Thoracic aortic aneurysm

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Thoracic aneurysms involve the aortic root, ascending aorta, arch or descending thoracic aorta. Cause and location matter: degenerative disease behaves differently from bicuspid-valve aortopathy, Marfan syndrome, Loeys–Dietz syndrome, vascular Ehlers–Danlos syndrome or Turner syndrome-associated aortic disease.

Serial imaging should use the same modality, landmarks and measurement convention where possible. Growth is interpreted alongside absolute size, indexed size, family history and the precision of the technique rather than from one isolated number.

Elective thresholds are not one-size-fits-all. A multidisciplinary aortic team should individualise intervention and pregnancy advice; open surgery remains standard for many root/ascending lesions, while thoracic endovascular aortic repair is often considered for suitable descending disease.

Key points

Thoracic aortic aneurysm is usually silent and found on echocardiography, CT or MRI; symptoms may reflect compression, valve disease or impending complication.
Confirm the involved segment and obtain reproducible orthogonal measurements; echocardiography assesses the root/ascending aorta and valve, while CT or MRI maps the whole thoracic aorta.
At diagnosis, look for bicuspid aortic valve, coarctation, syndromic features and a family history of thoracic aneurysm, dissection or sudden unexplained death.
The 2024 ESC guideline recommends surgery for an ascending aortic aneurysm at a maximal diameter of at least 55 mm in the usual non-heritable setting.
Lower intervention thresholds may apply in heritable aortopathy, bicuspid valve with additional risk factors, rapid growth, pregnancy planning, small body size or when valve surgery is already planned.
A symptomatic aneurysm or rapid enlargement needs expedited aortic-team review regardless of a routine surveillance date.
Control blood pressure, stop smoking and avoid extreme isometric strain; the specific drug and target must reflect comorbidity and any genetic syndrome.
Acute dissection is a time-critical separate pathway: do not label sudden pain as a stable aneurysm symptom.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Degenerative aortic disease

Ageing, hypertension and smoking promote loss of elastic tissue and medial degeneration. Repeated pulsatile stress then favours enlargement, particularly in otherwise non-heritable thoracic aneurysm.

Bicuspid valve or coarctation

Bicuspid aortic valve and coarctation are associated with abnormal wall biology and altered flow. Either finding increases concern for root or ascending aortic enlargement.

Heritable aortopathy

Marfan, Loeys–Dietz, vascular Ehlers–Danlos, Turner syndrome and related familial disorders alter connective tissue or aortic geometry, increasing the risk of enlargement or dissection, sometimes at a younger age or smaller aortic diameter.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Medial weakening
Fragmentation of elastic fibres, smooth-muscle loss or abnormal connective tissue reduces the aortic wall’s ability to withstand cyclic pressure and shear stress.
2
Progressive dilatation
The weakened segment enlarges under pulsatile load. Increasing radius raises circumferential wall stress, encouraging further expansion and making serial growth clinically important.
3
Local anatomical effects
Root enlargement can prevent aortic leaflet coaptation and cause regurgitation, while arch or descending aneurysms may compress neighbouring airway, oesophagus or recurrent laryngeal nerve.
4
Wall failure
An intimal tear can split blood through the media as a dissection, whereas full-thickness failure causes rupture. Either event can abruptly compromise circulation and branch vessels.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Incidental dilatation

An enlarged root or ascending/descending thoracic aorta on echo, CT or MRI without attributable symptoms.

Compression or valve symptoms

Chest discomfort, hoarseness, cough, dysphagia, breathlessness or heart-failure features may reflect mass effect or aortic regurgitation; alternative causes remain common.

Heritable aortopathy

Young age, tall habitus or syndromic features, arterial tortuosity, hypertelorism, translucent/hyperextensible skin, bicuspid valve, coarctation or affected relatives should prompt specialist genetics/aortopathy assessment.

Acute aortic syndromeRed flag

Abrupt maximal-at-onset chest/back pain, migrating pain, pulse deficit, focal neurology, syncope, shock or new diastolic murmur requires emergency assessment.

