Vascular Imaging

Types of Arterial Approach

• • Right femoral artery

  • Left femoral artery

  • Left axillary artery

  • Right axillary artery

  • Translumbar aorta

  • Brachial arteries

  • Antegrade femoral artery

  • Through a surgical graft

Right Femoral Approach (Preferred)

• • Easily accessible for manipulations and hemostasis

  • Large-caliber vessel

  • Well-defined landmarks exist.

  • Most angiographers are right-handed.

  • Low complication rate compared with other approaches

Standard Femoral Approach: Seldinger Technique

• • Double-wall technique is preferred.

  • Advantages of “single-wall” puncture are only theoretical.

  • Use fluoroscopy to determine puncture level.

    • Artery entry: midfemoral head

    • Skin entry: inferior margin of femoral head

  • Local anesthesia at skin entry site: 1%–2% lidocaine

  • Palpate artery above site

  • Advance 18-gauge Seldinger needle (45–60 degree angle) to bone.

  • Remove central stylet and withdraw slowly.

  • Advance guidewire through needle while good pulsatile flow jets out of the hub.

  • Always use fluoroscope when advancing a guidewire.

  • Never advance guidewire against resistance.

  • Exchange needle over wire for dilator or catheter.

Advantage of Puncturing Symptomatic Extremity

• • Inflow can be assessed by obtaining pull-down pressures.

  • Should complications arise (i.e., emboli, thrombosis), they will affect the already compromised extremity.

  • Conversion to antegrade approach is possible if necessary.

Disadvantage of Puncturing Symptomatic Extremity

• • May interfere with surgical procedure if complication develops (e.g., hematoma)

  • If a severe stenosis is present, a catheter may obturate the vessel completely.

Axillary Artery Approach

• • Main indication for this approach is nonpalpable femoral pulses (i.e., aortic occlusion)

  • Left-sided approach is preferred.

    • Easier to access descending aorta

    • Left-sided approach crosses fewer central nervous system (CNS) arteries.

  • 3J wire is preferred.

  • Disadvantages:

    • Difficult to compress

    • Relatively high incidence of complications (e.g., stroke, bleeding, thrombosis)

    • Brachial plexus injury

  • Always check for blood pressure (BP) differential to detect occult arterial disease.

Translumbar Approach (TLA)

• • Main indication for this approach is nonpalpable peripheral pulses.

  • High TLA is preferred: above abdominal aortic aneurysm (AAA), grafts, diseased distal aorta

  • Disadvantages:

    • Patient must lie prone for entire study.

    • Higher incidence of bleeding (debatable)

    • More difficult to manipulate catheters

  • Use an 18-gauge needle/sheath system

Antegrade Femoral Approach

• • The main indication for this approach is a distal extremity intervention (e.g., percutaneous transluminal angioplasty [PTA] of the superficial femoral artery [SFA]).

  • Retrograde catheterization may be converted to antegrade access with a Simmons 1 catheter and a 3J or angled guidewire.

  • Difficult to manage in obese patients

Puncture Site Complications

• • Minor hematoma, >5%

  • Major hematoma that requires surgical therapy, <0.5%

  • Arteriovenous fistula (AVF), 0.05%

  • Pseudoaneurysm, 0.01%

  • Vessel thrombosis, 0.1%

  • Neuritis

  • Infection

Contrast Complications (see Chapter 13 )

• • Renal failure

  • Cardiac failure

  • Phlebitis (venography)

  • Anaphylactoid reactions (rare with arteriography)

Catheter-Related Complications

• • Cholesterol emboli

  • Thromboembolism

  • Cerebrovascular accident (CVA)

  • Arterial dissection

Pearls

• • Complications can be limited by:

    • Careful preangiography assessment (e.g., correct coagulopathies)

    • Appropriate approach (e.g., history and pulse examination)

    • Good technique (e.g., trained angiographer)

  • Risk factors for development of AVF or pseudoaneurysm:

    • Low puncture

    • Heparinization

    • Large catheters

  • Most puncture site complications can be prevented by good manual compression and correction of coagulopathies before angiography.

  • Always reassess patient after the procedure.

Generic Types

• • Diagnostic catheters

    • High-flow catheters with side holes are used for central vessels (>10 mL/s).

