Aortic Dissection Riya Chacko, md

Aortic Dissection

• Riya Chacko, MD

• November 4, 2009

• Background

• Pathophysiology

• Imaging Modalities

• Management

• Incidence 3/100,000 per year

• Men more likely to have aortic dissections compared to women

• 78% have chronic hypertension

• Peak for proximal dissection 50-55, distal 60-70

• At least 20% die before arriving at the hospital

• 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

• 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

Variants of Acute Aortic Syndromes

• Aortic intramural hematoma

• Aortic 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

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

Classification of Aortic Dissections

• 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

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 dissections

• Spinal cord ischemia in 10% with distal involvement

• Intercostal 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

• CT

• MRI

• TEE

• TTE

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%

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

TTE

• Sensitivity 35-80%

• Specificity 39-96%

Xray

• 30-60% have mediastinal widening

• Bulges to the right with ascending and left with descending

• Left 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 arteriosum

• Entry site can be identified 88% of the time (Adachi et al.)

Differentiating Intimal Tear vs. Reverberation

• Intimal Tear Reverberation

Preferred Imaging Modalities

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

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 years

• 40-50% at 10 years

Distal Dissection Follow up

• 75% survival regardless of medical/surgical management if treated