Aorta (lil more info)

Blood vessel anatomy

Tunica intima - inner layer endothelial cells

Tunica media - Middle layer, muscle thicker and more organized layer in arteries

Tunica Adventitia/Externa - outer later, epithelial cells, connective tissue

First branches of ascending aorta are

Coronary arteries

Aortic arch starts at level of ___________ and extends distal to left subclavian artery

Innominate artery

Bovine arch

Most common anatomic variant of the arch anatomy

Two branch arch formation: the innominate and left CCA origin are combine and the left subclavian artery is the second branch

Although “bovine” indicates a cow, this arch formation is NOT related to the arch formation in cattle

Aorta is ________ to IVC until umbilicus

Posterior

__________ resistance in the upper abdominal aorta due to low resistance branches

Lower

__________ resistance in the distal aorta due to high resistance branches

Higher

Common iliac arteries

Originates at the aortic bifurcation at L3 or L4, umbilicus level

Supply blood to the legs pelvis

Bifurcate into the internal and external iliac arteries

High resistance flow

Common iliac arteries are anterior to the common iliac veins

Eval to arterial pathology in long and trans

Internal iliac artery

Hypogastric artery

Travels medially and supplies the pelvic organs, NOT GONADS

Tri or Bi, lower resistance than the common iliac

External iliac artery

Travels laterally and passes under the inguinal ligament to become the common femoral artery

Courses along medial side of the psoas muscle

Supplies the extremities with blood

Tri, high resistance

USA abdominal indications

Abdominal pain

Pulsatile mass

AAA on plain film

F/U AAA

Trauma

Decreased pedal pulses

The distal aorta can usually be palpated by pressing on the ___________ at the level of the iliac crest

Abdomen

US in aorta

Best anatomic landmark for abdominal structures

Long and trans

Coronal can show Aorta and IVC

AP and trans measurements should be obtained

Gradual distal tapering and becomes more anterior distally

Common iliac artery ends at distal bifurcation into external and internal iliac arteries

Normal Aorta measurements:

Proximal: 2.0-2.6cm

Mid: 1.6-2.4cm

Distal: 1.1-2cm

Iliacs: 0.6-1.4cm

Doppler of aorta

Velocity: 70-100cm/s

Biphasic above renal arteries due to low resistance branches

Triphasic below renal arteries

Coarctation

Congenital defect causing narrowing of the aorta

Occurs with other heart defects and is component of Shone complex

Occurs distal to the origin of left subclavian

Causes lower extremity ischemia

Decreased bilateral pedal pulses

Systemic HTN usually present

Elevated pressures is activated causing increased systemic pressure

Takayasu arteritis

Presents as hypertrophic areas of inflamed tissue usually found in aorta and its branches

Commonly affects subclavian and carotid arteries

Can also affect renal arteries

Most commonly seen in young females

Aortic ectasia

Lack of tapering of the Ao as it travels distally, size remains constant from proximal to distal portions

Can be precursor to aneurysm formation

AAA is most commonly caused by

Degenerative disease

Symptoms of AAA

Pulsatile mass, low back pain, abdominal bruit

AAA most commonly forms in __________ segment

Infrarenal

>60% of pts with a pop aneurysm also have a

AAA

Iliac artery considered aneurysmal when diameter exceeds _____ or when diameter increased by 50% as compared to adjacent segment

1.5cm

AAA above the renal arteries -

Surgical intervention asap

AAA below renal arteries -

Most common; surgical intervention at a diameter >5.5cm

Fusiform AAA

Vessel wall stretches in a circumferential manner; all three wall layers intact

Saccular AAA

Formed with a stalk connecting dilated wall portion to main vessel; usually associated with wall dissection

Berry AAA

Tiny out pouching, usually found in cerebrum/circle of Willis; usually congenital

Mycotic AAA

Due to infection in the artery and the arterial wall; syphilis most common

Vasculitis AAA

Due to inflammatory process of vasa vasorum and tunica adventitia

Aneurysm diameter change of >4mm on a yearly follow up exam, the next follow up should be at __________

3 months

Ruptured AAA can cause

Hypotension, severe abdominal pain, shock, death

Complications of AAA

Rupture is MOST COMMON and most critical

Decreased flow extremities

Blue Toe syndrome with thrombus accumulation and embolization to the toes

Affects renal circulation and systemic BP if proximal to renal artery

Aneurysmal measurement ____

>3cm

Possible ________ accumulation causes increased echogenicity in AAA

Thrombus

Blue toe syndrome

Thromboembolic disease

Embolic material lodges in distal artery

Causes acute ischemia distal to location of embolism and blue color changes in distal tissues

Causes of Blue toe syndrome

Thrombus in prox aneurysm

Arteritis

Ulcerated atherosclerotic lesions

Some angioplasty procedures

Thrombus in a vein

Cardiac arrythmias

EVAR

Used to improve and streamline flow through a stenosis or AAA

Easier and better for PT

Kissing stents used for stenosis at the origin of the common iliac arteries

Intravascular ultrasound (IVUS)