    • Low-flow catheters with end holes are used for selective arterial work.

  • Therapeutic catheters

    • Balloon catheters (percutaneous transluminal angioplasty [PTA] and balloon occlusion)

    • Atherectomy catheters

    • Coaxial infusion catheters

    • Embolization catheters

Measurements

• • Outer diameter (OD): catheter size is determined by the OD and given in “French” size. French (Fr) = the circumference in millimeters. Divide French size by 3 to obtain OD in millimeters.

  • Inner diameter (ID): measured in 1/1000 of an inch

  • Length: measured in centimeters. 65 cm is commonly used for abdominal studies. 100 cm is usually used for arch and carotid studies.

SPECIFIC CATHETERS

Catheter Type	Use
Pigtail	Aorta, pulmonary
Cobra (C)	Mesenteric, renal, contralateral iliac
Simmons (S)	Mesenteric, arch vessels
Headhunter (H)	Carotid, arch vessels
Berenstein	Carotid
Davis	Arch, carotids, upper extremity
Tracker	Coaxial subselection

Materials

• • Thermoplastic materials (polyurethane and polyethylene) are very commonly used for catheter manufacturing.

  • Nylon: combined with polyurethane to manufacture high-flow, small French catheters

  • Teflon: very stiff, low-friction material

  • Braided catheters: internal wire mesh improves torquability.

Pearls

• • Rate and volume of contrast are reduced for digital subtraction angiography.

  • Rate and volume always depend on rate of blood flow and size of vessel observed under fluoroscopy.

  • Shorter catheters allow for higher flow rates and easier exchangeability.

  • The larger the ID, the better the flow dynamics.

  • It is good practice to size catheters, sheaths, and wires before their use; considerable discrepancy of dimensions may occur (variable among manufacturers).

  • Maximum flow rate and pressure tolerance of catheters are specified by manufacturer on package or insert.

Measurements

• • Length: 145 cm is the standard length and allows exchanges of 65-cm catheters. “Exchange length” wires are 220–250 cm in length and are used for long catheters.

  • OD: guidewires are designated by OD in 1/1000 of an inch: 0.018–0.038 is the most common size range.

  • J tip: refers to the radius of wire curvature in millimeters (i.e., a 3J wire has a 3-mm distal curvature)

Indication

• • Hemorrhage

    • Gastrointestinal (GI) bleeding

    • Varices

    • Traumatic organ injury

    • Bronchial artery hemorrhage

    • Tumors

    • Postoperative bleeding

  • Vascular lesions

    • Arteriovenous malformation (AVM) or fistula (AVF)

    • Pseudoaneurysms

  • Preoperative devascularization

    • Renal cell carcinoma (RCC)

    • AVM

    • Vascular bone metastases

  • Other

    • Hypersplenism

    • Gonadal varices

    • Hepatic chemoembolization

General Principles

• • • Proximal occlusion is equivalent to surgical ligation. It does not compromise collateral flow. For this reason, it may be ineffective to control bleeding if collaterals continue to supply the bleeding site.

    • Distal embolization usually infarcts tissue and is followed by necrosis.

    • Temporary versus permanent embolization: tumors, vascular lesions, varices, and preoperative embolizations are usually permanent occlusions. GI bleeding is best treated with Gelfoam at first (if vasopressin has failed).

    • Be as selective as possible (i.e., use tracker catheter).

    • Prevent reflux of embolic material into other vessels.

    • Document preangiographic and postangiographic appearance.

Embolic Agents

• • Temporary

    • Surgical gelatin (Gelfoam): not U.S. Food and Drug Administration (FDA)–approved for embolization. Pledgets are cut to size or occlude large vessels; Gelfoam powder occludes distal vessels and causes infarction.

  • Permanent

    • Steel coils of variable sizes are commercially available; coils obstruct proximal vessels.

    • Microcoils (platinum) are used to occlude more distal vessels.

    • Detachable balloons are used for large vessel occlusion. FDA restricted. Useful for pulmonary AVF, carotid cavernous fistula (CCF).

    • Polyvinyl alcohol (Ivalon): small particles for distal occlusion. 200–1000 µm. Suspend in albumin–contrast agent mixture.

