1. Non-Invasive Conference: Aortic Dissection
Ali R. Rahimi, MD MPH
September 24, 2008

2. Anatomy
Tunica intima, media and adventitia

3. Aortic Dissection
“a splitting of the layers of the aortic wall (within the media), permitting longitudinal propagation of a blood-filled space within the aortic wall”
Most common cause of death related to the human aorta
Incidence  2.6 to 3.5 per 100,000 person-years
65% men with mean age of 63 years

4. Pathophysiology
Degeneration of aortic media, or cystic medial necrosis, is prerequisite for nontraumatic dissection
Primary rupture of intima with secondary dissection of the media vs. hemorrhage within the media and subsequent rupture of overlying intima
Propagation can occur both distal and proximal

6. Risk Factors Systemic hypertension (72%) Atherosclerosis (31%)
Pre-existing aortic aneurysm (13% known)
more common < 40 yo (19%)
Vasculitis (giant cell arteritis, Takayasu arteritis, rheumatoid arthritis, syphilitic aortitis)

7. Risk Factors
Disorders of collagen (eg, *Marfan syndrome, Ehlers-Danlos syndrome, annuloaortic ectasia)
*Present in 50% of those < 40 yo vs. 2% of older patients
Bicuspid aortic valve
Present in 9% < 40 yo vs. 1% over age 40
Enlargement of aortic root and/or ascending aorta
Aortic coarctation, Turner Syndrome, CABG (0.04%), Prior AVR, Cardiac Cath (2%), Trauma (deceleration injury), Weight lifting, Crack cocaine

8. Ascending aortic dissections ~ 2x as common
It classifies dissections that involve the ascending aorta as type A, regardless of the site of the primary intimal tear, and all other dissections as type B. In comparison, the DeBakey system is based upon the site of origin with type 1 originating in the ascending aorta and propagating to at least the aortic arch, type 2 originating in and confined to the ascending aorta, and type 3 originating in the descending aorta and extending distally or proximally
Ascending aortic dissections ~ 2x as common
Right lateral wall of ascending aorta most common site
Aortic arch involvement ~ 30%

9. Variants
Class I - classic separation of intima/media and dual lumens; flap between true and false aneurysm and clot in false lumen;
Class II - intramural hematoma with separation of intima/media but no tear or flap;
Class III - limited intimal tear without hematoma and eccentric bulge at tear site;
Class IV - atherosclerotic ulcer penetrating to adventitia with surrounding hematoma;
Class V- iatrogenic or traumatic dissection

10. Clinical Presentation
Severe, sharp or "tearing" posterior chest or back pain (distal to L subclavian) or anterior CP (ascending dissection)
Isolation or with syncope, CVA, MI, CHF, …
HTN more common in type B dissection (70% vs. 36%)
Pulse deficit in 19-30% with an acute type A dissection vs. 9-21% with a type B dissection

11. Clinical Finding Artery or Structure
Aortic insufficiency or CHF
Aortic valve
AMI
Coronary artery (right)
Tamponade
Pericardium
Hemothorax
Thorax
CVA or Syncope
Brachiocephalic, CC, Left subclavian
UE pulselesness, low BP, pain
Subclavian
Paraplegia
Intercostal
LE pain, pulselessness, weakness
Common iliac
Abdominal pain, mesenteric ischemia
Celiac or mesenteric
Back or flank pain; ARF
Renal artery
Horner syndrome
Superior cervical sympathetic ganglion

12. Differential Diagnosis
Acute Coronary Syndrome
Pericarditis
Pulmonary embolus
Aortic regurgitation without dissection
Aortic aneurysm without dissection
Musculoskeletal pain
Mediastinal tumors
Pleuritis
Cholecystitis
Atherosclerotic or cholesterol embolism
Peptic ulcer disease or perforating ulcer
Acute pancreatitis

13. Diagnosis Clinical Prediction of Aortic Dissection
Study of 250 pts with acute chest and/or back pain (128 with AD) found 96% with acute AD identified using 3 clinical features:
Abrupt onset of thoracic or abdominal pain with a sharp, tearing and/or ripping character
Mediastinal and/or aortic widening on chest radiograph
Variation in pulse (absence of a proximal extremity or carotid pulse) and/or blood pressure (>20 mmHg difference in the right and left arm)
Any 2 out of 3 variables (77% of dissections): ≥83%
Additional imaging studies obtained in 98% of pts due to limited sensitivity of CXR, especially in type B dissections

