1 stress echocardiography susan a. raaymakers, mpas, pa-c, rdcs (ae)(pe) radiologic and imaging...

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Stress EchocardiographyStress Echocardiography

Susan A. Raaymakers, MPAS, PA-C, RDCS (AE)(PE)Radiologic and Imaging Sciences - EchocardiographyGrand Valley State University, Grand Rapids, Michigan

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Brief HistoryBrief History

1980s Improvement in image quality Development of digital acquisition

technology (“frame grabbers”)

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Physiologic BasisPhysiologic Basis

1930s: Tennant and Wiggers Relationship between systolic contraction

and myocardial blood supply to the left ventricle

Demonstrated rapid and predictable development of dyskinesis

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Physiologic stress results in An increase in heart rate and Contractility

HR and contractility maintained by an increase in myocardial blood flow

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Increase in Systolic wall thickening Endocardial excursion Global contractility

Leads to decrease in end-systolic volume Increase in ejection fraction May be blunted in advanced age,

hypertension or in presence of beta blocker therapy

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Presence of coronary artery stenosis Increased oxygen demand not adequately

accommodated (supply-demand mismatch) Development of ischemic cascade

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Stressor elimination Myocardial oxygen demand is reduced and

ischemia resolves Normalization may occur rapidly

Typically recovery takes 1 to 2 minutes depending on severity of ischemia

Stunned myocardium: functional abnormalities persist after transient ischemia for a longer period

May last days or weeks

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Utility Of Echocardiography In Utility Of Echocardiography In Conjunction With Stress TestingConjunction With Stress Testing Wall motion abnormalities at rest

Infarction Cardiomyopathy Myocarditis Left bundle branch block Hypertension/afterload mismatch Hibernating myocardium Stunned myocardium Toxins (e.g., alcohol) Postoperative state Paced rhythm Right ventricular volume/pressure overload

Wall Motion abnormalities during stress Ischemia Translational cardiac motion Cardiomyopathy Rate-dependent left bundle branch block

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MethodologiesMethodologies

Advantage: versatility Exercise

Treadmill Supine bicycle Upright bicycle Handgrip Stair step

Non-exercise Dobutamine Dipyridamole Adenosine Pacing

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TreadmillTreadmill

Most commonly form of stress testing in U.S.

Provides useful clinical information Exercise capacity Blood pressure response Arrhythmias

Protocols: Bruce, Balke, Naughton, etc.

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TreadmillTreadmill

Addition of echocardiography Not intended to alter exercise protocol

Echocardiography images obtained pre- and post-exercise

Challenge of obtaining images immediately post exercise

Ischemia may resolve quickly after exercise Must obtain images with 1 to 1.5 minutes

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Treadmill Exercise Stress Treadmill Exercise Stress EchocardiographyEchocardiography

Traditional approach Parasternal long-axis Parasternal short-axis Apical four chamber Apical two chamber

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Treadmill Exercise Stress EchocardiographyTreadmill Exercise Stress Echocardiography

Protocol Patient is prepared for treadmill stress testing

Instructions provided on transition from the treadmill to the examination table after exercise

Resting echocardiographic images obtained, reviewed, and stored (both digitally and on videotape)

Standard treadmill exercise examination performed

Patient moves as quickly as possible after exercise to the examination table

Post exercise imaging acquiring and recorded on videotape and digitally

Digital images reviewed and representative loops selected

Digital images stored on permanent medium

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Treadmill Exercise Stress EchocardiographyTreadmill Exercise Stress EchocardiographyRapid Recovery – Images acquired in 75 secondsRapid Recovery – Images acquired in 75 seconds

Anterior ischemia Long and short axis Four chamber

Resolved in two chamber over the course of post-stress image acquisition

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Supine Bicycle Exercise Stress Echocardiography Supine Bicycle Exercise Stress Echocardiography

Rapid Recovery - Images acquired in 75 secondsRapid Recovery - Images acquired in 75 seconds

Apical Wall Motion Abnormality

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Bicycle ErgometryBicycle Ergometry

Stationary bicycle ergometry: first form of exercise in conjunction with echocardiography

