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Aortic Dissection and Acute Aortic Syndromes

TL;DR — Acute aortic dissection is the main lethal endpoint of TAA. It is classified anatomically (Stanford A/B by ascending involvement; DeBakey I/II/III by origin and extent) because anatomy dictates therapy: type A is a surgical emergency, type B is managed medically unless complicated (Daily 1970, PMID 5458238; DeBakey 1965, PMID 14261867; Hagan 2000, PMID 10685714). IRAD, the field's defining registry (>7,300 patients since 1996), shows a diverse, often classic-sign-free presentation, in-hospital mortality of 27% overall in the first report, and — over 17–20 years — rising CT diagnosis, near-universal surgery for type A (mortality 31%→22%), and growth of TEVAR for type B (7%→31%) without change in type B hospital mortality (Hagan 2000, PMID 10685714; Pape 2015, PMID 26205591; Evangelista 2018, PMID 29685932). Most type A dissections occur below surgical size thresholds (59% <5.5 cm), the "aortic size paradox" (Pape 2007, PMID 17709637). Intramural hematoma and penetrating ulcer are flap-free variants — older, hypertensive, descending-predominant, and rupture-prone (Coady 1999, PMID 10589337). After the acute phase, the dissected aorta degenerates aneurysmally in most medically managed patients (73% aortic growth/new aneurysm at 5 years), driven by false-lumen patency (Fattori 2013, PMID 23968705; Tsai 2007, PMID 17652650).

Classification

Anatomic systems

System Category Definition Origin paper
DeBakey I Entry tear in ascending aorta; dissection extends to arch and typically beyond (DeBakey 1965, PMID 14261867)
DeBakey II Confined to the ascending aorta (DeBakey 1965, PMID 14261867)
DeBakey III Originates in the descending aorta (distal to left subclavian), extending distally (DeBakey 1965, PMID 14261867)
Stanford A Any involvement of the ascending aorta, regardless of entry-tear site (≈ DeBakey I + II) (Daily 1970, PMID 5458238)
Stanford B Ascending aorta not involved (≈ DeBakey III) (Daily 1970, PMID 5458238)

The Stanford scheme won clinically because it maps one-to-one onto management: ascending involvement → operate; not involved → medical therapy first (Daily 1970, PMID 5458238; Isselbacher 2022, PMID 36334952). In IRAD, 62.3% of dissections were type A (Hagan 2000, PMID 10685714); in population-based Olmsted data 85% involved the ascending aorta (Clouse 2004, PMID 14959911); pooled population incidence is ~3.0/100,000/yr (type A) vs ~1.6 (type B) (Gouveia e Melo 2022, PMID 34560218).

Temporal and syndromic

  • Acute vs chronic: the classical convention defines "acute" as the first 2 weeks after symptom onset and "chronic" as beyond 2 weeks; IRAD investigators proposed a finer 4-type scheme (hyperacute <24 h, acute 2–7 d, subacute 8–30 d, chronic >30 d), and SVS/STS reporting standards define a similar contemporary 4-type temporal classification (Isselbacher 2022, PMID 36334952; Lombardi 2020, PMID 32001058). IRAD analyses and the outcome trends on this page concern dissections presenting acutely (Evangelista 2018, PMID 29685932).
  • Acute aortic syndrome (AAS) spans classic dissection, intramural hematoma (IMH), and penetrating atherosclerotic ulcer (PAU) — clinically similar chest/back-pain emergencies with distinct imaging anatomy (Coady 1999, PMID 10589337; Evangelista 2018, PMID 29685932).

Acute aortic syndrome variants: IMH and PAU

Yale re-review of 214 imaging studies initially read as dissection found 36 (>1 in 8) were flap-free variants — "no flap, no dissection" (Coady 1999, PMID 10589337).

Feature Classic dissection IMH PAU
Defining lesion Intimal flap + double lumen Aortic-wall hematoma without flap or ulcer crater Ulcer crater penetrating from lumen through intima, usually atherosclerotic
Mean age 56.5 yr (type A) 73.9 yr 74.0 yr
Hypertension common ~94% ~94%
Location ascending or descending 71% descending 90% descending
Aortic size at event 5.2 cm 5.5 cm 6.2 cm
Branch-vessel ischemia characteristic absent absent
Associated AAA — 29.4% 42.1%
Sources (Coady 1999, PMID 10589337) (Coady 1999, PMID 10589337) (Coady 1999, PMID 10589337)
  • PAU (Yale series, 15/198 initially diagnosed as dissection = 7.6%): mean age 76.6, mean diameter 6.5 cm, 86.7% descending; rupture occurred in 40% vs 7% (type A) and 3.6% (type B) classic dissection — a more, not less, dangerous lesion (Coady 1998, PMID 9652462).
  • IMH of the descending aorta (IRAD): vs classic type B dissection, IMH-B patients were older (69 ± 12 vs 63 ± 14), more often had periaortic hematoma (22% vs 13%), were managed medically in 88% (vs 62%), with in-hospital mortality 7% vs 11% (NS) and less late aortic enlargement (39% vs 61%) — a somewhat more benign course once past the acute phase (Tolenaar 2013, PMID 24060392).

