PowerPoint Presentation

ARRS 2016 Making Waves: Pearls and Pitfalls in the Ultrasound Evaluation of Arterial Stent Complications

AY Mian, G Gunabushanam, J Pellerito, L Scoutt, MV RevzinYale University School of MedicineNew Haven, CT

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BackgroundArterial stenting is a proven and ubiquitous treatment for arterial insufficiency; the list of medical applications continues to grow.

To date, there has been no generalized radiological review of ultrasound findings common to the various types of arterial stents.

Here we discuss broadly applicable principles for ultrasound imaging of arterial stents, emphasizing recognition of the most common and serious complications.

Indications for Arterial Stents in Modern Medical PracticePeripheral vascular disease Carotid artery stenosisRenal artery stenosisCeliac/SMAExtremitiesHepatic stenting, TIPSCardiacVasculitis, stricture

Types of Stents

Stent types (images used courtesy of various industry websites) : Clockwise from top left, a. drug eluting stent, b. various designs for metallic stents used in peripheral vascular disease, c. covered stent0graft and d. metallic expandable aortoiliac stent. These are generally similar in appearance by ultrasound. (Boston Scientific, www.unmc.edu, Biotextiles 2012, Stable Microsystems.)a. b. c. d.

Ultrasound ProtocolGrayscale images through the stent are obtained in sagittal and transverse plane to look for luminal plaque, aneurysm, collections and stent integrity.Color Doppler is obtained to assess stent patency and possible stenosis (look for aliasing).Spectral Doppler is obtained for peak systolic velocities and waveforms proximal, within and distal to the stent.

General US features of Arterial Stent EvaluationBoth greyscale and duplex evaluation is neededAssess for:Patency: velocity/turbulenceLocation: placement/expansion/migrationIntegrity: kinking/ruptureCollections: infection/leak/pseudoaneurysm

DissectionRestenosisPost-stenosisRupture/pseudoaneurysmKinkInfection

Waveforms for Common Arterial Stent Complications

Tortuosity branch stenosis, poorly selected angle false elev velocities, occlusion use power doppler/lower scale, kinking vs breakage, jxn of stents versus rupture, high velocities/turbulence, bruit artifact, although many articles exist on the assessment of stents, there is no unified article analysis, metallic, tandem, perforated, covered av fistula8

Three Categories of Arterial Stent ComplicationsNative VesselStent ItselfLumen

9

Dissection in native vessel proximal to stent.

Native VesselHistory: 69yo F with dissection proximal to the femoral to popliteal artery stentFindings: Dissection flap is seen on greyscale cine loop (arrow) and false lumen is noted on color Doppler cine (arrow). Note the distal stent (S) is intact on the greyscale image. Aliasing (A) on the color Doppler image indicates turbulent flow.SA

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Occlusion distal to the aortoiliac stentNative VesselHistory: 72yo M with leg pain, history of aortobiiliac stent graft repair of AAAFindings: Greyscale and power Doppler images show no flow in the distal SFA (arrow). Spectral Doppler shows no appreciable waveform (arrow), findings compatible with complete SFA occlusion. Aortobiiliac stent-graft is seen on coronal CT spanning a 7cm AAA (arrow) and on a fluoroscopic image (arrow).

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Pseudoaneurysm

Native VesselHistory: 45yo M without h/o trauma presents with a 3d h/o swelling and left hand numbness 4 days after L subclavian artery stent graftingFindings: Color Doppler images shows the stent (S) with a focal leak just distal to the stent margin, within the native vessel (arrow), known as a type 1B endoleak, and the classic yin-yang pattern (Y) within the pseudoaneurysm from to-and-fro flow. Angiogram shows pseudoaneurysm (arrow). Coronal CT shows partial thrombosis of the pseudoaneurysm (arrow). SY

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Pseudoaneurysm (cont) 3 month followup

Native VesselFindings: Color Doppler image in the same patient 3 months later shows the patent stent (S) with complete pseudoaneurysm thrombosis (arrow). Angiogram shows resolution of the pseudoaneurysm (arrow). Axial and coronal CT shows the stent (S) is patent, slightly angulated at the distal vessel, with complete thrombosis of the pseudoaneurysm (arrow). SS

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Stenosis Distal to the Stent.Native Vessel

Findings: Long segment stenosis of the native SFA/popliteal artery distal to stent due to atherosclerotic plaque (arrow). Elevated PSV in the SFA (357cm/s) and aliasing (arrow) seen on color and spectral Doppler.History: 92yo F with leg pain, remote history of SFA stent

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Stent Infection.