Currently: Availability of supine bicycle systems permit a variety of patient positions

Advantage: ability to image throughout exercise, particularly at peak stress Avoids potential problem of rapid recovery Allows onset of wall motion abnormality to be documented Wall motion abnormalities are more easily seen in peak

exercise versus post exercise Image acquisition is less rushed lending itself to better quality

images

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Bicycle ErgometryBicycle Ergometry

Disadvantage Workload

Bicycling in supine position may be uncomfortable for some patients

Supine position appears to facilitate the induction of ischemia Perhaps by increasing venous return and preload Associated with greater blood pressure response Ischemia occurs at a lower heart rate during supine

versus upright exercise

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Bicycle Ergometry ProtocolBicycle Ergometry Protocol

Patient prepared for standard stress testing

Patient instructed how to perform bicycle exercise

Patient positioned on supine ergometer and secured in place

Rest images obtained (table inclined to optimize images)

Exercise protocol begins at a workload of 25 W and a cadence of 60 rpm

Images monitored throughout exercise

At peak exercise, a full series of images is obtained

After cessation of exercise, wall motion is monitored to document resolution of induced ischemia

Representative images are selected and rearranged for digital storage

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Dobutamine Stress EchocardiographyDobutamine Stress Echocardiography

Dobutamine: synthetic catecholamine causes Inotropic and chronotropic effects

Affinity for ß1, ß2 and α receptors in the myocardium and vasculature

Cardiovascular effects are dose dependent Augmented contractility occurring at lower doses followed by a

progressive chronotropic response at increasing doses Peripheral effects may result in either predominant:

Vasoconstriction or vasodilation Changes in vascular resistance (i.e. blood pressure) are

unpredictable

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Distinction between exercise and Dobutamine Change in venous return is increased in exercise Autonomic nervous system-mediated changes in

systemic and pulmonary vascular resistance are quite different

Heart rate is less important with Dobutamine compared with exercise

Ischemia may be induced even if target heart rate is not achieved due to greater augmentation of contraction

Primary indication for Dobutamine as a substitute for exercise stress echocardiography

Patients unwilling or unable to exercise adequately Detection of viable myocardium

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Atropine May be used in conjunction with Dobutamine

to augment heart rate increases Patients on beta blockers

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Protocol for Dobutamine Stress Protocol for Dobutamine Stress EchocardiographyEchocardiography

Patient preparation for stress testing

IV access obtained

Digital images obtained for baseline study

Continuous EKG and BP monitoring

Dobutamine infusion of 5 (or 10) µg/kg/min

Infusion rate is increased every 3 minutes to doses of 10, 20, 30, and 40 µg/kg/min

EKG, Echocardiograms and BP are monitored continuously

Low-dose images are acquired at 5 or 10 µg/kg/min (at first sign of increased contractility)

Atropine in aliquots of 0.5 to 1.0 mg can be given during the mid and high doses to augment the heart rate response

Mid-dose images are acquired at either 20 or 30 µg/kg/min

Peak images are acquired before termination of the infusion

Post-stress images are recorded after return to baseline

The patient is monitored until he or she returns to baseline status

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End Points and Reasons to Terminate End Points and Reasons to Terminate Dobutamine Infusion During Stress TestingDobutamine Infusion During Stress Testing

Exceeding target heart rate of 85% age-predicted maximum

Development of significant angina Recognition of a new wall motion

abnormality Arrhythmias such as atrial

fibrillation or non-sustained ventricular tachycardia

Limiting side effects or symptoms

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Safety of DobutamineSafety of Dobutamine

Short-half life May be utilized in patients with

bronchospastic disease Common side effects

Minor arrhythmias Palpitations or anxiety

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Dipyridamole and AdenosineDipyridamole and Adenosine

Potent vasodilators

Adenosine: short-acting direct coronary vasodilator

Dipyridamole: slower acting. Inhibits adenosine uptake

Adenosine and dipyridamole generally cause changes less significant and shorter lived than Dobutamine

Used in nuclear imaging studies more often than echocardiography

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Choosing Among the Different Choosing Among the Different Stress ModalitiesStress Modalities

