📚 Guideline basis
Isselbacher EM, Preventza O, Hamilton Black J, et al. 2022 ACC/AHA guideline for the diagnosis and management of aortic disease (Circulation 2022;146:e334–482); Goldstein SA, et al. ASE/EACVI recommendations for multimodality imaging of diseases of the aorta (JASE 2015;28:119–82); 2014 ESC guidelines on aortic diseases; Hahn RT, et al. comprehensive TEE examination (JASE 2013).
Measurement conventions — state which one you used
Two conventions coexist and they differ by approximately 2 mm, which is clinically meaningful at surgical thresholds.
Convention | Source | Application |
Leading edge to leading edge, at end-diastole | Historical echocardiographic standard (ASE 2015) | Most published echocardiographic thresholds derive from this |
Inner edge to inner edge | Advocated by the 2022 ACC/AHA guideline for consistency with CT and MRI | Aligns echocardiography with cross-sectional imaging, on which surgical decisions are usually made |
The report must state which convention was used. Serial surveillance that switches convention generates a spurious 2 mm "growth" and can trigger an unnecessary operation.
Measure perpendicular to the long axis of the vessel at defined levels: aortic annulus (mid-systole, inner edge to inner edge, by convention), sinuses of Valsalva, sinotubular junction, mid-ascending aorta, arch, and descending aorta. Index to body surface area and height where borderline.
Reference thresholds
Dimension | Significance |
Ascending aorta > 4.0 cm | Dilated; warrants surveillance |
≥ 4.5 cm | Closer surveillance; lower intervention threshold in bicuspid aortopathy and heritable thoracic aortic disease |
≥ 5.5 cm | Conventional surgical threshold for degenerative ascending aneurysm |
≥ 5.0 cm | Threshold in Marfan syndrome and some other heritable conditions, and at lower diameters with adverse features |
Rapid growth (> 0.5 cm/year) | Independent indication for intervention |
These are ambulatory surgical thresholds; their relevance in the ICU is chiefly to identify the patient in whom an acute aortic syndrome is plausible and to communicate accurate dimensions to the surgical team.
Acute aortic syndromes
Three entities on a continuum, all presenting identically:
Entity | Pathology |
Aortic dissection | Intimal tear with propagation of blood into the media, creating true and false lumina |
Intramural haematoma | Haemorrhage within the media without a demonstrable intimal tear; a crescentic thickening of the wall |
Penetrating atherosclerotic ulcer | Ulceration through the internal elastic lamina, often with adjacent intramural haematoma |
The Stanford classification governs management: type A involves the ascending aorta and is a surgical emergency; type B does not, and is managed medically unless complicated.
The limits of transthoracic echocardiography
TTE cannot exclude type A dissection. Its sensitivity is inadequate, and a normal transthoracic study in a patient with a compatible presentation must not close the pathway.
What TTE contributes:
Finding | Value |
Dilated aortic root or ascending aorta | Raises probability |
Intimal flap in the root or arch (PLAX, suprasternal) | Specific when unambiguous |
New aortic regurgitation | Present in a substantial proportion of type A dissections |
Pericardial effusion | Suggests retrograde rupture — a marker of extreme urgency |
Regional wall motion abnormality | Coronary ostial involvement, most often the right |
Abdominal aortic imaging | May show the flap extending distally |
The combination of chest pain, a new diastolic murmur, and a pericardial effusion is type A dissection until disproven, whatever the transthoracic images show.
Transesophageal echocardiography for dissection
TEE achieves sensitivity and specificity approaching CT angiography for the ascending aorta, arch and descending aorta, and it can be performed on a patient too unstable to travel.
The blind spot
Air in the trachea and left main bronchus interposes between the oesophagus and the distal ascending aorta and proximal arch. This segment is not reliably visualised. A TEE report that concludes "no dissection" without acknowledging this limitation is incomplete, and the omission has clinical consequences.
Distinguishing a true flap from artefact
This is the highest-stakes artefact problem in the book (Chapter 3).
