Approach to Intervention in Type B Aortic Dissection on CT Angiography
In type B aortic dissection, the decision to intervene depends on identifying specific high-risk features on CT angiography: emergency TEVAR is indicated for complicated dissection (malperfusion, rupture, rapid expansion, intractable pain), while uncomplicated cases receive medical management with consideration for subacute TEVAR (14-90 days) if high-risk anatomical features are present. 1
CT Angiography Analysis Framework
When reviewing the CT angiogram, systematically evaluate for features that determine management:
Immediate Intervention Required (Complicated Dissection)
Emergency TEVAR is the first-line therapy when CT demonstrates: 1
- Rupture signs: Periaortic or mediastinal hematoma, hemothorax, or contrast extravasation 1, 2
- Malperfusion syndrome: Visceral vessel involvement (mesenteric, renal, iliac arteries showing compromised flow from true lumen compression), limb ischemia, or spinal cord ischemia 1, 2
- Rapid aortic expansion: Progressive enlargement on serial imaging despite medical therapy 1, 2
- Dissection in pre-existing aneurysm: Dissection occurring within a previously aneurysmatic aorta 2
High-Risk Features Warranting Subacute TEVAR (14-90 Days)
For uncomplicated acute dissections, identify anatomical features that predict adverse outcomes: 1
- Maximum aortic diameter: ≥40 mm in the acute phase suggests higher rupture risk 1
- False lumen characteristics: Patent false lumen with diameter >22 mm, complete false lumen thrombosis paradoxically may indicate higher risk 1
- Entry tear location: Proximal descending aorta tears (within 2 cm of left subclavian) have worse prognosis 1
- Extent of dissection: Extension into abdominal aorta involving visceral vessels 1
The 2024 ESC guidelines recommend considering TEVAR in the subacute phase (14-90 days) for uncomplicated dissections with these high-risk features, as this timing balances intervention benefits against acute-phase risks. 1
Medical Management Criteria (Uncomplicated Dissection)
CT findings supporting conservative management include: 1
- Stable aortic diameter: <40 mm without rapid expansion 1
- Preserved true lumen flow: Adequate perfusion to all branch vessels 1
- Absence of complications: No rupture, malperfusion, or periaortic hematoma 1
- Distal entry tear location: Tears beyond proximal descending aorta 1
These patients require aggressive anti-impulse therapy targeting systolic BP <120 mmHg and heart rate ≤60 bpm with IV beta-blockers (labetalol preferred), transitioning to oral agents after 24 hours. 1, 2
Chronic Dissection Thresholds
For chronic type B dissection (>90 days), CT measurements guide intervention: 1
- Descending thoracic aortic diameter ≥60 mm: Treatment recommended in reasonable surgical risk patients 1
- Diameter ≥55 mm: Consider intervention in low procedural risk patients 1
- Acute symptoms: Emergency intervention for new malperfusion, rupture, or rapid progression regardless of diameter 1
Critical Pitfalls to Avoid
Never use vasodilators without prior beta-blockade, as reflex tachycardia increases aortic wall shear stress and propagates dissection. 1, 2, 3 If beta-blockers alone fail to control BP, add IV sodium nitroprusside or dihydropyridine calcium channel blockers only after adequate beta-blockade. 1
Measure blood pressure in both arms to rule out pseudo-hypotension from brachiocephalic trunk involvement—place arterial line in right radial artery unless brachiocephalic involvement suspected. 1, 2
In cases of malperfusion, higher MAP may be necessary to optimize perfusion to threatened organs, even if this exceeds standard BP targets of 100-120 mmHg. 1, 2 The priority shifts to restoring end-organ perfusion over strict hemodynamic control.
Surveillance Protocol
All type B dissections require serial imaging regardless of initial management: 1, 3