The original report (12 centers, 464 patients, 1996–1998)

  • Mean age 63; 65.3% male; 62.3% type A (Hagan 2000, PMID 10685714).
  • Presentation defies the classics: sudden severe pain is the most common symptom, but aortic regurgitation murmur was present in only 31.6%, pulse deficit in 15.1%; chest x-ray and ECG were normal in 12.4% and 31.3% respectively. CT was the initial imaging test in 61.1% (Hagan 2000, PMID 10685714).
  • Mortality (in-hospital): 27.4% overall; type A with surgery 26%, type A without surgery 58%; type B medical 10.7%, type B surgical 31.4% (an era before TEVAR, with surgery reserved for complications) (Hagan 2000, PMID 10685714).
  • Early IRAD modeling put type A in-hospital mortality at 32.5%, with death predicted by age ≥70 (OR 1.70), abrupt chest pain (OR 2.60), hypotension/shock/tamponade (OR 2.97), renal failure (OR 4.77), pulse deficit (OR 2.03), and abnormal ECG (OR 1.77) (Mehta 2002, PMID 11790701).
Metric Early IRAD Late IRAD Source
CT as diagnostic test, type A 46% 73% (Pape 2015, PMID 26205591)
Surgical management, type A 79% 90% (Pape 2015, PMID 26205591)
In-hospital mortality, type A 31% 22% (Pape 2015, PMID 26205591)
Surgical mortality, type A 25% 18% (Pape 2015, PMID 26205591)
Endovascular management, type B 7% 31% (Pape 2015, PMID 26205591)
In-hospital mortality, type B 12% 14% (no significant trend) (Pape 2015, PMID 26205591)

Presenting symptoms and physical findings did not change across eras; the mortality gains in type A track the shift to prompt CT diagnosis and near-universal operative therapy; type B hospital mortality has been static despite TEVAR uptake (Pape 2015, PMID 26205591; Evangelista 2018, PMID 29685932).

  • Sex differences: women are 32.1% of IRAD dissections, older, present later, more often with coma/altered mental status and signs of contained rupture; adjusted in-hospital mortality is higher than men (OR 1.4), with type A surgical mortality 32% vs 22% (Nienaber 2004, PMID 15197151).
  • Registry blind spot: prehospital deaths — 48.6% of incident type A dissections in the Oxford Vascular Study died before hospital assessment, so IRAD-type mortality figures are conditional on surviving to a referral center (Howard 2013, PMID 23599348).

Aneurysm diameter and dissection risk

  • Dissection risk rises steeply with aneurysm size — the ascending hinge point sits at ~6.0 cm, where lifetime rupture/dissection probability reaches ~31%, and >6 cm carries ~6.9%/yr rupture-or-dissection (Coady 1997, PMID 9081092; Elefteriades 2002, PMID 12440685; Davies 2002, PMID 11834007).
  • Yet 59% of type A dissections occur at <5.5 cm and 40% at <5.0 cm (mean 5.3 cm) — below elective thresholds (Pape 2007, PMID 17709637). Hypertension (OR 2.17) and older age predict small-size dissection; Marfan patients dissect large (OR 14.3) (Pape 2007, PMID 17709637).
  • The paradox resolves at the population level (small aortas are overwhelmingly more numerous; a ≥4.5 cm aorta is ~6,305× more dissection-prone than a <3.5 cm one — relative risk 346.8 vs 0.055) and absolute risk at 4.0–5.5 cm is low (~0.1%/patient-yr) (Paruchuri 2015, PMID 25997607; Kim 2016, PMID 27609684). Full analysis in epidemiology-and-natural-history; threshold implications in risk-stratification-and-size-thresholds.
  • Population-attributable risk of hypertension for dissection is ~54%, and uncontrolled premorbid blood pressure is the dominant treatable risk factor (Landenhed 2015, PMID 25609416; Howard 2013, PMID 23599348) — see medical-therapy.

Malperfusion

Branch-vessel compromise (static or dynamic) drives much of dissection's mortality:

  • Pulse deficit at presentation independently predicts death in type A (OR 2.03), as do hypotension/shock/tamponade and renal failure (Mehta 2002, PMID 11790701).
  • Mesenteric malperfusion complicates 3.7% of type A dissections and carries 63.2% in-hospital mortality vs 23.8% without it; mortality by management was 95.2% (medical), 72.7% (endovascular), 41.7% (surgical/hybrid) — an argument for aggressive reperfusion-plus-repair strategies (Di Eusanio 2013, PMID 22341418).
  • IMH and PAU characteristically lack branch-vessel occlusion — ischemic manifestations argue for classic dissection (Coady 1999, PMID 10589337).

