1. Jason S. Finkelstein, M.D. Cardiology Fellow Tulane University 8/11/03
Aortic Dissection
Jason S. Finkelstein, M.D.
Cardiology Fellow
Tulane University
8/11/03

2. Overview
Incidence of aortic dissection is at least 2000 new cases per year
Peak incidence is in the sixth to seventh decade
Men are affected twice as commonly as women
Mortality in the first 48 hours is 1% per hour
Early diagnosis is essential

3. Pathophysiology
The chief predisposing factor is degeneration of collagen and elastin in the aortic intima media
Blood passes through the tear into the aortic media, separating the media from the intima and creating a false lumen
Dissection can occur both distal and proximal to the tear

4. Classification Debakey system Type I Type II Type III
Originates in the ascending aorta, propagates to the aortic arch and beyond it distally
Type II
Confined to the ascending aorta
Type III
Confined to the descending aorta, and extends distally, or rarely retrograde into the aortic arch

5. Classification The Stanford system Type A Type B
All dissections involving the ascending aorta
Type B
All other dissections regardless of the site of the primary intimal tear
Ascending aortic dissections are twice as common as descending

7. Predisposing factors Age, 60-80 yrs old
Long standing history of hypertension
80% of cases have co-existing HTN
Takayasu’s arteritis
Giant cell arteritis
Syphilis
Collagen disorders
Marfan syndrome (6-9% of aortic dissections)
Ehlers-Danlos syndrome

8. Other Risk Factors Congenital Cardiac Anomalies
Bicuspid aortic valve (7-14% of cases)
Coarctation of the aorta
Cocaine
Abrupt HTN, due to catecholamine release
Trauma
Pregnancy (50% of dissections in women <40 yrs)
Iatrogenic (cardiac cath, IABP, cardiac surgery, s/p valve replacement)

9. Clinical Symptoms
Severe, sharp, “tearing” posterior chest pain or back pain (occurs in 74-90% of pts)
Pain may be associated with syncope, CVA, MI, or CHF
Painless dissection relatively uncommon
Chest pain is more common with Type A dissections
Back or abdominal pain is more common with Type B dissections

10. Physical Exam Pulse deficit Acute Aortic Insufficiency
Weak or absent carotid, brachial, or femoral pulses
these patients have a higher rate of mortality
Acute Aortic Insufficiency
Diastolic decrescendo murmur
Best heard along the right sternal border

11. Clinical signs Acute MI Cardiac tamponade Pleural effusions
RCA most commonly involved
Cardiac tamponade
Pleural effusions
Hypertension or hypotension
Hemothorax
Variation in BP between the arms (>30mmHg)
Neurologic deficits
Stroke or decreased consciousness

12. Clinical Signs Involvement of the descending aorta Splanchnic ischemia
Renal insufficiency
Lower extremity ischemia
Spinal cord ischemia

13. Diagnosis Generally suspected from the history and PE
In a recent study in 2000, 96% of acute dissection patients could be identified based upon a combination of three clinical features
Immediate onset of chest pain
Mediastinal widening on CXR
A variation in pulse and/or blood pressure (>20 mmHg difference between R & L arm
Incidence >83% when any combination of all three variables occurred

14. Differential Diagnosis
Acute Coronary Syndrome
Pericarditis
Pulmonary embolus
Pleuritis
Cholecystitis
Perforating ulcer

15. Diagnostic Tests EKG CXR Cardiac Enzymes
Absence of EKG changes usually helps distinguish dissection from angina
Usually non-specific ST-T wave changes seen
CXR
Cardiac Enzymes

16. Chest X-Ray
May show widening of the aorta with ascending aorta dissections
Present in 63 % of patients with Type A dissections

17. Diagnostic Imaging Not performed until the patient is medically stable
Has been a dramatic shift from invasive to non-invasive diagnostic strategy
Spiral CT scan
TEE
MRI
Angiography

18. Imaging Can identify aortic dissection and other features such as:
Involvement of the ascending aorta
Extent of dissection
Thrombus in the false lumen
Branch vessel or coronary artery involvement
Aortic insufficiency
Pericardial effusion with or without tamponade
Sites of entry and re-entry