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Interpretation of Stress Interpretation of Stress EchocardiographyEchocardiography Most analyzed based on subjective assessment of regional wall

motion Wall thickness and endocardial excursion at baseline and during

stress Normal response is development of global hyperdynamic wall motion

Some heterogeneity of response may be expected

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Abnormal response to exerciseAbnormal response to exercise

Increase in LV systolic dimension Increase in RV

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Strain Rate ImagingStrain Rate Imaging

Relies on tissue Doppler imaging to quantify myocardial deformation in response to applied stress

Strain Simply the change in length of tissue that

occurs when force is applied Strain rate

First derivative of strain or how strains changes over time

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Strain Rate ImagingStrain Rate Imaging

Measured as difference in velocity between two points normalized for the distance between them

Theoretic advantages: Relative independence of translational

movement and tethering

This will be covered in more depth in future lecture

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Wall Motion Score IndexWall Motion Score Index

16 segment 1989 ASE recommendation

6 segments both basal and mid ventricular levels (12 total) 4 segments at apex Commonly used in echocardiography Nuclear perfusion imaging, cardiovascular magnetic resonance

and cardiac computed tomography commonly use more segments

Did not include apical cap

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17 segment model 2002 American Heart Association Writing Group on

Myocardial Segmentation and Registration for Cardiac Imaging attempt to establish common segmentation for all types of imaging

Includes apical cap

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1: normal 2: hypokinesis 3: akinesis 4: dyskinesis 5: aneurysmal 6: akinetic/scar 7: dyskinetic/scar

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Characterization of Wall MotionCharacterization of Wall Motion

Hypokinesis Mildest form of abnormal function Preservation of some degree of thickening and

inward motion of endocardium during systole but less than normal (<5 mm of endocardial excursion)

Truly abnormal if: Limited to a region or territory that corresponds to the

distribution of one coronary artery and Associated with normal (or hyperdynamic) wall motion

elsewhere Tardokinesis

Delayed, sometimes post systolic, inward motion or thickening

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Characterization of Wall MotionCharacterization of Wall Motion

Akinesis Absence of systolic myocardial thickening and

endocardial excursion

Dyskinesis Most extreme form of a wall motion abnormality Systolic thinning and outward motion or bulging of

the myocardium during systole

Scar Thin and/or highly echogenic

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Example of Wall Motion Scoring Example of Wall Motion Scoring IndexIndex

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Wall Motion Response to StressWall Motion Response to Stress

Wall motion that increases or augments with stress is normal

Development of wall motion abnormalities with stress is considered resultant of ischemia

Abnormal segments at rest remaining unchanged with stress: infarcted sans additional ischemia

Hypokinetic baseline that worsens with exercise: ischemic

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Localization of Coronary Artery LesionsLocalization of Coronary Artery LesionsPractical ApplicationPractical Application

Predict presence of disease in specific coronary arteries or branches In general

Stress echocardiography is more sensitive in patients with multi-vessel disease in comparison to single-vessel disease

More accurate specifically identifying disease in the left anterior descending artery or right coronary artery in comparison to left circumflex

Variability in coronary artery distribution Left circumflex versus right coronary artery

distribution not always possible

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Localized Apical Ischemia Induced Localized Apical Ischemia Induced with Dobutaminewith Dobutamine

Normal at 20 µg/kg/min stage

Abnormal at higher stage and heart rate

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Previous Anterior MI, Development Previous Anterior MI, Development of Inferior Ischemiaof Inferior Ischemia

Baseline: basal inferior wall akinesis

Entire inferior wall dyskinesis

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Multi-Vessel DiseaseMulti-Vessel Disease

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Correlation with Symptoms and Correlation with Symptoms and Electrocardiographic ChangesElectrocardiographic Changes

Most instances ECG, symptoms and echocardiography concordance

Discordance Limitation of interpretation of ECG changes and

symptoms Virtually every study indicates

Wall motion more sensitive and specific than symptoms and/or ST-segment changes for CAD