Post-dissection aneurysmal degeneration

The survivor of an acute dissection trades an emergency for a chronic aneurysm risk concentrated in the false lumen:

  • Late aortic growth is the rule: aortic growth or new aneurysm occurred in 73.3% of medically managed and 62.7% of TEVAR-treated IRAD type B patients by 5-year Kaplan-Meier estimate (Fattori 2013, PMID 23968705); 59.4% of medically managed type B patients showed diameter growth within 24 months (Kamman 2017, PMID 28390915).
  • False-lumen physiology stratifies risk: post-discharge 3-year mortality in type B was 13.7% with a patent false lumen, 31.6% with partial thrombosis (independent predictor, RR 2.69), 22.6% with complete thrombosis (Tsai 2007, PMID 17652650). Complete false-lumen thrombosis predicts freedom from growth (HR 3.64); a fully patent false lumen, dissection origin at the left subclavian, female sex, and larger sinotubular junction predict growth (Kamman 2017, PMID 28390915).
  • Preemptive TEVAR reshapes the chronic phase: in randomized stable type B dissection (INSTEAD-XL), TEVAR + medical therapy vs medical therapy alone reduced 5-year aorta-specific mortality (6.9% vs 19.3%) and disease progression (27.0% vs 46.1%), with stent-graft-induced false-lumen thrombosis in 90.6% (Nienaber 2013, PMID 23922146). IRAD observational data concur: 5-year death 15.5% (TEVAR) vs 29.0% (medical) (Fattori 2013, PMID 23968705).
  • Surveillance of the residual dissected aorta follows the same measurement discipline as aneurysm surveillance — see anatomy-and-classification and imaging-and-surveillance.

Management principles (summary only)

Details, techniques, and outcomes belong to surgical-and-endovascular-repair, medical-therapy, and guidelines; the load-bearing facts:

  1. Type A = emergency surgery. Unoperated in-hospital mortality was 58% vs 26% with repair in early IRAD; surgical uptake is now ~90% and type A mortality has fallen to ~22% (Hagan 2000, PMID 10685714; Pape 2015, PMID 26205591).
  2. Uncomplicated type B = medical anti-impulse therapy first. In-hospital mortality ~11–14% with medical management (Hagan 2000, PMID 10685714; Pape 2015, PMID 26205591).
  3. Complicated type B (malperfusion, rupture, refractory pain/hypertension) = TEVAR, now 31% of type B management in IRAD (Pape 2015, PMID 26205591; Fattori 2013, PMID 23968705).
  4. Stable type B, suitable anatomy: preemptive TEVAR improves 5-year aorta-specific survival and remodeling (Nienaber 2013, PMID 23922146) — patient selection remains contested (see Open questions).
  5. Malperfusion first-order priority: mesenteric malperfusion mortality is halved (though still 41.7%) with surgical/hybrid strategies vs medical management (Di Eusanio 2013, PMID 22341418).

Open questions

  • Type B in-hospital mortality has not improved in 20 years of registry data despite TEVAR uptake (12%→14%) — which type B patients benefit from early intervention, and can randomized selection criteria be defined beyond INSTEAD-XL's stable-survivor population? (Pape 2015, PMID 26205591; Nienaber 2013, PMID 23922146)
  • Partial false-lumen thrombosis is a mortality risk factor, not an intermediate on the way to benign complete thrombosis — the hemodynamic mechanism (diastolic false-lumen pressurization?) is unproven in humans (Tsai 2007, PMID 17652650; Kamman 2017, PMID 28390915).
  • IMH natural history: IRAD descending IMH looks more benign than classic type B, but series are small (n=107) and progression-to-dissection estimates vary; optimal imaging-based triggers for intervention are undefined (Tolenaar 2013, PMID 24060392).
  • Since half of type A deaths occur prehospital, what diagnostic or screening strategy could shift mortality that hospital-era improvements cannot touch? (Howard 2013, PMID 23599348)
  • Why do women present later, with more contained rupture, and die more often after adjustment — biology, aorta size vs body size, or diagnostic delay? (Nienaber 2004, PMID 15197151)

