Vascular Ultrasound

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FUNDAMENTALS FUNDAMENTALS OFOF

VASCULARVASCULARULTRASOUNDULTRASOUND

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steve henao mdsteve henao mdnew mexico heart institutenew mexico heart institute

CarotidCarotidCarotidCarotid

•Carotid disease accounts

for 25%25% of all strokes

•detection by physical

exam is poorpoor

•stroke is the result of

embolizationembolization

•lesions are typically at

the posterolateral wall of

the internal carotid

artery

•Carotid disease accounts

for 25%25% of all strokes

•detection by physical

exam is poorpoor

•stroke is the result of

embolizationembolization

•lesions are typically at

the posterolateral wall of

the internal carotid

artery

CAROTID ULTRASOUNDCAROTID ULTRASOUND

• The most common clinical application is for the detection of proximal ICA atherosclerotic plaque and estimation of stenosis severity.

• The extent of ICA bifurcation diameter reduction predicts the risk for stroke and thus assists clinicians in identifying patients who may benefit from carotid intervention (endarterectomy, stent angioplasty) based on clinical trial results

Scanning the ICAScanning the ICA

grayscale, color Doppler and Pulse-wave Doppler

proximal, middle, and distal portions

>50% stenosis of the proximal ICA renders flow turbulent in the distal ICA

severe stenosis yields parvus et tardus waveforms

proxmial ICA stenosis severity is established proxmial ICA stenosis severity is established on the baisis of :on the baisis of :

GRAYSCALE APPEARANCE

PEAK SYSTOLIC VELOCITY OF THE ICA

END DIASTOLIC VELOCITY OF THE ICA

PEAK SYSTOLIC VELOCITY OF THE COMMON CAROTID ARTERY

velocity ratios

Grayscale imaging is Grayscale imaging is performed to localize performed to localize

and characterize and characterize plaque severity as:plaque severity as:

Grayscale imaging is Grayscale imaging is performed to localize performed to localize

and characterize and characterize plaque severity as:plaque severity as:

•less than 50%less than 50%•greater than or equal to 50%greater than or equal to 50%

•occlusionocclusion

•less than 50%less than 50%•greater than or equal to 50%greater than or equal to 50%

•occlusionocclusion

Color Doppler flow Color Doppler flow mapping is usefulmapping is useful Color Doppler flow Color Doppler flow mapping is usefulmapping is useful

to define the lumen- to define the lumen- because hypoechoic because hypoechoic

plaque and restenosis plaque and restenosis material material may be may be

inapparent by regular inapparent by regular grayscale grayscale

to define the lumen- to define the lumen- because hypoechoic because hypoechoic

plaque and restenosis plaque and restenosis material material may be may be

inapparent by regular inapparent by regular grayscale grayscale

assessment of stenosisassessment of stenosis

• angiographyangiography is the traditional gold standard

• ultrasoundultrasound has developed steadily with sufficiently reliable preoperative results

assessment of stenosisassessment of stenosis

• there arethere are MANYMANY differences in the carotid reference standard to establish percent stenosis

stenosis ‘standards’stenosis ‘standards’

Consensus panel grayscale and doppler ultrasound criteria for diagnosis of internal

carotid artery stenosis (2003)

validating the consensus document (2011)

“receiver operatingreceiver operatingcharacteristiccharacteristic”

The ROC curve was first developed by electrical engineers and radar engineers during World War II for detecting enemy objects in battlefields and was soon introduced to psychology to account for perceptual detection of stimuli.

ROC analysis since then has been used in medicine, radiology, biometrics, and other areas for many decades and is increasingly used in machine learning and data mining research.

Source: Journal of Vascular Surgery 2011; 53:53-60 (DOI:10.1016/j.jvs.2010.07.045 )

analysis

the parameter with the highest Pearson correlate to angiography was the PSVPSV (0.813), in contrast to both EDV (0.7) and ICA/CCA PSV ratios (0.57, P < .0001)

A PSVPSV of >230 cm/s was the most sensitive in the diagnosis of 70% to 99% stenosis, and adding other parameters (EDV or ratios) did not improve the overall accuracy

analysis

Using a PSVPSV of >230 cm/s with an EDVEDV of >100 cm/s or a systolic ratiosystolic ratio of >4 would improve the PPV to 99% and the specificity to 97%

analysis

the ICA/CCA PSV ratio and the ICA EDV are useful parameters when the ICA PSV may not be representative of the extent of carotid disease because of technical or clinical factors:

• presence of contralateral high-grade stenosis or occlusionpresence of contralateral high-grade stenosis or occlusion

• discrepancy between visual assessment of the carotid discrepancy between visual assessment of the carotid plaque and the ICA PSVplaque and the ICA PSV

• elevated CCA velocity, low cardiac output, or elevated CCA velocity, low cardiac output, or hyperdynamic cardiac statehyperdynamic cardiac state

analysis

patients with low cardiac low cardiac output would have a low ICA PSV, which is disproportionate when compared with the ICA/CCA PSV ratio.

