Aortic Dissection

Riya Chacko, MD

November 4, 2009

BackgroundPathophysiologyImaging ModalitiesManagement

Incidence 3/100,000 per yearMen more likely to have aortic dissections

compared to women78% have chronic hypertensionPeak for proximal dissection 50-55, distal

60-70At least 20% die before arriving at the

hospital

Michael Ellis Debakey 1908-2008

http://www.nytimes.com/2008/07/13/health/13debakey.html?pagewanted=1&_r=1

High mortality rate: 25% during 1st 24 hours, 70% in 1st week, 80% at 2 weeks for proximal dissections, 10% in distal in 24 hours

Acute versus chronic – present of symptoms within 2 weeks

30% are chronic 50% start in ascending aorta

Khan et al. Chest 2002.

Death from: aortic rupture, aortic regurgitation, branch vessel rupture

75% of proximal untreated aortic dissections will rupture into pericardium, left pleural cavity, and mediastinum

Pathophysiology

Medial degeneration Intimal tear

Disorders Associated with Increased Risk

Hypertension Marfan’s – most common cause of dissection in patients

<40 years of age Ehlers-Danlos syndrome Turner’s syndrome Biscupid aortic valve Cocaine Trauma Pregnancy Noonan syndrome Aortitis Aortic coarctation

Trauma

Double Barrel Sign – Aortic Disruption

Presentation

Von Kodolitsch et al studied 3 variables: mediastinal widening, acute onset chest pain, and BP differential.

Dissection probability high with any combo of 3 or isolated pulses/BP differential (>83%)

Aortic pain 31%Mediastinal widening 39%Absence of all 37%

IRAD registry: Severe sharp pain

84.8% 31% nonspecific

EKG changes 12.7% presented

with syncope

Golledge et al. Lancet 2008.

Variants of Acute Aortic Syndromes

Aortic intramural hematomaAortic ulceration

Aortic intramural hematoma

No intimal flap Rupture of vasa vasorum Occurs in 10-15% acute aortic

syndromes Descending thoracic aorta Atherosclerosis Crescentic shape Can result in pseudoaneurysm High incidence of aortic

rupture, prognosis SAME as dissection

Ascending hematoma same risk as ascending dissection

Intramural Hematoma

On TEE, see localized thickening of aortic wall >7 mm, echo-free spaces within the aortic wall, centrally displaced calcium, or absence of dissection flap/communication

MRI can detect age of the hematoma (methemoglobin)

30-47% will lead to dissection, tamponade, or aortic rupture

Pseudoaneurysm 20-45%

Hematoma <1.0 cm better prognosis

Aortic Ulceration

2.3-7.6% of acute aortic syndromes

Also seen in elderly patients with hypertension, severe atherosclerosis

Descending thoracic aorta (AAA) Ulcer crater with thickened aortic

wall extending from elastic lamina to media

May lead to aneurysms and/or dilation

Less commonly dissections Rare to have thromboembolism MRI most accurate 40% lead to aortic rupture

Khan et al. CHEST / 122 / 1 / JULY, 2002

Classification of Aortic Dissections

Golledge et al. Lancet. 2008.

Copyright ©2007 BMJ Publishing Group Ltd.

Ince, H. et al. Heart 2007;93:266-270

Figure 1 Classification of distal or proximal aortic dissection. De Bakey: type I, originates in the ascending aorta, propagates at least to the aortic arch and often beyond it distally; type II,

originates in and is confined to the ascending aorta; type III, originates in the descending aorta and extends distally down to the aorta or, rarely, retrograde into the aortic arch and ascending aorta. Stanford: type A, all dissections involving the ascending aorta, regardless of the site of origin; type B, all dissections not involving the ascending aorta. Adapted from Nienaber et al.3

Aortogram in a Patient with a Type A Aortic Dissection. The anterior view is shown. The well-opacified true lumen (T) and the poorly opacified false lumen (F) are separated by an intimal flap (I), which is visible in some parts of this image as a thin radiolucent line within the aorta. In addition, the proximal portions of both coronary arteries are well visualized. Cigarroa JE, Isselbacher EM et al. NEJM. Volume 328:35-43 January 7, 1993 Number 1

Ascending aortic dissections posterior and to the right, above the right coronary artery ostium

Descending aortic dissections posterior and to the left, more commonly affecting left renal and left iliofemoral arteries

Organ Involvement

Cardiovascular Neurologic

The left oblique view is shown. The aortic root is dilated. The true lumen (T) and the false lumen (F) are separated by a faintly visible radiolucent line, which is the intimal flap (I). Note the abundance of contrast agent in the left ventricle (LV), which is indicative of substantial aortic insufficiency.