Native VesselFindings: The stent (S) and an adjacent area of heterogeneous soft tissue without flow by grayscale (arrows), color Doppler (arrow) and MRI (arrow). WBC scintigraphy shows uptake around the aorta, compatible with infection (arrow). (Note the normal splenic uptake.)History: 89yo M s/p aorto-bifemoral stent-graft and celiac stent presents with fever.SS

Stent Infection (Companion case)

Findings: The stent (S) and an adjacent area of heterogeneous soft tissue by grayscale (arrow), without flow by spectral Doppler. Coronal CT shows wall thickening and adjacent fluid (arrow). WBC scintigraphy shows focal uptake in the left groin, compatible with infection (arrows).History: 70yo F with Left SFA stent complicated by infection/peri-stent phlegmonS

Native Vessel

Stent Fracture and PseudoaneurysmStent Itself

Findings: Grayscale US shows a fracture of the carotid stent (arrow) . Biphasic flow (Yin Yang) is seen outside of the carotid lumen on Color Doppler (arrow) with biphasic flow at the neck on spectral Doppler (B). Radiograph shows the stent fracture (arrow), and a pseudoaneurym is seen on neck CTA (arrow).History: 68yo F with 2 days of neck swelling

BB

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Stent Fracture (companion)

Findings: Angulation of the proximal fracture fragment seen on grayscale (circle and arrows) with pseudoaneurysm (Yin-Yang) on color Doppler (arrow).

Stent ItselfHistory: 81yo M with bruit , h/o carotid stent

Renal Stent FragmentationStent Itself

History: 60yo F with renal artery stenosis presents with HTN

Findings: No abnormalities of the stent are seen on grayscale images, color Doppler shows only partial filling of the lumen with color Doppler (arrow), and elevated PSV on spectral Doppler (=324 cm/s) in the proximal stent (arrow). IR images show fragmentation of the proximal stent resulting in stenosis (see next slide).

Renal Stent Fragmentation (cont)

Stent Itself

History: 60yo F with renal artery stenosis presents with HTN

Findings: Color Doppler shows only partial filling of the lumen with color Doppler (arrow). Fluoroscopic images show fragmentation of the proximal stent resulting in stenosis (arrow). Subtracted angiogram shows stenosis at the RRA origin.

Stent FractureStent Itself

History: 47yo F with history of AV fistula in the forearm presents with swelling and pain.Findings: Grayscale images show a fractured loop AV fistula in the right forearm in sagittal (arrow) and axial (arrow) planes . Color Doppler shows flow in the lumen and no pseudoaneurysm (arrow).

Stent KinkStent Itself

History: 61 yo M with a kinked R SFA stentFindings: Grayscale images show angulation of the kinked area with turbulent flow (arrow). Velocities and waveforms were normal (arrow). Color Doppler shows the kinked area with turbulent flow in the lumen (arrow) .

Proximal Stent MigrationStent Itself

History: 81yo M with left arm pain and swelling, h/o of left subclavian stenosis s/p stent in mid subclavian artery.Findings: Grayscale images show left subclavian stent has migrated proximally into the aortic arch (arrow). Color Doppler shows mild retrograde flow into arch in diastole, turbulent flow in systole (arrows). Spectral doppler shows an area of stenosis and biphasic flow (arrow). CTA shows the stent has migrated into the aortic arch (arrow) .

Systole Diastole

In-Stent Re-stenosis

Findings: Grayscale image showing a stent (S) and in-stent stenosis at the origin of the left renal artery. Color Doppler shows luminal narrowing and turbulent flow (arrow). Spectral Doppler shows elevated velocity = 567cm/s (arrow) at the stenosis and distal tardus parvus waveforms in the left renal parenchyma due to proximal stenosis (arrow) .

