aortic Root Measurement

ASE Quantification Guideline

• View: PLAX AV Zoom
• Location: Largest diameter
• Location: Lead edge - leading edge
• Timing: End-diastole

• Why leading edge to leading edge?
• CT and MRI use inner edge - inner edge
• Echo switch was debated but long standing references are based on leading edge
• Leading edge provides larger diameter (by 2-4mm) and switching may cause a safety issue
• Guidelines (ASE and ESC) still recommend leading edge

Aortic Root Measurement Notes

Aortic Root Measurement Notes

"The NORRE study provides normal values of proximal aorta dimensions as assessed by echocardiography. Reference ranges for different anatomical levels using different (i) measurement conventions and (ii) at different times of the cardiac cycle (i.e. mid-systole and end-diastole) are provided. Age, gender, and body size were significant determinants of aortic dimensions."

Aortic Root Measurement Notes

BSE 2020 Guidelines:

• Aortic dimensions should be measured using 2D imaging from the PLAX window.
• Indices should be obtained using the inner-edge to inner-edge (IE-IE) methodology in end-diastole, defined as the onset of the QRS complex.
• All values should be indexed to height and not BSA.
• For those echo labs that currently employ the leading-edge to leading-edge (LE-LE) technique, it is reasonable to continue doing so for continuity and consistency.
• The BSE suggests that echo labs include the method of assessment within the echo report to ensure transparency for clinicians.

Aortic Root Measurement Notes

BSE 2020 Guidelines:

• "Historical measurements of aortic root size used the LE-LE methodology owing to the poor resolution available at the time."
• "Aortic dimensions are 1.2 mm smaller when using IE-IE compared to LE-LE. The BSE believes that this is unlikely to have a significant impact on clinical decision-making: patients who are close to the cut-off for surgery invariably undergo additional imaging such as CT or MRI."
• "Adult nomograms have some limitations: small sample size, poorly defined ‘normal’ subjects, bias to BSA 

Aortic Root Measurement Notes

• Aortic Root should be measured by 2D echo
• Guidelines recommend not measuring by M-Mode as during the m-mode cardiac motion may result in change of the m-mode cursor relative to the maximal diameter

123sonography

Ascending Aorta Measurement Notes

• Tubular ascending aorta is often not well visualized in usual PLAX view
• Moving tranducer closer to sternum and/or to a higher intercostal space may allow improved visualization of the tubular ascending aorta

Ascending Aorta Measurement Notes

• Right parasternal can also be used to visualize the ascending aorta, especially when dilated
• 2nd or 3rd intercostal space at the right sternal edge (roughly 1 interspace up from PLAX)
• Probe marker at 1 o'clock or left shoulder
• Probe tilted up 45 degrees

Aortic Arch

Kelley JD, Kerndt CC, Ashurst JV. Anatomy, Thorax, Aortic Arch. [Updated 2020 Aug 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.

Aortic Arch

• Best visualized in the SSN
• Aortic arch width better done from TEE
• Assess for dissection, coarctation and flow reversal in descending aorta

ASE Aorta Guideline

Descending Thoracic Aorta

Descending Thoracic Aorta

• Incompletely visualized
• Short axis visible in the PLAX (right)
• Long axis visible in 2 chamber (left) by tilting posteriorly
• Also partially visible in the SSN (previous)
• Measurement best from TEE

EchoSAP

Descending Abdominal Aorta

• Well visualized in subcostal view
• Both longitudinal and transverse planes are useful
• The celiac and superior mesenteric arteries are sometimes visible

EchoSAP

Thoracic Aorta Dilation

Thoracic Aorta Dilation

• Can occur at the level of the root, ascending aorta or any distal segment
• Size varies by age, gender, and BSA
• Nomograms/formulas exist (systematically lower in smaller than in larger normal adults)

ASE Quantification Guidelines

Thoracic Aorta Dilation

• Hypertension does not have much affect on the aortic root size at the level of the sinus of valsalva
• More affected by BSA and Age thus recommended using nomogram

ASE Quantification Guidelines

Thoracic Aorta Dilation

• Degenerative most common: older, athersclerotic risk factors (particularly smoking and hypertension)
• High risk patients:
  • Bicuspid aortic valve
  • Marfan syndrome
  • Familial thoracic aortic disease
  • Ehlers Danlos, Turner Syndrome, Loeys-Dietz

