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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 BasisPhysiologic Basis
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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Physiologic BasisPhysiologic Basis
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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Physiologic BasisPhysiologic Basis
Presence of coronary artery stenosis Increased oxygen demand not adequately
accommodated (supply-demand mismatch) Development of ischemic cascade
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Physiologic BasisPhysiologic Basis
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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Dobutamine Stress EchocardiographyDobutamine Stress Echocardiography
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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Dobutamine Stress EchocardiographyDobutamine Stress Echocardiography
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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Wall Motion Score IndexWall Motion Score Index
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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Wall Motion Score IndexWall Motion Score Index
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
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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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Use of Myocardial Contrast Techniques in Use of Myocardial Contrast Techniques in Stress EchocardiographyStress Echocardiography
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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Use of Myocardial Contrast Techniques in Use of Myocardial Contrast Techniques in Stress EchocardiographyStress Echocardiography
Following imageDelay in rate of replenishment of
the microbubbles: inferior wall perfusion defect
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Use of Myocardial Contrast Techniques in Use of Myocardial Contrast Techniques in Stress EchocardiographyStress Echocardiography
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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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Stress Echocardiography in Valvular Heart DiseaseStress Echocardiography in Valvular Heart Disease
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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Stress Echocardiography in Valvular Heart DiseaseStress Echocardiography in Valvular Heart Disease
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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Stress Echocardiography in Valvular Heart DiseaseStress Echocardiography in Valvular Heart Disease
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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Stress Echocardiography in Valvular Heart DiseaseStress Echocardiography in Valvular Heart Disease
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
What type of test is being performed? Is this a normal response?
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ReviewReview
What type of test is being performed? Is this a normal response?
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ReviewReview
What type of test is being performed? Is this a normal response?
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ReviewReview
History: patient with diabetes, smoking and peripheral vascular disease
What type of test is being performed? Is this a normal response?
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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.