Lumen

History: 65-year-old F s/p partial right nephrectomy with left renal artery stenosis at the ostium, status post stent placement, presenting with hypertension.S

In-Stent Re-stenosis (Companion case)

Findings: Grayscale image showing a stent (S) and in-stent stenosis in the L SCA (arrow) . Spectral Doppler shows elevated velocity (= 375) cm/s (circle) and high resistance waveforms (arrow). Angiogram shows the area of focal re-stenosis (arrow).Lumen

History: 55-year-old F with subclavian stent placed for stenosis presents with recurrent arm painS

In-Stent Occlusion with collateralFindings: Power Doppler shows luminal occlusion (arrow) with collateral formation (arrow) . Color Doppler image shows distal reconstitution (arrow)

Lumen

History: 70yo M with left distal CFA stent presents with pain.S

Progressive Stent Thrombosis/EmbolismHistory: 60yo M with high grade carotid stenosis, TIA 1 day after LCCA stent.LumenFindings: Color Doppler shows severe luminal narrowing and turbulent flow (arrow) within the stent (s) . Angiogram shows filling defects consistent with foci of severe in-stent stenosis (arrow). Spectral Doppler shows elevated velocity (=273 cm/s) (circle) and compensatory low diastolic resistance (arrow) at the stenosis

s

(Cont) Now complete stent thrombosis/distant embolism

Findings: Color Doppler now shows complete occlusion (arrow). CTA shows thrombosed lumen (arrow). Acute infarcts in the brain are now seen with restricted diffusion on DWI/ADC (arrows).

History: 60yo M with high grade carotid stenosis, TIA 1 day after LCCA stent, now with aphasia.Lumen

Lumen

Stent Malposition with PseudoaneurysmFindings: Color Doppler shows a malpositioned carotid stent (S) and a retained catheter fragment (arrow), and a pseudoaneurysm is seen (arrow). Biphasic flow (Yin Yang) is seen outside of the carotid lumen on Color Doppler. RCCA angiogram shows wide-necked, contained pseudoaneurysm (arrow).History: 72yo M with neck pain and swelling, s/p carotid stent

S

History: 62yo male with bruit, h/o RCCA stent 4 years ago. Candy wrapper re-stenosis distal to the stentLumen

Findings: Color Doppler shows luminal narrowing and turbulent flow (arrow). Spectral Doppler shows elevated velocity (arrow) at the stenosis. Angiogram shows RCCA re-stenosis at the distal edge of the stent (arrow).

Tortuosity branch versus stenosis, Poorly selected angle: false versus elevated velocities, Occlusion use of power doppler/lower scale, Kinking versus breakage, Junction of stents versus rupture, High velocities/turbulence versus bruit artifact.Pitfalls in DiagnosisPitfalls

Pitfalls

Pitfall: tortuous vessel causing elevated velocity

Pitfalls

Findings: Grayscale and color Doppler show narrowing of the lumen due to external compression from the plaque that was there when stent was placed, it didnt fully expand the lumen (arrow) .History: 50yo M with no symptoms, carotid stenosis s/p stent.Pitfall: pre-existing plaque mistaken for re-stenosis

PitfallsStent pitfall- no flow due to post-operative airHistory: 64yo M s/p R axillary pseudoaneurysm repair with thrombin injection, presents with pain and cold digits. IR performed the procedure on the same day and found the stent was patent .

Findings: Grayscale image shows the stent (s) but deeper structures are not well seen (arrow) due to dirty shadowing. Color Doppler shows flow on either side of the dirty shadowing (arrow). Power Doppler shows flow throughout the stent (arrow). Spectral Doppler initially shows no flow (arrow) in the stent, but once an appropriate angle is chose without intervening air, normal flow is seen (F). sF

Pitfalls

Pitfall: Bulging portion of stent in carotid, can mimic pseudoaneurysm, cause turbulent flow.

Summary PointsUltrasound is a reliable, powerful and cost-effective means of evaluating arterial stents.

By keeping in mind basic protocol methods and avoiding pitfalls that lead to erroneous findings, ultrasound proves vital for assessing arterial stents.

Complications are common in arterial stents, and will become more common as their uses expand.

In-stent stenosis, occlusion, fracture and fragmentation are readily diagnosed by ultrasound, and have characteristic imaging features. Pseudoaneurysm, and infection are important complications that warrant a high index of suspicion.

Further investigation into the imaging appearance of the newer stents on the market may prove useful as these effective devices continue to find new applications.

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