References

  1. Daily PO, et al. Management of acute aortic dissections. Ann Thorac Surg. 1970;10:237-47. PMID 5458238
  2. DeBakey ME, et al. Surgical management of dissecting aneurysms of the aorta. J Thorac Cardiovasc Surg. 1965;49:130-49. PMID 14261867
  3. Hagan PG, et al. The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. JAMA. 2000;283:897-903. PMID 10685714
  4. Mehta RH, et al. Predicting death in patients with acute type a aortic dissection. Circulation. 2002;105:200-6. PMID 11790701
  5. Pape LA, et al. Presentation, Diagnosis, and Outcomes of Acute Aortic Dissection: 17-Year Trends From the International Registry of Acute Aortic Dissection. J Am Coll Cardiol. 2015;66:350-8. PMID 26205591
  6. Evangelista A, et al. Insights From the International Registry of Acute Aortic Dissection: A 20-Year Experience of Collaborative Clinical Research. Circulation. 2018;137:1846-1860. PMID 29685932
  7. Nienaber CA, et al. Gender-related differences in acute aortic dissection. Circulation. 2004;109:3014-21. PMID 15197151
  8. Howard DP, et al. Population-based study of incidence and outcome of acute aortic dissection and premorbid risk factor control: 10-year results from the Oxford Vascular Study. Circulation. 2013;127:2031-7. PMID 23599348
  9. Clouse WD, et al. Acute aortic dissection: population-based incidence compared with degenerative aortic aneurysm rupture. Mayo Clin Proc. 2004;79:176-80. PMID 14959911
  10. Gouveia e Melo R, et al. A systematic review and meta-analysis of the incidence of acute aortic dissections in population-based studies. J Vasc Surg. 2022;75:709-720. PMID 34560218
  11. Coady MA, et al. Pathologic variants of thoracic aortic dissections. Penetrating atherosclerotic ulcers and intramural hematomas. Cardiol Clin. 1999;17:637-57. PMID 10589337
  12. Coady MA, et al. Penetrating ulcer of the thoracic aorta: what is it? How do we recognize it? How do we manage it? J Vasc Surg. 1998;27:1006-15. PMID 9652462
  13. Tolenaar JL, et al. The differences and similarities between intramural hematoma of the descending aorta and acute type B dissection. J Vasc Surg. 2013;58:1498-504. PMID 24060392
  14. Pape LA, et al. Aortic diameter >or=5.5 cm is not a good predictor of type A aortic dissection: observations from the International Registry of Acute Aortic Dissection (IRAD). Circulation. 2007;116:1120-7. PMID 17709637
  15. Paruchuri V, et al. Aortic Size Distribution in the General Population: Explaining the Size Paradox in Aortic Dissection. Cardiology. 2015;131:265-72. PMID 25997607
  16. Kim JB, et al. Risk of Aortic Dissection in the Moderately Dilated Ascending Aorta. J Am Coll Cardiol. 2016;68:1209-1219. PMID 27609684
  17. Coady MA, et al. What is the appropriate size criterion for resection of thoracic aortic aneurysms? J Thorac Cardiovasc Surg. 1997;113:476-91. PMID 9081092
  18. Davies RR, et al. Yearly rupture or dissection rates for thoracic aortic aneurysms: simple prediction based on size. Ann Thorac Surg. 2002;73:17-27. PMID 11834007
  19. Elefteriades JA. Natural history of thoracic aortic aneurysms: indications for surgery, and surgical versus nonsurgical risks. Ann Thorac Surg. 2002;74:S1877-80. PMID 12440685
  20. Landenhed M, et al. Risk profiles for aortic dissection and ruptured or surgically treated aneurysms: a prospective cohort study. J Am Heart Assoc. 2015;4:e001513. PMID 25609416
  21. Di Eusanio M, et al. Clinical presentation, management, and short-term outcome of patients with type A acute dissection complicated by mesenteric malperfusion: observations from the International Registry of Acute Aortic Dissection. J Thorac Cardiovasc Surg. 2013;145:385-390.e1. PMID 22341418
  22. Fattori R, et al. Survival after endovascular therapy in patients with type B aortic dissection: a report from the International Registry of Acute Aortic Dissection (IRAD). JACC Cardiovasc Interv. 2013;6:876-82. PMID 23968705
  23. Kamman AV, et al. Predictors of Stable Aortic Dimensions in Medically Managed Acute Aortic Syndromes. Ann Vasc Surg. 2017;42:143-149. PMID 28390915
  24. Tsai TT, et al. Partial thrombosis of the false lumen in patients with acute type B aortic dissection. N Engl J Med. 2007;357:349-59. PMID 17652650
  25. Nienaber CA, et al. Endovascular repair of type B aortic dissection: long-term results of the randomized investigation of stent grafts in aortic dissection trial. Circ Cardiovasc Interv. 2013;6:407-16. PMID 23922146
  26. Isselbacher EM, et al. 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease. J Am Coll Cardiol. 2022;80:e223-e393. PMID 36334952
  27. Lombardi JV, et al. Society for Vascular Surgery (SVS) and Society of Thoracic Surgeons (STS) reporting standards for type B aortic dissections. J Vasc Surg. 2020;71:723-747. PMID 32001058