Diseases of Aorta - Aortic Dissection

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AORTIC DISSECTION
Aortic dissection is a condition which involves a
tear in the inner layer of aorta. Aortic wall has
three layers. When the tear occurs in the intima,
blood flowing inside the aorta under pressure
creeps into the layers of aortic wall and
dissects it. One of the major contributing
factors is uncontrolled hypertension. The extent
of the split can vary and this decides the
severity and symptoms of Aortic dissection.
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• Aortic dissection can be classified based on
• Location and extent of dissection
• Duration of symptoms

Types according to location of Aortic
Dissection Different segments of aorta can be
affected by the dissection.
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Type A Dissection When the ascending aorta is
affected irrespective of the extent Type B
Dissection When Ascending Aorta is not affected.
Here usually dissection is limited to the
Descending aorta.
Types according to onset and duration Acute
Aortic dissection Sudden and recent onset is
described as acute. Usually less than 4 weeks in
duration Chronic Aortic Dissection Duration
more than 4 weeks
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Symptoms Pain Aortic dissection is usually
associated with severe pain. Site of pain may
vary depending on the location of dissection.
For example, ascending and arch dissection will
have severe chest pain. Descending thoracic
aortic dissection may have chest and upper back
pain. Abdominal aortic dissection presents with
severe lower back pain and abdominal pain.
Other Symptoms Depending on the aortic branches
affected by the dissection some symptoms may
appear. When the abdominal branches are involved
pain may be predominant. Dissection can affect
the lower limb vessels and that can cause severe
leg pain. If coronary arteries are involved, the
symptoms may be severe and patient may have
angina or even heart attack (MI). Involvement of
Carotid arteries can rarely cause strokes.
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Diagnosis Clinical suspicion is very crucial in
clinching the diagnosis, as the situation can
mimic many conditions. The definite diagnosis is
made by an ECHO and CT aortogram. Echo can
detect the dissection flap and the extent can be
seen. Aortic valve can be assessed. CT aortogram
can give precise location, extent, branch
involvement and any rupture of pseudo lumen. Due
to the accuracy and detail, CT aortogram is the
GOLD STANDARD in aortic dissection. Treatment Tr
eatment broadly depends on the type of
dissection. As a rule of thumb, Acute type A
dissection warrants an emergency surgery. This is
because it can potentially affect the coronaries
and can be fatal. The mortality approaches 60
with out surgical intervention. On the contrary,
type B dissections are largely managed
conservatively. Surgery is generally reserved
for complications like visceral, renal or limb
artery ischemia or aneurysm of pseudolumen.
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Type A Aortic Dissection As soon as the
diagnosis is made, planning of treatment should
be started. The extent of dissection, aneurysm
formation, presence of rupture and the branch
involvement usually dictates the type of
surgery. The commonest scenario is a dissection
starting at the ascending aorta just above the
level of Right Coronary Artery and extending to
variable distance of aorta. The tear usually
involves the arch partly or completely. It may
even involve one or more of the major arch
vessels. But as long as the perfusion to these
vessels are intact and there is no aneurysm
formation of the pseudolumen, surgical
intervention of arch is not indicated. The
treatment then would be an Aortic root
replacement. The valve may be replaced or
preserved depending on the presence or absence
of valve or annulus involvement. When the arch of
aorta is badly damaged or the psuedolumen is
aneurysmal in this area, the arch should be
addressed during surgery. Depending on the extent
of involvement, part (Hemiarch) or entire (Total
Arch) arch may be replaced.
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• Type B Aortic Dissection
• Traditionally, type B dissections (Dissections
  beyond the left subclavian artery) are treated
  conservatively unless one of the following
  situations is present.
• Aneurysm of pseudolumen.
• Tear or leak of the psudolumen
• Viscral branch or limb branch involvement causing
  decrease in perfusion of an organ.
• However, persisting pain not responding to
  conservative treatment is a relative indication
  for intervention now a days. Various methods of
  interventional procedures are attempted to
  control the primary tear in the intima.
• One common interventional method is to stent
  across the proximal intimal tear.
• This prevents the blood from entering the
  pseudo-lumen and eventually blood in the
  pseudo-lumen gets thrombosed.
• Whenever decision is made to treat the type B
  Dissection conservatively, a close follow up is
  mandatory. CT Aortogram/MR Aortogram should be
  performed at 3 months and one year.

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