20. Angiography First definitive test for aortic dissection
Traditionally considered “the gold standard”
Involves injection of contrast media into the aorta
Identifies the site of the dissection
Major branches of the aorta
Communication site between true & false lumen
Can detect thrombus in the false lumen
Disadvantages
Not very practical in critically ill patients
Nephrotoxic contrast
Risks of an invasive procedure

22. Spiral CT Sensitivity 83% Specificity 90 - 100%
Two distinct lumens with a visible intimal flap can be identified
Advantages
Noninvasive
Readily available at most hospitals on an emergency basis
Can differentiate dissection from other causes of aortic widening (tumor, periaortic hematoma, fat)
Disadvantages
Sensitivity lower than TEE and MRI
Intimal flap is seen < 75% of cases
Nephrotoxic contrast is required
Cannot reliably detect AI, or delineate branch vessels

26. TTE First used to diagnose aortic dissections in the ’70s
Sensitivity 59-85%, specificity 63-96%
Image quality limited by obesity, lung disease, and chest wall deformities

28. TEE Sensitivity 98% Specificity 95% Advantages
Close proximity of the esophagus to the thoracic aorta
Portable procedure
Yields diagnosis in < 5 minutes
Useful in patients too unstable for MRI
True and false lumens can be identified
Thrombosis, pericardial effusion, AI, and proximal coronary arteries can be readily visualized

29. TEE
Lower specificity attributed to reverberations atherosclerotic vessels or calcified aortic disease producing echo images that resemble an aortic flap
Disadvantages
Contraindicated in patients with esophageal varices, tumors, or strictures
Potential complications: bradycardia, hypotension, bronchospasm

32. MRI Most accurate noninvasive for evaluating the thoracic aorta
Sensitivity 98%
Specificity 98%
Advantages
Safe
Can visualize the whole extent of the aorta in multiple planes
Ability to assess branch vessels, AI, and pericardial effusion
No contrast or radiation
Disadvantages
Not readily available on an emergency basis
Time consuming
Limited applicability in pts with pacemakers or metallic clips

34. Conclusions
Conventional TTE is of limited diagnostic value in assessment of the thoracic aorta
Both TEE and MRI have excellent sensitivity, however MRI is more specific
MRI is the study of choice for stable patients
TEE is the study of choice for unstable patients

35. Treatment
Acute dissections involving the ascending aorta are considered surgical emergencies
Dissections confined to the descending aorta are treated medically
Unless patient demonstrates continued hemorrhage into the pleural or retroperitoneal space

36. Surgical Options Excision of the intimal tear
Obliteration of entry into the false lumen proximally
Reconstitution of the aorta with interposition of a synthetic vascular graft

37. Type A Dissections Operative mortality varies from 7-35%
27% post-op mortality
Patients who died had a higher rate of in-hospital complications such as strokes, renal failure, limb ischemia, & mesenteric ischemia

38. Poor prognostic factors
Hypotension or shock
Renal failure
Age> 70 yrs
Pulse deficit
Prior MI
Underlying pulmonary disease
Preoperative neurologic impairment
Renal and/or visceral ischemia
Abnormal EKG, particularly ST elevation

39. Medical therapy
Reduce systolic BP to 100 to 120 mmHg or the lowest level that is tolerated
IV Beta blockers
Propanolol (1-10 mg load, 3mg/hr)
Labetalol (20 mg bolus, 0.5 to 2 mg/min)
If SBP remains >100mmHg, nitroprusside should be added
Do not use without beta blockade
Avoid hydralazine
Surgical intervention for Type B dissections reserved for patients with a complicated course

40. Long Term Outcome Type A Type B Survival at 5 yrs – 68%
Spontaneous healing of dissection is uncommon

41. Long-Term Management Medical therapy Serial imaging
Oral Beta-blockers (reduces aortic wall stress)
Keep BP < 135/80 mmHg (combination therapy)
Avoidance of strenuous physical activity
Serial imaging
Thoracic MR scan prior to discharge
f/u scans at 3, 6, and 12 months
Subsequent screening studies done every 1-2 yrs if no evidence of progression