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Introduction to Carotid Ultrasound and Transcranial Doppler

Ultrasound

Ryan Hakimi, DO, MSDirector, Critical Care Neurology

Assistant ProfessorDepartment of Neurology

The University of Oklahoma Health Sciences CenterJanuary 16, 2015

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Disclosures

Many of the slides have been adapted from slides presented at the American Society for Neuroimaging Annual Meetings by my mentors

FINANCIAL DISCLOSURE Nothing to disclose

UNLABELED/UNAPPROVED USES DISCLOSURE Nothing to disclose

Andre Alexandrov, MD Zsolt Garami, MD Charles Tegeler, MD Alex Razumovsky, PhD

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Objectives Review the basic principles of carotid ultrasound (CUS)

and transcranial Doppler ultrasound (TCD) Illustrate the process of plaque morphology and

assignment of range of carotid stenosis Illustrate the process of determining vasospasm by TCD Discuss some of the current applications of TCD

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Principles of Ultrasound

Blood flow velocity through a cross sectional area of a particular vessel (cm/s)

Blood flow velocity is directly related to Doppler shiftIf you measure the Doppler shift you can

derive the blood flow velocity Carotid ultrasound and transcranial Doppler

ultrasound can accomplish this

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Ultrasound Physics

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Carotid Ultrasound

IndicationsIschemic stroke or TIAAssessment of carotid bruitAssessment of carotid stenosis or occlusionPre-operative assessment for cardiovascular

surgeryPost carotid endarterectomy or stenting

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Principles of Carotid Duplex

Duplex (B-mode and Doppler)B-mode (brightness mode)

Grayscale, used for visualization of structures and assessment of plaque morphology

• Hyperechoic (bright white: bone, calcium), causes a shadow posterior to it

• Hypoechoic (black or grey: thrombus)

Doppler velocities (peak systolic and end diastolic) Used to determine the direction of blood flow Used to estimate the range of stenosis Each lab should have own validated parameters of the

velocities to be used for assignment of stenosis, not just use published values

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Assignment of Carotid Stenosis

Carotid Artery Stenosis: Gray-Scale and Doppler US Diagnosis—Society of Radiologists in Ultrasound Consensus Conference Grant et al., 2003

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Transverse Right ICA B-Mode

common carotid artery

(Transverse Right Proximal Common Carotid Artery)

Skin surface

internal jugular vein

muscle

Fat and subcutaneous tissue

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Longitudinal Right ICA B-mode Plaque

(Longitudinal Right Proximal Internal Carotid Artery)

Focal irregular, heterogeneous plaque in the R Prx ICA

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Right ICA B-mode with Color Doppler

Patient’s Head

Flow(away from probe)

- Flow(away from probe)

+ Flow(toward probe)

(Right Proximal Internal Carotid Artery)

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Right ICA Doppler Velocities

(Right Proximal Internal Carotid Artery)

Cardiac irregularity

+ Flow(away from probe)- Flow(away from probe)

Patient’s Head

Flow(away from probe)

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Report

Focal plaque in the right internal carotid artery No hemodynamically significant stenosis demonstrated in the right internal

carotid artery. High resistance with focal plaque in the right internal carotid artery Cardiac irregularity was noted

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Longitudinal Left CCA B-mode Plaque

(Longitudinal Left Mid Common Carotid Artery)

Plaque with fibrous cap and lipid rich core

Hyperechoic plaque with posterior acoustic shadowing

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Longitudinal Left CCA B-mode Plaque

Heterogeneous plaque with posterior acoustic shadowing

(Longitudinal Left Distal Common Carotid Artery)

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Longitudinal Left ICA Color Doppler

Noise(sample volume picking up multiple velocity jets)

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Carotid US vs Transcranial Doppler US

Carotid UltrasoundDirectly visualize the vesselStenosis determined by peak systolic velocity

TCDBlind insonationUses mean velocity

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Transcranial Doppler Ultrasound

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TCD Wave

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TCD Spectra

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Pulsatility Indices

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Pulsatility Indices

Low PIAVMlow ejection fractionaortic regurgitation

High PI: intracranial atherosclerosis increased intracranial pressure

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Insonation of Brain

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TCD use in Carotid Occlusive Disease

Allows for evaluation of:Collateral flowCerebral embolismPoor vasomotor reserve i.e. progression of

carotid stenosis

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TCD use in Carotid Occlusive Disease

Slide courtesy Z. Garami, MD

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Risk of Ipsilateral Stroke: Number of Activated Collaterals (ACA, PCOM, OA)

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Subarachnoid Hemorrhage Detection of vasospasm

Clinical exam (usually somnolence or non-focal symptoms), not very sensitive

Daily TCD (non-invasive, 90% sensitivity, often precedes clinical vasospasm)

TCD or CTA can be used to screen for “plasty-able” lesions

Images from 1. http://www.spencertechnologies.com/products.html#thumb 2. www.viswiki.com/en/Transcranial_doppler, 3. http://depts.washington.edu/uwtcdlab/images/tcd/tcd3_lg.gif all accessed on 1/24/2010 4. Cerebrovascular Ultrasound in Stroke Prevention

and Treatment

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Thresholds for Anterior Circulation Vasospasm

Should be validated at the given centerMild vasospasm 120-140 cm/s, Lindegaard

Ratio (MCA velocity/extracranial ICA) 3-4Moderate vasospasm 140-180 cm/s,

Lindegaard Ratio (MCA velocity/extracranial ICA) 4-6Severe vasospasm >200 cm/s, Lindegaard

Ratio (MCA velocity/extracranial ICA) >6Less reliable in posterior circulation (due to

greater anatomic variance)

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Data on TCD Monitoring

Courtesy Mauro Oddo, MD

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Subarachnoid Hemorrhage Triple-H therapy (hypertension, hypervolemia,

hemodilution) Introduced in 1970’s to prevent delayed cerebral

ischemia from vasospasmProphylactic triple-H (in absence of vasospasm) does

not prevent vasospasm (Treggiari et al. J. Neurosurg 2008)

Double-H therapy (hypertension and hypervolemia as hemodilution is consequence of hypervolemia)Must be individualized and titrated to clinical exam

and TCDCan result in pulmonary edema, hyponatremia, MI,

etc.

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Brain Death

Uniform Determination of Death ActLegally acknowledged brain death as a

mechanism of deathDefined death as:

Irreversible cessation of circulatory and respiratory functions OR

Irreversible cessation of all functions of the entire brain, including the brain stem

1. Guidelines for the determination of death: report of the medical consultants on the diagnosis of death to the President’s commission on the ethical problems in medicine and biochemical and behavioral research. JAMA 1981;246:2184-2186.

2. Uniform Determination of Death Act, 12 uniform laws annotated 589 (West 1993 West suppl 1997)

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AAN recommendations on use of ancillary testing

AAN Clinician Guideline Supplement: Ancillary Testing; Update: Determining Brain Death in Adults. 2010.

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Diagnosis of Patent Foramen Ovale (PFO)

Slide courtesy Alex Razumovsky, PhD

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Diagnosis of Patent Foramen Ovale (PFO)

PFO is a residual channel between the right and left atrium which originally allowed oxygenated placental blood to pass from the right to left atrium bypassing the fetal lungs

Usually closes by age 2, but can persist in 25-30% of the general population

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Diagnosis of PFO by TCD

Agitated saline studyMonitor the MCA

Slide courtesy Z. Garami, MD

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Diagnosing subclavian steal by TCD

Image the vertebral arteryIschemic cuff test

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Subclavian Steal Syndrome

Slide courtesy Z. Garami, MD

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Questions

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Thank you