Aortic Dissection and Acute Aortic Syndromes

25.1Definition and presentation

Acute aortic syndrome spans three overlapping, life-threatening entities that share this presentation and follow the same anatomic decision logic: classic dissection, an intimal flap separating true and false lumens; intramural hematoma (IMH), blood within the aortic media without a demonstrable entry tear; and penetrating aortic ulcer (PAU), an atherosclerotic ulcer eroding through the intima into the media. Dissection is the most common and typically presents with abrupt severe chest, back, or abdominal pain. Clinical risk is elevated when pain is accompanied by specific physical findings indicating propagation or end-organ compromise ACC/AHA 2022 · ESC 2014.

High-risk presenting features include:

• Pulse or pressure deficit.
• New aortic-regurgitation murmur.
• Focal neurological signs.
• Syncope.
• Renal or visceral ischemia.
• Asymmetric limb perfusion.

25.2Diagnosis and classification

Computed tomography angiography of the chest and abdomen is the primary confirmatory study, detailing the intimal flap, true and false lumens, branch-vessel involvement, rupture signs, and disease extent ACC/AHA 2022 · ESC 2014. Transthoracic and transoesophageal echocardiography are bedside alternatives for unstable patients or for immediate assessment of the ascending aorta and valve ACC/AHA 2010.

Disease disposition is determined by the Stanford classification IRAD 2000. Stanford type A involves the ascending aorta. Stanford type B originates distal to the left subclavian artery without ascending involvement. DeBakey terminology defines anatomic extent. Contemporary reporting standards for type B disease add chronicity (acute, subacute, chronic), complication status, entry-tear location, false-lumen status, and branch-vessel consequences to guide endovascular planning Lombardi 2020. These phases run from symptom onset: hyperacute within 24 hours, acute at 1 to 14 days, subacute at 15 to 90 days, and chronic beyond 90 days. Pre-emptive TEVAR is preferentially performed in the subacute window, where it achieves the best balance of aortic remodeling and acceptable procedural rupture risk ACC/AHA 2022.

High-risk features in type A disease include tamponade, severe aortic regurgitation, coronary involvement, neurological injury, and malperfusion. Type B disease is classified as complicated if there is persistent pain, refractory hypertension, rupture, rapid diameter change, or renal, visceral, spinal, or limb malperfusion ACC/AHA 2022 · Lombardi 2020.

Intramural hematoma and penetrating ulcer are identified on the same computed tomography angiogram and staged by the same Stanford system. Intramural hematoma appears as smooth crescentic high-attenuation wall thickening greater than 5 mm without an intimal flap or false-lumen flow, best appreciated as a hyperdense wall on non-contrast images. Penetrating ulcer appears as a focal contrast-filled outpouching projecting through the intima into a heavily atheromatous wall, often with adjacent hematoma. Both are type A when the ascending aorta is involved and type B when confined distal to the left subclavian artery, and both can progress to classic dissection, pseudoaneurysm, or rupture ACC/AHA 2022 · ESVS 2017 · ESC 2014.

25.3Immediate medical therapy

Medical treatment begins immediately upon suspicion of acute dissection to reduce aortic wall shear stress and prevent propagation. Intravenous beta-blockade is the initial pharmacologic intervention ACC/AHA 2022 · ESC 2014 · Liisberg 2025. Vasodilators such as nicardipine or clevidipine are added only after rate control is established; premature vasodilation risks reflex tachycardia and increased physiologic shear stress. Hemodynamic limits are relaxed if suspected malperfusion causes end-organ compromise at standard target pressures.

25.4Treatment decision

Management is dictated by Stanford classification and the presence of complicated features. The objective is to stabilize the aorta and restore perfusion while mitigating the risk of rupture.

The decision sequence for acute presentation is:

1. Stanford classification is assigned based on ascending involvement to determine the need for emergency open repair.
2. Immediate medical rate and pressure control is initiated.
3. Type B patients are assessed for complicated features (malperfusion, rupture, uncontrolled pain) dictating urgent thoracic endovascular aortic repair (TEVAR).
4. Medical therapy alone is continued for uncomplicated type B patients, with suitable cases selected for delayed subacute TEVAR if anatomical features predict high late aneurysmal risk.
5. Open repair is reserved for complicated descending disease unsuitable for endovascular techniques.
6. Intramural hematoma and penetrating ulcer follow the same location-based logic: type A lesions go to urgent open repair, uncomplicated type B lesions are managed medically with surveillance, and complicated or high-risk type B lesions (persistent pain, growth, associated hematoma, or a large or ulcer-like projection) are treated with TEVAR ACC/AHA 2022 · ESVS 2017.