Can be used to guide the graft during placement

Physician uses an US catheter to visualize the lumen prior to the procedure and eval best location for endoluminal graft placement

Advantages of IVUS over Angiography during angioplasty

No need to cut the aorta to insert the graft

No radiation

No contrast

Can provide 2D and 3D images of vessel

Limitations of IVUS

Catheter size limits vessels that can be evaluates

Introduction of the catheter can lead to arterial spasm

Significant atherosclerosis can blur the image

Images suffer from ringdown artifact caused by dead space

Cost of disposable catheter; cannot be heated/sterilized b/c the elements will lose their US properties

Intraoperative Duplex US

Used to assess the flow changes during and after procedure

Surgeon places transducer directly on open wound or exposed vessel; requires sterile technique

Sonographer may be asked to assess distal flow at the ankles during and after procedure

Ankle pressures should demonstrate a mild increase after the graft is placed

Complications of EVAR

Stenosis, thrombosis, endoleak

Endoleak type 1

Leak at site of attachment

• 1a - leak at prox attachment site

• 1b - leak at distal attachment site

• Flow pattern resembles the flow pattern within the graft

• Most dangerous type

Type 2 endoleak

Will see retrograde flow into aneurysm sac and increases AAA diameter

IMA, internal iliac, lumbar arteries and accessory arteries are potential sources for leak

Bidirectional flow pattern, Doppler waveform reflects end source pathology

MOST COMMON

Type 3 endoleak

Caused by tear in the graft or separation of the main graft from the iliac limbs

Type 4 endoleak

Transgraft leak through porous material of the graft

Type 5 endoleak

Endotension - no leak but there is continued expansion of the aneurysmal sac greater than 5cm

Post surgical EVAR US

Performed 1 month post-op, then at 3, 6, 9, 12 and 18 months followed by annual exams

Measure outer wall to outer diameter of AAA to compare to prior exam

>0.5cm increase in diameter from last exam = possible leak

Use color and PW

Document proximal attachment site and confirm it has not migrated

Eval velocities prior and distal to EVAR

True endoleak will be reproducible

Potential signs of an unstable AAA sac

Echolucent areas within the sac

Changes in aneurysm shape and/or sac size

Increased pulastility of sac

Normal Endovascular stent

Endograft leak

Dissection

Intimal layers tear and allows flow between intima and media layers into a blind pocket

Causes weakened vessel wall, increased risk of rupture

Most commonly in ascending aorta

Second most commonly is just distal to subclavian

Significant AAA can lead to dissection (>5cm)

CTA is preferred for diagnosis

Dissection is most commonly found in

Ascending aorta

USA dissection

Linear echogenicity seen in lumen of the vessel, separating it into two channels

Color flow demonstrates two lumens, both with turbulence

Bidirectional flow

Stanford Classification:

• Type A: dissections that involve the ascending aorta and arch

• Type B: Dissections that involve the aorta from the left subclavian artery to iliac bifurcation

DeBakey Classification:

• Type 1: Dissection that involves the ascending AO and Descending

• Type 2: Dissections that involve only the ascending AO

• Type 3: Dissections that involve descending AO only

Aortic dissection

Aortic stenosis is most commonly caused by

Atherosclerotic changes

Aortic stenosis

Resistance will increase proximal to stenosis

Distal stenosis = tardus parvus

If the stenosis is superior to the renal artery, renal ischemia will activate renin-angiotensin system causing systemic HTN

Effects will be similar to coarctation

Leriche syndrome is also known as

Aortoiliac occlusive disease

Leriche syndrome

Due to occlusion of the abdominal aorta just above the site of its bifurcation

Causes BILATERAL symptoms

Cause of erectile dysfunction

Low resistance waveforms and post-stenotic changes in legs

Leriche syndrome symptoms

Fatigue of both lower limbs, intermittent bilateral claudication with ischemic pain, absent or diminished femoral pulses and pallor or coldness of both lower extremities

Retroperitoneal fibrosis is also known as

Ormond disease

Retroperitoneal fibrosis most commonly occurs at the level of the

Bifurcation

Retroperitoneal fibrosis

Idiopathic overgrowth of fibrous tissue around atherosclerotic aorta

Can be ruptured to drugs, infection, malignancy or cancer therapy

May lead to ureteral obstruction causing hydro, IVC compression causing bilateral edema, scrotal swelling from compression of gonadal vein

Retroperitoneal fibrosis USA

Soft tissue mass surrounding great vessels

Hypoechoic

Smooth borders

Retroperitoneal fibrosis

If the aortic arch only has two branches instead of 3, what is this variant called

Bovine arch

The external iliac arteries become the common femoral arteries when:

They cross under the inguinal ligament

AP measurements of AO are most accurate in what plane

Long

What causes elevated brachial pressures and diminished ankle pressures bilaterally?

Coarctation

Most common complication of AAA

Rupture

Ying-Yang sign is seen on Doppler related to ?

Aneurysm

Kissing stents are used to correct:

Iliac artery stenosis

Which of the following arteries are involved in a Type 2 EVAR endoleak?

Lumbar and inferior mesenteric

Hallmark sign for endoleak

Increased in aortic sac size