In these situations, the clinician must rely on the presence of the plaque and perhaps the ICA/CCA ratio rather than the absolute ICA PSV

carotid endarterectomythe PSV threshold of 230 cm/s for detecting ≥70% stenosis can be used before CEA for symptomaticsymptomatic patients since surgery has been proven to be beneficial, even for ≥50% symptomatic stenosis

A higher PSV (eg, ≥280 cm/s), which has a PPV of 97%, or a PSV of >230 cm/s with an EDV of >100 cm/s, or a systolic ratio of >4 (PPV of 99%) may be considered in asymptomatic patientsasymptomatic patients

POST-CAROTID STENTING CRITERIA

Interpretation of high-grade (>75% to 80%) in-stent stenosis should be based on elevation of EDV beyond 125 to 140

cm/second

SUMMARY(2014)

The variability in carotid stenosis interpretationvariability in carotid stenosis interpretation across accredited facilities undermines the usefulness of this important diagnostic modality.

The IAC Vascular Testing Board of Directors feels that more standardization of carotid duplex ultrasound diagnostic criteria will address these concerns and will enhance the accuracy, reproducibility, portability and value of duplex sonography for the diagnosis of carotid disease.

lower extremitylower extremityarterialarterial

Indications for Indications for Duplex Arterial TestingDuplex Arterial Testing

• Acute limb ischemiaAcute limb ischemia as a result of arterial thrombosis caused by atherosclerosis, thromboembolism, trauma, or peripheral aneurysm

• Chronic arterial occlusion/stenosis with intermittent intermittent claudicationclaudication or an abnormal (<0.9) ankle-brachial index (ABI)

• Chronic arterial occlusion and threatened limb loss caused by rest pain, ischemia, ulceration, or gangrene (i.e., critical limb critical limb ischemiaischemia)

• Aneurysmal diseaseAneurysmal disease, including false aneurysm after catheter-based interventions, or screening for abdominal aortic aneurysm (AAA) in “selected,” high-risk patients

• SurveillanceSurveillance for hemodynamic failure of arterial interventions (percutaneous transluminal angioplasty [PTA], stent-grafts, bypass grafting, dialysis access procedures)

criteria for classifyingcriteria for classifyingperipheral artery lesionsperipheral artery lesions

triphasic waveform

no spectral broadening

triphasic with minimal spectral broadening

PSV increased PSV increased <30%<30% relative to adjacent proximal segment (<150 cm/s)

proximal and distal waveforms remain normal

Triphasic wave usually maintained

reverse flow component may be diminished

spectral broadening prominent

filling in of clear area under the systolic peak

PSV increased 30 - 100%PSV increased 30 - 100% relative to the adjacent proximal segment (150-200cm/s)

proximal and distal waveforms remain normal

monophasic wave with loss of reverse flow component and forward flow throughout cardiac cycle

extensive spectral broadening

PSV >100%PSV >100% relative to proximal segment (>200-300cm/s)

distal wave monophasic with reduced systolic velocity

• no flow detected

• distal waveforms monophasic with reduced systemic velocities

Vein Bypass Evaluation

CharacteristicsCharacteristicsofof

vein graft stenosisvein graft stenosis

Graft Stenosis: Less Than 20% Less Than 20%

• Velocity ratio less than 2

• Mild turbulence in systole

• PSV less than 200 cm/sec

Graft Stenosis: 20% to 50%20% to 50%

• Velocity ratio greater than 2

• Turbulence throughout

• Velocity ratio greater than 2.5

• Severe turbulence with reversed flow components

• PSV greater than 200 cm/sec

Velocity ratio greater than 3.5

End-diastolic velocity in flow jet greater than 100 cm/sec

PSV greater than 300 cm/sec

Impending Graft ThrombosisImpending Graft Thrombosis

• Velocity ratio greater than 3.5

Risk Stratification for graft thrombosis based Risk Stratification for graft thrombosis based on vascular lab testing dataon vascular lab testing data

approximately 20% of infrainguinal vein bypasses will have a category I or II stenosis identified within the

first year after grafting

AORTAAORTAAORTAAORTA

AortaAorta

Normal Infrarenal abdominal aorta 2cm (range, 1.4 to 3 cm)