Rapid changeRed flag

New symptoms or credible interval enlargement beyond expected measurement variability should trigger earlier cross-sectional imaging and aortic-team review.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

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
Transthoracic echocardiographyFirst step
Why
Measure the root/proximal ascending aorta and assess aortic valve morphology, regurgitation and LV response.
Interpretation and limitations
Useful for serial proximal measurements; incomplete visualisation of the arch/descending aorta requires CT or MRI.
02
ECG-gated CT angiography
Why
Map the whole aorta and branch anatomy with high spatial resolution; evaluate acute aortic syndrome and plan intervention.
Interpretation and limitations
Measure perpendicular to the centreline and document segment, maximal diameter and comparison; weigh iodinated contrast/radiation against urgency.
03
Cardiovascular MRI
Why
Radiation-free serial imaging and assessment of the entire thoracic aorta and flow/valve function.
Interpretation and limitations
Particularly useful for younger patients and repeated follow-up when stable; availability and implanted-device compatibility may limit use.
04
Family history, examination and genetic testing pathway
Why
Identify heritable thoracic aortic disease and relatives needing screening.
Interpretation and limitations
A pathogenic variant can alter surgical and family-screening thresholds; a negative panel does not erase a strong clinical pedigree.
05
Baseline renal function, ECG and operative-risk assessment
Why
Prepare for contrast imaging and possible repair, and identify cardiovascular comorbidity.
Interpretation and limitations
Results modify imaging and procedural strategy, not the diagnosis itself.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Acute aortic dissection

Abrupt maximal-at-onset chest or back pain, pulse deficit, neurological signs, shock or new aortic regurgitation suggests an acute aortic syndrome rather than stable aneurysm.

Acute coronary syndrome

Pressure-like chest pain with territorial ECG change and a dynamic troponin pattern supports myocardial ischaemia, although coronary malperfusion can also complicate dissection.

Pulmonary embolism

Pleuritic pain, hypoxaemia, tachycardia and right-heart strain point towards pulmonary embolism. Appropriate cross-sectional imaging distinguishes pulmonary arterial obstruction from aortic enlargement.

Mediastinal mass

A widened mediastinum, cough, hoarseness or dysphagia may reflect tumour or lymphadenopathy. Contrast CT defines whether the abnormal contour is vascular or solid tissue.

Isolated aortic regurgitation

A primary leaflet lesion can cause a diastolic murmur and left-ventricular dilatation without root aneurysm. Echocardiography defines valve morphology and proximal aortic dimensions.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01emergencyPossible acute aortic syndromeFirst stepSudden severe chest/back pain or aneurysm plus neurological, perfusion, valve or shock features.

1First: immediate ABC assessment, monitoring, IV access, analgesia and senior cardiothoracic/vascular contact.
2Next: urgent ECG-gated CTA from chest through the aorta when feasible; use TOE/MRI only when clinically appropriate and without harmful delay.
3Next: begin monitored anti-impulse therapy under the acute aortic team when hypertensive, generally controlling heart rate before adding vasodilation.
4EscalationEscalation: type A dissection requires emergency surgical evaluation; complicated type B disease needs urgent specialist endovascular/surgical assessment.

02new findingNew asymptomatic thoracic dilatationThoracic aorta enlarged on echo or cross-sectional imaging.

1First: confirm segment and diameter with appropriate echo plus CT or MRI of the full aorta.
2Next: assess valve, BP, smoking, coarctation, syndromic signs and a three-generation aortic/sudden-death history.
3Next: refer to an aortic clinic to set a modality- and cause-specific surveillance interval.
4EscalationEscalation: genetics review for young onset, syndromic features or familial disease; earlier aortic-team review for symptoms or growth.

03electiveIntervention decisionLarge, enlarging or symptomatic aneurysm, or a high-risk genetic/valve context.

1First: confirm diameter and growth with high-quality gated CT or MRI and review indexed size where body size is relevant.
2Next: in usual ascending aneurysm, surgery is recommended at at least 55 mm; do not transfer this threshold uncritically to heritable disease.
3Next: consider lower thresholds for genetic syndrome—including Turner syndrome-associated aortic disease—bicuspid valve plus risk factors, rapid growth, family dissection, pregnancy planning or concomitant valve surgery.
4EscalationEscalation: discuss at a multidisciplinary aortic team with shared decision-making on open, valve-sparing or endovascular options.

