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Stress Echocardiography
Susan A. Raaymakers, MPAS, PA-C, RDCS (AE)(PE)
Radiologic and Imaging Sciences - Echocardiography
Grand Valley State University, Grand Rapids, Michigan
1
Brief History

1980s
Improvement in image quality
 Development of digital acquisition
technology (“frame grabbers”)

2
Physiologic Basis

1930s: Tennant and Wiggers
Relationship between systolic contraction
and myocardial blood supply to the left
ventricle
 Demonstrated rapid and predictable
development of dyskinesis

3
Physiologic Basis

Physiologic stress results in
An increase in heart rate and
 Contractility


HR and contractility maintained by an
increase in myocardial blood flow
4
Physiologic 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
5
therapy

Physiologic Basis

Presence of coronary artery stenosis


Increased oxygen demand not adequately
accommodated (supply-demand mismatch)
Development of ischemic cascade
6
Physiologic 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
7
Utility Of Echocardiography In
Conjunction 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
8
Methodologies

Advantage: versatility

Exercise






Treadmill
Supine bicycle
Upright bicycle
Handgrip
Stair step
Non-exercise




Dobutamine
Dipyridamole
Adenosine
Pacing
9
Treadmill
Most commonly form of stress
testing in U.S.
 Provides useful clinical information

Exercise capacity
 Blood pressure response
 Arrhythmias


Protocols: Bruce, Balke, Naughton,
etc.
10
Treadmill
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
11
Treadmill Exercise Stress
Echocardiography

Traditional approach




Parasternal long-axis
Parasternal short-axis
Apical four chamber
Apical two chamber
12
Treadmill 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
13
Treadmill Exercise Stress Echocardiography
Rapid 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
14
Supine Bicycle Exercise Stress
Echocardiography
Rapid Recovery - Images acquired in 75 seconds

Apical Wall Motion Abnormality
15
Bicycle 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
16
images
Bicycle 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
17
Bicycle 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
18
Dobutamine 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
19
Dobutamine 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
20
Dobutamine Stress Echocardiography

Atropine

May be used in conjunction with Dobutamine
to augment heart rate increases
 Patients
on beta blockers
21
Protocol for Dobutamine Stress
Echocardiography

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
22
End Points and Reasons to Terminate
Dobutamine 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
23
Safety of Dobutamine
Short-half life
 May be utilized in patients with
bronchospastic disease
 Common side effects

Minor arrhythmias
 Palpitations or anxiety

24
Dipyridamole 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
25
Choosing Among the Different
Stress Modalities
26
Interpretation of Stress
Echocardiography

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
27
Abnormal response to exercise
Increase in LV systolic dimension
 Increase in RV

28
Strain 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
29
Strain 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
30
Wall 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
31
Wall 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
32
Wall Motion Score Index







1: normal
2: hypokinesis
3: akinesis
4: dyskinesis
5: aneurysmal
6: akinetic/scar
7: dyskinetic/scar
33
Characterization 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
34
Characterization of Wall Motion

Akinesis


Dyskinesis



Absence of systolic myocardial thickening and
endocardial excursion
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
35
Example of Wall Motion Scoring
Index
36
Wall 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
37
Localization of Coronary Artery Lesions
Practical 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
38
Localized Apical Ischemia Induced
with Dobutamine

Normal at 20
µg/kg/min
stage

Abnormal at
higher stage
and heart rate
39
Previous Anterior MI, Development
of Inferior Ischemia

Baseline: basal
inferior wall
akinesis

Entire inferior
wall dyskinesis
40
Multi-Vessel Disease
41
Correlation with Symptoms and
Electrocardiographic 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
42
Detection of Coronary Artery
Disease – 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 endsystolic wall stress at peak Dobutamine infusion may account
for reduced sensitivity in this subgroup
43
Detection of Coronary Artery Disease –
Significant LVH W/CAD
44
Detection of Coronary Artery Disease –
False 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
45
Comparison 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
46
Stress Echocardiography After Revascularization

Used to
Evaluate initial success of the procedure
 Look for recurrence of disease
 Assess symptoms in patients with known
CAD

47
Pre-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
48
Stress Echocardiography in Women

Higher rates of false positive ECG
response
49
Assessment 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 nonviable
 Resting echocardiogram non-sensitive, need
stress echocardiography (Dobutamine)

50
Assessment of Viability
Anterior And Lateral Viability Is Demonstrated
51
Use of Myocardial Contrast Techniques in
Stress 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
52
Use of Myocardial Contrast Techniques in
Stress 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
53
Use of Myocardial Contrast Techniques in
Stress Echocardiography
 Following
image
 Delay
in rate of replenishment of
the microbubbles: inferior wall
perfusion defect
54
Use of Myocardial Contrast Techniques in
Stress Echocardiography
55
Stress Echocardiography in Valvular
Heart 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
56
Stress Echocardiography in Valvular Heart Disease
Utilization Specifically For Valvular Heart Disease
Correlation 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
57
Stress Echocardiography in Valvular Heart Disease
Utilization 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
58
Stress Echocardiography in Valvular Heart Disease
Review of Utilization of Dobutamine Stress
Echocardiography 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)
59
Stress Echocardiography in Valvular Heart Disease
Review of Utilization of Dobutamine Stress
Echocardiography 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
60
Stress Echocardiography in Valvular Heart Disease
Review of Utilization of Dobutamine Stress
Echocardiography 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
61
Stress Echocardiography in Valvular Heart Disease

Prosthetic valves




Detection of exercise


Increase substantially with exercise
Helpful in understanding differences in
hemodynamics of different prosthetic valves
Patient-prosthetic valve mismatch
Induced changes in pulmonary artery pressure in
patients with chronic lung disease
LVOT obstruction
62
Practice
63
Review
What type of test is this?
 Is this a normal response?

64
Review


What type of test was performed?
Would you consider this as a normal response?
65
Review
What type of test is being performed?
 Is this normal?

66
Review
What type of test is being performed?
 Is this a normal response?

67
Review
What type of test is being performed?
 Is this a normal response?

68
Review
What type of test is being performed?
 Is this a normal response?

69
Review
What type of test is being performed?
 Is this a normal response?

70
Review



History: patient with diabetes, smoking and peripheral
vascular disease
What type of test is being performed?
Is this a normal response?
71
Sources

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.
72