CCS Throacic Aorta Guidelines

Thoracic Aorta Dilation

• Serial imaging to monitor rate of growth
• Serial measurements should be performed using same imaging protocol and modality, in the same lab
• Recommended every 6-12 months depending on aortic size and rate of change
• Role of TTE
  • If dilation only involves root or proximal ascending aorta than TTE reasonable alternative to CT or MRI
  • If diagnosed by TTE, need CT or MRI to visualize entire aorta
• Role of TEE
  • TEE reserved for those with nondiagnostic TTE images

Thoracic Aorta Dilation

• Screening important for patients and family members with genetic aortopathy

CCS Throacic Aorta Guidelines

Acute Aortic Syndromes

Acute Aortic Syndromes

• Aortic Dissection
• Intramural Hematoma
• Penetrating Ulcer
• Aortic Aneurysm Rupture

Aortic Dissection

ASE Aorta Guidelines

Aortic Dissection

• Role of TTE:
  • Sensitivity 85% in Type A dissection thus may be used as initial modality in the emergency room
  • Should not be considered definitive, requires further imaging
  • Sensitivity is low for Type B dissection
• TEE highly accurate for both type A and type B dissections with sensitivity approaching 100%
• First line imaging is still CT as per guidelines but TEE recommended if patient unable to be transferred, nondiagnostic CT or intraoperative imaging when dissection flap seen on TTE

Aortic Dissection

ASE Aorta Guidelines

Case

1. Proximal ascending aorta severely dilated. Consider Type A aortic dissection with dissection flap

evident above Sinus of Valsalva proximally to at least distal ascending aorta / proximal arch distally.

2. The aortic valve is tricuspid.

3. The left ventricular ejection fraction is normal.

4. There is mild to moderate mitral regurgitation.

• Aortic root: 3.5 cm (F<3.7 cm and M<4.1cm)
• Ascending aorta: 4.8 cm (F<3.6 and M<3.9cm)

TEE

1. Normal left and right ventricular sizes and global systolic function.
2. Mild aortic sclerosis. Trace aortic regurgitation.
3. Thickened mitral valve leaflets. Mild to moderate mitral regurgitation.
4. No left atrial or left atrial appendage thrombus. Intact atrial septum to colour Doppler.
5. Mildly dilated aortic root (39 mm). Severely dilated ascending aorta (proximal ascending 52 mm).
No dissection flap noted.

CT

Level of the Annulus:                                                            27 x 21 mm
Level of the Sinuses of Valsalva (convexity to commissure):         35 x 36 x 38 mm
Level of the Sinotubular junction:                                             40 x 36 mm
Ascending Aorta at the Level of the Right Pulmonary Artery:          52 x 51 mm
Aortic Arch Proximal to the Origin of the Innominate Artery:           43 x 40 mm
Aortic Arch Proximal to the Origin of the Left Subclavian Artery:      33 x 31 mm
Descending Aorta at the Level of the Right Pulmonary Artery:        30 x 28 mm

CONCLUSION
1. Aneurysmal dilatation of the ascending aorta to 52 mm, it tapers to a normal caliber
2. No evidence for dissection

Case 2

• Linear structure with independent mobility seen in distal aortic arch, with differential flow, consistent with dissection flap. No definite dissection flap seen in abdominal or proximal ascending aorta.
• The aortic root is mildly dilated.
• The proximal ascending aorta is severely dilated.
• The aortic arch is mildly dilated.

Other Aortic Diseases

• Aortic Coarctation
• Sinus of Valsalva Aneurysm
• Aortic Abscesses
• Aorta and Branch Artery Athersclerosis

Sinus of Valsalva Aneurysm

• Rare condition that is either congenital or acquired (ie. infection or trauma)
• NCC and RCC thought to be more likely congenital and LCC acquired
• Characterized by focal outpouching of one of the three sinuses

ASE SoV Position Statement

Sinus of Valsalva Aneurysm

• Management not clear
• Both transcatheter and surgical interventions are possible
• Cutoffs exptrapolated from other aortic cutoffs and whether has ruptured or not

Case 3