14. Chest X-Ray Type A Type B
63% with mediastinal widening, 11% with no abnormality
Type B
56% with mediastinal widening, 16% with no abnormality

15. Electrocardiogram 31% normal 42% non-specific ST and T wave changes
15% ischemic changes
5% changes c/w AMI

16. Advanced Imaging Modalities
Aortic Dissection
Involvement of the ascending aorta
The extent of dissection and the sites of entry and reentry
Thrombus in the false lumen
Branch vessel or coronary artery involvement
Aortic insufficiency
Pericardial effusion

17. Advanced Imaging Modalities
Based on year 2000 IRAD:
mean 1.83 studies per patient
61% CT
33% Echocardiography
4% Aortography
2% MRI

18. ESC Guidelines for Diagnostic Imaging of Acute Aortic Dissection
Class I - TTE followed by TEE
Class II – CT, CTA to define anatomy
Class IIa – CTA in stable pts, MRI in stable pts, Intravascular US
Class IIb - CT if detection of tears is crucial, CTA in unstable pts, intravascular US to guide intervention
Class III – MRI in hemodynamically unstable patients, routine pre-op CTA

19. ESC Guidelines for Diagnostic Imaging of Chronic Aortic Dissection
Class I – MRI
Class IIa – TTE, TEE, CTA

20. CT Scan

21. CT Scan

22. CT Scan

23. CT Scan Sensitivity 83-98% Specificity 87-100% Advantages:
availability at most hospitals
ID of intraluminal thrombus and pericardial effusion
Disadvantages:
Intimal flap seen < 75% of cases and site of entry is rarely identified
Potentially nephrotoxic iodinated contrast
Unable to assess for aortic insufficiency
Accuracy of CT is improved with spiral CT and electron beam or multidetector CT
Spiral CT may be more accurate than MRI or TEE in the detection of aortic arch vessel involvement
Limitation: Without ECG gating  simulate artifact ~ aortic dissection

24. TTE

25. TTE

26. TTE

27. TTE

28. TTE

29. TTE

30. TTE
Limited utility for evaluation of the thoracic aorta for dissection
unable to adequately visualize distal ascending, transverse, and descending aorta in a substantial majority of patients
Intimal flap in the proximal aorta may be seen, though the sensitivity and specificity of TTE are inferior compared to CT, MRI, and TEE
Most useful for assessment of cardiac complications of dissection, including AI, pericardial effusion/tamponade, and regional LV dysfunction

31. TEE

32. TEE

33. TEE

34. TEE

35. TEE

36. TEE

37. TEE

38. TEE Advantages sensitivity 97 – 99%
close proximity of esophagus to thoracic aorta and absence of an intervening lung or chest wall
portable procedure
diagnosis within minutes
useful in patients too unstable for CT or MRI
intimal dissection flaps can be identified with high spatial resolution
true and false lumens can be identified
thrombosis in the false lumen, pericardial effusion, aortic regurgitation, and the proximal coronary arteries can be visualized
135º long axis view can define severity and mechanism of aortic regurgitation that complicates acute type A dissections

39. TEE Disadvantages Specificity as low as 77-85%
false-positive findings in the ascending aorta
artifacts can be detected by addition of M-mode imaging, increasing specificity to almost 100%
Requires sedation and esophageal intubation
TEE requires availability of experienced operators (both physicians and technicians) to assure accurate results

40. 30 Day Mortality Rates for Acute Aortic Dissection
Data from the international registry of acute aortic dissection – published in JAMA in 2000
Acute Type A dissection treated medically -
20% mortality rate at 24 hours
30% at 48 hours
40% at one week
50% by one month
Hagan, Etc, JAMA :897

41. Mechanical Composite Root Repair with and w/o Hemiarch Repair

43. Homograft Repair

44. Porcine BioRoot Replacement

45. Valve Sparing Replacement

46. Aortic Dissection Repair: Teflon Felt as Neomedia

47. Endovascular Aortic Stent Grafts

48. Endovascular Aortic Stents

49. References Hurst the Heart, 11th Edition
Manning, W. UpToDate Online Clinical manifestations and diagnosis of aortic dissection.