01OverviewDefinition, clinical context and the essential points that orientate the chapter.
Thoracic aortic aneurysm is a pathological enlargement of the root, ascending aorta, arch, descending thoracic aorta or a thoracoabdominal segment. A diameter more than 1.5 times predicted is the conventional aneurysm definition, but reporting the measured segment and diameter is more useful than applying one label to every body size. Root and ascending disease is commonly associated with medial degeneration, bicuspid aortic valve or heritable thoracic aortic disease; descending disease more often accompanies age, hypertension and atherosclerosis. Inflammation, infection, trauma and chronic dissection create additional phenotypes.
Most TAAs are incidental. Symptoms arise from expansion, aortic regurgitation, compression or an acute complication: chest or back pain, dyspnoea, hoarseness from recurrent laryngeal nerve compression, dysphagia, superior vena cava obstruction or cough. Rupture and dissection risk rises with diameter but is not determined by diameter alone. Growth, resistant hypertension, saccular shape, penetrating ulcer, family history, pregnancy plans, genetic variant and short stature may justify earlier discussion.
Measurement must be reproducible. TTE assesses the valve, root and proximal ascending aorta, but cannot reliably visualize the distal ascending aorta, arch or descending thoracic aorta. ECG-gated CT gives excellent spatial detail and defines calcification, branch anatomy and the whole aorta; MRI avoids ionizing radiation and is valuable for lifelong follow-up when stable and compatible. Measurements should be perpendicular to the aortic centreline, use the same edge convention and segment, and be compared with the original images rather than report text alone.
Elective thresholds are segment- and disease-specific. ESC 2024 recommends surgery at 55 mm for sporadic root or ascending dilatation with a tricuspid valve and for suitable asymptomatic isolated arch aneurysm. Selected low-operative-risk ascending patients may be considered above 52 mm or at 50 mm with risk modifiers. For non-heritable unruptured descending thoracic aneurysm, elective repair is recommended at 55 mm and TEVAR is preferred when anatomy is suitable; selected high-risk patients may be considered below 55 mm. Degenerative thoracoabdominal aneurysm uses 60 mm, with repair considered from 55 mm for high-risk features or very low procedural risk in expert centres. Marfan, Loeys-Dietz, vascular Ehlers-Danlos, ACTA2-related disease, bicuspid valve and pregnancy require their own gene-, family- and body-size-informed thresholds.
At diagnosis, image again in six to twelve months according to cause and starting size to establish stability. Annual imaging is reasonable when stable, shortened to about six months for rapid expansion or proximity to intervention, and potentially lengthened after years of stability in smaller non-genetic disease. Root or ascending expansion of at least 3 mm per year is a high-risk feature in ESC guidance; descending aneurysm growth at least 10 mm per year or 5 mm in six months is similarly concerning.
Key points
- Thoracic aneurysm risk depends on segment, maximal orthogonal diameter, growth, symptoms, morphology, valve anatomy, genetic cause, body size and operative fitness.
- Sudden severe chest or back pain, collapse, neurological deficit or new aortic regurgitation demands an acute aortic syndrome pathway rather than outpatient surveillance.
- Image the entire aorta at diagnosis and assess the aortic valve; tandem aneurysms and extension across conventional segment labels are common.
- For non-heritable root or ascending aneurysm with a tricuspid valve, ESC recommends repair at 55 mm; selected low-risk patients may be considered earlier.
- Asymptomatic isolated arch aneurysm is generally considered for open repair at 55 mm when operative risk is low.
- Non-heritable descending thoracic aneurysm is repaired from 55 mm, whereas degenerative thoracoabdominal aneurysm uses 60 mm, with 55 mm consideration for high-risk features in expert centres.
- Confirm root or proximal ascending TTE measurements with CT or MR; use CT or MR for distal ascending, arch, descending and thoracoabdominal surveillance.
- Indexing to height or body surface area can refine decisions in unusually small or large adults, but does not replace gene- and segment-specific assessment.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Degenerative and hypertensive disease
Age, hypertension, smoking and atherosclerotic burden predominate in descending thoracic aneurysm and influence competing cardiovascular risk.
Heritable aortopathy
Pathogenic variants and syndromes including Marfan and Loeys-Dietz weaken the media and permit dissection at smaller diameters.
Valve-associated disease
Bicuspid aortic valve can accompany root or ascending dilatation, altered flow and a family pattern of aortopathy.