Feature | True dissection flap | Reverberation / side-lobe artefact |
Motion | Independent, out of phase with the aortic wall | Moves with the aortic wall |
Colour Doppler | Interrupts flow; differential flow in the two lumina | Colour crosses it freely, undisturbed |
Persistence | Present in two orthogonal planes and across gain settings | Disappears on rotation or gain change |
Geometry | Anatomically plausible; arises from an intimal tear | Often at twice the depth of a strong reflector; extends beyond the vessel wall |
M-mode | Rapid, independent oscillation | Motion locked to the wall |
True versus false lumen
Feature | True lumen | False lumen |
Size | Usually smaller, expands in systole | Usually larger |
Flow | Systolic antegrade, higher velocity | Slow, delayed, or absent; spontaneous echo contrast common |
Thrombus | Rare | Common |
Relationship to the flap | The flap bows away from the true lumen in systole | — |
Features determining surgical urgency
- Ascending aortic involvement — type A
- Aortic regurgitation and its mechanism — annular dilatation, cusp prolapse from flap prolapse, or flap prolapse into the LVOT; the mechanism determines repair versus replacement
- Pericardial effusion or tamponade — retrograde rupture
- Coronary ostial involvement — regional wall motion abnormality
- Entry tear location and extent
- Malperfusion — branch vessel involvement, better assessed on CT
Other ICU aortic problems
Problem | Assessment |
Traumatic aortic injury | Deceleration injury tears preferentially at the isthmus, distal to the left subclavian; CT is the reference standard, TEE the alternative in the untransportable patient (Chapter 37) |
Aortic atheroma | Graded on TEE; mobile plaque or plaque ≥ 4 mm in the arch carries embolic and stroke risk, and is relevant to cannulation and cross-clamp site selection before cardiac surgery |
Post-cardiotomy aortic complications | Dissection at the cannulation or cross-clamp site; new AR; pseudoaneurysm (Chapter 36) |
Device positioning | IABP tip distal to the left subclavian artery, above the coeliac axis; VA-ECMO arterial cannula and its retrograde jet in the descending aorta (Chapter 35) |
Aortic root abscess and pseudoaneurysm | Endocarditis complication; TEE and CT complementary (Chapter 24) |
Coarctation | Suprasternal PW/CW showing a high-velocity jet with diastolic runoff ("sawtooth"); rare as a new ICU diagnosis but a cause of refractory hypertension |
Aortic diastolic flow reversal | Holodiastolic reversal in the proximal descending aorta with end-diastolic velocity ≥ 20 cm/s is a specific sign of severe aortic regurgitation (Chapter 19) |
ICU-Specific Limitations
Confounder | Effect | Response |
Tracheal air (TEE) | Distal ascending aorta / proximal arch blind spot | State the limitation; CT for definitive exclusion |
Poor transthoracic windows | Root and arch not assessable | TEE; do not report exclusion |
Haemodynamic instability during TEE sedation | Dissection patients are frequently borderline | Optimise pressure first; have vasopressor drawn up (Chapter 25) |
Hypertension during imaging | Ongoing propagation risk | Control heart rate and blood pressure before and during imaging — beta-blockade first to reduce dP/dt, then vasodilator |
Reverberation artefact | Mimics or masks a flap | Two planes, colour, gain variation |
Renal impairment | Limits contrast CT | TEE becomes more attractive |
Therapeutic Logic
Finding | Action |
Type A dissection | Emergency surgery. Concurrently: control dP/dt with beta-blockade (target heart rate ~60/min) before adding a vasodilator, to avoid reflex tachycardia and increased shear |
Type A with tamponade | Surgery. Do not drain the pericardium — the tamponade is limiting haemorrhage and drainage can precipitate exsanguination (Chapter 15) |
Type A with acute severe AR | Surgery; intra-aortic balloon pump is contraindicated (Chapter 19) |
Uncomplicated type B | Medical: heart rate and blood pressure control, analgesia, serial imaging |
Complicated type B (malperfusion, rupture, refractory pain or hypertension) | Endovascular repair |
Intramural haematoma of the ascending aorta | Managed as type A in most current guidance |
Traumatic isthmic injury | Endovascular repair, usually after other life-threatening injuries are addressed |
The echocardiographic contribution to type A dissection is not primarily to make the diagnosis — CT usually does that — but to characterise the aortic regurgitation mechanism, the pericardium, and ventricular function, which the surgical team needs and which CT does not provide.
🛑 Critical pitfall: Reporting "no dissection" after a transthoracic study. TTE cannot exclude type A dissection, and this wording will be relied upon.
🛑 Critical pitfall: Reporting "no dissection" after TEE without stating the distal ascending aorta blind spot. Tracheal air makes that segment unreliable.
🛑 Critical pitfall: Draining a pericardial effusion in suspected type A dissection. This converts a contained rupture into an uncontained one.
🛑 Critical pitfall: Switching measurement convention between serial studies. A change from inner-edge to leading-edge measurement fabricates ~2 mm of growth.
- 💡 Clinical pearl: In any hypotensive patient with a new diastolic murmur, image the aortic root and look for a pericardial effusion before anything else. That triad is dissection until proven otherwise.
- 💡 Clinical pearl: A true flap moves independently of the aortic wall and interrupts colour flow. Make the two-plane, colour, gain-variation check reflexive before reporting one.
- 💡 Clinical pearl: Control heart rate and blood pressure before performing the diagnostic study in suspected dissection. The imaging is not more urgent than reducing shear stress, and the sedation for TEE will destabilise the patient if the pressure is uncontrolled.
References
- Isselbacher EM, Preventza O, Hamilton Black J, et al. 2022 ACC/AHA guideline for the diagnosis and management of aortic disease. Circulation 2022;146:e334–482.
- Goldstein SA, Evangelista A, Abbara S, et al. Multimodality imaging of diseases of the thoracic aorta in adults: from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr 2015;28:119–82.
- Erbel R, Aboyans V, Boileau C, et al. 2014 ESC guidelines on the diagnosis and treatment of aortic diseases. Eur Heart J 2014;35:2873–926.
- Hahn RT, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination. J Am Soc Echocardiogr 2013;26:921–64.