Echo relied upon heavily for final report Most common indications for echocardiography with stress

testing due to anticipation of abnormal or non-diagnostic ECG

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Detection of Coronary Artery Detection of Coronary Artery Disease – False NegativesDisease – False Negatives

Single Vessel Sensitivity is higher with multivessel disease

Left ventricular hypertrophy Studies shown: patients with LVH in setting of normal mass

(small chamber size) have a disproportionately high frequency of false-negative results

Concentric remodeling (thick walls with small internal chamber size): common finding in elderly patients with hypertension

(Smart et al., 2000) Authors postulated blunted increase in end-systolic wall stress at peak Dobutamine infusion may account for reduced sensitivity in this subgroup

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Detection of Coronary Artery Disease – Detection of Coronary Artery Disease – Significant LVH W/CADSignificant LVH W/CAD

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Detection of Coronary Artery Disease – Detection of Coronary Artery Disease – False Negative: Left Bundle Branch BlockFalse Negative: Left Bundle Branch Block

Abnormal septal motion both at rest and stress Preservation of septal thickening

Evidence against ischemia as cause of abnormal endocardial excursion

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Comparison with Nuclear TechniquesComparison with Nuclear Techniques

Gold standard: angiographic testing Nuclear: more sensitive Echocardiographic: more specific Overall accuracy: nuclear and

echocardiography are similar Both operator dependent

Advantages of echocardiography: versatility of technique, lower cost of test, and avoidance of radiation exposure

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Stress Echocardiography After RevascularizationStress Echocardiography After Revascularization

Used to Evaluate initial success of the procedure Look for recurrence of disease Assess symptoms in patients with known

CAD

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Pre-Operative Risk AssessmentPre-Operative Risk Assessment

Non-cardiac surgery Dobutamine stress echocardiography

most commonly used Absence of inducible wall motion

abnormality Very favorable prognosis with negative

predictive value of 93% to 100% Predictive ability: identification of patients who

subsequently experience perioperative events

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Stress Echocardiography in WomenStress Echocardiography in Women

Higher rates of false positive ECG response

http://www.sanbenito.k12.tx.us/District/WebPages2001/FamousWomen/betsy_ross.htm

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Assessment of Myocardial ViabilityAssessment of Myocardial Viability

Viable Myocardium that has potential for functional

recovery Stunned or hibernating

More severe wall motion abnormality, less likely to be viable (i.e. dyskinetic regions are less viable than hypokinetic regions)

Thinned, scarred segments likely to be non-viable

Resting echocardiogram non-sensitive, need stress echocardiography (Dobutamine)

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Assessment of ViabilityAssessment of ViabilityAnterior And Lateral Viability Is DemonstratedAnterior And Lateral Viability Is Demonstrated

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Use of Myocardial Contrast Techniques in Use of Myocardial Contrast Techniques in Stress EchocardiographyStress Echocardiography

Two Distinct Categories Left ventricular opacification for border

enhancement Covered in previous lecture

Myocardial perfusion imaging Perfusion defect precedes regional wall motion

abnormality Differing protocols

Bolus vs. continuous infusion Continuous vs. intermittent triggered imaging Most studies rely on vasodilator stress (dipyridamole or

adenosine) to induce regional changes in blood flow

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Vasodilator and intermittent triggered imaging during continuous infusion of an experimental agent

Displayed image recorded from the fourth cycle after bubble destruction (long enough for contrast to adequately replenish within the tissue)

Peak exercise: bubbles should refill more quickly (one to two cycles) due to vasodilation

Approval for contrast agents for specific purpose of perfusion imaging is not yet approved by U.S. Food and Drug Administration Experimental and clinical studies have demonstrated feasibility

of myocardial perfusion studies in comparing with nuclear and angiography

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Following imageDelay in rate of replenishment of

the microbubbles: inferior wall perfusion defect

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Stress Echocardiography in Valvular Stress Echocardiography in Valvular Heart DiseaseHeart Disease

Echocardiogram and stress echocardiogram

Study (Gauer et al., 2003) 1,272 consecutive patients

5% significant mitral regurgitation 13% aortic regurgitation Approximately 1% each aortic or mitral stenosis

