Type B aortic dissection occurs when blood flows within the aortic wall separating the layers of the media. Computed tomography angiography is useful for establishing the diagnosis by showing two distinct lumens separated by an intimal flap, and for determining the location of the primary intimal tear and extent of dissection. Initial medical management aims to control blood pressure and pain. Intervention may be indicated for complications such as persistent pain, expansion of the dissection, or impaired blood flow to organs. Both open surgical repair and endovascular techniques can be used to treat type B dissection, with endovascular options becoming more common due to lower risks.

1. Type B Aortic dissection

2. Origin Of Type B Dissection

3. Origin Of Type B Dissection

4. Type B dissection- PIT
• Smooth muscle degeneration
in aortic media.
• Initial event- PIT
• Blood flows within aortic wall
seperating layers of media.
• Outer third of media.
• Left posterolateral wall.
• Antegrade / retrograde propagation.
• Distal reentry multiple- sheared-off ostia of arterial branches – “imperfect natural
cure of the disease”.

5. Type B Dissection- PAU
• PAU: localized intimal lesion burrowing into media
leading to localized dissection.
• Mushroom cap appearance on CT / MRI Scan

6. Type B Dissection- IMH
• Spontaneous rupture of vasa vasorum within outer third of aortic media.
• No intimal defect.
• Mechanism- Spontaneously in predisposed individuals
Secondary to rupture of atheromatous plaque
• Type B IMH higher propensity for aortic rupture-
severe symptoms / associated deep PAU

7. Factors influencing dissection propagation
• Rate of increase of aortic systolic pressure
dP/dT.
• Aortic diastolic elastic recoil pressure.
• Mean arterial pressure.
• Aortic wall integrity.

8. Fate of False Lumen
• Patent false lumen multiple reentry.
• Thrombosis (partial or complete): rare

9. Fate of False Lumen
• Rupture:
Pleural cavity
Abdomen
• Contained leak.
• Proximal extension:
Retro-A Dissection.

10. Fate Of False Lumen
• Visceral malperfusion:
Paraplegia.
Renal ischemia.
Mesenteric ischemia.
Limb ischemia
• Obstruction to flow-
dynamic / static obstruction.
• Pseudoaneurysm: False
lumen prone for progressive
expansion.

11. AIMS of Investigation
• Confirm diagnosis.
Type of dissection
Extent of dissection.
Location of PIT.
• Aortic branch compromise-
Thoracoabdominal visceral malperfusion
Peripheral limb ischemia.
• Coronary evaluation.

12. True Vs False Lumen

13. C.T. Angiography
• Rapid, non invasive
• Confirms diagnosis:
Two distinct lumens in DTA separated by intimal flap.
Displaced intimal calcification.

14. C.T. Angiography
• Location of PIT.
• Thrombosis of false
lumen

15. C.T. Angiography
• Extent of dissection

16. C.T. Angiography
• Perfusion status of
individual branches.

17. C.T. Angiography
Involvement of limb
vessels
Compression of true
lumen

18. C.T. Angiography
Active extravasation PAU / IMH / Hemothorax

19. C.T. Angiography
CT
Angiography
Sensitivity Specificity Positive
predictive
value
Negative
predicitve
value
82 - 100 % 89 – 100 % 80% 98%
• Drawback: Intravenous Contrast
administration

20. Trans Esophageal Echocardiography
• Rapid, convinent, non-invasive.
• Intimal flap, PIT, secondary
fenestrations.
• Limitations:
Abdominal branch vessel
involvement.
Extent of dissection below
diaphragm.

21. M.R.A
• Delineate entire thoracoabdominal aorta.
• Demonstrate intimal flap, TL, FL.
• Involvement of major aortic branches.
• High sensitivity and specificity.
• Not suitable for critically ill patients.
• Useful for long term follow up of chronic
dissection and post-operative or medically
treated patients.

22. Aortography
• Diagnostic importance- Historical.
• Invasive, time consuming.
• Contrast use, technique carries risk of morbidity and mortality.
• Indication:
Persistent peripheral vascular complication after proximal
aortic repair, to delineate mechanism of aortic branch vessel
compromise before endovascular intervention.

