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

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aortic dissection

Aortic Dissection

Jason S. Finkelstein, M.D.

Cardiology Fellow

Tulane University

8/11/03

overview
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
pathophysiology
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
classification
Classification
  • Debakey system
    • Type I
      • 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
classification5
Classification
  • The Stanford system
    • Type A
      • 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
predisposing factors
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
other risk factors
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)
clinical symptoms
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
physical exam
Physical Exam
  • Pulse deficit
    • 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
clinical signs
Clinical signs
  • Acute MI
    • 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
clinical signs12
Clinical Signs
  • Involvement of the descending aorta
    • Splanchnic ischemia
    • Renal insufficiency
    • Lower extremity ischemia
    • Spinal cord ischemia
diagnosis
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
differential diagnosis
Differential Diagnosis
  • Acute Coronary Syndrome
  • Pericarditis
  • Pulmonary embolus
  • Pleuritis
  • Cholecystitis
  • Perforating ulcer
diagnostic tests
Diagnostic Tests
  • EKG
    • Absence of EKG changes usually helps distinguish dissection from angina
    • Usually non-specific ST-T wave changes seen
  • CXR
  • Cardiac Enzymes
chest x ray
Chest X-Ray
  • May show widening of the aorta with ascending aorta dissections
    • Present in 63 % of patients with Type A dissections
diagnostic imaging
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
imaging
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
angiography
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
spiral ct
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
slide26
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
slide28
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
slide29
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
slide32
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
conclusions
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
treatment
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
surgical options
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
type a dissections
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
poor prognostic factors
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
medical therapy
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
long term outcome
Long Term Outcome
  • Type A
    • Survival at 5 yrs – 68%
    • Survival at 10 yrs – 52 %
  • Type B
    • 5 yrs – 60 - 80%
    • 10 yrs – 40 – 80%
    • Spontaneous healing of dissection is uncommon
long term management
Long-Term Management
  • Medical therapy
    • 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