AORTIC DISSECTION!

Dr. Nikrish S Hegde

LEARNING OBJECTIVES! Identify the two types of aortic

dissection and list the indications for treatment.

Describe the imaging parameters and the typical and atypical imaging findings in aortic dissections.

Discuss the imaging features of complications that can arise from aortic dissections.

IMPORTANCE! Most common

Fatal outcome

Prompt diagnosis and treatment.

AORTA made of three layers, called from the

luminal side outward, the tunica intima, the tunica media and the tunica adventitia

What is aortic dissection? Dissection is the result of a spontaneous

longitudinal separation of the aortic intima and adventitia caused by circulating blood gaining access to and splitting the media of the aortic wall

TYPES:-DeBakey

Standford

Type A dissections account for 60%–70% of cases and typically require urgent surgical intervention.

Stanford type B dissection involves the descending thoracic aorta distal to the left subclavian artery and accounts for 30%–40% of cases. Management takes the form of medical treatment of hypertension.

Indications for immediate surgery Hemodynamic instabilty.Uncontrolled HTN.Diameter > 6cm. Ischaemic Complications.

PRESENTATION. CHEST PAIN SYNCOPE RIGHT HYPOCHONDRIAL

PAIN ..ABNORMAL LFT OLIGURIA ..ANURIA ..ABNORMAL RFT NAUSEA ..VOMITING..PAIN

ABDOMEN..BLOODY DIARRHOEA.. LOWER LIMB ISCHAEMIA

ACUTE VS CHRONIC The dissection is termed acute when it

is diagnosed within 14 days after the first symptoms appear.

It is termed chronic when it is diagnosed later .

HELICAL CT AND AORTIC DISSECTION. Aortography. Shorter acquisition time, wide availability,

and high diagnostic accuracy and has, therefore, classically been the modality of choice for the evaluation of aortic dissection.

The intimal flap, type and extent of dissection ,presence of thrombus and the presence of associated complications and follow up changes.

TECHNIQUE The examination begins with

conventional unenhanced CT.

Coverage begins 2 cm above the aortic arch and continues to the superior aspect of the femoral head.

We then inject 100 mL of nonionic at a rate of 2 mL/sec through a 20-gauge catheter positioned in the right arm. Helical CT is performed 30 seconds after administration of contrast

TYPICAL AORTIC DISSECTION The classic feature of aortic dissection is

a partition between the true and false channels.

Secondary findings include internal displacement of intimal calcifications or a hyperattenuating intima; delayed enhancement of the false lumen; widening of the aorta; and mediastinal, pleural, or pericardial hematoma .

STANDFORD TYPE A

STANFORD B

How do we distinguish false lumen from the true lumen?? SIZE POSITION-False channel usually arises

anterior in the ascending aorta and spirals to posterior and left lateral in descending aorta.

FLOW SECONDARY CHANGES – THROMBOSIS BEAK’S SIGN

BEAK’S SIGN

THROMBOSED FALSE LUMEN

ATYPICAL AORTIC DISSECTION

INTRAMURAL HEMATOMA:Unenhanced CT shows a cuff or crescent of high attenuation and displacement of intimal calcifications. On enhanced CT scans, a smooth region of low attenuation can be seen

Penetrating atherosclerotic ulcer is defined as an atherosclerotic lesion with ulceration that penetrates the internal elastic lamina; such penetration facilitates hematoma formation within the media of the aortic wall

Ruptured Type B Dissection

Atypical Configuration of the Intimal Flap

circumferential intimal flap

filiform

Mercedes-Benz sign

CHANGES DURING FOLLOW-UP

Pseudoaneurysm

Healing of intramural hematoma

Progression of Intramural Hematoma

Aneurysm of the false lumen

PITFALLS The CT appearances of several entities

can cause them to be mistaken for atypical AAD.

Mural thrombus

CT scan shows an atheromatous thrombus with an irregular internal border in the thoracic descending. A thrombosed aortic dissection usually demonstrates a smooth internal border.

periaortic lymphoma

PSEUDODISSECTION

Perivenous streaks combination of beam hardening and

motion orientation of such streaks typically

varies from section to section and extends beyond the confines of the aortic wall

minimize perivenous streaks by performing bolus injection into the right arm at a rate of 2 mL/sec

Aortic motion artifact ascending aorta and is related to

movement of the aortic wall artifact is seen at the left anterior and

right posterior margins of the aortic circumference

a serrated appearance of the left anterior ascending aorta on two- or three-dimensional reconstruction images

BRANCH VESSEL OCCLUSION There are two types of branch-vessel occlusion.

1)STATIC2)DYNAMIC

STATIC the intimal flap intersects or enters the

branch-vessel origin. Static obstruction is treated locally with an intravascular stent

DYNAMIC the intimal flap spares the branch-vessel

wall but prolapses across the branch-vessel origin and covers it like a curtain . Dynamic obstruction is treated with a fenestration procedure

ADVANCES

TEEMRITRIPLE-RULE-OUT -CT

Transesophageal echocardiography secondary signs of an aortic dissection

such as aortic root dilatation, aortic regurgitation, coronary ostial patency, pericardial effusions, or regional abnormal wall motion can be diagnosed.

TEE can be performed in the emergency department at the bedside of unstable patients.

MR angiography suitable for the investigation of aortic

dissection in medically stable patients or those with chronic dissections

including lack of nonionizing radiation, multiplanar evaluation, and greater vessel coverage at high resolution with fewer sections.

It cannot be performed in unstable patients due to longer acquisition time and difficulty in monitoring, and it is not appropriate for patients with implanted electronic devices

TRIPLE-RULE-OUT -CT Assess the aorta, coronary arteries, and

pulmonary arteries and the middle and lower portions of the lungs during a single scan with use of several optimally timed boluses of contrast material and ECG gating.

Biphasic injection of iodinated contrast material (≤100 mL)