23. Additional Investigations
• Renal USG and Doppler:
Renal parenchymal assessment.
Renal doppler
• Doppler for lower limb arterial system.
• Cardiac fuction evaluation:
ECHO
CT Coronary

24. Intra Vascular Ultrasound (IVUS)
• Novel technique.
• Highest accuracy.
• Imporatant in
endovascular
treatment

25. Management strategy
• Aim of therapy-
Prevent death
Prevent irreversible end organ damage.
• Optimal treatment strategy- debated ????

26. Optimal treatment strategy ???

27. Optimal treatment strategy???

28. Approach to type B Dissection
Arguments in favour of medical treatment
• Medical treatment prevents death in majority.
• Operative mortality type B dissection high.
• Similar long term outcome of surgically and
medically managed patients.
• “Complication Specific” approach for Type B
Dissection

29. Indications for Intervention
• Persistent pain.
• Refractory arterial hypertension.
• Progression / expansion of dissection.
• Aortic rupture / impending rupture.
• Impaired distal organ perfusion.
• Sizable localized false aneurysm.
• Young with CTD- Marfan syndrome without complications.

30. Management Strategy for IMH
• Uncomplicated Type B IMH: Medical.
• Type B IMH with persistent pain / associated
large – deep PAU: high incidence of aortic
rupture.
• Intervention for complicated Type B IMH

31. Initial Medical Treatment
• Goal of medical treatment:
Relieve pain.
Control blood pressure.
Limit extension of dissection.
• Extensive monitoring:
• ECG / Radial – Femoral arterial line / CVP /
Pulse Oxymeter / Foley catheter.

32. Anti impulsive therapy
• Target: Mean arterial pressure = 60 – 75mmhg
Systolic presure = 100 – 110mm hg
Heart rate = 60 – 80bpm
• Eliminate Pain: Morphine.
• Beta blockade:
Esmolol- 500mcg/kg iv bolus
50 mcg/kg/min infusion (max 200mcg/kg/min)
Propranolol – 1mg every 5 min to achieve target HR
(max 10 mg)
• SNP – 20 mcg/min (max 800mcg/min)
• Refractory hypertension: ACEI - Enalapril

33. Definitive long term medical management
• Oral beta blockers-
Labetalol, Metoprolol, Atenolol.
• Calcium channel antagonists.
• Oral ACEI / ARB
Lisinopril.
• Hydralizine avoided-
Incorporated into mucopolysaccharides of media and
weaken aortic wall.

34. Aims Of Intervention
(Surgical / Endovascular)
• Seal the entry Point.
• Seal area of leak (if any).
• Establish perfusion to branch arteries.
• Expansion of true lumen and obliteration of false
lumen.

35. Surgical Principles
Acute Type B Dissection
No visceral malperfusion Visceral malperfusion
Replace the tear point Fenestation
Graft replacement
with visceral
artery reconstruction

36. Surgical Approach
• Full CPB
• Venous Cannulation- Right Femoral Vein.
• Arterial Cannulation- Left subclavian artery.
Undissected ascending aorta
Descending aortic true lumen
• Moderate hypothermia 25 – 28oC.
• Open Proximal Anastamosis (OPA) in distal arch
under HCA.

41. Management of visceral malperfusion
Aortic dissection + Visceral malperfusion
Dynamic Obstruction Static Obstruction
Visceral artery Visceral artery
from true lumen from false lumen
Central aortic repair Central aortic repair
visceral artery revascularisation

42. Surgical fenestration

43. Mortality according to indication for surgery

44. Endovascular treatment
• JACC 2008

45. Endovascular therapy
• Medical management
70% patients- persistent patent false lumen
20 – 30% eventually aneurysmal
• Surgical replacement:
High mortality – 20 – 30%
Visceral ischemia – 30 – 50%

46. Endovascular treatment
• Balloon Fenestration.
• Stenting
• Stent grafting

47. Endovascular Balloon Fenestration

48. Endovascular Balloon Fenestration

49. Visceral malperfusion- Stenting

50. Stent Graft

51. Stent Grafting

53. Penetrating Atherosclerotic Ulcer

54. Future developments in endovascular repair

55. Future developments in endovascular repair

56. Future developments in endovascular repair

57. Thank you