04surveillanceStable aneurysm follow-upBelow an intervention threshold and without acute features.

1First: record the same anatomical landmarks and measurement convention for every study.
2Next: optimise BP and other CVD risks; advise smoking cessation and avoidance of extreme straining/heavy isometric lifting.
3Next: repeat imaging at the specialist-set interval, sooner when close to a threshold or growth is suspected.
4EscalationEscalation: bring review forward for new pain, valve symptoms, pregnancy plans or interval enlargement.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Blood-pressure and impulse control when appropriate; especially considered in some heritable aortopathies.

Beta-blocker (example: bisoprolol)

For the licensed hypertension indication, a typical bisoprolol regimen starts at 5 mg orally once daily; the usual dose is 10 mg once daily and the SmPC maximum is 20 mg once daily. An aortopathy specialist may select a lower start according to heart rate and BP.

Individualise to heart rate and comorbidity; avoid or use specialist caution with marked bradycardia, heart block, decompensated heart failure or severe bronchospasm. Do not exceed 10 mg/day in severe renal or hepatic impairment under the cited SmPC. This is not acute-dissection dosing.

Hypertension treatment; may be selected in heritable aortopathy under specialist care.

Losartan

50 mg orally once daily, increased to 100 mg once daily if required and tolerated.

Monitor creatinine/eGFR and potassium; avoid in pregnancy and do not combine routinely with an ACE inhibitor.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Dissection

Blood entering through an intimal tear can separate the medial layers and create a false lumen that may propagate rapidly, obstruct branch vessels, cause severe aortic regurgitation or rupture into the pericardium.

Free rupture

Full-thickness wall failure causes catastrophic haemorrhage into the pleural space or mediastinum; proximal rupture may instead produce haemopericardium and cardiac tamponade.

Aortic regurgitation and heart failure

Progressive root dilatation separates otherwise normal valve leaflets, creating chronic volume overload. Acute root disruption can cause sudden severe regurgitation, pulmonary oedema and shock.

Compression syndromes

An enlarging arch or descending aneurysm can compress the recurrent laryngeal nerve, tracheobronchial tree or oesophagus, producing hoarseness, cough, breathlessness or dysphagia.

Branch-vessel ischaemia

Extension of dissection across coronary, cerebral, renal, mesenteric or limb arteries can interrupt perfusion, presenting as infarction, stroke, abdominal pain, kidney injury or limb ischaemia.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Document maximal diameter by segment, modality, cardiac phase and measurement convention.
Use the same imaging technique where possible; shorten intervals near a threshold or if growth is suspected.
Monitor clinic and home/ambulatory BP as appropriate, plus heart rate and postural symptoms after treatment changes.
Review aortic valve function, LV size/function and symptoms when root/ascending disease coexists with valve disease.
Revisit family screening, genetic results, pregnancy plans and exercise advice as circumstances change.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Segment-specific imaging

A reassuring proximal echo cannot exclude arch or descending disease; image the complete aorta at baseline.

Indexing can change concern

A 50 mm aorta has different implications in a very small adult and a very large adult; aortic teams may use indexed measures alongside absolute diameter.

Cause changes threshold

The familiar 55 mm threshold applies to usual ascending disease, not automatically to Marfan, Loeys–Dietz, vascular Ehlers–Danlos, Turner syndrome-associated aortic disease or pregnancy planning.

Family history is an investigation

First-degree relatives with dissection or sudden unexplained death can materially change surveillance and genetics decisions.

Growth needs confirmation

Small apparent changes across different scanners or conventions may be noise; confirm surprising growth without delaying review when symptoms are present.

11Common pitfallsFrequent interpretation and management errors.

01
Using 55 mm as a universal threshold for every thoracic aortopathy.
02
Following only the aortic root on echo when the rest of the thoracic aorta has never been mapped.
03
Calling abrupt severe pain an uncomplicated aneurysm symptom instead of activating an acute aortic pathway.
04
Comparing measurements made in different planes or cardiac phases as if they were identical.
05
Omitting genetic and first-degree-relative assessment in young or familial disease.