Secondary wall injury
Chronic dissection, inflammatory aortitis, infection, penetrating ulcer and trauma can produce fusiform, saccular or pseudoaneurysmal enlargement.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Medial degeneration
Elastic fibre fragmentation, smooth-muscle loss and extracellular matrix change reduce aortic tensile strength and promote progressive dilatation.
- 2Wall stress amplification
Increasing radius and arterial pressure increase circumferential stress, while eccentric or saccular geometry may concentrate local mechanical load.
- 3Valve and root interaction
Root enlargement can separate valve commissures and cause aortic regurgitation, volume overload and heart failure before rupture occurs.
- 4Branch and structure compression
Large arch or descending aneurysms can compress airway, oesophagus, recurrent laryngeal nerve or venous structures and distort branch vessels.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Most thoracic aneurysms are found on echocardiography or cross-sectional imaging performed for another clinical question.
Persistent hoarseness, dysphagia, cough, dyspnoea or venous congestion can reflect pressure from an enlarging arch or descending aneurysm.
Aortic regurgitation, murmur or ventricular volume overload with root enlargement may precede pain or acute dissection.
Abrupt severe chest or back pain, syncope, pulse deficit, neurological deficit or shock signals dissection or rupture.
Young presentation, tall or syndromic habitus, arterial tortuosity, hypertelorism, translucent skin or family sudden death supports genetic assessment.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
First-line anatomical study: TTE plus CT or MR confirmationFirst stepFirst line - Why
- Define root, ascending aorta and valve while mapping full aortic extent.
- Interpretation and limitations
- Confirm TTE baseline with ECG-gated CCT or CMR; disagreement of at least 3 mm means cross-sectional imaging should drive follow-up.
- 02
Cardiovascular CT angiography - Why
- Measure the entire aorta and define branches, wall and repair anatomy.
- Interpretation and limitations
- Use centreline-orthogonal diameters and ECG gating proximally; account for radiation and iodinated contrast during repeated surveillance.
- 03
Cardiovascular magnetic resonance - Why
- Provide serial cross-sectional measurements without ionizing radiation exposure.
- Interpretation and limitations
- Useful for stable long-term follow-up, especially younger patients; availability, examination time, implants and motion can limit quality.
- 04
Transthoracic echocardiography - Why
- Assess aortic valve, root, proximal ascending aorta and ventricular response.
- Interpretation and limitations
- Reliable when the same proximal segment is well seen, but ESC advises against using it alone for distal ascending, arch or descending aneurysm.
- 05
Genetic and family assessment - Why
- Identify heritable thoracic aortic disease and at-risk relatives.
- Interpretation and limitations
- Age, syndrome features and family history guide genetic testing; a pathogenic variant can lower intervention thresholds and broaden arterial surveillance.
- 06
Preoperative multidisciplinary assessment - Why
- Balance natural-history risk against cardiac, cerebral, spinal and renal procedural risk.
- Interpretation and limitations
- Segment, anatomy, frailty, life expectancy and centre expertise determine open, hybrid or endovascular suitability rather than diameter alone.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Acute aortic syndrome
Abrupt severe pain, flap, intramural blood or penetrating ulcer indicates an acute wall event rather than uncomplicated stable dilatation.
Mediastinal mass
Malignancy, lymphadenopathy and cysts can widen the mediastinum or compress adjacent structures without continuity with the aortic lumen.
Pulmonary or coronary disease
Pulmonary embolism, acute coronary syndrome and pericarditis may cause chest pain but require parallel urgent testing when clinically plausible.
Aortic tortuosity
Elongation and unfolding can mimic enlargement on a plain radiograph, so orthogonal cross-sectional measurement is needed for diagnosis.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Worked caseAssess an incidental ascending aneurysmFirst stepCross-sectional imaging reports a 51 mm ascending aorta in an otherwise stable adult.+
- 1Confirm the exact segment, valve morphology, centreline-orthogonal maximal diameter and previous growth using original images and a consistent convention.
- 2Elicit pain or compression symptoms, blood pressure, family history, sudden deaths, syndromic features, pregnancy plans and previous aortic or valve surgery.
- 3Obtain TTE for valve and ventricular assessment and complete aortic CT or MR, then refer for multidisciplinary aortic review rather than applying one threshold blindly.
- 4Compare the measurement with the sporadic tricuspid-valve threshold and lower gene-, valve-, family-, growth- or body-size-informed thresholds where applicable.
- 5Arrange repeat imaging in six to twelve months or sooner if risk is high, and verify blood-pressure control, counselling and family or genetic follow-up.
