Aortic Dissection



Yüklə 455 b.
tarix06.02.2017
ölçüsü455 b.


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

  • Mortality in the first 48 hours is 1% per hour

    • Early diagnosis is essential


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

  • 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


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

  • 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

  • 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

  • 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

  • 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

  • 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 Signs

  • Involvement of the descending aorta

    • Splanchnic ischemia
    • Renal insufficiency
    • Lower extremity ischemia
    • Spinal cord ischemia


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

  • Acute Coronary Syndrome

  • Pericarditis

  • Pulmonary embolus

  • Pleuritis

  • Cholecystitis

  • Perforating ulcer



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

  • May show widening of the aorta with ascending aorta dissections

    • Present in 63 % of patients with Type A dissections


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

  • 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

  • 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

  • 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








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





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


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






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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • Surgical intervention for Type B dissections reserved for patients with a complicated course



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

  • 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






Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©azkurs.org 2019
rəhbərliyinə müraciət

    Ana səhifə