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
