What is the prognosis of a Stanford type B aortic dissection?

Prognosis of Stanford Type B Aortic Dissection

Stanford Type B aortic dissection carries a significantly better prognosis than Type A, with 30-day mortality of approximately 9-20% for medically managed uncomplicated cases and 1-year survival of 70-85%, though outcomes worsen dramatically when complications develop. 1, 2

Acute Mortality Rates

Uncomplicated Type B dissection managed medically demonstrates:

• 30-day mortality: 8.5-9% 1, 2
• In-hospital mortality: 9% when treated medically 1
• Mortality increases by 1% per hour if left completely untreated, though this rate is lower than Type A dissection 1

Complicated Type B dissection requiring intervention shows:

• 30-day mortality: 20% with thoracic endovascular aortic repair (TEVAR) 2
• Mortality: 20-50% with open surgical repair 3, 2
• Mortality: 65-95% when mesenteric malperfusion develops 4

Long-Term Survival

The prognosis extends beyond the acute phase with notable attrition over time:

• 1-year survival: 70-85% for Type B dissection 1
• 2-year survival: 60-70% 1
• 5-year survival: 56-72% for medically managed patients 2
• 5-year survival: 43.7% for patients requiring TEVAR intervention 2

These survival rates are substantially better than Type A dissection, which shows 1-year survival of only 34-52% even with surgical intervention 1

Prognostic Factors That Worsen Outcomes

High-Risk Anatomic Features

• Complete patency of the false lumen predicts progressive dilatation and rupture 1
• Large false lumen size increases risk of expansion 1
• Maximum aortic diameter ≥40 mm at presentation 1
• Involvement of the aortic arch (without ascending aorta involvement) carries higher mortality than dissection limited to the descending aorta 1

Clinical Complications Requiring Intervention

Approximately one-third of Type B dissections develop complications that transform prognosis from favorable to life-threatening 5:

• Rupture or impending rupture (periaortic/mediastinal hematoma)
• Malperfusion syndromes affecting visceral organs, kidneys, or limbs
• Refractory pain despite optimal medical therapy
• Rapidly expanding aortic diameter
• Inability to control blood pressure medically 6, 7, 8

Patient Factors

• Age >70 years predicts adverse events 1
• Uncontrolled hypertension at presentation 1
• Preoperative renal dysfunction, chronic pulmonary disease, and cerebrovascular disease predict postoperative complications when intervention is required 9

Natural History and Disease Progression

Dissected aortas tend to dilate progressively over time, requiring lifelong surveillance 1:

• The proximal descending thoracic aorta (just beyond the left subclavian artery) is most prone to early and late dilatation 1
• Intervention becomes necessary when the dissected segment expands to ≥6.0 cm or demonstrates rapid growth 1
• Risk of second acute dissection exists, either from the chronic dissection itself or de novo from undissected aorta 1
• Spontaneous healing is rare (occurs in only 4-7% of cases), typically requiring complete thrombosis of the false lumen 1
• Less than 10% of patients show obliteration of the false lumen after intervention 1

Surveillance Requirements

Patients require serial imaging at 1,3,6, and 12 months post-dissection, then annually if stable, to detect threatening enlargement in a timely fashion 1. This applies to both medically managed patients and those with persistent distal dissection following any intervention 1.

Critical Prognostic Distinctions

The key prognostic determinant is whether the dissection remains uncomplicated or develops complications:

• Uncomplicated Type B dissection managed medically has 26.2% re-intervention rate but acceptable long-term survival 2
• Complicated Type B dissection requiring emergency intervention carries 2-10 times higher mortality than uncomplicated cases 2
• Medical management alone for complicated dissection results in mortality rates approaching 50-95% depending on the complication 4, 3

Type B dissection involving only the descending thoracic aorta (DeBakey Type IIIa) has better prognosis than extension below the diaphragm (Type IIIb), though both are managed similarly initially 1.