Definition
Dissecting aneurysm, splitting or dissection of an
arterial wall by blood entering through an intimal tear or by
interstitial hemorrhage; more common in the aorta, with an intimal
tear near the aortic valve and distal dissection of the media for a
variable distance, frequently rupturing through the outer wall.
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| Radiographic Appearance
X-ray Chest
Widening of the mediastinum, localized
dilatation of the aortic knuckle (hump sign), pleural effusion,
lateral displacement of the trachea
Angiography
Catheter tip needs to be placed in the
aortic root so that the whole of the ascending aorta can be
visualized and the contrast medium can enter the false lumen if the
tear is a proximal one. Usually both the false and true lumen will
fill with the displaced intima appearing as a linear band separating
the two. Sometimes, only the true lumen may fill, but it may be
compressed by the false lumen, giving rise to the twisted tape sign.
CT & MRI
Are both useful in confirming a diagnosis
of dissection. Intravenous contrast is required for CT, and both
modalities reveal the dilated aorta, with true and false lumens
separated by the intimal flap. MRI does have the added advantage of
saggital and coronal imaging.
De Bakey classification is as follows:
Type I starts in the ascending aorta and extends
throughout the arch and descending aorta to the iliacs
Type II starts in the ascending aorta but does not extend beyond the
arch
Type III starts in the distal arch and extends down to the iliacs
Type II is least common and is associated with Marfans syndrome.
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Pathology
Clinical features include acute chest pain, or symptoms due to
involvement of aortic branches, such as hemiplegia and vertebral
symptoms (cerebral branches), paraplegia following occlusion of
intercostal or lumbar vessels, mesenteric ischemia or pancreatitis,
retrograde spread to pericardium could lead to cardiac tamponade,
anuria due to renal artery occlusion, or lower limb ischaemia due to
iliac occlusion.
A dissecting aneurysm occurs when blood gets through a lengthwise
tear between layers of the wall of an artery (a blood vessel
carrying blood from the heart to the body). These layers then
separate and swell, making a balloon-shaped formation that causes
severe pain. This condition can be fatal if the artery bursts.
How does it occur?
This condition can be caused by a disease, birth defect, or injury.
It is usually caused by arteriosclerosis, a common disorder that
causes narrowing of arteries and reduces circulation. High blood
pressure also contributes to this disease.
Symptoms include:
extreme chest, abdominal, or back pain
sudden, extreme pain that moves toward the back between your
shoulder blades, and may affect the hips and legs
coughing up blood
shortness of breath
nausea and vomiting
blood in bowel movements
fainting
difficulty swallowing
headache.
Diagnostic methods
chest x-ray
Ultrasound
electrocardiogram (ECG, records electrical impulses of your heart)
CT scan (computerized x-rays)
angiogram (x-rays after a dye has been injected into an artery)
cardiac ultrasonography (a moving image of the heart and blood
vessels)
blood tests.
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Treatment:
The treatment of a dissecting aneurysm initially involves lowering
the blood pressure with drugs to reduce the force on the tear in the
aorta. Then the surgeon must decide if it is safe to attempt to
replace the dissected part of the aorta with a synthetic graft. The
closer the dissection is to the heart, the more likely it is that
surgery will be performed. The majority of people with an untreated
dissecting aneurysm will die within a few weeks. However, if the
operation is successful and the patient survives the first few weeks
after the operation then the outlook is quite good so long as the
blood pressure is carefully monitored and controlled.
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| Images
1) Dissecting Thoracic Aortic Aneurysm MRI
2) Dissecting Abdominal aneurysm
Ultrasound
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Useful Link
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