    • Absolute ethanol: causes tissue necrosis. Used with proximal balloon occlusion to minimize shunting and reflux. Useful for solid organ necrosis (i.e., malignant tumors).

    • Plastic polymers: glue, tissue adhesives

Complications

• • Postembolization syndrome (fever, elevated white blood cell [WBC] count), 40%

  • Infection of embolized area (administer prophylactic antibiotics)

  • Reflux of embolic material (nontarget embolization)

  • Alcohol causes skin, nerve, and muscle infarction if used in the periphery; its use should be restricted to parenchymal organs.

Indication

• • Arterial graft thrombosis

  • Native vessel acute thrombosis

  • Before percutaneous intervention

  • Hemodialysis AVF or graft

  • Venous thrombosis

    • Axillosubclavian

    • Portal vein (PV), superior mesenteric vein (SMV)

    • Inferior vena cava (IVC)

General Principles ( Fig. 8.1 )

• • Always obtain a diagnostic angiogram before thrombolysis.

  • Streptokinase is no longer used (antigenic side effects).

  • Recombinant tissue plasminogen activator (r-tPA) is no more effective than urokinase (UK) but is much more expensive.

  • Favorable prognostic factors for thrombolysis:

    • Recent clot (<3 months)

    • Good inflow/outflow

    • Positioned in thrombus

  • End points of thrombolytic therapy:

    • No lysis present after 12 hours of infusion

    • Major complication develops

    • Severe reperfusion syndrome

    • Progression to irreversible ischemia

  • Successful thrombolysis is defined as:

    • >95% lysis of thrombus

    • Clinical reperfusion

  • Always treat underlying lesions.

  • Overall success:

    • Grafts, 90%

    • Native arteries, 75%

  • Heparinize concomitant with UK infusion

  • Monitor in intensive care unit (ICU)

  • No good correlation among success, complications, and blood tests

Techniques

• • Low-dose technique (constant)

    • 100,000 U/hr of UK

    • Repeat angiogram after 12 hours

  • High-dose technique (graded)

    • 250,000 U/hr × 4 hours of UK

    • Repeat angiogram and then 125,000 U/hr

  • Pulse spray ultrahigh dose

    • 600,000 U/hr in 5000 U of UK bolus doses

    • Aliquots every 30 s

  • Catheter placement

    • Coaxial dual infusion is best.

    • 5-Fr catheter lodged in proximal thrombus

    • T3 or infusion wire (Katzen) coaxially into distal thrombus

    • Split infusion of UK into proximal and distal catheters

    • Secure skin entry site

  • Tissue plasminogen activator (tPA) infusion

    • tPA (arterial): infuse at 1 mg/hr total dose divided among infusion sites. Total maximum dose per patient is 100 mg. tPA has half-life of 6 min.

    • tPA (venous): same infusion rate as arterial, lower bleeding complication rate

    • tPA (line clearance): 0.5 mg/hr × 3–4 hours

Contraindications

• • Absolute

    • Active bleeding

    • Intracranial lesion (stroke, tumor, recent surgery)

    • Pregnancy

    • Nonviable limb

    • Revascularization of nonviable limb will cause acute renal failure and cardiovascular collapse because of lactic acid and myoglobin

    • Infected thrombus

  • Relative

    • Bleeding diathesis

    • Cardiac thrombus

    • Malignant hypertension (HTN)

    • Recent major surgery

    • Postpartum

  • Complications

    • Major hemorrhage requiring termination of UK, surgery, or transfusion (e.g., intracranial hemorrhage, massive puncture site bleed), 7%

    • Minor hemorrhage, 7%

    • Distal embolization

    • Pericatheter thrombosis

    • Overall, termination of therapy is required in 10%.

Indication

• • Claudication or rest pain

  • Tissue loss

  • Nonhealing wound

  • Establish inflow for a distal bypass graft

  • Hemodialysis AVF or grafts

General Principles

• • Premedication with aspirin and 10 mg of nifedipine

  • Ipsilateral approach is preferred.

  • Heparinize (5000–10,000 U) after the lesion is crossed.

  • Diagnostic angiogram is obtained before PTA.

  • Measure pressure gradients with borderline lesions.

