| Print Date: | May 18, 2013, 10:52 am |
| Title | Aortic Dissection |
| Text | Def: blood within the medial of the aortic wall resulting from…
(1) intimal tear (VAST MAJORITY/95+% of cases) (2) intramural hematoma (vasa vasorum) CONTRIBUTING FACTORS (3): *medial degeneration *wall stress from persistent aortic motion *HTNаhydrodynamic forces Classifications Schemes (2) I. DeBakey (memory aid: “the world’s #1 surgeon!”, and this classification system uses numbers) Type I (29-34%): involves ascending and descending aorta Type II (12-21%): involves ascending aorta only Type III (50%!!!): IIIA and IIIB (B = “Below diaphragm”) Memory aid: “I = II + III” (Jack H, 2002) II. Stanford: Type A (70%) Type B (30%) Incidence: 3/1,000 1/205 autopsies approximately 2,000 cases/year in the U.S. M:F = 3:1 Predisposing factors: cystic medial necrosis/aortic wall disease PEARLS: *28% start in fusiform aortic aneurysms (>5 cm in diameter) *when in females, 50% occur during pregnancy *re-entry into the aortic lumen occurs in a minority (10%) *important associations: HTN (in 60-90% of cases), Marfan’s (16%), ED, Relapsying Polychondritis, Valvular AS, Turner’s, Behcet’s, Coarctations, Bicuspid Aortic Valves, s/p Prosthetic Valves, Traumatic (rare), s/p Catheterization, Pregnancy, Aortitis (e.g., SLE), Cocaine abuse Signs & Symptoms: *tearing, sharp chest pain (ddx includes acute MI) *asymmetric or absent peripheral pulses *shock (in 25%) *neurologic deficits (in 25%), including anterior spinal artery syndrome *persistent oliguria *signs of tamponade Clinical classification: ACUTE: if present < 2 weeks CHRONIC: > 2 weeks old Helical Flow Pattern: *Ascending aorta: anterior/right lateral wall *Arch: superior and posterior wall *Proximal/thoracic descending aorta: posterior and left lateral wall *Abdominal aorta: (1) usually terminates in the left iliac artery (80%) (2) involves the left renal artery in 50% RADIOLOGIC FINDINGS: *CXR-->compare to priors -normal in 20-25% of cases -displace intimal calcifications in descending aorta -increased aortic diameter -widened mediastinum (>8cm)аfrom hemorrhage -enlargement of the cardiac silhouette (LVH,hemopericardium) -L-sided pleural effusion (27%) -Rightward deviation of the trachea, endotracheal tube -left apical pleural cap *ECHO: TEE > TTE in sensitivity (99%) and specificity (77-97%); intravascular ECHO may also be performed -intimal flap *ANGIO: 1st choice for final confirmation and staging; use a percutaneous right (not left) femoral artery approach; ensure the rapid washout of contrast material during the test injection (especially if a false lumen is present) -esp. good for demarcating entry and re-entry pints -detecting branch vessel involvement -AI -false negatives: if complete thrombosis of false lumen is present or if intimal flap is not tangential to the x-ray beam Contrast-enhanced CT: -crescentic high attenuation clot within the false lumen -internally displaced intimal calcifications -intimal flap separating 2 aortic channels may be seen without contrast in anemic patients -FALSE NEGATIVES: *inadequate contrast opacification *misinterpreted as aortic aneurysm with mural thrombus -FALSE POSITIVES: *streak artifact secondary to cardiac/aortic motion-->can mimic the intimal flap *opacifiec normal sinus of Valsalva *normal pericardial recess mistaken form thrombus -CT protocol: AORTA Contrast: precontrast images prn, then 150 ml IV contrast @ 2-3 ml/sec with 20 sec delay Coverage: top of arch through iliac bifurcation in suspended inspiration Parameters: 5 mm collimationat 5 mm intervals with pitch of 1.5 MR (95-100% sensitive and specific) -white blood GE sequences and phase reconstruction techniques can help identify slowing flowing blood in the false channel -limitation = resolution of the arch vessels -”black blood” images (SE) -phase image reconstructions! -get GE cine study Treatment (1) DeBakey Type III/Stanford Type B: medical management to maintain blood pressures <120/70 mmHg (2) DeBakey Types I & II/Stanford Type A: immediate surgical graft re-inforcement of aortic wallаprevents both rupture and progressive AI -surgical procedure: 80% retain opacification of both lumens after surgery *Bentall Prodecure Without treatment… *death immediately (2%) *death within one day (20-30%) *death within one week (50%) *death within three weeks (60%) *death within one month (75%) *death within three months (80%) *death within one year (80-95%). With treatment… *5-10% mortality rate following timely surgery. *40% 10-year survival once out of the hospital. |
| References: | Dahnert W. Radiology Review Manual, Fourth Edition.
Lippincott Williams & Wilkins: Philadelphia, 2000. Miller SW. Cardiac Radiology, The Requisites. Mosby Inc.: St. Louis, 1996: pp. 391-400. Slone RM, et. Al. Body CT, A Practical Approach. McGraw- Hill: New York, 2000, pp. 1-3, 86-87. |
| Contributor | Richard P. Moser, III (Walter Reed Army Medical Center) |
| Peer Reviewer | David S. Feigin, M.D. (Johns Hopkins Hospitals) |
| Record Number | : 3803 |
| Created | 2002-05-14 17:43:24-04 |
| Modified | 2003-12-19 03:06:02-05 |
| Category: | Vascular |
| Location: | Cardiovascular (inc. Heart) |
| Sublocation: | Aorta |
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