02Emergency presentationExclude acute aortic syndromeA patient with known or possible TAA develops abrupt severe pain, collapse or a new deficit.+
- 1Use ABCDE, monitoring, two large-bore lines, blood tests and immediate cardiothoracic or vascular aortic-team contact.
- 2Obtain urgent ECG-gated CTA from neck to pelvis when feasible while providing analgesia and controlled anti-impulse treatment if dissection is suspected.
- 3DefinitiveDo not wait for outpatient records or surveillance measurements before arranging definitive transfer and repair planning.
03Elective decisionApply segment-specific repair thresholdsSymptoms, rapid growth or diameter brings the aneurysm near a guideline intervention boundary.+
- 1For sporadic tricuspid-valve root or ascending disease, use 55 mm as the standard recommendation while evaluating earlier surgery in selected low-risk or high-risk contexts.
- 2For asymptomatic isolated arch disease consider open repair at 55 mm when operative risk is low and centre expertise is appropriate.
- 3For non-heritable descending thoracic disease use 55 mm, while degenerative thoracoabdominal disease uses 60 mm with 55 mm consideration in selected high-risk expert-centre cases.
- 4Use separate heritable and bicuspid-valve recommendations, indexed size, family events and pregnancy plans before final shared decision making.
04Longitudinal careProve stability with consistent imagingThe aneurysm remains below its individualized threshold without emergency features.+
- 1Repeat imaging at six to twelve months after diagnosis to establish growth, using the same technique and centre when possible.
- 2Continue annual or individualized surveillance, shorten to six months for rapid growth or proximity to repair and consider longer intervals only after sustained low-risk stability.
- 3Control cardiovascular risk, advise prompt emergency attendance for acute symptoms and maintain family or genetic pathways where indicated.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Aortic dissection
An intimal tear or intramural injury can propagate along weakened aorta, compromise branches and cause tamponade or regurgitation.
Free or contained rupture
Wall failure can produce mediastinal, pleural or retroperitoneal haemorrhage with pain, shock and high immediate mortality.
Aortic regurgitation
Root distortion prevents leaflet coaptation, leading to progressive ventricular dilatation or acute haemodynamic collapse if dissection supervenes.
Compression and embolization
Large aneurysms may cause hoarseness, dysphagia or airway symptoms, while mural thrombus can embolize into branch circulation.
Repair-related injury
Open or endovascular repair carries stroke, spinal cord ischaemia, renal injury, bleeding, endoleak and later re-intervention risks.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Record blood pressure and optimize hypertension management through the responsible clinician, because pressure contributes to wall stress and overall cardiovascular risk.
- Measure the same named aortic segments with the same method and compare actual images to distinguish growth from technical variation.
- Reassess symptoms, valve function, ventricular size and new regurgitation alongside diameter when root or ascending disease is present.
- Shorten imaging intervals when growth accelerates, symptoms develop or diameter approaches the individualized repair threshold.
- After repair monitor the residual aorta and procedure-specific complications; replacing one segment does not eliminate disease elsewhere.
- Ensure genetic results, family screening recommendations and pregnancy advice are communicated across primary, cardiac and vascular care.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
Segment determines modality
TTE is useful proximally, whereas distal ascending, arch and descending aneurysms need CT or MR for dependable serial measurement.
Indexing refines risk
Height, body surface area and cross-sectional area can help interpret absolute diameters in very small or large adults.
Growth must be real
A few millimetres may reflect plane, gating or edge convention, so rapid growth requires confirmation with comparable high-quality studies.
Fifty-five is contextual
The familiar 55 mm threshold applies to common sporadic root, ascending and arch contexts, not every gene or thoracic segment.
Whole-aorta disease
Tandem aneurysms and later distal enlargement justify complete baseline imaging and continued surveillance beyond the treated segment.
11Common pitfallsFrequent interpretation and management errors.
- 01
Do not use one diameter threshold for root, arch, descending, thoracoabdominal, bicuspid-valve and heritable aneurysms.
- 02
Do not rely on TTE to follow the distal ascending aorta, arch or descending thoracic aorta.
- 03
Do not diagnose rapid growth from measurements made in different planes or with inconsistent edge conventions without image review.
- 04
Do not overlook family history, syndromic features, pregnancy plans or short stature when interpreting an apparently subthreshold diameter.
- 05
Do not reassure from absence of pain because most thoracic aneurysms remain silent until complication.
- 06
Do not stop surveillance after segmental repair because residual native aorta remains at risk.