Cardiac Involvement

Aortic regurgitation in 18-50%Pericardial effusion most commonly from

transudation of fluid through intact false lumen, NOT rupture or leak

Regional wall motion abnormalities 10-15% due to low coronary perfusion

38% of patients have pulse differential (right and left arm)

31-60% have EKG changes

Mechanism of Aortic Regurgitation

Neurologic Involvement

Stroke 5-10% of all aortic dissectionsSpinal cord ischemia in 10% with distal

involvementIntercostal arteries, artery of Adamkiewicz

and thoracic radicular arteries

The Aortic Dissection

Distinguishing true and false lumen False lumen has spontaneous echo contrast

with delayed/reverse flow Thrombus only in false lumen – usually distal to

entry site True lumen expands during systole,

compressed during diastole False lumen usually larger (not always true) Color flow: true lumen forward systolic flow,

false lumen variable

Thrombus in False Lumen

Imaging Modalities To Assess Dissections

CTMRI TEETTE

Goals of Imaging

Barbant et al reported in 1992 results from CT, MRI and TEE

PPV for all three in high-risk patients >85%

In low-risk patients, PPV <50% for CT and TEE but 100% for MRI

NPV high for all three >85%

Cigarroa JE, Isselbacher EM et al. NEJM. Volume 328:35-43 January 7, 1993 Number 1

CT

Sensitivity for ascending aorta <80% but up to 94% in descending and 87-100% specific overall

Limitations: use of IV contrast, identifying intimal tear, branch vessel involvement, aortic regurgitation

Helical CT superior

MRI

Sensitivity and specificity 95-100%Limitations: lack of immediate availability,

scan timing, restricted vitals monitoring

MRI of the Ascending Aorta in a Patient with a Type A Aortic Dissection. The coronal plane is shown. The aortic root (AR) and the pulmonary artery (P) are visualized. In the ascending aorta an intimal flap (I) separates the true (T) and false (F) lumens.

TTE

Sensitivity 35-80%Specificity 39-96%

Xray

30-60% have mediastinal wideningBulges to the right with ascending and left

with descendingLeft pleural effusion

TEE

Sensitivity 98% Specificity 63-96% Identifies: entry site with intimal flap, thrombus,

abnormal flow, involvement of coronary and arch vessels, pericardial effusion, aortic valve regurgitation, left ventricular function

Limitations: operater experience, limited to thoracic and proximal abdominal aorta (cannot see below the celiac trunk), also “blind spot” proximal aortic arch where trachea and left mainstem bronchus along between esophagus and aorta

Methods by TEE of Assessing Aorta

Understand relationship of aorta to esophagus – distal arch, aorta is anterior to the esophagus, at diaphragm aorta is posterior to the esophagus

Communicating location – try to identify relative to known surgical structures (ie aortic valve, subclavian artery) versus incisors (less helpful to surgeons, helpful for serial exams)

Focus on area just above aortic valve (Type A) and area just beyond left subclavian (Type B)

Difficult to assess distal aortic arch because of trachea (between aorta and esophagus)

Ascending Aorta

30-35 cm from incisors Start at 0 ME 5 chamber view Spin to 40-60 for AV short axis Spin to 90-120 AV long axis – measure sinus of

Valsalva and ST junction Slowly withdraw to see additional 2-3 cm of

ascending aorta Beware of swan catheters (artifact) Decrease to 60 then 0 and withdraw

Descending Aorta

Adjust depth to 6-8 cm so descending aorta enlarged

Advance to stomach, rotate and spin to 90 degrees, slowly withdraw gradually rotating

Intimal tear in 70% of dissections occurs 1-3 cm above sinus of Valsalva

20-30% at ligamentum arteriosumEntry site can be identified 88% of the time

(Adachi et al.)

Differentiating Intimal Tear vs. Reverberation

Intimal TearReverberation

Undulates with cardiac cycle

Distinct borders

Crosses anatomic borders

Blurred borders

Does NOT undulate

Preferred Imaging Modalities

Moore, A. et al. Am J Cardiology, 89:1235-1238, 2002

Medical Treatment

B-blocker + nitroprusside (Beta-blocker 1st) or

Labetalol (alpha and beta-blocker)

Surgical Treatment

Operative mortality 5-10%, higher if complications present

Goal is to replace the ORIGIN of dissection, not entire involved segment

Mortality of surgery higher than medical therapy in Type B dissections

15% treated surgically require a 2nd operation

Copyright ©2007 BMJ Publishing Group Ltd.

Ince, H. et al. Heart 2007;93:266-270

Figure 2 Fourteen-day mortality in 645 patients from the International Registry of Aortic Dissection (IRAD) registry stratified by medical and surgical treatment in both type A and B

aortic dissection. Adapted from Hagan et al.1

Endovascular Stents

Success rate of 76-100% with 25% 30-day mortality

Palliative or those unsuitable for surgery

13% of aortic dissections receive stents

Proximal Dissection Followup

65-80% survival if treated at 5 years40-50% at 10 years

Distal Dissection Follow up

75% survival regardless of medical/surgical management if treated