  • Significant gradient >10 mm Hg at rest; >20 mm Hg after vasodilator; >10% systolic BP

  • Pharmacologic adjuncts

    • Intraarterial (IA) nitroglycerin or tolazoline for vasospasm and provoked pressure measurements

  • Balloon size: sized to adjacent normal artery

    • Common iliac artery: 8–10 mm

    • External iliac artery: 6–8 mm

    • Superficial femoral artery (SFA): 4–6 mm

    • Renal artery: 4–6 mm

    • Popliteal artery: 3–4 mm

  • Wire should always remain across lesion

  • Repeat angiogram and pressure measurements after angioplasty.

  • Postprocedure heparin with “limited flow” results (dissection, thrombus)

Prognostic Indicators

• • Large vessels/proximal lesions respond better than small vessel/distal lesions.

  • Stenoses respond better to PTA than occlusions.

  • Short stenoses respond better to PTA than long stenoses.

  • Isolated disease responds better to PTA than multifocal disease.

  • Poor inflow or poor outflow decreases success.

  • Limb salvage interventions have a poor prognosis.

  • Diabetics have a poorer prognosis than nondiabetic patients.

PTA Results

• • Iliac system

    • 95% initial success

    • 70%–80% 5-year patency

  • Femoral-popliteal

    • 90% initial success

    • 70% 5-year patency

  • Renal artery

    • 95% initial success

    • Fibromuscular dysplasia (FMD): 95% 5-year patency

    • Atherosclerosis: 70%–90% 5-year patency

    • Ostial lesions have a poorer prognosis.

  • Acute failures are due to thrombosis, dissection, or inability to cross a lesion.

  • Recurrent stenosis

    • Intimal hyperplasia (3 months–1 year)

    • Progression of disease elsewhere (>1 year)

Complications

• • Groin complications (same as diagnostic angiography)

  • Distal embolism

  • Arterial rupture (rare)

  • Renal infarction or failure (with renal PTA)

Indications for Metallic Stents

• • Unsuccessful PTA

  • Recurrent stenosis

  • Venous obstruction, thrombosis

  • Transjugular intrahepatic portosystemic shunt (TIPS)

Indications for Stents in Revascularization Procedures

• • Long-segment stenosis

  • Total occlusion

  • Ineffective or unsuccessful PTA:

    • Residual stenosis >30%

    • Residual pressure gradient >5 mm Hg rest, >10 mm Hg posthyperemia

    • Hard, calcified plaque

    • Large post-PTA dissection flap

  • Recurrent stenosis after PTA

  • Ulcerated plaque

  • Renal ostial lesions

Stent Results

• • Iliac artery: over 90% 5-year patency (better than PTA)

  • Renal artery and other vessels: limited long-term data

Established Indications

• • Portal HTN with variceal bleeding that has failed endoscopic treatment

  • Refractory ascites

  • Hepatic pleural effusion (hydrothorax)

Controversial Indications

• • Budd-Chiari syndrome

  • Pretransplant

  • Hepatorenal syndrome

  • Venoocclusive disease

General Principles

• • Confirm PV patency before procedure (US, CT, or angiography).

  • Preprocedure paracentesis may be helpful.

  • Right internal jugular vein (RIJV) is the preferred access vessel.

  • Goal: portosystemic gradient <10 mm Hg, decompression of varices

Contraindications

• • Absolute

    • Severe right-sided heart failure with elevated central venous pressure

    • Severe polycystic liver disease

    • Uncontrolled systemic infection or sepsis

    • Liver abscess

    • Unrelieved biliary obstruction

    • Portal HTN from arterioportal fistula

  • Relative

    • Severe encephalopathy

    • PV thrombosis

    • Hepatic vein obstruction/thrombosis

    • Severe coagulopathy (INR >5)

    • Thrombocytopenia (<20,000/cm ³ )

    • Moderate pulmonary HTN

    • Severe stenosis or occlusion of celiac or HA

    • Large liver hypervascular tumor (hepatoma)

    • Severe liver failure (TIPS have unclear survival benefit)

Technique ( Fig. 8.3 )

• • RIJV approach

  • Obtain wedged hepatic pressure and venogram

  • Create tract from right hepatic vein to PV with 16-gauge needle

  • Advance catheter over wire into portal venous system

  • Obtain portal venogram

  • Measure portal pressures

  • Dilate tract with PTA balloon (8 mm)