‘dilated’ = AP diameter 3 to 3.5 cm

‘aneurysm’ = > 3.5 cm, especially if mural thrombus is imaged

AORTAAORTA

Reporting should include:

• morphology (saccular, fusiform)

• extent

• presence of mural thrombus or dissection

• outside wall-to-wall diameter

AORTAAORTA• typical growth rate for AAA= 3 to

4 mm/year

RENAL RENAL arteryarteryRENAL RENAL arteryartery

Renal Artery Duplex

HTNHTN and sudden deterioration in renal deterioration in renal functionfunction are the most common indications

• atherosclerosisatherosclerosis 95%

• 1 to 6% of HTN patients, but most common cause of HTN in pts >50

• men affected 2x women

arterial fibrodysplasiaarterial fibrodysplasia 5%

RARRAR

• interpretation of renal artery stenosis is based on the maximum PSV obtained from the aorta above the renal arteries (at the level of the SMA) and the renal artery itself

renal interpretation& reporting

Normal Study:

• PSV: 80 ± 20 cm/second

• Renal-to-aortic PSV ratio (RARRAR): less than 3.5

• Normal waveform: biphasicbiphasic

• No focal velocity increase

• Low resistance waveformLow resistance waveform (RI <0.8)

• - similar to internal carotid

Less Than 60% Diameter Reduction

• Low resistanceLow resistance waveform

• RARRAR: less than 3.5

• PSV: less than 180 cm/sec

• Focal velocity increase

Greater Than 60% Diameter Reduction

• RARRAR: greater than 3.5

• True post-stenotic turbulence

• Focal PSV increase greater than 180 cm/sec

NORMAL KIDNEYNORMAL KIDNEY

• LENGTH: 9 TO 13 CM

• WIDTH: 4 TO 6 CM

• REASONABLE DIFFERENCE IN LENGTH BETWEEN KIDNEYS: 1 CM

• length difference greater than 1 cm suggests that the smaller kidney is abnormal

renalrenalspectral velocity

criteria

• biphasic: normal (similar to internal carotid artery)

• triphasic: highly abnormal

• monophasic: highly abnormal, consistent with distal occlusion or significant renal malfunction

renovascular resistance

RI: measured in the body of the kidney vasculature to assess renal resistance and suggest perfusion

• RI < 0.7 NORMAL

• RI 0.7 to 0.8 questionably elevated

• RI >0.8 ABNORMAL

CELIACCELIACSMASMAIMAIMA

Celiac

NORMAL

• PSV = 90 to 110 cm/second

• low-resistance flow pattern

• no plaque visualized

• laminar and forward flow throughout diastole

celiac

< 70% Stenosis

• PSV: < 200 cm/second

• EDV: < 55 cm/ second

• resistive index similar to that of the ICA

celiac

> 70% stenosis

• PSV > 200 cm/second

• EDV > 55 cm/ second with retrograde hepatic artery flow

NORMAL

• PSV: 95 to 150 cm/second

• high-resistance flow pattern in fasting state

• EDV > 0 after a meal

• no plaque visualized

• laminar and forward flow throughout diastole

< 70% Stenosis

• PSV <300 cm/second

• EDV < 45 cm/ second with diastolic flow reversal in the distal SMA

• plaque visualized

• color doppler evidence of focal and post-stenotic turbulence

> 70% Stenosis

• PSV > 300 cm/second

• EDV > 45 cm/ second with loss of diastolic flow reversal

• mesenteric - aorta ratio > 3

• velocity spectra change with test meal

• increase in PSV at sites of stenosis with damping of the distal waveform

LOWER EXTREMITYLOWER EXTREMITYVENOUSVENOUS

VENOUS REFLUX

• a prospective study has demonstrated that the acceptable physiologic flow reversal is different for different veins

Jeanneret C, Labs KH, Aschwanden M, et al: Physiological reflux and venous diameter change in the proximal lower limb veins during a standardised Valsalva manoeuvre. Eur J Vasc Endovasc Surg 1999; 17:398-403.

VENUS REFLUX

the theory supporting this concept is that larger veins have fewer valves

• the expected time for the valve leaflets to come together is longer than that for smaller, shorter veins

venous reflux

REFLUX = 1000 milliseconds

• common femoral

• femoral

• popliteal

venous reflux

• superficial

• deep femoral

• deep calf axial

• muscular veins

venous reflux

• perforating veins

part onepart one

steve henao mdsteve henao mdnew mexico heart institutenew mexico heart institute

Vascular Ultrasound

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