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Stress Echocardiography in Valvular Heart DiseaseStress Echocardiography in Valvular Heart DiseaseUtilization Specifically For Valvular Heart DiseaseUtilization Specifically For Valvular Heart DiseaseCorrelation Of Symptoms With SeverityCorrelation Of Symptoms With Severity

Some patients with relatively mild disease may have significant increase in mean gradient during exercise

MS: may have inappropriate increase in pulmonary artery pressure

MR: unexpected worsening with exercise Worsening of mitral regurgitation has been reported in the absence of ischemia or LV dilation

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Stress Echocardiography in Valvular Heart DiseaseStress Echocardiography in Valvular Heart Disease

Utilization specifically for valvular heart diseaseUtilization specifically for valvular heart disease

LV dysfunction and moderate aortic valve gradient Resting study often fails to differentiate

between moderate and severe aortic stenosis based on

gradient alone

Dobutamine Increasing transvalvular flow can be used to

distinguish moderate

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Review of Utilization of Dobutamine Stress Review of Utilization of Dobutamine Stress Echocardiography for Aortic StenosisEchocardiography for Aortic Stenosis

Dobutamine infusion 5 µg/kg/min If leaflets are relatively flexible (mild to

moderate stenosis) Valve area will increase in response to increasing

stroke volume Increase in velocity outflow tract will be much

greater than that of the jet Ratio of LVOT/Ao velocity will increase

Example: Baseline: LVOT velocity of 1.0 and Ao velocity of 2.0 (ratio ½) Exercise: LVOT velocity 2.0 and Ao velocity of 2.0 (ratio 1/1)

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Review of Utilization of Dobutamine Stress Review of Utilization of Dobutamine Stress Echocardiography for Aortic StenosisEchocardiography for Aortic Stenosis True severe aortic stenosis is associated with a fixed

valve area Maximal velocity of both outflow tract and jet will

proportionately increase Ratio of LVOT/Ao peak velocity remains the same

Example: Baseline: LVOT velocity of 1.0 and Ao velocity of 2.0 (ratio ½) Exercise: LVOT velocity 2.0 and Ao velocity of 4.0 (ratio 2/4 or 1/2)

Limitation: study non-diagnostic if ventricular does not respond to Dobutamine with an increase in

contractility, which may occur with significant coronary artery disease

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Review of Utilization of Dobutamine Stress Review of Utilization of Dobutamine Stress Echocardiography for Aortic StenosisEchocardiography for Aortic Stenosis

Rest: 0.6/2.8 = 0.21

20 mcg/kg: 0.8/3.6 = 0.22

30 mcg/kg: 0.9/3.8 = 0.23

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Prosthetic valves Increase substantially with exercise Helpful in understanding differences in

hemodynamics of different prosthetic valves Patient-prosthetic valve mismatch

Detection of exercise Induced changes in pulmonary artery pressure in

patients with chronic lung disease

LVOT obstruction

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PracticePractice

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ReviewReview

What type of test is this? Is this a normal response?

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ReviewReview

What type of test was performed? Would you consider this as a normal response?

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ReviewReview

What type of test is being performed? Is this normal?

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ReviewReview

What type of test is being performed? Is this a normal response?

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ReviewReview


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ReviewReview


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ReviewReview


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ReviewReview

History: patient with diabetes, smoking and peripheral vascular disease


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SourcesSources

Feigenbaum H, Armstrong W. (2004). Echocardiography. (6th Edition). Indianapolis. Lippincott Williams & Wilkins.

Goldstein S., Harry M., Carney D., Dempsey A., Ehler D., Geiser E., Gillam L., Kraft C., Rigling R., McCallister B., Sisk E., Waggoner A., Witt S., Gresser C.. (2005). Outline of Sonographer Core Curriculum in Echocardiography.

Otto C. (2004). Textbook of Clinical Echocardiography. (3rd Edition). Elsevier & Saunders.

Reynolds T. (2000). The Echocardiographer's Pocket Reference. (2nd Edition). Arizona. Arizona Heart Institute.

1 stress echocardiography susan a. raaymakers, mpas, pa-c, rdcs (ae)(pe) radiologic and imaging...

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