  • Deploy metallic stent (Palmaz or Wallstent) or stent graft

  • Dilate stent until gradient <10 mm Hg

  • Coil embolization of varices optional

Results

• • Patency: 50% at 1 year

  • Recurrent bleeding in 10%

Complications

• • Hepatic encephalopathy 10%; more likely when residual gradient is <10 mm Hg

  • Bleeding

  • Shunt thrombosis or stenosis

  • Right-sided heart failure

  • Renal failure

Signs of Malfunction

• • No flow

  • Low-velocity flow (<50–60 cm/s) at portal venous end of shunt

  • Reversal of flow in hepatic vein away from IVC

  • Hepatopedal flow in intrahepatic PV

  • Reaccumulation of ascites; varices; recanalized umbilical vein

Alternatives to Tips

• • Direct intrahepatic portocaval shunt (DIPS)–modified TIPS with intravascular US guidance

  • Balloon-occluded retrograde transvenous obliteration (BRTO)–gastric varices

  • Partial splenic embolization (PSE)–variceal hemorrhage

  • These techniques increase portal venous pressure and may result in worsening of untreated varices

Technique

• • RIJV approach preferred.

  • Right hepatic vein is selected with wire/catheter, and sheath advanced.

  • Core biopsy device (18- to 19-gauge) is advanced into the liver parenchyma.

Venous DSA

• • Catheter in central venous structure; a combined large volume and high concentration of contrast agent is given as a bolus.

  • Adequate results in only 70% of patients

  • Invasive study

Arterial DSA

• • Advantages: lower iodine concentration required than that for cut radiograph, less pain, speedy

  • Disadvantages: less resolution, motion, and bowel gas artifacts

Monitoring Heparin Therapy

• • Activated clotting time (ACT) is the method of choice for monitoring heparin therapy.

    • Preheparin administration: <120 s

    • Heparin drip: <300 s

    • Catheter and percutaneous transluminal coro­nary angioplasty (PTCA): >200 s

    • Postprocedure/sheath removal: <200 s

Heparin

Mechanism of action: Potentiates the action of antithrombin III and thereby inactivates thrombin (as well as activated coagulation factors IX, X, XI, XII, and plasmin) and prevents the conversion of fibrinogen to fibrin; heparin also stimulates release of lipoprotein lipase (lipoprotein lipase hydrolyzes triglycerides to glycerol and free fatty acids). Half-life: 1–2 hours, depending on route. Stop 2 hours before procedure.

Coumadin (Warfarin)

Mechanism of action: Interferes with hepatic synthesis of vitamin K-dependent coagulation factors (II, VII, IX, X). Duration of action is 2–5 days. Stop 4 days before procedure.

Fragmin (Dalteparin)

Low-molecular-weight heparin. Subcutaneous (SC) dose, once daily after the loading dose. Duration: >12 hours; half-life: 2–5 hours. Stop the dose 24 hours before procedure.

Argatroban

Direct thrombin inhibitor, IV infusion; half-life: 39–51 min. Stop 4 hours before procedure.

Arixtra (Fondaparinux)

Factor X inhibitor; half-life: 17–21 hours, SC dose once. Stop 24 hours before procedure.

Plavix (Clopidogrel)

Platelet aggregation inhibitor. Pharmacodynamic/kinetic peak effect: 75 mg/day; bleeding time: 5–6 days. Platelet function: 3–7 days; half-life: ~8 hours. Discontinue 7 days before procedure.

ReoPro (Abciximab)

Glycoprotein IIb/IIIa inhibitor. IV dosage. Phar­macodynamic/kinetic half-life: ~30 min. Platelet function returns to normal 24–48 hours after discontinuation of infusion. Antiplatelet effects can be reversed with platelet transfusions.

Other Antiplatelet Agents

Aspirin, cilostazol, dipyridamole, eptifibatide, ticlopidine, tirofiban. Stop most of the antiplatelet agents 5 days before procedure.