25.5Operative and endovascular management

Emergency open surgery for Stanford type A dissection aims to replace the ascending aorta and control the proximal tear. Concomitant root, valve, coronary, hemiarch, or arch reconstruction is dictated by the entry tear, aortic-regurgitation mechanism, arch involvement, connective-tissue phenotype, and patient reserve Biancari 2023 · IRAD 2000. Survival improves with rapid regionalised surgical care Hemli 2022 · IRAD 2018.

For complicated type B dissection, TEVAR is the default intervention. The procedural steps are sequential: cover the dominant proximal entry tear, expand the true lumen to relieve dynamic malperfusion, and promote false-lumen thrombosis Spinelli 2023 · Nienaber 2011. Adjunctive fenestration, branch stenting, or staged repair is added if primary coverage fails to restore end-organ flow or compromises essential arch vessels Tsai 2007 · Shen 2022. Open repair is reserved for patients unsuitable for endovascular management.

The role of TEVAR in uncomplicated type B dissection involves timing and patient selection. The INSTEAD trial demonstrated no early mortality advantage for TEVAR plus medical therapy over medical therapy alone at 2 years, but the INSTEAD-XL extension showed lower aortic-specific mortality and less disease progression at 5 years in stable patients INSTEAD-XL · 2013 · INSTEAD · 2009. Consequently, early TEVAR is selected in the subacute phase for patients with high-risk anatomical features such as a large total aortic diameter, large false lumen, partial false-lumen thrombosis, or a dominant proximal entry tear, provided the proximal landing zone permits durable coverage without prohibitive arch or spinal risk ACC/AHA 2022 · Weissler 2023 · Jubouri 2022. These features carry numeric thresholds: initial total aortic diameter above 40 mm, false-lumen diameter of 22 mm or more, and a primary entry tear larger than 10 mm, particularly one on the lesser curve near the left subclavian. Partial rather than complete false-lumen thrombosis carries the same elevated late risk ESVS 2017.

25.6Long-term management and surveillance

Long-term outpatient management targets sustained impulse-pressure reduction to prevent late aortic events. Beta-blockade is the primary agent for chronic follow-up ACC/AHA 2022 · ESC 2014 · Liisberg 2025. An angiotensin receptor blocker or ACE inhibitor is layered for refractory hypertension; angiotensin receptor blockers are specifically selected for patients with genetic aortopathy such as Marfan syndrome. Lifestyle modification includes smoking cessation, weight management, and avoidance of high-intensity isometric exertion or competitive contact sports.

Surveillance detects adverse remodelling, aneurysmal degeneration, or malperfusion. Elective repair of a chronic dissection-related descending thoracic or thoracoabdominal aneurysm is indicated once the diameter reaches 55 mm or more, with a lower threshold near 50 mm in patients with heritable thoracic aortopathy such as Marfan syndrome ACC/AHA 2022 · ESC 2014. Cross-sectional imaging, typically computed tomography angiography, is performed at 1 month, 6 months, and 12 months, followed by annual imaging for stable disease ESVS 2017 · IRAD 2018. Magnetic resonance angiography is an alternative for younger patients to limit cumulative radiation and iodinated contrast exposure. Imaging assessment tracks segment diameters, true-lumen caliber, false-lumen patency, new entry tears, and stent-graft integrity. Intervals are shortened immediately if symptoms, diameter growth, malperfusion, or adverse remodelling occur.

25.7Areas of controversy

The optimal application and timing of TEVAR for uncomplicated type B dissection remains debated. Evidence for late aortic benefit is derived from trials (INSTEAD and INSTEAD-XL) enrolling stable subacute and chronic patients, leaving the generalizability of early intervention in acute presentation unsettled INSTEAD-XL · 2013 · INSTEAD · 2009. The ADSORB trial addressed this gap directly, randomizing 61 patients with acute uncomplicated type B dissection to TEVAR plus best medical therapy versus best medical therapy alone; TEVAR improved false-lumen thrombosis and drove favorable aortic remodeling at 1 year but showed no early mortality benefit and was underpowered for hard clinical endpoints Brunkwall 2014. Additionally, while open surgery remains the standard for Stanford type A disease, the role of endovascular repair for selected type A scenarios with ascending involvement continues to evolve, with its indications and long-term durability yet to be definitively established ACC/AHA 2022 · Jiang 2023. The management of type A intramural hematoma is similarly unsettled: Western guidelines favor urgent surgery in line with type A dissection, whereas East Asian series report acceptable outcomes with initial medical therapy and close imaging in selected patients with a small hematoma, no ulcer-like projection, and an aortic diameter below 50 mm ESC 2014.