Recommended

• • All biliary, renal, and other nonvascular interventions

  • Stent placements, TIPS, ports

  • (Chemo)embolizations

  • Patients with increased risks: endocarditis, transplant

  • G-tube in patients with head and neck cancer

  • Solid organ biopsies

Not Recommended

• • Diagnostic angiography

  • Vena cava filter

  • Regular G-tube (nonhead and neck cancer patients)

  • Simple biopsies: thyroid, subcutaneous

  • Paracentesis and thoracentesis

Computed Tomography

• • Indications:

    • Diagnosis and surveillance of aneurysms

    • Aneurysm rupture

    • Aortic dissection

  • Spiral CT is currently expanding CT indications.

  • CT is not yet validated as the sole evaluation of traumatic arch injuries.

Magnetic Resonance Imaging

• • Indications:

    • Diagnosis and surveillance of aneurysms

    • Aortic dissection

  • Allows evaluation of the aortic root better than CT

  • MRA of great vessels is gaining in diagnostic importance.

Aortography

• • Indications:

    • Preoperative aneurysm assessment

    • Traumatic arch injury

    • Equivocal CT or MRI

  • Remains the gold standard diagnostic tool but is rarely the initial diagnostic examination for the thoracic aorta.

Transesophageal Echocardiography

• • Indications:

    • Aortic dissection

    • Associated cardiac disease (aortic insufficiency [AI], left ventricle [LV] dysfunction)

  • Not validated to evaluate traumatic aortic injury

Thoracic Aortography Technique

• • Catheter: 7- to 8-Fr pigtail

  • Contrast: Hypaque 76 or nonionic equivalent

  • Rate: 30–40 mL/s × 2 s (total: 60–80 mL)

  • Fast filming: 3/s × 3. Higher rate for DSA.

  • Always perform imaging in at least two orthogonal views.

Causes

• • Atherosclerosis

  • Dissection

  • Cystic medial generation

  • Connective tissue diseases (Marfan, Ehlers-Danlos)

  • Syphilis

  • Posttraumatic pseudoaneurysm

  • Mycotic aneurysm

  • Aortitis

    • Takayasu arteritis

    • Giant cell aortitis

    • Collagen vascular diseases (rheumatoid arthritis, ankylosing spondylitis)

Pearls

• • True aneurysms tend to be fusiform.

  • False aneurysms tend to be saccular.

  • Posttraumatic, mycotic, and postsurgical aneurysms are false aneurysms.

  • Bicuspid aortic valve is a risk factor for thoracic aortic aneurysm

  • Ascending aorta aneurysm associated with annuloaortic ectasia, syphilis, postoperative aneurysm, aortic valve disease, or aortitis.

  • thoracic aortic aneurysm mimics: ductus diverticulum, aortic spindle

Complications

• • Expansion

    • Pain

    • Hoarseness, dysphagia

    • Aortic insufficiency

  • Rupture (uncommon if <5 cm)

    • Rupture into pericardial or pleural space, trachea, mediastinum, esophagus

    • Rupture into SVC (aortocaval fistula), PA (aortopulmonary fistula)

Radiographic Features

Angiography ( Fig. 8.8 )

• • Most useful in preoperative assessment of asymptomatic patients

  • Appearance

    • Fusiform > saccular

    • Determine proximal and distal extent (often thoracoabdominal)

    • Determine branch involvement

    • Coexistent aneurysmal or occlusive disease

  • Not accurate in determining aneurysm size because of:

    • Magnification

    • Layering of contrast

    • Thrombus in the lumen

  • An indicator of an impending rupture is focal ectasia (so-called pointing aneurysm, or nipple of aneurysm)

Computed Tomography

• • Mural thrombus well seen

  • Dual energy CT (DECT) may be helpful in characterizing plaques by generating calcium and iodine images

  • Extraluminal extent and contained rupture better seen than by angiography

  • Signs of rupture (see also AAA below)

    • High attenuation crescent in the mural thrombus

    • Draped aorta sign—posterior aortic wall closely apposed to the spine

    • Penetrating ulcer

    • Hemothorax

Radiographic Features ( Fig. 8.9 )

• • Symmetric sinus involvement (“tulip bulb”)

  • Ascending aorta is most commonly involved.

  • Dissection is a frequent complication.

  • Calcifications are rare.

Radiographic Features ( Fig. 8.10 )

• • Asymmetric saccular sinus involvement

  • Tree-bark calcification is common.

  • Dissections are rare.